Bradycardia: Cardiac arrhythmias that are characterized by excessively slow HEART RATE, usually below 50 beats per minute in human adults. They can be classified broadly into SINOATRIAL NODE dysfunction and ATRIOVENTRICULAR BLOCK.Heart Rate: The number of times the HEART VENTRICLES contract per unit of time, usually per minute.Heart: The hollow, muscular organ that maintains the circulation of the blood.Heart Rate, Fetal: The heart rate of the FETUS. The normal range at term is between 120 and 160 beats per minute.Blood Pressure: PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.Heart Failure: A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (VENTRICULAR DYSFUNCTION), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as MYOCARDIAL INFARCTION.Autonomic Nervous System: The ENTERIC NERVOUS SYSTEM; PARASYMPATHETIC NERVOUS SYSTEM; and SYMPATHETIC NERVOUS SYSTEM taken together. Generally speaking, the autonomic nervous system regulates the internal environment during both peaceful activity and physical or emotional stress. Autonomic activity is controlled and integrated by the CENTRAL NERVOUS SYSTEM, especially the HYPOTHALAMUS and the SOLITARY NUCLEUS, which receive information relayed from VISCERAL AFFERENTS.Hemodynamics: The movement and the forces involved in the movement of the blood through the CARDIOVASCULAR SYSTEM.Apnea: A transient absence of spontaneous respiration.Electrocardiography: Recording of the moment-to-moment electromotive forces of the HEART as projected onto various sites on the body's surface, delineated as a scalar function of time. The recording is monitored by a tracing on slow moving chart paper or by observing it on a cardioscope, which is a CATHODE RAY TUBE DISPLAY.Baroreflex: A response by the BARORECEPTORS to increased BLOOD PRESSURE. Increased pressure stretches BLOOD VESSELS which activates the baroreceptors in the vessel walls. The net response of the CENTRAL NERVOUS SYSTEM is a reduction of central sympathetic outflow. This reduces blood pressure both by decreasing peripheral VASCULAR RESISTANCE and by lowering CARDIAC OUTPUT. Because the baroreceptors are tonically active, the baroreflex can compensate rapidly for both increases and decreases in blood pressure.Heart Diseases: Pathological conditions involving the HEART including its structural and functional abnormalities.Heart Block: Impaired conduction of cardiac impulse that can occur anywhere along the conduction pathway, such as between the SINOATRIAL NODE and the right atrium (SA block) or between atria and ventricles (AV block). Heart blocks can be classified by the duration, frequency, or completeness of conduction block. Reversibility depends on the degree of structural or functional defects.Hypotension: Abnormally low BLOOD PRESSURE that can result in inadequate blood flow to the brain and other vital organs. Common symptom is DIZZINESS but greater negative impacts on the body occur when there is prolonged depravation of oxygen and nutrients.Reflex: An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.Sinoatrial Node: The small mass of modified cardiac muscle fibers located at the junction of the superior vena cava (VENA CAVA, SUPERIOR) and right atrium. Contraction impulses probably start in this node, spread over the atrium (HEART ATRIUM) and are then transmitted by the atrioventricular bundle (BUNDLE OF HIS) to the ventricle (HEART VENTRICLE).Vagus Nerve: The 10th cranial nerve. The vagus is a mixed nerve which contains somatic afferents (from skin in back of the ear and the external auditory meatus), visceral afferents (from the pharynx, larynx, thorax, and abdomen), parasympathetic efferents (to the thorax and abdomen), and efferents to striated muscle (of the larynx and pharynx).Fetal Heart: The heart of the fetus of any viviparous animal. It refers to the heart in the postembryonic period and is differentiated from the embryonic heart (HEART/embryology) only on the basis of time.Heart Defects, Congenital: Developmental abnormalities involving structures of the heart. These defects are present at birth but may be discovered later in life.Sympathetic Nervous System: The thoracolumbar division of the autonomic nervous system. Sympathetic preganglionic fibers originate in neurons of the intermediolateral column of the spinal cord and project to the paravertebral and prevertebral ganglia, which in turn project to target organs. The sympathetic nervous system mediates the body's response to stressful situations, i.e., the fight or flight reactions. It often acts reciprocally to the parasympathetic system.Heart Transplantation: The transference of a heart from one human or animal to another.Atropine: An alkaloid, originally from Atropa belladonna, but found in other plants, mainly SOLANACEAE. Hyoscyamine is the 3(S)-endo isomer of atropine.Arrhythmia, Sinus: Irregular HEART RATE caused by abnormal function of the SINOATRIAL NODE. It is characterized by a greater than 10% change between the maximum and the minimum sinus cycle length or 120 milliseconds.Electrocardiography, Ambulatory: Method in which prolonged electrocardiographic recordings are made on a portable tape recorder (Holter-type system) or solid-state device ("real-time" system), while the patient undergoes normal daily activities. It is useful in the diagnosis and management of intermittent cardiac arrhythmias and transient myocardial ischemia.Respiration: The act of breathing with the LUNGS, consisting of INHALATION, or the taking into the lungs of the ambient air, and of EXHALATION, or the expelling of the modified air which contains more CARBON DIOXIDE than the air taken in (Blakiston's Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (= OXYGEN CONSUMPTION) or cell respiration (= CELL RESPIRATION).Adrenergic beta-Antagonists: Drugs that bind to but do not activate beta-adrenergic receptors thereby blocking the actions of beta-adrenergic agonists. Adrenergic beta-antagonists are used for treatment of hypertension, cardiac arrhythmias, angina pectoris, glaucoma, migraine headaches, and anxiety.Heart Atria: The chambers of the heart, to which the BLOOD returns from the circulation.Tachycardia: Abnormally rapid heartbeat, usually with a HEART RATE above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia.Parasympathetic Nervous System: The craniosacral division of the autonomic nervous system. The cell bodies of the parasympathetic preganglionic fibers are in brain stem nuclei and in the sacral spinal cord. They synapse in cranial autonomic ganglia or in terminal ganglia near target organs. The parasympathetic nervous system generally acts to conserve resources and restore homeostasis, often with effects reciprocal to the sympathetic nervous system.Cardiovascular System: The HEART and the BLOOD VESSELS by which BLOOD is pumped and circulated through the body.Pressoreceptors: Receptors in the vascular system, particularly the aorta and carotid sinus, which are sensitive to stretch of the vessel walls.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Diving: An activity in which the organism plunges into water. It includes scuba and bell diving. Diving as natural behavior of animals goes here, as well as diving in decompression experiments with humans or animals.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Myocardial Contraction: Contractile activity of the MYOCARDIUM.Telemetry: Transmission of the readings of instruments to a remote location by means of wires, radio waves, or other means. