Fibrillation of the ventricles - definition of Fibrillation of the ventricles in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia.

Ventricular Fibrillation

Definition

Ventricular fibrillation is a very rapid, uncoordinated, ineffective series of contractions throughout the lower chambers of the heart. Unless stopped, these chaotic impulses are fatal.

Description

When the ventricles begin to quiver and do not employ coordinated contractions, the heart is said to be fibrillating. In this condition the ventricles cannot pump blood from the heart. Ventricular fibrillation (V-fib) is the worst kind of abnormal heart rhythm, and is a form of cardiac arrest. It involves the pumping of the lower chambers of the heart, while atrial fibrillation involves the upper chambers.

Causes and symptoms

Ventricular fibrillation often is associated with acute ischemic events (ischemia involves the deprivation of oxygenated blood to an area of tissue), and with chronic ischemic heart disease. It is frequently seen immediately following a heart attack. It also may develop during hypoxia, atrial fibrillation, or improper grounding of electrical devices. An extremely low level of potassium in the blood also can cause ventricular fibrillation.

The first, and usually the only, symptom of V-fib is sudden unconsciousness.

Diagnosis

When an individual suddenly collapses, the possibility of ventricular fibrillation should be considered immediately. A quick assessment usually shows no pulse or heartbeat. The diagnosis of ventricular fibrillation is confirmed with an electrocardiogram.

Treatment

Basic life support with standard cardiopulmonary resuscitation (CPR) must be started within a few minutes, followed as soon as possible with cardioversion. Cardioversion is an electric shock delivered to the heart to stop the fibrillating. Early defibrillation is the key to survival. If left untreated, irreversible brain damage, due to lack of oxygen to the brain, occurs after about five minutes. After the heart resumes its normal rhythm, medications are given to help maintain the rhythm.

Research continues into methods to deliver defibrillation as soon as possible to those experiencing ventricular fibrillation. One of the studies addressed in 2003 researched various clinical trials that implanted defibrillators into patients to prevent sudden cardiac death. The devices worked in many instances but more proof of their success was needed for widespread use.

Prognosis

Early and effective CPR may provide the time necessary for medical personnel to arrive with a defibrillator. If a defibrillator is able to promptly restore a normal rhythm, up to 25% of victims are able to leave the hospital without evidence of brain damage.

If ventricular fibrillation occurs in the hospital in conjunction with a heart attack, defibrillation has a 95% success rate. If shock and heart failure are present at the time, even with immediate defibrillation, only about 30% of those stricken are successfully restored to a normal heart rate.

Prevention

A healthy lifestyle to reduce the risk of heart diseases which lead to ventricular fibrillation is the best prevention. For people who have experienced an episode of V-fib, an internal cardioverter-defibrillator may prevent further episodes.

Key terms

Atrial fibrillation — A condition in which the upper chambers of the heart quiver instead of contracting effectively

Cardiopulmonary resuscitation (CPR) — Using rescue breathing and chest compressions to help a person whose breathing and heartbeat have stopped

Cardioversion — An electrical shock delivered to the heart to restore a normal rhythm

Electrocardiogram — A visual representation of the heart beat

Heart failure — A term used when the heart is unable to pump enough blood to supply the needs of the body

Hypoxia — Insufficient oxygen in the cells of the body

Ischemic — Insufficient blood reaching the tissues

Resources

Periodicals

Ezekowitz, Justin A., et al. "Implantable Cardioverter Defibrillators in Primary and Secondary Prevention: A Systematic Review of Randomized, Controlled Trials." Annals of Internal Medicine January 2002: 445.

Organizations

American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org.

fibrillation /fi·bril·la·tion/ (fĭ″brĭ-la´shun)

1. the quality of being made up of fibrils.

2. a small, local, involuntary, muscular contraction, due to spontaneous activation of single muscle cells or muscle fibers whose nerve supply has been damaged or cut off.

3. the initial degenerative changes in osteoarthritis, marked by softening of the articular cartilage and development of vertical clefts between groups of cartilage cells.

atrial fibrillation atrial arrhythmia marked by rapid randomized contractions of small areas of the atrial myocardium, causing a totally irregular, and often rapid, ventricular rate.

ventricular fibrillation cardiac arrhythmia marked by fibrillary contractions of the ventricular muscle due to rapid repetitive excitation of myocardial fibers without coordinated ventricular contraction and by absence of atrial activity.

ventricular fibrillation

n. Abbr. VF

An often fatal form of arrhythmia characterized by rapid, irregular fibrillar twitching of the ventricles of the heart instead of normal contractions, resulting in a loss of pulse. Also called v-fib.

ventricular fibrillation (VF),

a cardiac arrhythmia marked by rapid depolarizations of the ventricular myocardium. The condition is characterized by a complete lack of organized electric activity and of ventricular ejection. Blood pressure falls to zero, resulting in unconsciousness. Death may occur within 4 minutes. Cardiopulmonary resuscitation must be initiated immediately, with defibrillation and resuscitative medications given according to advanced cardiac life support protocol.

