Syncope
Syncope, Vasovagal
Bradycardia
Midodrine
Electrocardiography
Pacemaker, Artificial
Electrocardiography, Ambulatory
Carotid Sinus
Unconsciousness
Heart Block
Cardiac Pacing, Artificial
Arrhythmias, Cardiac
Autonomic Denervation
Long QT Syndrome
Death, Sudden, Cardiac
Defibrillators, Implantable
Tachycardia, Ventricular
Sick Sinus Syndrome
Etilefrine
Dizziness
Orthostatic Intolerance
Heart Arrest
Atrioventricular Block
Reflex, Abnormal
Head-Down Tilt
Electrophysiologic Techniques, Cardiac
Autonomic Nervous System
Effects of moderate exercise training on plasma volume, baroreceptor sensitivity and orthostatic tolerance in healthy subjects. (1/868)
The effect of physical training on an individual's ability to withstand an orthostatic stress is unclear. This study was undertaken to determine the effects on orthostatic tolerance in healthy volunteers of training at a level appropriate for unfit subjects and cardiorespiratory patients. In 11 asymptomatic, untrained subjects the following assessments were made: plasma volume by Evans Blue dye dilution and blood volume derived from haematocrit; carotid baroreceptor sensitivity from the slope of the regression of change in cardiac interval against pressure applied to a neck chamber; orthostatic tolerance as time to presyncope in a test of head-up tilting combined with lower body suction; exercise test relating heart rate to oxygen consumption. Subjects were then given a training schedule (5BX/XBX, Royal Canadian Air Force) involving 11-12 min of mixed exercises per day until an age/sex related 'target' was reached. Following training all subjects showed evidence of improved fitness, seen as decreases in heart rate at an oxygen uptake (Vo2) of 1.5 1 min-1 and in the elevation of the regression line between heart rate and Vo2. All also had increases in plasma and blood volumes and decreases in baroreceptor sensitivity. Seven of the subjects showed increases in orthostatic tolerance. Improvement in orthostatic tolerance was related to a low initial tolerance, and was associated with increases in plasma volume and decreases in baroreceptor sensitivity. These results show that moderate exercise training increases orthostatic tolerance in subjects who do not already have a high initial tolerance and suggest that training may be of value in the management of untrained patients with attacks of syncope due to orthostatic intolerance. (+info)The misdiagnosis of epilepsy and the management of refractory epilepsy in a specialist clinic. (2/868)
We assessed the frequency, causes and consequences of erroneous diagnosis of epilepsy, and the outcome of patients referred with 'refractory epilepsy', by retrospective analysis of the case records of 324 patients. The sample was divided into those exposed to anti-epileptic drugs (n = 184), of whom 92 were said to have refractory seizures, and those who had not received treatment (n = 140). The latter group is reported elsewhere. The overall misdiagnosis rate was 26.1% (46/184), with incomplete history-taking and misinterpretation of the EEG equally responsible. Side-effects were reported by 19/40, while unnecessary driving restrictions and employment difficulties were encountered by 12/33 and 5/33, respectively. Of those labelled 'refractory epilepsy', 12 did not have epilepsy. Sixteen were rendered seizure-free and 25 significantly improved by the optimal use of anti-epileptic drugs or surgery. Diagnostic and management services for patients with suspected and established epilepsy are suboptimal, with psychological and socio-economic consequences for individual patients. The resulting economic burden on the health and welfare services is probably substantial. (+info)Comparing two different protocols for tilt table testing: sublingual glyceryl trinitrate versus isoprenaline infusion. (3/868)
OBJECTIVE: To assess the diagnostic value and safety of sublingual glyceryl trinitrate tilt testing compared with isoprenaline infusion in patients with unexplained syncope. DESIGN: Glyceryl trinitrate and isoprenaline tilt tests were performed in two successive days on a random basis in cases and controls. SETTING: Outpatient cases with syncope referred to Shahid Rajaii Heart Hospital. SUBJECTS: 65 consecutive patients with unexplained syncope after thorough work up; 20 healthy volunteers. RESULTS: Positive responses were observed in 20 patients during the passive phase. Of the other 45 patients, positive responses occurred in 25 cases during the glyceryl trinitrate phase and in 26 cases during the isoprenaline phase. In the control group, positive responses during the passive, glyceryl trinitrate, and isoprenaline phases occurred in one, one, and two cases, respectively. The sensitivity and specificity of the protocols were 55% and 94.7%, respectively, for glyceryl trinitrate v 58% and 89.4% for isoprenaline. Owing to discordant responses in 75% of the cases, the sequential use of the tests (if one was negative) would increase the sensitivity to 84% while decreasing the specificity slightly (to 84%). Side effects were less frequent with glyceryl trinitrate. CONCLUSIONS: Sublingual glyceryl trinitrate tilt testing is an effective and safe alternative to the isoprenaline infusion test and can be used as a complementary test. (+info)Hypokalemia with syncope caused by habitual drinking of oolong tea. (4/868)