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Propranolol: A widely used non-cardioselective beta-adrenergic antagonist. Propranolol has been used for MYOCARDIAL INFARCTION; ARRHYTHMIA; ANGINA PECTORIS; HYPERTENSION; HYPERTHYROIDISM; MIGRAINE; PHEOCHROMOCYTOMA; and ANXIETY but adverse effects instigate replacement by newer drugs.Cardiovascular Physiological Phenomena: Processes and properties of the CARDIOVASCULAR SYSTEM as a whole or of any of its parts.Myocardium: The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.Anesthesia: A state characterized by loss of feeling or sensation. This depression of nerve function is usually the result of pharmacologic action and is induced to allow performance of surgery or other painful procedures.Cardiac Pacing, Artificial: Regulation of the rate of contraction of the heart muscles by an artificial pacemaker.Pacemaker, Artificial: A device designed to stimulate, by electric impulses, contraction of the heart muscles. It may be temporary (external) or permanent (internal or internal-external).Exercise Test: Controlled physical activity which is performed in order to allow assessment of physiological functions, particularly cardiovascular and pulmonary, but also aerobic capacity. Maximal (most intense) exercise is usually required but submaximal exercise is also used.Oxygen Consumption: The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346)Arrhythmias, Cardiac: Any disturbances of the normal rhythmic beating of the heart or MYOCARDIAL CONTRACTION. Cardiac arrhythmias can be classified by the abnormalities in HEART RATE, disorders of electrical impulse generation, or impulse conduction.Heart Valves: Flaps of tissue that prevent regurgitation of BLOOD from the HEART VENTRICLES to the HEART ATRIA or from the PULMONARY ARTERIES or AORTA to the ventricles.Syncope: A transient loss of consciousness and postural tone caused by diminished blood flow to the brain (i.e., BRAIN ISCHEMIA). Presyncope refers to the sensation of lightheadedness and loss of strength that precedes a syncopal event or accompanies an incomplete syncope. (From Adams et al., Principles of Neurology, 6th ed, pp367-9)Reflex, Oculocardiac: Change of heartbeat induced by pressure on the eyeball, manipulation of extraocular muscles, or pressure upon the tissue remaining in the orbital apex after enucleation.Vagotomy: The interruption or removal of any part of the vagus (10th cranial) nerve. Vagotomy may be performed for research or for therapeutic purposes.BiguanidesCardiac Output: The volume of BLOOD passing through the HEART per unit of time. It is usually expressed as liters (volume) per minute so as not to be confused with STROKE VOLUME (volume per beat).Anti-Arrhythmia Agents: Agents used for the treatment or prevention of cardiac arrhythmias. They may affect the polarization-repolarization phase of the action potential, its excitability or refractoriness, or impulse conduction or membrane responsiveness within cardiac fibers. Anti-arrhythmia agents are often classed into four main groups according to their mechanism of action: sodium channel blockade, beta-adrenergic blockade, repolarization prolongation, or calcium channel blockade.Heart Function Tests: Examinations used to diagnose and treat heart conditions.Stroke Volume: The amount of BLOOD pumped out of the HEART per beat, not to be confused with cardiac output (volume/time). It is calculated as the difference between the end-diastolic volume and the end-systolic volume.Sick Sinus Syndrome: A condition caused by dysfunctions related to the SINOATRIAL NODE including impulse generation (CARDIAC SINUS ARREST) and impulse conduction (SINOATRIAL EXIT BLOCK). It is characterized by persistent BRADYCARDIA, chronic ATRIAL FIBRILLATION, and failure to resume sinus rhythm following CARDIOVERSION. This syndrome can be congenital or acquired, particularly after surgical correction for heart defects.Tilt-Table Test: A standard and widely accepted diagnostic test used to identify patients who have a vasodepressive and/or cardioinhibitory response as a cause of syncope. (From Braunwald, Heart Disease, 7th ed)Cardiotonic Agents: Agents that have a strengthening effect on the heart or that can increase cardiac output. They may be CARDIAC GLYCOSIDES; SYMPATHOMIMETICS; or other drugs. They are used after MYOCARDIAL INFARCT; CARDIAC SURGICAL PROCEDURES; in SHOCK; or in congestive heart failure (HEART FAILURE).Atenolol: A cardioselective beta-1 adrenergic blocker possessing properties and potency similar to PROPRANOLOL, but without a negative inotropic effect.Physical Exertion: Expenditure of energy during PHYSICAL ACTIVITY. Intensity of exertion may be measured by rate of OXYGEN CONSUMPTION; HEAT produced, or HEART RATE. Perceived exertion, a psychological measure of exertion, is included.Clonidine: An imidazoline sympatholytic agent that stimulates ALPHA-2 ADRENERGIC RECEPTORS and central IMIDAZOLINE RECEPTORS. It is commonly used in the management of HYPERTENSION.Atropine Derivatives: Analogs and derivatives of atropine.Norepinephrine: Precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers and of the diffuse projection system in the brain arising from the locus ceruleus. It is also found in plants and is used pharmacologically as a sympathomimetic.Heart Arrest: Cessation of heart beat or MYOCARDIAL CONTRACTION. If it is treated within a few minutes, heart arrest can be reversed in most cases to normal cardiac rhythm and effective circulation.Ventricular Function, Left: The hemodynamic and electrophysiological action of the left HEART VENTRICLE. Its measurement is an important aspect of the clinical evaluation of patients with heart disease to determine the effects of the disease on cardiac performance.Medulla Oblongata: The lower portion of the BRAIN STEM. It is inferior to the PONS and anterior to the CEREBELLUM. Medulla oblongata serves as a relay station between the brain and the spinal cord, and contains centers for regulating respiratory, vasomotor, cardiac, and reflex activities.Myocardial Ischemia: A disorder of cardiac function caused by insufficient blood flow to the muscle tissue of the heart. The decreased blood flow may be due to narrowing of the coronary arteries (CORONARY ARTERY DISEASE), to obstruction by a thrombus (CORONARY THROMBOSIS), or less commonly, to diffuse narrowing of arterioles and other small vessels within the heart. Severe interruption of the blood supply to the myocardial tissue may result in necrosis of cardiac muscle (MYOCARDIAL INFARCTION).Parasympatholytics: Agents that inhibit the actions of the parasympathetic nervous system. The major group of drugs used therapeutically for this purpose is the MUSCARINIC ANTAGONISTS.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.Chemoreceptor Cells: Cells specialized to detect chemical substances and relay that information centrally in the nervous system. Chemoreceptor cells may monitor external stimuli, as in TASTE and OLFACTION, or internal stimuli, such as the concentrations of OXYGEN and CARBON DIOXIDE in the blood.Propanolamines: AMINO ALCOHOLS containing the propanolamine (NH2CH2CHOHCH2) group and its derivatives.Consciousness: Sense of awareness of self and of the environment.Carotid Sinus: The dilated portion of the common carotid artery at its bifurcation into external and internal carotids. It contains baroreceptors which, when stimulated, cause slowing of the heart, vasodilatation, and a fall in blood pressure.Rest: Freedom from activity.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Immersion: The placing of a body or a part thereof into a liquid.Coronary Disease: An imbalance between myocardial functional requirements and the capacity of the CORONARY VESSELS to supply sufficient blood flow. It is a form of MYOCARDIAL ISCHEMIA (insufficient blood supply to the heart muscle) caused by a decreased capacity of the coronary vessels.Posture: The position or attitude of the body.Phenylephrine: An alpha-1 adrenergic agonist used as a mydriatic, nasal decongestant, and cardiotonic agent.Sympatholytics: Drugs that inhibit the actions of the sympathetic nervous system by any mechanism. The most common of these are the ADRENERGIC ANTAGONISTS and drugs that deplete norepinephrine or reduce the release of transmitters from adrenergic postganglionic terminals (see ADRENERGIC AGENTS). Drugs that act in the central nervous system to reduce sympathetic activity (e.g., centrally acting alpha-2 adrenergic agonists, see ADRENERGIC ALPHA-AGONISTS) are included here.Exercise: Physical activity which is usually regular and done with the intention of improving or maintaining PHYSICAL FITNESS or HEALTH. Contrast with PHYSICAL EXERTION which is concerned largely with the physiologic and metabolic response to energy expenditure.Syncope, Vasovagal: Loss of consciousness due to a reduction in blood pressure that is associated with an increase in vagal tone and peripheral vasodilation.Isoproterenol: Isopropyl analog of EPINEPHRINE; beta-sympathomimetic that acts on the heart, bronchi, skeletal muscle, alimentary tract, etc. It is used mainly as bronchodilator and heart stimulant.Atrioventricular Block: Impaired impulse conduction from HEART ATRIA to HEART VENTRICLES. AV block can mean delayed or completely blocked impulse conduction.Metoprolol: A selective adrenergic beta-1 blocking agent that is commonly used to treat ANGINA PECTORIS; HYPERTENSION; and CARDIAC ARRHYTHMIAS.