Ventricular fibrillation

What it is

Reading a tachycardia begins with QRS width. A wide QRS is ventricular: regular means ventricular tachycardia, irregular means ventricular fibrillation. A narrow QRS is atrial: regular means SVT, sinus tachycardia or atrial flutter, irregular means atrial fibrillation or MAT.

In cardiac arrest that single division decides everything. Ventricular fibrillation stands with pulseless ventricular tachycardia on the side where defibrillation is possible; asystole and pulseless electrical activity stand on the side where defibrillation is not possible.

How it is diagnosed

On the ECG:

• Chaotic irregular deflections of varying amplitude.
• No identifiable P waves, QRS complexes, or T waves.
• Rate 150 to 500 per minute.