We have assessed parameters of myocardial electrical instability in patients with postinfarction atherosclerosis before and in one year after coronary bypass surgery. Inclusion criteria were history of myocardial infarction, surgical myocardial revascularization between 1 and 2 years before; stable course of coronary heart disease during previous month; preserved ejection fraction ( more or equal 50%), stable sinus rhythm. Heterogeneity of myocardial electrophysiological properties has diminished after coronary bypass surgery due to improvement of coronary perfusion and restoration of function of ischemic myocardium. This have been associated with positive dynamics of interval QT dispersion, parameters of turbulence and variability of cardiac rhythm, reduction of the rate of registration of ventricular late potentials.