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Epinephrine: The active sympathomimetic hormone from the ADRENAL MEDULLA. It stimulates both the alpha- and beta- adrenergic systems, causes systemic VASOCONSTRICTION and gastrointestinal relaxation, stimulates the HEART, and dilates BRONCHI and cerebral vessels. It is used in ASTHMA and CARDIAC FAILURE and to delay absorption of local ANESTHETICS.Supine Position: The posture of an individual lying face up.Echocardiography: Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic.Body Temperature: The measure of the level of heat of a human or animal.Double-Blind Method: A method of studying a drug or procedure in which both the subjects and investigators are kept unaware of who is actually getting which specific treatment.Decerebrate State: A condition characterized by abnormal posturing of the limbs that is associated with injury to the brainstem. This may occur as a clinical manifestation or induced experimentally in animals. The extensor reflexes are exaggerated leading to rigid extension of the limbs accompanied by hyperreflexia and opisthotonus. This condition is usually caused by lesions which occur in the region of the brainstem that lies between the red nuclei and the vestibular nuclei. In contrast, decorticate rigidity is characterized by flexion of the elbows and wrists with extension of the legs and feet. The causative lesion for this condition is located above the red nuclei and usually consists of diffuse cerebral damage. (From Adams et al., Principles of Neurology, 6th ed, p358)Myocytes, Cardiac: Striated muscle cells found in the heart. They are derived from cardiac myoblasts (MYOBLASTS, CARDIAC).Myocardial Infarction: NECROSIS of the MYOCARDIUM caused by an obstruction of the blood supply to the heart (CORONARY CIRCULATION).Cardiac Output, Low: A state of subnormal or depressed cardiac output at rest or during stress. It is a characteristic of CARDIOVASCULAR DISEASES, including congenital, valvular, rheumatic, hypertensive, coronary, and cardiomyopathic. The serious form of low cardiac output is characterized by marked reduction in STROKE VOLUME, and systemic vasoconstriction resulting in cold, pale, and sometimes cyanotic extremities.Heart Arrest, Induced: A procedure to stop the contraction of MYOCARDIUM during HEART SURGERY. It is usually achieved with the use of chemicals (CARDIOPLEGIC SOLUTIONS) or cold temperature (such as chilled perfusate).Sympathomimetics: Drugs that mimic the effects of stimulating postganglionic adrenergic sympathetic nerves. Included here are drugs that directly stimulate adrenergic receptors and drugs that act indirectly by provoking the release of adrenergic transmitters.Oxygen: An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.Solitary Nucleus: GRAY MATTER located in the dorsomedial part of the MEDULLA OBLONGATA associated with the solitary tract. The solitary nucleus receives inputs from most organ systems including the terminations of the facial, glossopharyngeal, and vagus nerves. It is a major coordinator of AUTONOMIC NERVOUS SYSTEM regulation of cardiovascular, respiratory, gustatory, gastrointestinal, and chemoreceptive aspects of HOMEOSTASIS. The solitary nucleus is also notable for the large number of NEUROTRANSMITTERS which are found therein.Anoxia: Relatively complete absence of oxygen in one or more tissues.Regional Blood Flow: The flow of BLOOD through or around an organ or region of the body.Microinjections: The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.Models, Cardiovascular: Theoretical representations that simulate the behavior or activity of the cardiovascular system, processes, or phenomena; includes the use of mathematical equations, computers and other electronic equipment.Monitoring, Physiologic: The continuous measurement of physiological processes, blood pressure, heart rate, renal output, reflexes, respiration, etc., in a patient or experimental animal; includes pharmacologic monitoring, the measurement of administered drugs or their metabolites in the blood, tissues, or urine.Muscarinic Antagonists: Drugs that bind to but do not activate MUSCARINIC RECEPTORS, thereby blocking the actions of endogenous ACETYLCHOLINE or exogenous agonists. Muscarinic antagonists have widespread effects including actions on the iris and ciliary muscle of the eye, the heart and blood vessels, secretions of the respiratory tract, GI system, and salivary glands, GI motility, urinary bladder tone, and the central nervous system.Catecholamines: A general class of ortho-dihydroxyphenylalkylamines derived from tyrosine.Denervation: The resection or removal of the nerve to an organ or part. (Dorland, 28th ed)Injections, Intravenous: Injections made into a vein for therapeutic or experimental purposes.Autonomic Nerve Block: Interruption of sympathetic pathways, by local injection of an anesthetic agent, at any of four levels: peripheral nerve block, sympathetic ganglion block, extradural block, and subarachnoid block.Autonomic Nervous System Diseases: Diseases of the parasympathetic or sympathetic divisions of the AUTONOMIC NERVOUS SYSTEM; which has components located in the CENTRAL NERVOUS SYSTEM and PERIPHERAL NERVOUS SYSTEM. Autonomic dysfunction may be associated with HYPOTHALAMIC DISEASES; BRAIN STEM disorders; SPINAL CORD DISEASES; and PERIPHERAL NERVOUS SYSTEM DISEASES. Manifestations include impairments of vegetative functions including the maintenance of BLOOD PRESSURE; HEART RATE; pupil function; SWEATING; REPRODUCTIVE AND URINARY PHYSIOLOGY; and DIGESTION.Glycopyrrolate: A muscarinic antagonist used as an antispasmodic, in some disorders of the gastrointestinal tract, and to reduce salivation with some anesthetics.Heart Conduction System: An impulse-conducting system composed of modified cardiac muscle, having the power of spontaneous rhythmicity and conduction more highly developed than the rest of the heart.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Anesthesia, General: Procedure in which patients are induced into an unconscious state through use of various medications so that they do not feel pain during surgery.Hypertension: Persistently high systemic arterial BLOOD PRESSURE. Based on multiple readings (BLOOD PRESSURE DETERMINATION), hypertension is currently defined as when SYSTOLIC PRESSURE is consistently greater than 140 mm Hg or when DIASTOLIC PRESSURE is consistently 90 mm Hg or more.Rabbits: The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.Adrenergic beta-1 Receptor Antagonists: Drugs that bind to and block the activation of ADRENERGIC BETA-1 RECEPTORS.Long QT Syndrome: A condition that is characterized by episodes of fainting (SYNCOPE) and varying degree of ventricular arrhythmia as indicated by the prolonged QT interval. The inherited forms are caused by mutation of genes encoding cardiac ion channel proteins. The two major forms are ROMANO-WARD SYNDROME and JERVELL-LANGE NIELSEN SYNDROME.Electric Stimulation: Use of electric potential or currents to elicit biological responses.Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Atrioventricular Node: A small nodular mass of specialized muscle fibers located in the interatrial septum near the opening of the coronary sinus. It gives rise to the atrioventricular bundle of the conduction system of the heart.Blood Circulation: The movement of the BLOOD as it is pumped through the CARDIOVASCULAR SYSTEM.