A 61-year-old woman developed hypokalemia, atrioventricular block and ventricular tachycardia with syncope after habitual drinking 2 to 3 liters of oolong tea per day. She had been suffering from rheumatoid arthritis and Sjogren's syndrome and her serum albumin was decreased (2.9 g/dl). Oolong tea contains caffeine at approximately 20 mg/dl. Great quantities of caffeine can induce hypokalemia. The serum protein binding caffeine is albumin. Accordingly, in patients with hypoalbuminemia, caffeine is apt to induce hypokalemia. This case suggested that great quantities of oolong tea, one of the so-called "healthy" drinks, result in serious symptoms for patients with hypoalbuminemia. (+info)Carotid sinus hypersensitivity--a modifiable risk factor for fractured neck of femur. (5/868)
BACKGROUND: the potential impact on morbidity, mortality and health care economics makes it important to identify patients at risk of fracture, in particular fractured neck of femur (FNOF). Older patients with carotid sinus hypersensitivity (CSH) are more likely to have unexplained falls and to experience fractures, particularly FNOF. Our objective was to determine the prevalence of CSH in patients with FNOF. DESIGN: case-controlled prospective series. METHODS: consecutive cases were admissions over 65 years with FNOF. Controls were consecutive patients admitted for elective hip surgery, frail elderly people admitted to hospital medical wards and day-hospital patients. All patients had a clinical assessment of cognitive function, physical abilities and history of previous syncope, falls and dizziness, in addition to repeated carotid sinus massage with continuous heart rate and phasic blood pressure measurement. RESULTS: heart rate slowing and fall in systolic blood pressure was greater for patients with FNOF than those admitted for elective hip surgery (P < 0.05 and P < 0.001). CSH was present in 36% of the FNOF group, none of the elective surgery group, 13% of the acutely ill controls and 17% of the outpatients. It was more likely to be present in FNOF patients with a previous history of unexplained falls or an unexplained fall causing the index fracture. The heart rate and systolic blood pressure responses to carotid sinus stimulation were reproducible. CONCLUSION: older patients with an acute neck of femur fracture who do not give a clear history of an accidental fall or who have had previously unexplained falls are likely to have CSH. CSH may be a modifiable risk factor for older patients at risk of hip fracture. (+info)Outcome of patients with nonischemic dilated cardiomyopathy and unexplained syncope treated with an implantable defibrillator. (6/868)
OBJECTIVES: The purpose of this study was to determine the outcome of patients with nonischemic dilated cardiomyopathy, unexplained syncope and a negative electrophysiology test who are treated with an implantable defibrillator. BACKGROUND: Patients with nonischemic cardiomyopathy and unexplained syncope may be at high risk for sudden cardiac death, and they are sometimes treated with an implantable defibrillator. METHODS: This study prospectively determined the outcome of 14 consecutive patients who had a nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test and who underwent defibrillator implantation (Syncope Group). Nineteen consecutive patients with a nonischemic cardiomyopathy and a cardiac arrest who were treated with a defibrillator (Arrest Group) served as a control group. RESULTS: Seven of 14 patients (50%) in the Syncope Group received appropriate shocks for ventricular arrhythmias during a mean follow-up of 24+/-13 months, compared with 8 of 19 patients (42%) in the Arrest Group during a mean follow-up of 45+/-40 months (p = 0.1). The mean duration from device implantation until the first appropriate shock was 32+/-7 months (95% confidence interval [CI], 18 to 45 months) in the Syncope Group compared to 72+/-12 months (95% CI, 48 to 96 months) in the Arrest Group (p = 0.1). Among patients who received appropriate shocks, the mean time from defibrillator implantation to the first appropriate shock was 10+/-14 months in the Syncope Group, compared with 48+/-47 months in the Arrest Group (p = 0.06). Recurrent syncope was always associated with ventricular tachyarrhythmias. CONCLUSIONS: The high incidence of appropriate defibrillator shocks and the association of recurrent syncope with ventricular arrhythmias support the treatment of patients with nonischemic cardiomyopathy, unexplained syncope and a negative electrophysiology test with an implantable defibrillator. (+info)Neurally mediated cardiac syncope: autonomic modulation after normal saline infusion. (7/868)
OBJECTIVES: This study assessed the heart variability response to orthostatic stress during tilt table testing before and after normal saline administration. BACKGROUND: The efficacy of sodium chloride and mineralocortoid in the treatment of neurally mediated cardiac syncope is attributed to intravascular volume expansion; however, their modulation of autonomic nervous system activity has not been evaluated. METHODS: Heart rate variability analysis was performed on 12 adolescents with a history of syncope or presyncope (mean age 15.2+/-0.7 years) during tilt table testing. Subjects were upright 80 degrees for 30 min or until syncope. After normal saline administration, the patient was returned upright for 30 min. Heart rate variability analysis data were analyzed by an autoregression model (Burg method). RESULTS: All subjects reproducibly developed syncope during control tilt table testing; median time to syncope was 9.4+/-2.1 min. After normal saline infusion, none of the subjects developed syncope after 30 min upright. In the control tilt, there was an initial increase followed by a progressive decrease in low frequency power until syncope. Repeat tilt after normal saline administration demonstrates that low frequency power increased but the magnitude of initial change was blunted when compared with control. In addition, low frequency power increased during normal saline tilt sequence compared with the control tilt, during which it decreased. CONCLUSIONS: Normal saline blunted low frequency power stimulation and prevented paradoxical low frequency power (sympathetic) withdrawal. Increasing intravascular volume with normal saline alters autonomic responses that may trigger neurally mediated syncope reflexes. (+info)Poor reproducibility of false-positive tilt testing results in healthy volunteers. (8/868)
