Atrial Premature Complexes: A type of cardiac arrhythmia with premature atrial contractions or beats caused by signals originating from ectopic atrial sites. The ectopic signals may or may not conduct to the HEART VENTRICLES. Atrial premature complexes are characterized by premature P waves on ECG which are different in configuration from the P waves generated by the normal pacemaker complex in the SINOATRIAL NODE.Ventricular Premature Complexes: A type of cardiac arrhythmia with premature contractions of the HEART VENTRICLES. It is characterized by the premature QRS complex on ECG that is of abnormal shape and great duration (generally >129 msec). It is the most common form of all cardiac arrhythmias. Premature ventricular complexes have no clinical significance except in concurrence with heart diseases.Moricizine: An antiarrhythmia agent used primarily for ventricular rhythm disturbances.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.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.Radiology Information Systems: Information systems, usually computer-assisted, designed to store, manipulate, and retrieve information for planning, organizing, directing, and controlling administrative activities associated with the provision and utilization of radiology services and facilities.Stroke: A group of pathological conditions characterized by sudden, non-convulsive loss of neurological function due to BRAIN ISCHEMIA or INTRACRANIAL HEMORRHAGES. Stroke is classified by the type of tissue NECROSIS, such as the anatomic location, vasculature involved, etiology, age of the affected individual, and hemorrhagic vs. non-hemorrhagic nature. (From Adams et al., Principles of Neurology, 6th ed, pp777-810)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.Anticoagulants: Agents that prevent clotting.Warfarin: An anticoagulant that acts by inhibiting the synthesis of vitamin K-dependent coagulation factors. Warfarin is indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, pulmonary embolism, and atrial fibrillation with embolization. It is also used as an adjunct in the prophylaxis of systemic embolism after myocardial infarction. Warfarin is also used as a rodenticide.International Normalized Ratio: System established by the World Health Organization and the International Committee on Thrombosis and Hemostasis for monitoring and reporting blood coagulation tests. Under this system, results are standardized using the International Sensitivity Index for the particular test reagent/instrument combination used.Brain Ischemia: Localized reduction of blood flow to brain tissue due to arterial obstruction or systemic hypoperfusion. This frequently occurs in conjunction with brain hypoxia (HYPOXIA, BRAIN). Prolonged ischemia is associated with BRAIN INFARCTION.Cardiac Complexes, Premature: A group of cardiac arrhythmias in which the cardiac contractions are not initiated at the SINOATRIAL NODE. They include both atrial and ventricular premature beats, and are also known as extra or ectopic heartbeats. Their frequency is increased in heart diseases.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.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.Catheter Ablation: Removal of tissue with electrical current delivered via electrodes positioned at the distal end of a catheter. Energy sources are commonly direct current (DC-shock) or alternating current at radiofrequencies (usually 750 kHz). The technique is used most often to ablate the AV junction and/or accessory pathways in order to interrupt AV conduction and produce AV block in the treatment of various tachyarrhythmias.Personnel Staffing and Scheduling Information Systems: Computer-based systems for use in personnel management in a facility, e.g., distribution of caregivers with relation to patient needs.Heart Rate: The number of times the HEART VENTRICLES contract per unit of time, usually per minute.New York CityNew YorkHeart: The hollow, muscular organ that maintains the circulation of the blood.Ballota: A plant genus of the family LAMIACEAE that contains phenylpropanoids.Tachycardia, Supraventricular: A generic expression for any tachycardia that originates above the BUNDLE OF HIS.Pulmonary Veins: The veins that return the oxygenated blood from the lungs to the left atrium of the heart.Tachycardia, Paroxysmal: Abnormally rapid heartbeats with sudden onset and cessation.Encyclopedias as Topic: Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)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).Heart Atria: The chambers of the heart, to which the BLOOD returns from the circulation.Angioplasty, Balloon: Use of a balloon catheter for dilation of an occluded artery. It is used in treatment of arterial occlusive diseases, including renal artery stenosis and arterial occlusions in the leg. For the specific technique of BALLOON DILATION in coronary arteries, ANGIOPLASTY, BALLOON, CORONARY is available.Angioplasty, Balloon, Coronary: Dilation of an occluded coronary artery (or arteries) by means of a balloon catheter to restore myocardial blood supply.Coronary Artery Disease: Pathological processes of CORONARY ARTERIES that may derive from a congenital abnormality, atherosclerotic, or non-atherosclerotic cause.Angioplasty: Reconstruction or repair of a blood vessel, which includes the widening of a pathological narrowing of an artery or vein by the removal of atheromatous plaque material and/or the endothelial lining as well, or by dilatation (BALLOON ANGIOPLASTY) to compress an ATHEROMA. Except for ENDARTERECTOMY, usually these procedures are performed via catheterization as minimally invasive ENDOVASCULAR PROCEDURES.Coronary Angiography: Radiography of the vascular system of the heart muscle after injection of a contrast medium.