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Torsades de Pointes: A malignant form of polymorphic ventricular tachycardia that is characterized by HEART RATE between 200 and 250 beats per minute, and QRS complexes with changing amplitude and twisting of the points. The term also describes the syndrome of tachycardia with prolonged ventricular repolarization, long QT intervals exceeding 500 milliseconds or BRADYCARDIA. Torsades de pointes may be self-limited or may progress to VENTRICULAR FIBRILLATION.Infant, Newborn: An infant during the first month after birth.Cardiomyopathies: A group of diseases in which the dominant feature is the involvement of the CARDIAC MUSCLE itself. Cardiomyopathies are classified according to their predominant pathophysiological features (DILATED CARDIOMYOPATHY; HYPERTROPHIC CARDIOMYOPATHY; RESTRICTIVE CARDIOMYOPATHY) or their etiological/pathological factors (CARDIOMYOPATHY, ALCOHOLIC; ENDOCARDIAL FIBROELASTOSIS).Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Atrial Fibrillation: Abnormal cardiac rhythm that is characterized by rapid, uncoordinated firing of electrical impulses in the upper chambers of the heart (HEART ATRIA). In such case, blood cannot be effectively pumped into the lower chambers of the heart (HEART VENTRICLES). It is caused by abnormal impulse generation.Injections, Intraventricular: Injections into the cerebral ventricles.Cross-Over Studies: Studies comparing two or more treatments or interventions in which the subjects or patients, upon completion of the course of one treatment, are switched to another. In the case of two treatments, A and B, half the subjects are randomly allocated to receive these in the order A, B and half to receive them in the order B, A. A criticism of this design is that effects of the first treatment may carry over into the period when the second is given. (Last, A Dictionary of Epidemiology, 2d ed)Cardiomegaly: Enlargement of the HEART, usually indicated by a cardiothoracic ratio above 0.50. Heart enlargement may involve the right, the left, or both HEART VENTRICLES or HEART ATRIA. Cardiomegaly is a nonspecific symptom seen in patients with chronic systolic heart failure (HEART FAILURE) or several forms of CARDIOMYOPATHIES.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Valsalva Maneuver: Forced expiratory effort against a closed GLOTTIS.Systole: Period of contraction of the HEART, especially of the HEART VENTRICLES.Adenosine: A nucleoside that is composed of ADENINE and D-RIBOSE. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.Signal Processing, Computer-Assisted: Computer-assisted processing of electric, ultrasonic, or electronic signals to interpret function and activity.Cardiomyopathy, Dilated: A form of CARDIAC MUSCLE disease that is characterized by ventricular dilation, VENTRICULAR DYSFUNCTION, and HEART FAILURE. Risk factors include SMOKING; ALCOHOL DRINKING; HYPERTENSION; INFECTION; PREGNANCY; and mutations in the LMNA gene encoding LAMIN TYPE A, a NUCLEAR LAMINA protein.Perfusion: Treatment process involving the injection of fluid into an organ or tissue.Tachycardia, Sinus: Simple rapid heartbeats caused by rapid discharge of impulses from the SINOATRIAL NODE, usually between 100 and 180 beats/min in adults. It is characterized by a gradual onset and termination. Sinus tachycardia is common in infants, young children, and adults during strenuous physical activities.Nitroprusside: A powerful vasodilator used in emergencies to lower blood pressure or to improve cardiac function. It is also an indicator for free sulfhydryl groups in proteins.Adrenergic beta-Agonists: Drugs that selectively bind to and activate beta-adrenergic receptors.Ganglionic Blockers: Agents having as their major action the interruption of neural transmission at nicotinic receptors on postganglionic autonomic neurons. Because their actions are so broad, including blocking of sympathetic and parasympathetic systems, their therapeutic use has been largely supplanted by more specific drugs. They may still be used in the control of blood pressure in patients with acute dissecting aortic aneurysm and for the induction of hypotension in surgery.Diastole: Post-systolic relaxation of the HEART, especially the HEART VENTRICLES.Ventricular Dysfunction, Left: A condition in which the LEFT VENTRICLE of the heart was functionally impaired. This condition usually leads to HEART FAILURE; MYOCARDIAL INFARCTION; and other cardiovascular complications. Diagnosis is made by measuring the diminished ejection fraction and a depressed level of motility of the left ventricular wall.Vasodilator Agents: Drugs used to cause dilation of the blood vessels.Rats, Inbred SHR: A strain of Rattus norvegicus with elevated blood pressure used as a model for studying hypertension and stroke.Anesthesia, Spinal: Procedure in which an anesthetic is injected directly into the spinal cord.Adrenergic alpha-Agonists: Drugs that selectively bind to and activate alpha adrenergic receptors.Intraoperative Complications: Complications that affect patients during surgery. They may or may not be associated with the disease for which the surgery is done, or within the same surgical procedure.Blood Flow Velocity: A value equal to the total volume flow divided by the cross-sectional area of the vascular bed.Benzazepines: Compounds with BENZENE fused to AZEPINES.Antihypertensive Agents: Drugs used in the treatment of acute or chronic vascular HYPERTENSION regardless of pharmacological mechanism. Among the antihypertensive agents are DIURETICS; (especially DIURETICS, THIAZIDE); ADRENERGIC BETA-ANTAGONISTS; ADRENERGIC ALPHA-ANTAGONISTS; ANGIOTENSIN-CONVERTING ENZYME INHIBITORS; CALCIUM CHANNEL BLOCKERS; GANGLIONIC BLOCKERS; and VASODILATOR AGENTS.Neurons, Efferent: Neurons which send impulses peripherally to activate muscles or secretory cells.Infusions, Intravenous: The long-term (minutes to hours) administration of a fluid into the vein through venipuncture, either by letting the fluid flow by gravity or by pumping it.Predictive Value of Tests: In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test.Autonomic Pathways: Nerves and plexuses of the autonomic nervous system. The central nervous system structures which regulate the autonomic nervous system are not included.Circadian Rhythm: The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs and stimuli, hormone secretion, sleeping, and feeding.Fetal Diseases: Pathophysiological conditions of the FETUS in the UTERUS. Some fetal diseases may be treated with FETAL THERAPIES.Fetal Monitoring: Physiologic or biochemical monitoring of the fetus. It is usually done during LABOR, OBSTETRIC and may be performed in conjunction with the monitoring of uterine activity. It may also be performed prenatally as when the mother is undergoing surgery.Pulse: The rhythmical expansion and contraction of an ARTERY produced by waves of pressure caused by the ejection of BLOOD from the left ventricle of the HEART as it contracts.Atrial Function: The hemodynamic and electrophysiological action of the HEART ATRIA.Preanesthetic Medication: Drugs administered before an anesthetic to decrease a patient's anxiety and control the effects of that anesthetic.Chloralose: A derivative of CHLORAL HYDRATE that was used as a sedative but has been replaced by safer and more effective drugs. Its most common use is as a general anesthetic in animal experiments.Ciguatera Poisoning: Poisoning caused by ingestion of SEAFOOD containing microgram levels of CIGUATOXINS. The poisoning is characterized by gastrointestinal, neurological and cardiovascular disturbances.Receptors, Adrenergic, beta: One of two major pharmacologically defined classes of adrenergic receptors. The beta adrenergic receptors play an important role in regulating CARDIAC MUSCLE contraction, SMOOTH MUSCLE relaxation, and GLYCOGENOLYSIS.Death, Sudden, Cardiac: Unexpected rapid natural death due to cardiovascular collapse within one hour of initial symptoms. It is usually caused by the worsening of existing heart diseases. The sudden onset of symptoms, such as CHEST PAIN and CARDIAC ARRHYTHMIAS, particularly VENTRICULAR TACHYCARDIA, can lead to the loss of consciousness and cardiac arrest followed by biological death. (from Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005)Postsynaptic Potential Summation: Physiological integration of multiple SYNAPTIC POTENTIAL signals to reach the threshold and initiate postsynaptic ACTION POTENTIALS. In spatial summation stimulations from additional synaptic junctions are recruited to generate s response. In temporal summation succeeding