Positive responses to head-up tilt testing occur in healthy subjects. However, the reproducibility of "false-positive" tilt testing results has not been clarified. To study the reproducibility of "false-positive" responses, we prospectively performed 2 tilt tests separated by 1 to 10 (mean 3.2) weeks in 20 healthy males aged 23 to 40 years (mean 30 years). The baseline tilt test (80 degrees for 30 minutes) ended positive in 4 (20%) subjects on the initial test and 2 (10%) on the second test with only 1 (5%) who had consecutive positive responses. No additional positive responses were noted during the isoproterenol (0.01 microgram/kg/min)-tilt test for 10 minutes. We demonstrated that a false-positive response occurred in 5 (25%) of 20 young males who underwent 2 tilt tests, however, only 1 (5%) subject had consecutive positive responses. Poor reproducibility may be characteristic of false-positive responses in head-up tilt testing. (+info)Syncope is a medical term defined as a transient, temporary loss of consciousness and postural tone due to reduced blood flow to the brain. It's often caused by a drop in blood pressure, which can be brought on by various factors such as dehydration, emotional stress, prolonged standing, or certain medical conditions like heart diseases, arrhythmias, or neurological disorders.
During a syncope episode, an individual may experience warning signs such as lightheadedness, dizziness, blurred vision, or nausea before losing consciousness. These episodes usually last only a few minutes and are followed by a rapid, full recovery. However, if left untreated or undiagnosed, recurrent syncope can lead to severe injuries from falls or even life-threatening conditions related to the underlying cause.
Vasovagal syncope is a type of fainting (syncope) that occurs when the body overreacts to certain triggers, such as the sight of blood or extreme emotional distress. This reaction causes the heart rate and blood pressure to drop, leading to reduced blood flow to the brain and loss of consciousness. Vasovagal syncope is usually not a cause for concern and does not typically indicate a serious underlying medical condition. However, it can be dangerous if it occurs during activities such as driving or operating heavy machinery. If you experience frequent episodes of vasovagal syncope, it is important to speak with a healthcare provider for evaluation and treatment options.
Bradycardia is a medical term that refers to an abnormally slow heart rate, typically defined as a resting heart rate of less than 60 beats per minute in adults. While some people, particularly well-trained athletes, may have a naturally low resting heart rate, bradycardia can also be a sign of an underlying health problem.
There are several potential causes of bradycardia, including:
* Damage to the heart's electrical conduction system, such as from heart disease or aging
* Certain medications, including beta blockers, calcium channel blockers, and digoxin
* Hypothyroidism (underactive thyroid gland)
* Sleep apnea
* Infection of the heart (endocarditis or myocarditis)
* Infiltrative diseases such as amyloidosis or sarcoidosis
Symptoms of bradycardia can vary depending on the severity and underlying cause. Some people with bradycardia may not experience any symptoms, while others may feel weak, fatigued, dizzy, or short of breath. In severe cases, bradycardia can lead to fainting, confusion, or even cardiac arrest.
Treatment for bradycardia depends on the underlying cause. If a medication is causing the slow heart rate, adjusting the dosage or switching to a different medication may help. In other cases, a pacemaker may be necessary to regulate the heart's rhythm. It is important to seek medical attention if you experience symptoms of bradycardia, as it can be a sign of a serious underlying condition.
Midodrine is a medication that belongs to a class of drugs called vasoconstrictors. It works by narrowing the blood vessels and increasing blood pressure. The medical definition of Midodrine is:
A synthetic derivative of the imidazole compound, adrenergic agonist, which is used in the treatment of orthostatic hypotension. Midodrine is a prodrug that is rapidly metabolized to its active form, desglymidodrine, after oral administration. It selectively binds to and activates alpha-1 adrenergic receptors, causing vasoconstriction and an increase in blood pressure. The drug's effects are most pronounced on the venous side of the circulation, leading to increased venous return and cardiac output. Midodrine is typically administered orally in divided doses throughout the day, and its use is usually reserved for patients who have not responded to other treatments for orthostatic hypotension.
