Phase detection of R waves in noisy electrocardiograms.

Ventricular fibrillation, a form of electrical instability of the myocardium, is strongly suspected to be a significant contributor to ``sudden'' coronary fatalities. Present evidence indicates that ventricular fibrillation is often preceded by other forms of abnormal electrical activity of the heart, especially ventricular premature beats (VPBs). Early detection of the presence of VPBs in the electrocardiogram may be important in making medical decisions to avert a later coronary attack.