stimuli signals are summed up to reach the threshold. The postsynaptic potentials can be either excitatory or inhibitory (EPSP or IPSP).Brain Stem: The part of the brain that connects the CEREBRAL HEMISPHERES with the SPINAL CORD. It consists of the MESENCEPHALON; PONS; and MEDULLA OBLONGATA.Aortic Bodies: Small clusters of chemoreceptive and supporting cells located near the ARCH OF THE AORTA; the PULMONARY ARTERIES; and the CORONARY ARTERIES. The aortic bodies sense PH; CARBON DIOXIDE; and OXYGEN concentrations in the BLOOD and participate in the control of RESPIRATION. The aortic bodies should not be confused with the PARA-AORTIC BODIES in the abdomen (which are sometimes also called aortic bodies).Respiratory Mechanics: The physical or mechanical action of the LUNGS; DIAPHRAGM; RIBS; and CHEST WALL during respiration. It includes airflow, lung volume, neural and reflex controls, mechanoreceptors, breathing patterns, etc.Myocardial Reperfusion Injury: Damage to the MYOCARDIUM resulting from MYOCARDIAL REPERFUSION (restoration of blood flow to ischemic areas of the HEART.) Reperfusion takes place when there is spontaneous thrombolysis, THROMBOLYTIC THERAPY, collateral flow from other coronary vascular beds, or reversal of vasospasm.Cats: The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Indoramin: An alpha-1 adrenergic antagonist that is commonly used as an antihypertensive agent.Chronic Disease: Diseases which have one or more of the following characteristics: they are permanent, leave residual disability, are caused by nonreversible pathological alteration, require special training of the patient for rehabilitation, or may be expected to require a long period of supervision, observation, or care. (Dictionary of Health Services Management, 2d ed)Heart Failure, Systolic: Heart failure caused by abnormal myocardial contraction during SYSTOLE leading to defective cardiac emptying.Physical Conditioning, Animal: Diet modification and physical exercise to improve the ability of animals to perform physical activities.Fetal Hypoxia: Deficient oxygenation of FETAL BLOOD.Medetomidine: An agonist of RECEPTORS, ADRENERGIC ALPHA-2 that is used in veterinary medicine for its analgesic and sedative properties. It is the racemate of DEXMEDETOMIDINE.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Sotalol: An adrenergic beta-antagonist that is used in the treatment of life-threatening arrhythmias.Anesthetics, Intravenous: Ultrashort-acting anesthetics that are used for induction. Loss of consciousness is rapid and induction is pleasant, but there is no muscle relaxation and reflexes frequently are not reduced adequately. Repeated administration results in accumulation and prolongs the recovery time. Since these agents have little if any analgesic activity, they are seldom used alone except in brief minor procedures. (From AMA Drug Evaluations Annual, 1994, p174)Guinea Pigs: A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.Physical Endurance: The time span between the beginning of physical activity by an individual and the termination because of exhaustion.Body Weight: The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms.Depression, Chemical: The decrease in a measurable parameter of a PHYSIOLOGICAL PROCESS, including cellular, microbial, and plant; immunological, cardiovascular, respiratory, reproductive, urinary, digestive, neural, musculoskeletal, ocular, and skin physiological processes; or METABOLIC PROCESS, including enzymatic and other pharmacological processes, by a drug or other chemical.Respiratory Physiological Phenomena: Physiological processes and properties of the RESPIRATORY SYSTEM as a whole or of any of its parts.Stellate Ganglion: A paravertebral sympathetic ganglion formed by the fusion of the inferior cervical and first thoracic ganglia.Adjuvants, Anesthesia: Agents that are administered in association with anesthetics to increase effectiveness, improve delivery, or decrease required dosage.Age Factors: Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time.Propofol: An intravenous anesthetic agent which has the advantage of a very rapid onset after infusion or bolus injection plus a very short recovery period of a couple of minutes. (From Smith and Reynard, Textbook of Pharmacology, 1992, 1st ed, p206). Propofol has been used as ANTICONVULSANTS and ANTIEMETICS.Ventricular Remodeling: The geometric and structural changes that the HEART VENTRICLES undergo, usually following MYOCARDIAL INFARCTION. It comprises expansion of the infarct and dilatation of the healthy ventricle segments. While most prevalent in the left ventricle, it can also occur in the right ventricle.Phentolamine: A nonselective alpha-adrenergic antagonist. It is used in the treatment of hypertension and hypertensive emergencies, pheochromocytoma, vasospasm of RAYNAUD DISEASE and frostbite, clonidine withdrawal syndrome, impotence, and peripheral vascular disease.Neuroendoscopy: PROCEDURES that use NEUROENDOSCOPES for disease diagnosis and treatment. Neuroendoscopy, generally an integration of the neuroendoscope with a computer-assisted NEURONAVIGATION system, provides guidance in NEUROSURGICAL PROCEDURES.Heart, Artificial: A pumping mechanism that duplicates the output, rate, and blood pressure of the natural heart. It may replace the function of the entire heart or a portion of it, and may be an intracorporeal, extracorporeal, or paracorporeal heart. (Dorland, 28th ed)Infant, Premature, DiseasesVentricular Fibrillation: A potentially lethal cardiac arrhythmia that is characterized by uncoordinated extremely rapid firing of electrical impulses (400-600/min) in HEART VENTRICLES. Such asynchronous ventricular quivering or fibrillation prevents any effective cardiac output and results in unconsciousness (SYNCOPE). It is one of the major electrocardiographic patterns seen with CARDIAC ARREST.Monitoring, Intraoperative: The constant checking on the state or condition of a patient during the course of a surgical operation (e.g., checking of vital signs).Coronary Circulation: The circulation of blood through the CORONARY VESSELS of the HEART.Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.
... the heart rate is known to naturally slow with age. It is only when bradycardia presents with signs and symptoms of shock that ... The most common indication for transcutaneous pacing is an abnormally slow heart rate. By convention, a heart rate of less than ... Normal heart rate varies substantially between individuals, and many athletes in particular have a relatively slow resting ... a heart rate is selected, and current (measured in milliamps) is increased until electrical capture (characterized by a wide ...
A heart rate that is too fast - above 100 beats per minute in adults - is called tachycardia and a heart rate that is too slow ... Bradycardia may also occur in some types of seizures. In adults and children over 15, resting heart rate faster than 100 beats ... The resting heart rate in children is much faster. In athletes, however, the resting heart rate can be as slow as 40 beats per ... than the rest of the heart and, therefore, is usually responsible for setting the heart rate and initiating each heart beat. ...
Tachycardia is a fast heart rate, defined as above 100 bpm at rest. Bradycardia is a slow heart rate, defined as below 60 bpm ... For healthy people, the Target Heart Rate or Training Heart Rate (THR) is a desired range of heart rate reached during aerobic ... A very slow heart rate (bradycardia) may be associated with heart block.[medical citation needed] It may also arise from ... Normal resting heart rates range from 50-90 bpm. Bradycardia is defined as a resting heart rate below 60 bpm. However, heart ...
Serious side effects that are advised to be reported immediately include symptoms of bradycardia (resting heart rate slower ... and a number of conditions involving an abnormally fast heart rate. It is also used to prevent further heart problems after ... Cruickshank JM (2010). "Beta-blockers and heart failure". Indian Heart Journal. 62 (2): 101-110. PMID 21180298. "Metoprolol ( ... congestive heart failure, and prevention of migraine headaches. Treatment of heart failure Vasovagal syncope Adjunct in ...