Electrocardiography (ECG or EKG) is a medical procedure that records the electrical activity of the heart. It provides a graphic representation of the electrical changes that occur during each heartbeat. The resulting tracing, called an electrocardiogram, can reveal information about the heart's rate and rhythm, as well as any damage to its cells or abnormalities in its conduction system.
During an ECG, small electrodes are placed on the skin of the chest, arms, and legs. These electrodes detect the electrical signals produced by the heart and transmit them to a machine that amplifies and records them. The procedure is non-invasive, painless, and quick, usually taking only a few minutes.
ECGs are commonly used to diagnose and monitor various heart conditions, including arrhythmias, coronary artery disease, heart attacks, and electrolyte imbalances. They can also be used to evaluate the effectiveness of certain medications or treatments.
An artificial pacemaker is a medical device that uses electrical impulses to regulate the beating of the heart. It is typically used when the heart's natural pacemaker, the sinoatrial node, is not functioning properly and the heart rate is too slow or irregular. The pacemaker consists of a small generator that contains a battery and electronic circuits, which are connected to one or more electrodes that are placed in the heart.
The generator sends electrical signals through the electrodes to stimulate the heart muscle and cause it to contract, thereby maintaining a regular heart rhythm. Artificial pacemakers can be programmed to deliver electrical impulses at a specific rate or in response to the body's needs. They are typically implanted in the chest during a surgical procedure and can last for many years before needing to be replaced.
Artificial pacemakers are an effective treatment for various types of bradycardia, which is a heart rhythm disorder characterized by a slow heart rate. Pacemakers can significantly improve symptoms associated with bradycardia, such as fatigue, dizziness, shortness of breath, and fainting spells.
Ambulatory electrocardiography, also known as ambulatory ECG or Holter monitoring, is a non-invasive method of recording the electrical activity of the heart over an extended period of time (typically 24 hours or more) while the patient goes about their daily activities. The device used to record the ECG is called a Holter monitor, which consists of a small, portable recorder that is attached to the patient's chest with electrodes.
The recorded data provides information on any abnormalities in the heart's rhythm or electrical activity during different stages of activity and rest, allowing healthcare providers to diagnose and evaluate various cardiac conditions such as arrhythmias, ischemia, and infarction. The ability to monitor the heart's activity over an extended period while the patient performs their normal activities provides valuable information that may not be captured during a standard ECG, which only records the heart's electrical activity for a few seconds.
In summary, ambulatory electrocardiography is a diagnostic tool used to evaluate the electrical activity of the heart over an extended period, allowing healthcare providers to diagnose and manage various cardiac conditions.
Posture is the position or alignment of body parts supported by the muscles, especially the spine and head in relation to the vertebral column. It can be described as static (related to a stationary position) or dynamic (related to movement). Good posture involves training your body to stand, walk, sit, and lie in positions where the least strain is placed on supporting muscles and ligaments during movement or weight-bearing activities. Poor posture can lead to various health issues such as back pain, neck pain, headaches, and respiratory problems.
Recurrence, in a medical context, refers to the return of symptoms or signs of a disease after a period of improvement or remission. It indicates that the condition has not been fully eradicated and may require further treatment. Recurrence is often used to describe situations where a disease such as cancer comes back after initial treatment, but it can also apply to other medical conditions. The likelihood of recurrence varies depending on the type of disease and individual patient factors.
The carotid sinus is a small, dilated area located at the bifurcation (or fork) of the common carotid artery into the internal and external carotid arteries. It is a baroreceptor region, which means it contains specialized sensory nerve endings that can detect changes in blood pressure. When the blood pressure increases, the walls of the carotid sinus stretch, activating these nerve endings and sending signals to the brain. The brain then responds by reducing the heart rate and relaxing the blood vessels, which helps to lower the blood pressure back to normal.
The carotid sinus is an important part of the body's autonomic nervous system, which regulates various involuntary functions such as heart rate, blood pressure, and digestion. It plays a crucial role in maintaining cardiovascular homeostasis and preventing excessive increases in blood pressure that could potentially damage vital organs.
Unconsciousness is a state of complete awareness where a person is not responsive to stimuli and cannot be awakened. It is often caused by severe trauma, illness, or lack of oxygen supply to the brain. In medical terms, it is defined as a lack of response to verbal commands, pain, or other stimuli, indicating that the person's brain is not functioning at a level necessary to maintain wakefulness and awareness.
Unconsciousness can be described as having different levels, ranging from drowsiness to deep coma. The causes of unconsciousness can vary widely, including head injury, seizure, stroke, infection, drug overdose, or lack of oxygen supply to the brain. Depending on the cause and severity, unconsciousness may last for a few seconds or continue for an extended period, requiring medical intervention and treatment.
