Recent progress in electrocardiography

Recent advances in electrocardiography (ECG) have revealed new and useful information concerning the electrophysiologic properties of the normal and diseased heart. 1) Evaluation of the frequency of ventricular premature contractions (VPCs) as a function of underlying heart rate with Holter ECG recordings is a useful approach to elucidate the mechanisms of ventricular arrhythmias and to predict the response of ventricular arrhythmias to antiarrhythmic agents. 2) Decreased heart rate variability, presence of late potential, prolonged QT interval, increased QT interval dispersion, and T wave alternans indicate lethal ventricular tachyarrhythmias and sudden cardiac death. 3) The multiple reentrant wave hypothesis has been widely accepted for the mechanism of atrial fibrillation (AF). Recently, spontaneous initiation of AF by ectopic beats originating from the superior vena cava and the pulmonary veins has been reported. Radiofrequency ablation of the focal source of AF completely prevented the recurrence of AF.