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 lifethreatening
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.