Heart block is a cardiac condition characterized by the interruption of electrical impulse transmission from the atria (the upper chambers of the heart) to the ventricles (the lower chambers of the heart). This disruption can lead to abnormal heart rhythms, including bradycardia (a slower-than-normal heart rate), and in severe cases, can cause the heart to stop beating altogether. Heart block is typically caused by damage to the heart's electrical conduction system due to various factors such as aging, heart disease, or certain medications.
There are three types of heart block: first-degree, second-degree, and third-degree (also known as complete heart block). Each type has distinct electrocardiogram (ECG) findings and symptoms. Treatment for heart block depends on the severity of the condition and may include monitoring, medication, or implantation of a pacemaker to regulate the heart's electrical activity.
Artificial cardiac pacing is a medical procedure that involves the use of an artificial device to regulate and stimulate the contraction of the heart muscle. This is often necessary when the heart's natural pacemaker, the sinoatrial node, is not functioning properly and the heart is beating too slowly or irregularly.
The artificial pacemaker consists of a small generator that produces electrical impulses and leads that are positioned in the heart to transmit the impulses. The generator is typically implanted just under the skin in the chest, while the leads are inserted into the heart through a vein.
There are different types of artificial cardiac pacing systems, including single-chamber pacemakers, which stimulate either the right atrium or right ventricle, and dual-chamber pacemakers, which stimulate both chambers of the heart. Some pacemakers also have additional features that allow them to respond to changes in the body's needs, such as during exercise or sleep.
Artificial cardiac pacing is a safe and effective treatment for many people with abnormal heart rhythms, and it can significantly improve their quality of life and longevity.
Fludrocortisone is a synthetic corticosteroid hormone, specifically a mineralocorticoid. It is often used to treat conditions associated with low levels of corticosteroids, such as Addison's disease. It works by helping the body retain sodium and lose potassium, which helps to maintain fluid balance and blood pressure.
In medical terms, fludrocortisone is defined as a synthetic mineralocorticoid with glucocorticoid activity used in the treatment of adrenogenital syndrome and Addison's disease, and as an adjunct in the treatment of rheumatoid arthritis. It is also used to treat orthostatic hypotension by helping the body retain sodium and water, thereby increasing blood volume and blood pressure.
It is important to note that fludrocortisone can have significant side effects, particularly if used in high doses or for long periods of time. These can include fluid retention, high blood pressure, increased risk of infection, and slowed growth in children. As with any medication, it should be used under the close supervision of a healthcare provider.
Cardiac arrhythmias are abnormal heart rhythms that result from disturbances in the electrical conduction system of the heart. The heart's normal rhythm is controlled by an electrical signal that originates in the sinoatrial (SA) node, located in the right atrium. This signal travels through the atrioventricular (AV) node and into the ventricles, causing them to contract and pump blood throughout the body.
An arrhythmia occurs when there is a disruption in this electrical pathway or when the heart's natural pacemaker produces an abnormal rhythm. This can cause the heart to beat too fast (tachycardia), too slow (bradycardia), or irregularly.
There are several types of cardiac arrhythmias, including:
1. Atrial fibrillation: A rapid and irregular heartbeat that starts in the atria (the upper chambers of the heart).
2. Atrial flutter: A rapid but regular heartbeat that starts in the atria.
3. Supraventricular tachycardia (SVT): A rapid heartbeat that starts above the ventricles, usually in the atria or AV node.
4. Ventricular tachycardia: A rapid and potentially life-threatening heart rhythm that originates in the ventricles.
5. Ventricular fibrillation: A chaotic and disorganized electrical activity in the ventricles, which can be fatal if not treated immediately.
6. Heart block: A delay or interruption in the conduction of electrical signals from the atria to the ventricles.
Cardiac arrhythmias can cause various symptoms, such as palpitations, dizziness, shortness of breath, chest pain, and fatigue. In some cases, they may not cause any symptoms and go unnoticed. However, if left untreated, certain types of arrhythmias can lead to serious complications, including stroke, heart failure, or even sudden cardiac death.
Treatment for cardiac arrhythmias depends on the type, severity, and underlying causes. Options may include lifestyle changes, medications, cardioversion (electrical shock therapy), catheter ablation, implantable devices such as pacemakers or defibrillators, and surgery. It is essential to consult a healthcare professional for proper evaluation and management of cardiac arrhythmias.
Autonomic denervation is a medical term that refers to the interruption or loss of nerve supply to the autonomic nervous system. The autonomic nervous system is the part of the nervous system that controls involuntary actions, such as heart rate, blood pressure, digestion, and pupil dilation.
