The fi rst 10 min of electrically provoked ventricular fi brillation in dogs with ischemic heart disease were characterized by organized myocardial activity evidenced by the dominant ECG frequency structure. During the fi rst 2 min of ventricular fi brillation, low-frequency oscillations (4-7 Hz) dominated, while on min 3 to 10 after the onset of fi brillation, the dominant frequencies were low and medium (4-12 Hz). After 10-min fi brillation, the oscillations became non-dominant. Thus, ischemic myocardium maintains the organized structure of ventricular fi brillation for the fi rst 10 min, which is important for the development of automatic diagnostics of abnormal cardiac activity in humans.