Ventricular tachycardias evaluation and treatment are complicated because
it often occurs in life-threatening situations that dictate rapid diagnosis
Ventricular tachycardia is defined as three or more beats of ventricular
origin (lower chamber of the heart) in succession at a rate greater than
100 beats/minute. The rhythm is usually regular, but may be slightly irregular.
It may be well-tolerated, but may also be associated with grave, life-threatening
Ventricular tachycardia can be referred to as sustained, lasting at least
30 seconds, or nonsustained. Sustained generally requires termination
by antiarrhythmia drugs, antitachycardia pacing techniques or electrical
cardioversion. Nonsustained ventricular tachycardia is short (three beats
or longer) and terminate spontaneously.
In general, ventricular tachycardia affects the diseased heart, although
it has been described in patients with apparently normal hearts. It is
usually associated with coronary artery disease. Patients who have ventricular
tachycardia in the absence of coronary artery disease have other cardiac
abnormalities, including cardiomyopathy, mitral valve prolapse, valvular
heart disease, QT interval prolongation and, in an otherwise normal heart,
an abnormality described as primary electrical instability. Other causes
of ventricular tachycardia include sarcoidosis, beginning treatment in
patients with myxedema and drugs such as digitalis, and other antiarrhythmia
agents. Occasional runs of tachycardia are initiated by a change in posture,
exercise, emotional excitement or vagal stimulation.
Ventricular tachycardia when sustained but stable is initially treated
with medications; however, ventricular tachycardia that is unstable should
be treated as a life threatening condition.