Autonomic denervation can occur due to various reasons, including surgical procedures, trauma, degenerative diseases, or medical conditions such as diabetes. The interruption of nerve supply can lead to a range of symptoms depending on the specific autonomic functions that are affected.
For example, autonomic denervation in the heart can lead to abnormal heart rhythms or low blood pressure. In the digestive system, it can cause problems with motility and secretion, leading to symptoms such as bloating, constipation, or diarrhea. Autonomic denervation in the eyes can result in pupil abnormalities, dry eyes, or light sensitivity.
Treatment for autonomic denervation depends on the underlying cause and the specific symptoms that are present. In some cases, medication may be used to manage symptoms, while in others, surgical intervention may be necessary to repair or restore nerve function.
Long QT syndrome (LQTS) is a cardiac electrical disorder characterized by a prolonged QT interval on the electrocardiogram (ECG), which can potentially trigger rapid, chaotic heartbeats known as ventricular tachyarrhythmias, such as torsades de pointes. These arrhythmias can be life-threatening and lead to syncope (fainting) or sudden cardiac death. LQTS is often congenital but may also be acquired due to certain medications, medical conditions, or electrolyte imbalances. It's essential to identify and manage LQTS promptly to reduce the risk of severe complications.
Sudden cardiac death (SCD) is a sudden, unexpected natural death caused by the cessation of cardiac activity. It is often caused by cardiac arrhythmias, particularly ventricular fibrillation, and is often associated with underlying heart disease, although it can occur in people with no known heart condition. SCD is typically defined as a natural death due to cardiac causes that occurs within one hour of the onset of symptoms, or if the individual was last seen alive in a normal state of health, it can be defined as occurring within 24 hours.
It's important to note that sudden cardiac arrest (SCA) is different from SCD, although they are related. SCA refers to the sudden cessation of cardiac activity, which if not treated immediately can lead to SCD.
An implantable defibrillator is a medical device that is surgically placed inside the chest to continuously monitor the heart's rhythm and deliver electrical shocks to restore a normal heartbeat when it detects a life-threatening arrhythmia, such as ventricular fibrillation or ventricular tachycardia.
The device consists of a small generator that is implanted in the upper chest, along with one or more electrode leads that are threaded through veins and positioned in the heart's chambers. The generator contains a battery and a microcomputer that constantly monitors the heart's electrical activity and detects any abnormal rhythms.
When an arrhythmia is detected, the defibrillator delivers an electrical shock to the heart to restore a normal rhythm. This can be done automatically by the device or manually by a healthcare provider using an external programmer.
Implantable defibrillators are typically recommended for people who have a high risk of sudden cardiac death due to a history of heart attacks, heart failure, or inherited heart conditions that affect the heart's electrical system. They can significantly reduce the risk of sudden cardiac death and improve quality of life for those at risk.
Heart rate is the number of heartbeats per unit of time, often expressed as beats per minute (bpm). It can vary significantly depending on factors such as age, physical fitness, emotions, and overall health status. A resting heart rate between 60-100 bpm is generally considered normal for adults, but athletes and individuals with high levels of physical fitness may have a resting heart rate below 60 bpm due to their enhanced cardiovascular efficiency. Monitoring heart rate can provide valuable insights into an individual's health status, exercise intensity, and response to various treatments or interventions.
Ventricular Tachycardia (VT) is a rapid heart rhythm that originates from the ventricles, the lower chambers of the heart. It is defined as three or more consecutive ventricular beats at a rate of 120 beats per minute or greater in a resting adult. This abnormal heart rhythm can cause the heart to pump less effectively, leading to inadequate blood flow to the body and potentially life-threatening conditions such as hypotension, shock, or cardiac arrest.
VT can be classified into three types based on its duration, hemodynamic stability, and response to treatment:
1. Non-sustained VT (NSVT): It lasts for less than 30 seconds and is usually well tolerated without causing significant symptoms or hemodynamic instability.
2. Sustained VT (SVT): It lasts for more than 30 seconds, causes symptoms such as palpitations, dizziness, shortness of breath, or chest pain, and may lead to hemodynamic instability.
3. Pulseless VT: It is a type of sustained VT that does not produce a pulse, blood pressure, or adequate cardiac output, requiring immediate electrical cardioversion or defibrillation to restore a normal heart rhythm.
VT can occur in people with various underlying heart conditions such as coronary artery disease, cardiomyopathy, valvular heart disease, congenital heart defects, and electrolyte imbalances. It can also be triggered by certain medications, substance abuse, or electrical abnormalities in the heart. Prompt diagnosis and treatment of VT are crucial to prevent complications and improve outcomes.
Sick Sinus Syndrome (SSS) is a term used to describe a group of abnormal heart rhythm disturbances that originates in the sinoatrial node (the natural pacemaker of the heart). This syndrome is characterized by impaired functioning of the sinoatrial node, resulting in various abnormalities such as sinus bradycardia (abnormally slow heart rate), sinus arrest (complete cessation of sinus node activity), and/or sinoatrial exit block (failure of the electrical impulse to leave the sinus node and spread to the atria).
