Ventricular tachycardia is a potentially lethal disruption of normal heartbeat (arrhythmia) that may cause the heart to become unable to pump adequate blood through the body. The heart rate may be 160 to 240 (normal is 60 to 100 beats per minute).

Ventricular tachycardia can occur in the absence of apparent heart disease. It can also develop as an early or a late complication of a heart attack, or during the course of cardiomyopathy, valvular heart disease, myocarditis, and following heart surgery.

Healed heart attacks evolve to form scar tissue which predisposes to ventricular tachycardia that may occur months after the heart attack. Ventricular tachycardia can also result from anti-arrhythmic medications (an undesired effect) or from altered blood chemistries (such as a low potassium level), pH (acid-base) changes, or insufficient oxygenation.

A common mechanism for ventricular tachycardia is reentry (re-stimulation of the electrical conductive pathway from a single initial stimulus). Ventricular tachycardia is classified as nonsustained (often defined as lasting less than 30 seconds) or sustained.

"Torsade de pointes" is a form of ventricular tachycardia with a specific variation in the conduction of the ventricular stimulus.

Ventricular tachycardia occurs in approximately 2 out of 10,000 people.