The ECG can detect sinus bradycardia, a resting heart rate of fewer than 60 beats per minute. This is often accompanied by ... bradycardia, cardiomegaly, and cardiac hypertrophy. Bradycardia is a slower than normal heartbeat, at around 40-60 beats per ... in which the human heart is enlarged, and the resting heart rate is lower than normal. The athlete's heart is associated with ... Athletic heart syndrome (AHS), also known as athlete's heart, athletic bradycardia, or exercise-induced cardiomegaly is a non- ...
Although atropine treats bradycardia (slow heart rate) in emergency settings, it can cause paradoxical heart rate slowing when ... Injections of atropine are used in the treatment of bradycardia (a heart rate < 60 beats per minute). Atropine was previously ... is a medication to treat certain types of nerve agent and pesticide poisonings as well as some types of slow heart rate and to ... Atropine has also been used in an effort to prevent a low heart rate during intubation of children; however, evidence does not ...
... is a condition wherein an individual has a slow heart rate, typically defined as a heart rate of under 60 beats per ... Beta-blocker medicines also can slow the heart rate and decrease how forcefully the heart contracts. Beta blockers may slow the ... a resting heart rate of 28 BPM. The word "bradycardia" is from the Greek βραδύς, bradys "slow", and καρδία, kardia, "heart". ... with a heart rate measured in 2014 of 26 BPM. Martin Brady holds the Guinness world record for the slowest heart rate with a ...
If SA nodal impulses occur at a rate less than 60bpm, the heart rhythm is known as sinus bradycardia. If SA nodal impulses ... Trained athletes, for example, usually show heart rates slower than 60bpm when not exercising. If the SA node fails to ... A resting heart that beats slower than 60 beats per minute, or faster than 100 beats per minute, is regarded as having an ... Some individuals, for example trained athletes, may have heart beats slower than 60 beats per minute when not exercising. If ...
Bradycardia is defined by a slower than normal heart rate, less than 60 bpm. (Normal range is 60-100 bpm). Ictal epileptic ... Slowing the heart beat down by more than 10 beats per minute below the average baseline. Ictal bradycardia is a potential cause ... This type of epileptic seizure is known as ictal tachycardia, in which the subject's heart rate increase of more than 10 beats ... Ictal bradycardia is a diagnosis in which people that have temporal lobe epilepsy experience bradycardia and is also ...
The slow heart rate may also lead to atrial, junctional, or ventricular ectopic rhythms. Bradycardia is not necessarily ... because their trained hearts can pump enough blood in each contraction to allow a low resting heart rate. Sinus bradycardia can ... Sinus bradycardia is a sinus rhythm with a rate that is lower than normal. In humans, bradycardia is generally defined to be a ... Heart rates considered bradycardic vary by species; for example, in the common housecat, a rate of under 120 beats per minute ...
... slowing the heart. As the heart slows, autonomic reflexes are triggered to increase blood pressure and heart rate. This is ... high heart beat) or sinus bradycardia (heart beat below 60). Typically, there are no changes / abnormalities related in the EKG ... If the heart rate drops too low for too long, catecholamines are released to counteract any lowering of blood pressure. ... This reduces the heart's ability to fill and increases the contractility of the heart to maintain homeostasis. The cranium ...
This induces bradycardia, or slowed heart rate, and signifies the second stage of the reflex. Bradycardia may also be caused by ... The sympathetic stimulation also increases the rate of heart contractions and cardiac output. Increased heart rate is also ... The Cushing reflex classically presents as an increase in systolic and pulse pressure, reduction of the heart rate (bradycardia ... As a result of the now defective regulation of heart rate and blood pressure, the physiologic response is decreased blood flow ...
... if the atrial fibrillation persists and is resulting in a rapid heart rate, treatment must be given to slow down that rate. ... Beta-blockers are the first-line therapy as they induce bradycardia and give time for ventricles to fill. There is some ... This is often seen in valvular heart disease and high-output heart failure. Neither of these situations constitutes a diastolic ... The term diastolic dysfunction should not be applied to the dilated heart. Dilated ("remodeled") hearts have increased volume ...
... the rate progressively slows from the SA node to the Purkinje fibers. Without the SA node, the AV node would generate a heart ... rates lower than 50 beats per minute would indicate a condition called bradycardia. Depending upon the specific individual, as ... Exercise and fitness levels, age and basal metabolic rate can all affect the heart rate. An athlete's heart rate can be lower ... Damaged hearts or those stimulated by drugs can contract at higher rates, but at these rates, the heart can no longer ...
Bradycardia is treated with atropine or an infusion of norepinephrine to increase coronary blood flow and heart rate. ... When flumazenil is indicated the risks can be reduced or avoided by slow dose titration of flumazenil. Due to risks and its ... Overdose Death Rates. By National Institute on Drug Abuse (NIDA). Wolf BC, Lavezzi WA, Sullivan LM, Middleberg RA, Flannagan LM ... bradycardia, cardiac arrest, and pulmonary aspiration, with the possibility of death. Severe consequences are rare following ...
Both tachycardia (fast heart rate) and bradycardia (slow heart rate) have been reported; these can be serious. Other serious ... 60 (1): 104-106. doi:10.1002/jps.2600600120. PMID 5548215. "New Drugs and Indications Reviewed at the May 2003 DEC Meeting" ( ...
... the heart rate of this will be 0 and be supplying no blood through the body like ventricular fibrillation. "Heart arrhythmia". ... however a slow rhythm can be distinguished when the rate is less than 60, the PR interval and QRS complex are normal. Sinus ... Sinus bradycardia is another regular rhythm however the ventricular rate is only between 40-60 bpm, with a normal PR interval ... the ventricular rate, which is the rate at which the ventricles contract, and the atrial rate, which is the rate at which the ...
He found out that heart rate slowed down prior to death and the heart was engaged with blood reflecting a state of diastole. ... Mammals would undergo states of bradycardia or hypoxia as an over-activation of parasympathetic vagus system. The organs of the ... Hofer interpreted the fear-inducing slowing of heart rate as a vagal phenomenon. This data suggests that vagus contributes to ... Richter monitored heart rate and determined whether the heart was in systole or diastole after death. ...
... a pathological slowing of the SA discharge, or a complete AV block. Rate: 35-60 bpm Rhythm: Irregular in single junctional ... It is a protective mechanism for the heart, to compensate for the SA node no longer handling the pacemaking activity, and is ... Junctional rhythms (if a bradycardia) can cause decreased cardiac output. Therefore, the person may exhibit signs and symptoms ... It occurs when the rate of depolarization of the sinoatrial node falls below the rate of the atrioventricular node. This ...
Slowing the heart rate reduces the cardiac oxygen consumption, and compensates for the hypertension due to vasoconstriction. ... This causes bradycardia and peripheral vasoconstriction. Blood is diverted from the limbs and all organs but the heart and the ... water as the metabolic rate increases to compensate for accelerated heat loss even when the heart rate is significantly slowed ... the human heart rate slows down ten to twenty-five percent. Seals experience changes that are even more dramatic, going from ...
... which have slower intrinsic rates. The accelerated idioventricular rhythm occurs when depolarization rate of a normally ... In the human heart the sinoatrial node is located at the top of the right atrium. The sinoatrial node is the first area of the ... This most commonly occurs in the setting of a sinus bradycardia. Accelerated idioventricular rhythm is the most common ... It can most easily be distinguished from VT in that the rate is less than 120 and usually less than 100 bpm. There may or may ...