People with SSS may experience symptoms such as palpitations, dizziness, fatigue, shortness of breath, or syncope (fainting) due to inadequate blood supply to the brain caused by slow heart rate. The diagnosis of SSS is typically made based on the patient's symptoms and the results of an electrocardiogram (ECG), Holter monitoring, or event recorder that shows evidence of abnormal sinus node function. Treatment options for SSS may include lifestyle modifications, medications, or implantation of a pacemaker to regulate the heart rate.
Etilefrine is a synthetic, sympathomimetic amine drug that acts as a direct-acting adrenergic agonist. It primarily stimulates alpha-1 and beta-1 adrenergic receptors, leading to increased heart rate, cardiac contractility, and blood pressure. Etilefrine is used clinically as a vasopressor agent to treat hypotension (low blood pressure) in certain conditions, such as shock or during surgical procedures. It should be administered under the supervision of a healthcare professional due to its potential serious side effects, including cardiac arrhythmias and hypertension.
Dizziness is a term used to describe a range of sensations, such as feeling lightheaded, faint, unsteady, or a false sense of spinning or moving. Medically, dizziness is often described as a non-specific symptom that can be caused by various underlying conditions or factors. These may include:
1. Inner ear disorders (such as benign paroxysmal positional vertigo, labyrinthitis, vestibular neuronitis, or Meniere's disease)
2. Cardiovascular problems (like low blood pressure, arrhythmias, or orthostatic hypotension)
3. Neurological issues (such as migraines, multiple sclerosis, or stroke)
4. Anxiety disorders and panic attacks
5. Side effects of medications
6. Dehydration or overheating
7. Infections (like viral infections or bacterial meningitis)
8. Head or neck injuries
9. Low blood sugar levels (hypoglycemia)
It is essential to consult a healthcare professional if you experience persistent dizziness, as it can be a sign of a more severe underlying condition. The appropriate treatment will depend on the specific cause of the dizziness.
Orthostatic intolerance is a condition in which an individual experiences lightheadedness, dizziness, or fainting when standing or maintaining an upright position for extended periods. It is caused by an abnormal physiological response to gravity and results in inadequate blood flow to the brain upon standing.
The medical definition of orthostatic intolerance includes symptoms that are exacerbated by upright posture and relieved by recumbent (lying down) position. The underlying mechanisms involve dysfunction in the autonomic nervous system, which controls involuntary bodily functions such as heart rate, blood pressure, and vasoconstriction.
Orthostatic intolerance can be a symptom of various medical conditions, including postural orthostatic tachycardia syndrome (POTS), neurogenic orthostatic hypotension, and other autonomic disorders. Proper diagnosis and management require a thorough evaluation by a healthcare professional to identify the underlying cause and develop an appropriate treatment plan.
The supine position is a term used in medicine to describe a body posture where an individual is lying down on their back, with their face and torso facing upwards. This position is often adopted during various medical procedures, examinations, or when resting, as it allows for easy access to the front of the body. It is also the position automatically assumed by most people who are falling asleep.
It's important to note that in the supine position, the head can be flat on the surface or raised with the use of pillows or specialized medical equipment like a hospital bed. This can help to alleviate potential issues such as breathing difficulties or swelling in the face and head.
Cardiac arrest, also known as heart arrest, is a medical condition where the heart suddenly stops beating or functioning properly. This results in the cessation of blood flow to the rest of the body, including the brain, leading to loss of consciousness and pulse. Cardiac arrest is often caused by electrical disturbances in the heart that disrupt its normal rhythm, known as arrhythmias. If not treated immediately with cardiopulmonary resuscitation (CPR) and defibrillation, it can lead to death or permanent brain damage due to lack of oxygen supply. It's important to note that a heart attack is different from cardiac arrest; a heart attack occurs when blood flow to a part of the heart is blocked, often by a clot, causing damage to the heart muscle, but the heart continues to beat. However, a heart attack can sometimes trigger a cardiac arrest.
Atrioventricular (AV) block is a disorder of the electrical conduction system of the heart that causes a delay or interruption in the transmission of electrical signals from the atria (the upper chambers of the heart) to the ventricles (the lower chambers of the heart). This results in an abnormal heart rhythm, also known as an arrhythmia.
There are three degrees of AV block:
1. First-degree AV block: In this type of AV block, there is a delay in the conduction of electrical signals from the atria to the ventricles, but all signals are eventually conducted. This condition may not cause any symptoms and is often discovered during a routine electrocardiogram (ECG).