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.Coronary Vessels: The veins and arteries of the HEART.Tachycardia, Ventricular: An abnormally rapid ventricular rhythm usually in excess of 150 beats per minute. It is generated within the ventricle below the BUNDLE OF HIS, either as autonomic impulse formation or reentrant impulse conduction. Depending on the etiology, onset of ventricular tachycardia can be paroxysmal (sudden) or nonparoxysmal, its wide QRS complexes can be uniform or polymorphic, and the ventricular beating may be independent of the atrial beating (AV dissociation).Myocardial Infarction: NECROSIS of the MYOCARDIUM caused by an obstruction of the blood supply to the heart (CORONARY CIRCULATION).Fractals: Patterns (real or mathematical) which look similar at different scales, for example the network of airways in the lung which shows similar branching patterns at progressively higher magnifications. Natural fractals are self-similar across a finite range of scales while mathematical fractals are the same across an infinite range. Many natural, including biological, structures are fractal (or fractal-like). Fractals are related to "chaos" (see NONLINEAR DYNAMICS) in that chaotic processes can produce fractal structures in nature, and appropriate representations of chaotic processes usually reveal self-similarity over time.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.Disorders of Excessive Somnolence: Disorders characterized by hypersomnolence during normal waking hours that may impair cognitive functioning. Subtypes include primary hypersomnia disorders (e.g., IDIOPATHIC HYPERSOMNOLENCE; NARCOLEPSY; and KLEINE-LEVIN SYNDROME) and secondary hypersomnia disorders where excessive somnolence can be attributed to a known cause (e.g., drug affect, MENTAL DISORDERS, and SLEEP APNEA SYNDROME). (From J Neurol Sci 1998 Jan 8;153(2):192-202; Thorpy, Principles and Practice of Sleep Medicine, 2nd ed, p320)Narcolepsy: A condition characterized by recurrent episodes of daytime somnolence and lapses in consciousness (microsomnias) that may be associated with automatic behaviors and AMNESIA. CATAPLEXY; SLEEP PARALYSIS, and hypnagogic HALLUCINATIONS frequently accompany narcolepsy. The pathophysiology of this disorder includes sleep-onset rapid eye movement (REM) sleep, which normally follows stage III or IV sleep. (From Neurology 1998 Feb;50(2 Suppl 1):S2-S7)Sleep: A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility.Polysomnography: Simultaneous and continuous monitoring of several parameters during sleep to study normal and abnormal sleep. The study includes monitoring of brain waves, to assess sleep stages, and other physiological variables such as breathing, eye movements, and blood oxygen levels which exhibit a disrupted pattern with sleep disturbances.Automobile Driving: The effect of environmental or physiological factors on the driver and driving ability. Included are driving fatigue, and the effect of drugs, disease, and physical disabilities on driving.Reaction Time: The time from the onset of a stimulus until a response is observed.Wakefulness: A state in which there is an enhanced potential for sensitivity and an efficient responsiveness to external stimuli.Bundle-Branch Block: A form of heart block in which the electrical stimulation of HEART VENTRICLES is interrupted at either one of the branches of BUNDLE OF HIS thus preventing the simultaneous depolarization of the two ventricles.Molecular Sequence Annotation: The addition of descriptive information about the function or structure of a molecular sequence to its MOLECULAR SEQUENCE DATA record.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.Heart Ventricles: The lower right and left chambers of the heart. The right ventricle pumps venous BLOOD into the LUNGS and the left ventricle pumps oxygenated blood into the systemic arterial circulation.Sperm Motility: Movement characteristics of SPERMATOZOA in a fresh specimen. It is measured as the percentage of sperms that are moving, and as the percentage of sperms with productive flagellar motion such as rapid, linear, and forward progression.Bundle of His: Small band of specialized CARDIAC MUSCLE fibers that originates in the ATRIOVENTRICULAR NODE and extends into the membranous part of the interventricular septum. The bundle of His, consisting of the left and the right bundle branches, conducts the electrical impulses to the HEART VENTRICLES in generation of MYOCARDIAL CONTRACTION.