This makes adenosine a useful medication for treating and diagnosing tachyarrhythmias, or excessively fast heart rates. This ... heart attack or cardiac arrest caused by nonperfusing bradycardias, adenosine has a negative effect on physiological ... In the brain, it slows metabolic activity by a combination of actions. At the neuron's synapse, it reduces synaptic vesicle ... Heart Circ. Physiol. 288 (3): H1411-6. doi:10.1152/ajpheart.00684.2004. PMID 15539423. Fredholm BB, IJzerman AP, Jacobson KA, ...
A heart rate less than normal is called bradycardia (. 100 in adults). A complication of this is when the atria and ventricles ... If the rate is too fast then it is sinus tachycardia and if it is too slow then it is sinus bradycardia. If it is not a sinus ... Heart rate, like other vital signs like blood pressure and respiratory rate, change with age. In adults, a normal heart rate is ... In a normal heart, the heart rate is the rate in which the sinoatrial node depolarizes as it is the source of depolarization of ...
... in these cases leading to excessive slowing of heart rate. The abnormality lies in this excessive vagal response. The tilt- ... Two major groups of arrhythmias are bradycardia and tachycardia. Bradycardia can be caused by heart blocks. Tachycardias ... Heart related causes may include an abnormal heart rhythm, problems with the heart valves or heart muscle and blockages of ... Heart related causes also often have little history of a prodrome. Low blood pressure and a fast heart rate after the event may ...
... f-channels are natural targets of drugs aimed to pharmacologically control heart rate. Several agents called "heart rate ... stimulation and able to explain a reduction of inward current during diastole and the resulting slower spontaneous rate. ... Familial sinus bradycardia associated with a mutation in the cardiac pacemaker channel. The New England Journal of Medicine, ... decreases the heart rate by the opposite action, that is by shifting the If activation curve towards more negative voltages. ...
... or to slow down (bradycardia) when the pressure rises above set point.[13] Thus the heart rate (for which there is no sensor in ... One of the effector organs is the heart whose rate is stimulated to rise (tachycardia) when the arterial blood pressure falls, ... Low pressure in the arteries, causes the opposite reflex of constriction of the arterioles, and a speeding up of the heart rate ... At the same time the heart is stimulated via cholinergic parasympathetic nerves to beat more slowly (called bradycardia), ...
Sinus bradycardia, which is when the heart rate beats slower or less than 60 beats per minute. ... Supraventricular tachycardia: The heart rate is abnormally fast when at rest.. *Heart block: When the heart beats more slowly, ... As the heart speeds up, during exercise, for example, the heart rate rhythm tends to become more regular. ... It occurs when a persons heart rate relates to their breathing cycle. In other words, when the person breathes in, their heart ...
Tachycardia is a fast heart rate, defined as above 100 bpm at rest. Bradycardia is a slow heart rate, defined as below 60 bpm ... For healthy people, the Target Heart Rate or Training Heart Rate (THR) is a desired range of heart rate reached during aerobic ... A very slow heart rate (bradycardia) may be associated with heart block.[medical citation needed] It may also arise from ... Normal resting heart rates range from 50-90 bpm. Bradycardia is defined as a resting heart rate below 60 bpm. However, heart ...
... slow heart rate) including: diagnosis, and an overview of treatment with Medtronic pacemakers. ... Bradycardia is defined as a slow heart rate or irregular heart rhythm. A healthy heart beats 60 to 100 times per minute, which ... By sending an impulse when the hearts rhythm is slow or interrupted, it effectively regulates the heart rate automatically, ... Those with bradycardia experience a heart rate of less than 60 beats per minute, often resulting in dizziness, shortness of ...
Bradycardia is defined by a slower than normal heart rate, less than 60 bpm. (Normal range is 60-100 bpm). Ictal epileptic ... Slowing the heart beat down by more than 10 beats per minute below the average baseline. Ictal bradycardia is a potential cause ... This type of epileptic seizure is known as ictal tachycardia, in which the subjects heart rate increase of more than 10 beats ... Ictal bradycardia is a diagnosis in which people that have temporal lobe epilepsy experience bradycardia and is also ...
elevated heart rate; more than 100 beats/min.. Bradycardia. slow heart rate; less than 60 beats/min. ... Pulse rate. speed of the heartbeat measured by the number of contractions of the heart per minute (bpm). ... force EXERTED on the walls of an artery created by pulsing blood under pressure from the HEART. ... clear, rhythmic tapping series that corresponds to the pulse rate and gradually increases in intensity. ...
Define bradycardia. *A slow heart rate. *Typically a resting heart rate of under 60 bpm ... Cells that are dedicated to the purpose of generating an impulse to maintain a heart rate commensurate with the bodys need are ... The slow movement delays ventricular activation *​Allowing the relaxed ventricle to fill with blood during atrial contraction ... Why is it important for the cardiac impulse to slow down as it moves through the AV node? ...
Bradycardia. *Tachycardia. *Slow heart rate (,60 bpm). *Fast heart rate (,100 bpm) ... slowed conduction. *unidiretional block - tissue capable of conduction in one direction but not the other. Often functional ... Rate augmented (increased) by sympathetic tone. *Beta-andrenergic stimulation increases the open probability of the pacemaker ... The hyperpolarizing current increases when a cell is forced to fire faster than its intrinsic pacemaker rate. The more ...
Bradycardia. Slow heart rate, usually fewer than 60 beats per minute in an adult human.. ... A rapid heart rate, especially one above 100 beats per minute in an adult.. ... Slowing of muscular movement of the stomach.. Gastric lavage. A procedure to empty the contents of the stomach, usually for ... An agent that slows or interferes with a chemical reaction; a substance that reduces the activity of another substance (as an ...
heart block* is an abnormal delay or, in extreme cases, complete block in the conduction of the electrical impulse from the ... Bradycardia- A slow heart rate, usually under 60 beats per minute.. Cite this article Pick a style below, and copy the text for ... Adams and Stokes both reported patients with persistent pulse rates around 30. The exceptionally slow heart rates in these ... it results in an overall slowing of the heart called bradycardia.. Third-degree block, also called complete heart block, is the ...
... a heart rate of less than 60 beats per minute (BPM) in adults. ... as the medical term for a heart rate thats too slow, ... Bradycardia = too slow. A heart rate of less than 60 beats per minute (BPM) in adults is called bradycardia. Whats too slow ... Physically active adults (and athletes) often have a resting heart rate slower than 60 BPM but it doesnt cause problems and is ... Elderly people are more prone to problems with a slow heart rate. ... Symptoms of bradycardia. A heart rhythm thats too slow can ...
He says my walking pace is so slow that its not doing me any good. Is he right? Can you help me resolve this conflict? ... However, your heart rate is unusually slow. The normal heart beats 60 to 100 times a minute. Some put the lower limit at 50. ... At my last physical exam, I was told I had bradycardia (a slow heartbeat). My heart beats on average in the 40s per minute and ... I have always had a slow heart rate, but it has gotten slower as I have aged. I read that a pacemaker is usually recommended ...
What is Bradycardia?. Bradycardia is the medical term for a low pulse, which indicates a slow heart rate. Normally, the heart ... Symptoms of Slow Heart Rate. A slow heart rate in athletes and when asleep or very relaxed is due to reduced sinus node ... Low Pulse - Causes of a Slow Heart Rate (Bradycardia). Posted by Dr. Chris ... This is also known as asymptomatic sinus bradycardia because a person does not feel unwell with such a slow heart rate and it ...
