ventricular tachycardia

Ventricular Tachycardia 

Definition

Ventricular tachycardia (V-tach) is a rapid heart beat that originates in one of the lower chambers (the ventricles) of the heart. To be classified as tachycardia, the heart rate is usually at least 100 beats per minute.

Description

A rapid heart rate can originate in either the left or right ventricle. Ventricular tachycardia which lasts more than 30 seconds is referred to as sustained ventricular tachycardia. A period of three to five rapid beats is called a salvo, and six beats or more lasting less than 30 seconds is called nonsustained ventricular tachycardia. Rapid ventricular rhythms are more serious than rapid atrial rhythms because they make the heart extremely inefficient. They also tend to cause more severe symptoms, and have a much greater tendency to result in death.

Although generally considered to be among the life-threatening abnormal rhythms, harmless forms of sustained V-tach do exist. These occur in people without any structural heart disease.

Causes and symptoms

Most ventricular tachycardias are associated with serious heart disease such as coronary artery blockage, cardiomyopathy, or valvular heart disease. V-tach is often triggered by an extra beat originating in either the right or left ventricle. It also occurs frequently in connection with a heart attack. V-tach commonly occurs within 24 hours of the start of the attack. It must be treated quickly to prevent fibrillation. After 48 to 72 hours of the heart attack, the risk of ventricular tachycardia is small. However, people who have suffered severe damage to the larger anterior wall of the heart have a second danger period, because V-tach often occurs during convalescence from this type of heart attack.

Sustained ventricular tachycardia prevents the ventricles from filling adequately so the heart can not pump normally. This results in loss of blood pressure, and can lead to a loss of consciousness and to heart failure.

The individual with V-tach almost always experiences palpitation, though some episodes cause no symptoms at all.

Diagnosis

Diagnosis is easily made with an electrocardiogram.

Treatment

Any episode of ventricular tachycardia that causes symptoms needs to be treated. An episode that lasts more than 30 seconds, even without symptoms, also needs to be treated. Drug therapy can be given intravenously to suppress episodes of V-tach. If blood pressure falls below normal, a person will need electric cardioversion ("shock") immediately.

Prognosis

With appropriate drug or surgical treatment, ventricular tachycardia can be controlled in most people.

Prevention

A person susceptible to sustained ventricular tachycardia often has a small abnormal area in the ventricles that is the source of the trigger event. This area can sometimes be surgically removed. If surgery is not an option, and drug therapy is not effective, a device called an automatic cardioverter-defibrillator may be implanted.

Key terms

Atrial — Having to do with the upper chambers of the heart.

Cardiomyopathy — A disease of the heart muscle.

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

Coronary artery — The artery that supplies blood to the heart muscle itself.

Electrocardiogram — A visual representation of the heart beat.

Fibrillation — Rapid, uncoordinated, quivering of the heart.

Palpitations — Uncomfortable feeling of the heart beat in the chest.

Valvular — Having to do with the valves inside the heart.

Resources

Organizations

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

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tachycardia /tachy·car·dia/ (-kahr´de-ah) abnormally rapid heart rate.tachycar´diac

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atrial tachycardia  a rapid cardiac rate, usually 160–190 per minute, originating from an atrial locus.

atrioventricular (AV) junctional tachycardia , atrioventricular (AV) nodal tachycardia junctional t.

atrioventricular nodal reentrant tachycardia  that resulting from reentry in or around the atrioventricular node; it may be antidromic, in which conduction is anterograde over the accessory pathway and retrograde over the normal conduction pathway or orthodromic, in which conduction is anterograde over the normal conduction pathway and retrograde over the accessory pathway.

atrioventricular reciprocating tachycardia  (AVRT) a reentrant tachycardia in which the reentrant circuit contains both the normal conduction pathway and an accessory pathway as integral parts.

chaotic atrial tachycardia  that characterized by atrial rates of 100 to 130 beats per minute, markedly variable P wave morphology, and irregular P–P intervals, often leading to atrial fibrillation.

circus movement tachycardia  reentrant t.

ectopic tachycardia  rapid heart action in response to impulses arising outside the sinoatrial node.

junctional tachycardia  that arising in response to impulses originating in the atrioventricular junction, i.e., in the atrioventricular node, with a heart rate greater than 75 beats per minute.

multifocal atrial tachycardia  (MAT) chaotic atrial t.

nonparoxysmal junctional tachycardia  a junctional tachycardia of slow onset, with a heart rate of 70 to 130 beats per minute; due to enhanced automaticity of the atrioventricular junctional tissue, often secondary to disease or trauma.

paroxysmal tachycardia  rapid heart action that starts and stops abruptly.

paroxysmal supraventricular tachycardia  (PSVT) supraventricular tachycardia occurring in attacks of rapid onset and cessation, usually due to a reentrant circuit.

reciprocating tachycardia  a tachycardia due to a reentrant mechanism and characterized by a reciprocating rhythm.

reentrant tachycardia  any tachycardia characterized by a reentrant circuit.

sinus tachycardia  (ST) tachycardia originating in the sinus node; normal during exercise or anxiety but also associated with shock, hypotension, hypoxia, congestive heart failure, fever, and various high output states.

supraventricular tachycardia  (SVT) any regular tachycardia in which the point of stimulation is above the bundle branches; it may also include those arising from large reentrant circuits that encompass both atrial and ventricular sites.

ventricular tachycardia  an abnormally rapid ventricular rhythm with aberrant ventricular excitation, usually above 150 beats per minute, generated within the ventricle, and most often associated with atrioventricular dissociation.

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ventricular tachycardia,

tachycardia of at least three consecutive ventricular complexes with a rate greater than 100 beats/min. It usually originates in a focus distal to the branching of the atrioventricular bundle.

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tachycardia

abnormally rapid heart rate.

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atrial tachycardia

rapid contraction of the atrium arising from an ectopic focus in the atrium. The heart rate remains normal.

ectopic tachycardia

rapid heart action in response to impulses arising outside the sinoatrial node.

idioventricular tachycardia

one occurring as a compensation for a sinus bradycardia and A-V block.

junctional tachycardia

that arising in response to impulses originating in the atrioventricular junction, i.e. the atrioventricular node.

orthostatic tachycardia

disproportionate rapidity of the heart rate on arising from a recumbent to a standing position.

paroxysmal tachycardia

episodes of an abrupt and marked increase in heart rate in a resting patient, with an equally sudden return to normal.

sinus tachycardia, simple tachycardia

an increase in heart rate from heightened activity of the sinoatrial node, such as occurs with excitement or pain.

Sinus tachycardia in a dog.By permission from Ettinger SJ, Feldman E, Textbook of Veterinary Internal Medicine, Saunders, 2004

supraventricular tachycardia

a combination of junctional tachycardia and atrial tachycardia.

ventricular tachycardia

see ventricular tachycardia.

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ventricular

pertaining to a ventricle.

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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.

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ventricular tachycardia

V tach, wide-complex tachycardia Cardiology A common, potentially life threatening abnormal rapid–160–240 beats/minheart beat initiated in the ventricles, characterized by 3 or more consecutive premature ventricular beats; VT may compromise systemic pumping of blood Triggers Spontaneous, post-acute MI, cardiomyopathy, mitral valve prolapse, myocarditis, post-heart surgery, antiarrhythmics, ↓ potassium, pH–acid-base changes, ↓ O₂ Types Nonsustained–eg, lasting < 30 secs, sustained, > 30 secs. See Torsade de pointes.