In vivo dispersion in repolarization and arrhythmias in the human heart.

IN THIS ISSUE of American Journal of Physiology-Heart and Circulatory Physiology, Chauhan and colleagues (5) have measured dispersion in ventricular repolarization time (RT) in patients with cardiomyopathy and an ejection fraction 40%. Such data are sparse in humans in general. The measurements have been made at the right ventricular (RV) endocardium and at the left ventricular (LV) epicardium by a catheter in the great cardiac vein. This study by Chauhan et al. (5) is one of the very few with data from the endocardium and epicardium in the same patients. Also, the patients were conscious. RT dispersion was in the order of 10–12 ms/mm in 12 patients in which either ventricular tachycardias (VT) could be provoked or in which there was positive microvolt T wave alternans (TWA). In 10 patients without VTs or TWA, RT dispersion was limited to 2–3 ms/mm. A similar increased dispersion in activation-recovery intervals (ARI; an index of local action potential duration), but not dispersion in activation times, was shown to underlie the difference in RT dispersion between the two patient groups.