ventricular fibrillation (ven·triˑ·ky

·ler fibˈ·r

·lāˑ·sh

n),

n an arrhythmia of the cardiac muscle distinguished by the ventricular myocardium's quick depolarization; characterized by ventricular ejection and the complete absence of organized electrical activity; blood pressure falls to zero; and the individual enters a state of unconsciousness. Within 4 minutes, death may result. The immediate initiation of cardiopulmonary resuscitation accompanied by defibrillation and the appropriate dosage of medications designed to resuscitate are necessary to sustain life. Also called
VF.

ventricular fibrillation (VF),

n a cardiac dysrhythmia marked by rapid, disorganized depolarizations of the ventricular myocardium. The condition is characterized by a complete lack of organized electric impulse, conduction, and ventricular contraction. Blood pressure falls to zero, resulting in unconsciousness. Death may occur within 4 minutes. Defibrillation and ventilation, i.e., cardiopulmonary resuscitation (CPR), must be initiated immediately.

fibrillation

1. a small, local, involuntary, muscular contraction, due to spontaneous activation of single muscle cells or muscle fibers.

2. the quality of being made up of fibrils.

3. the initial degenerative changes in osteoarthritis, marked by softening of the articular cartilage and development of vertical clefts between groups of cartilage cells.

atrial fibrillation

a cardiac arrhythmia marked by rapid randomized contractions of the atrial myocardium, causing a totally irregular, often rapid, ventricular rate. There is no synchronous atrial contraction and the ventricles beat irregularly. The heartbeat is irregular, the pulse is irregular in rhythm and amplitude. Common in the horse; an affected animal can still race but the performance is poor. Occurs in dogs in association with cardiac disease, particularly idiopathic congestive cardiomyopathy, and electrolyte disturbances.

ventricular fibrillation

a cardiac arrhythmia marked by fibrillatory contractions of the ventricular muscle due to rapid repetitive excitation of myocardial fibers without coordinated ventricular contraction. Ventricular fibrillation is a frequent cause of cardiac arrest. An apparatus called a defibrillator sometimes is used to alleviate fibrillation. The defibrillator delivers an electric shock to the heart muscle, depolarizing the muscle and ending the irregular contractions. The heart is then able to resume normal, regular contractions.

ventricular

pertaining to a ventricle.

ventricular assist device

a circulatory support device consisting of a pump with afferent and efferent conduits attached to the left ventricular apex and the ascending aorta, respectively, each conduit containing a porcine valve to ensure unidirectional blood flow; the pump rests on the external chest wall and is connected to an external pneumatic power source and control circuit.

ventricular asystole

see asystole.

ventricular bands

folds of mucosa, parallel and craniolateral to the vocal cords. Called also false vocal cords, vestibular folds.

double right ventricular outlet

a cardiac anomaly rarely seen in animals in which both the aorta and pulmonary artery arise from the right ventricle and there is a defect in the ventricular septum.

excessive ventricular moderator bands

a rare syndrome of cardiomyopathy in cats caused by an excessive number of moderator bands in the left ventricle, extending from the papillary muscles to the ventricular septum.

ventricular extrasystoles

see ventricular extrasystole.

ventricular fibrillation

see ventricular fibrillation.

ventricular function curve

see starling curves.

ventricular hypertrophy

see ventricular hypertrophy.

ventricular outflow obstruction

flow of blood from the ventricles is impaired by lesions or congenital abnormalities in the outflow tract. This is usually associated with hypertrophy of the ventricle and can be demonstrated with echocardiography or contract radiography. Left outflow obstruction occurs with stenosis and other anomalies of the aorta; right outflow obstruction occurs with pulmonic stenosis, pulmonic insufficiency, tetralogy of Fallot, and double-chambered right ventricle.

ventricular premature contraction (VPC)

see premature heartbeats.

ventricular rupture

due to focal weakness causes sudden death due to cardiac tamponade.

ventricular septal defect

a congenital heart defect in which there is persistent patency of the ventricular septum in either the muscular or fibrous portion most often due to failure of the bulbar septum to completely close the interventricular foramen. The defect permits flow of blood directly from one ventricle to the other, bypassing the pulmonary circulation and producing varying degrees of cyanosis because of oxygen deficiency. Its clinical characteristics also include a systolic murmur and a palpable thrill on both sides of the chest, dyspnea and poor exercise tolerance. The occurrence is sporadic except that it is inherited in goats and dogs.

ventricular septum

the muscular wall between the ventricles. A small section, between the aortic vestibule and the right atrium, is membranous. Failure of the septum to close completely during fetal growth causes a septal or subaortic defect.

ventricular shortening fraction

in echocardiography, the percentage change in diameter from diastole to systole. Calculated from the internal systolic and diastolic dimensions. It is a measure of mycocardial function.

ventricular slice method

a method for examination of fixed heart by cutting it into 0.5 inch thick slices, perpendicular to the plane of the ventricular septum, from apex to base. Useful in examination of myocardial lesions and cardiomyopathy.

ventricular tachycardia

is manifested by a high heart rate with or without arrhythmia. In both cases there is severe cardiac disease and often acute heart failure.