If you find out that you have a heart rhythm disorder, also known as an arrhythmia, it does not mean that you can never ... How to Treat Heart Rhythm Disorders with Exercise. ... exercise again.http://www.heart.org/HEARTORG/Conditions/ ... Bradycardia: Bradycardia is a slow heart rate (lower than 60 beats per minute (bpm). Physically fit adults often have a heart ... The irregular heart rate can lead to stagnant blood flow in the heart, which can cause clots. These clots can travel to other ...
Slow heart rate of less than 60 bpm. bradycardia. Spread of cancer from its primary site to other places in the body. ...
What you want is not too fast, not too slow, and not too erratic. In fact, most of… ... When it comes to your heart rate, its a bit like the speed of your car. ... Rigorous exercise will raise your heart rate to 70% to 80% of your maximum heart rate. Whats your maximum heart rate? Just ... On the other hand, a slow heart rate can be a sign of disease, such as:. *heart attack or other heart disease (such as "sick ...
Bradycardia - an easy to understand guide covering causes, diagnosis, symptoms, treatment and prevention plus additional in ... Bradycardia is an abnormally slow heart rate of less than 60 beats per minute. A normal heartbeat is between 60 and 100 beats ... In other cases, bradycardia can be a form of cardiac arrhythmia, a heart-rate abnormality. Cardiac arrhythmia can be caused by ... You may be asked to do some sit-ups or other exercise so that your doctor can see if your heart rate rises normally when your ...
bradycardia: A slow heart rate, usually below 60 beats per minute.. brain imaging: Technologies that allow doctors to view the ... slows the heart rate, and decreases the hearts need for oxygen by blocking the movement of calcium into the heart and the ... congestive heart failure: An older term for heart failure, a disorder caused by a decrease in the hearts ability to pump blood ... calcium: A mineral that the body needs for many vital functions, including bone formation, regulation of heart rate and blood ...
Palpitations are feelings or sensations that your heart is pounding or racing. They can be felt in your chest, throat, or neck. ... If your heart rate is fast (over 100 beats per minute), this is called tachycardia. A heart rate slower than 60 is called ... bradycardia. An occasional extra heartbeat out of rhythm is known as extrasystole. ... Does your heart rate feel slow or fast when you have the palpitations? ...
... also called bradycardia, is defined as a resting heart rate (pulse) less than 60 beats per minute. Having a heart rate less ... People with certain heart conditions may take medications which lower the heart rate as one of the goals of therapy. ... In fact, people in good cardiovascular shape have a low heart rate. ... Slow Heart Rate (Overview) Slow heart rate, also called bradycardia, is defined as a resting heart rate (pulse) less than 60 ...
If people have symptomatic bradycardia ie dizzy light headedness etc. The may need a pacemaker. If pts heart rates are low ... pauses or longer and arent on any thing like beta blockers etc a pacemaker will help keep the heart rate at a programmed rate ... Fowler on what can relieve symptoms of bradycardia: ... Slow Heart Rate (Definition) Slow heart rate, also called ... A pacemaker: If people have symptomatic bradycardia ie dizzy light headedness etc. The may need a pacemaker. If pts heart rates ...
... heart block explanation free. What is heart block? Meaning of heart block medical term. What does heart block mean? ... Looking for online definition of heart block in the Medical Dictionary? ... Bradycardia - A slow heart rate, usually under 60 beats per minute.. heart block. impairment of conduction in heart excitation ... In heart block the pulse is generally very slow, as the lower chambers can only beat at their intrinsically low rate. Heart ...
PNS or vagus nerve stimulation slow the heart rate ( Bradycardia) , 60 bpm. Factors that raise the heart rate are called ... heart rate slows down. As low as 20 bpm. Heart on its own would go 100. bpm, but vegas nerve keeps it at about 70 bpm.. Think ... stress by slowing the heart rate and reducing the force of heart muscle. contractions. They also reduce blood vessel ... binds to beta-adrenergic receptors in the heart and increases the heart rate.. Peak is at 160-180 bpm SA node can not go any ...
Bradycardia- abnormally slow heart rate (Usual= 60bpm and 100bpm). Arrhythmia- irregular heart beat ... a) is a reflection of the hearts stroke volume.. stroke volume=(SV) the amount of blood pumped out of the heart (left ... a) a heart rate above 60 beats per minute (b.p.m) ... an irregular heart rate. d) the normal variation of heart rate ... a) is a reflection of the hearts stroke volume.. b) reflects the blood volume in the arteries during diastole.. c) ...
Bradycardia-An abnormally slow heart rate (below 60 beats per minute).. *Sudden cardiac arrest-A condition that causes the ... Atrial fibrillation-An irregular, often rapid heart rate that commonly causes poor blood flow. ... Subspecialist Treats Arrhythmia and Other Heart Conditions Western Yavapai County residents of all ages who suffer from heart ... Atrial flutter-An arrhythmia that occurs when the hearts upper chambers (the atria) beat too fast and complicates the heart ...
  • Specific causes of bradycardia - acute myocardial infarction, elevated intracranial pressure, medication toxicity and metabolic derangements (i.e. potassium) - must be rapidly excluded from the differential diagnosis. (clinicaladvisor.com)
  • The causes of bradycardia range from benign to potentially serious, so it is crucial to determine its cause with the help of a physician or cardiologist. (azcentral.com)
  • If you have frequent episodes of chest pain or discomfort, heart palpitations, irregular or rapid heartbeats, unexplained wheezing or shortness of breath, fainting or near fainting, or you're feeling lightheaded or dizzy, see your doctor promptly. (mayoclinichealthsystem.org)
  • In severe cases symptoms, such as shortness of breath, chest pain and enlargement of the heart, can develop. (shl-telemedicine.com)
  • Some children with congenital heart defects have no signs while others may exhibit shortness of breath, cyanosis, syncope, heart murmur, under-developing of limbs and muscles, poor feeding or growth, or respiratory infections. (lumenlearning.com)
  • Your doctor will ask about symptoms (shortness of breath, chest pain and sweating) more likely caused by a heart problem. (hartfordhealthcare.org)
  • Because the heart may not be pumping enough blood throughout the body, this slow heart rate can lead to light-headedness, shortness of breath, fainting or chest pain. (kttc.com)
  • Health professionals need to reassess the merits of continued therapy in patients who develop bradycardia while taking these drugs," she says. (healthcanal.com)
  • In patients who develop bradycardia at the recommended initial dosage, consider reducing the dosage to 0.02 mg/kg twice daily. (rxlist.com)
  • It is the contraction of the left ventricle that produces the pulse rate. (hse.ie)
  • Electrolyte imbalances - Alcohol and tobacco.Right atrium receives oxygen-poor blood veins thatreturn the organs to the heart and directs it to theright ventricle. (slideshare.net)
  • Left ventricle, the mostvoluminous pumps blood into the arteries and hencethroughout the body.For the heart to pump blood effectively as billions ofcells in the upper chambers and the ventricles have tocontract simultaneously. (slideshare.net)
  • It originates from the left ventricle of the heart and ends in the pelvis, where it divides into two femoral arteries, each of which supplies one of the lower extremities, the right and the left, respectively. (shl-telemedicine.com)
  • Most pacemakers can analyse and store information about your natural heart rhythms. (hse.ie)
  • Your doctor might also check your heart rhythms with a Holter monitor, which records your ECG for 24 hours as you go about your daily activities. (healthcentral.com)
  • Although there is limited amount of information about ictal bradycardia, as it is a relatively new discovery and is considered to be rare condition, researchers suggest that early diagnosis and treatment of ictal bradycardia can eliminate the chances of sudden unexpected death in epilepsy. (wikipedia.org)