2. Second-degree AV block: In this type of AV block, some electrical signals from the atria are not conducted to the ventricles. There are two types of second-degree AV block: Mobitz type I and Mobitz type II. Mobitz type I is characterized by a progressive prolongation of the PR interval (the time between the electrical activation of the atria and ventricles) until a QRS complex (which represents the electrical activation of the ventricles) is dropped. Mobitz type II is characterized by a constant PR interval with occasional non-conducted P waves.
3. Third-degree AV block: In this type of AV block, no electrical signals are conducted from the atria to the ventricles. The atria and ventricles beat independently of each other, resulting in a slow heart rate (bradycardia) and an irregular rhythm. This condition can be life-threatening if not treated promptly.
The causes of AV block include aging, heart disease, medications, and certain medical conditions such as hypothyroidism and Lyme disease. Treatment depends on the severity of the condition and may include medication, a pacemaker, or surgery.
An abnormal reflex in a medical context refers to an involuntary and exaggerated response or lack of response to a stimulus that is not expected in the normal physiological range. These responses can be indicative of underlying neurological disorders or damage to the nervous system. Examples include hyperreflexia (overactive reflexes) and hyporeflexia (underactive reflexes). The assessment of reflexes is an important part of a physical examination, as it can provide valuable information about the functioning of the nervous system.
Head-down tilt (HDT) is a positioning technique often used in medical settings, particularly during diagnostic procedures or treatment interventions. In this position, the person lies down on a specially designed table with their head tilted below the horizontal plane, typically at an angle of 6 degrees to 15 degrees, but sometimes as steep as 90 degrees. This posture allows for various medical evaluations such as carotid sinus massage or intracranial pressure monitoring. It is also used in space medicine to simulate some effects of weightlessness on the human body during spaceflight. Please note that prolonged exposure to head-down tilt can have physiological consequences, including changes in blood pressure, heart rate, and eye function, which should be monitored and managed by healthcare professionals.
Electrophysiologic techniques, cardiac, refer to medical procedures used to study the electrical activities and conduction systems of the heart. These techniques involve the insertion of electrode catheters into the heart through blood vessels under fluoroscopic guidance to record and stimulate electrical signals. The information obtained from these studies can help diagnose and evaluate various cardiac arrhythmias, determine the optimal treatment strategy, and assess the effectiveness of therapies such as ablation or implantable devices.
The electrophysiologic study (EPS) is a type of cardiac electrophysiologic technique that involves the measurement of electrical signals from different regions of the heart to evaluate its conduction system's function. The procedure can help identify the location of abnormal electrical pathways responsible for arrhythmias and determine the optimal treatment strategy, such as catheter ablation or medication therapy.
Cardiac electrophysiologic techniques are also used in device implantation procedures, such as pacemaker or defibrillator implantation, to ensure proper placement and function of the devices. These techniques can help program and test the devices to optimize their settings for each patient's needs.
In summary, cardiac electrophysiologic techniques are medical procedures used to study and manipulate the electrical activities of the heart, helping diagnose and treat various arrhythmias and other cardiac conditions.
The Autonomic Nervous System (ANS) is a part of the peripheral nervous system that operates largely below the level of consciousness and controls visceral functions. It is divided into two main subdivisions: the sympathetic and parasympathetic nervous systems, which generally have opposing effects and maintain homeostasis in the body.
The Sympathetic Nervous System (SNS) prepares the body for stressful or emergency situations, often referred to as the "fight or flight" response. It increases heart rate, blood pressure, respiratory rate, and metabolic rate, while also decreasing digestive activity. This response helps the body respond quickly to perceived threats.
The Parasympathetic Nervous System (PNS), on the other hand, promotes the "rest and digest" state, allowing the body to conserve energy and restore itself after the stress response has subsided. It decreases heart rate, blood pressure, and respiratory rate, while increasing digestive activity and promoting relaxation.
These two systems work together to maintain balance in the body by adjusting various functions based on internal and external demands. Disorders of the Autonomic Nervous System can lead to a variety of symptoms, such as orthostatic hypotension, gastroparesis, and cardiac arrhythmias, among others.
Tachycardia is a medical term that refers to an abnormally rapid heart rate, often defined as a heart rate greater than 100 beats per minute in adults. It can occur in either the atria (upper chambers) or ventricles (lower chambers) of the heart. Different types of tachycardia include supraventricular tachycardia (SVT), atrial fibrillation, atrial flutter, and ventricular tachycardia.
Tachycardia can cause various symptoms such as palpitations, shortness of breath, dizziness, lightheadedness, chest discomfort, or syncope (fainting). In some cases, tachycardia may not cause any symptoms and may only be detected during a routine physical examination or medical test.
The underlying causes of tachycardia can vary widely, including heart disease, electrolyte imbalances, medications, illicit drug use, alcohol abuse, smoking, stress, anxiety, and other medical conditions. In some cases, the cause may be unknown. Treatment for tachycardia depends on the underlying cause, type, severity, and duration of the arrhythmia.