Ventricular tachycardia (VT) is an arrhythmia that impairs the heart’s ability to properly eject blood into the systemic circulation. It is a precursor to ventricular fibrillation. VT can affect the left ventricular ejection fraction, which can cause hemodynamic instability, particularly in situations where the heart rate is very high, or the duration of the VT is very long.
At high rates, ventricular filling and ventricular ejection are compromised. Prolonged VT augments hemodynamic deterioration. VT occurs when there are three or more PVCs with QRS complexes > 0.12 seconds each and a heart rate of 100–240 bpm.
Heart rates of up to 300 bpm have been documented. There are no P waves in VT. A “sustained” VT lasts > 30 seconds; a “nonsustained” VT lasts for < 30 seconds.
The ECG shows altered repolarization morphologies with either ST elevation or ST depression along with T wave inversion.