The aim of the research was to compare electrophysiological properties of myocardium in patients with acute myocardial infarction (AMI) and preserved left ventricular ejection fraction, complicated by acute heart failure (AHF), Killip class II–III. The data of 528 pts with Q-wave AMI were studied. We used noninvasive markers of heterogeneity in ventricular depolarization and repolarization, markers of short-term heart rate variability and late potentials (LP). Markers of heterogeneity in ventricular depolarization (QRScD) and repolarization (JTcD) were higher in a AHF group than in controls (by 41% for QRScD, and by 32% for JTcD), and marker of shortterm heart-rate variability (SDRR) was lower in a AHF group (by 34% less than in controls, Р<0,01). Also patients with AHF had high rate of LP compared to the control group.