[Changes in hemodynamics and ECG in dogs following whole-body external gamma-irradiation]

Experiments were made on dogs of both sexes aged 2 to 4 with the body mass of 15.3 +/- +/- 1.1 kg. The animals were exposed to single external whole-body gamma-beam irradiation with 60Co at a dose rate of 1.03-1.3 mA/kg. The exposure dose was 51.6 mC/kg. It was shown that the irradiated dogs developed hemodynamic shifts indicating the formation of conditions first for the overstrain of the left cardiac region (arterial hypertension and a decrease in the vascular coefficient indicating an increase in the precapillary tension of the greater circulation) and then for that of the right cardiac region (an increase in the vascular coefficient, concomitant weakening of the precapillary tension of the greater circulation and an elevated influx of the venous blood to the right cardiac region). According to the ECG results, gamma-beam irradiation at a dose of 51.6 mC/kg resulted in noticeable stabilization of cardiac rhythm as compared to the initial one in the course of one month. Later on the irradiated animals developed more marked tachycardia as compared to the control animals of the same age. In most cases tachycardia was combined with bradycardia. After 3.5-4,5 years 75% of the dogs showed signs of the left ventricular overstrain which 6.5-7 yrs later were supplemented in 50% of the animals by the "P-pulmonale" complex typical of the overstrain of the right atrium. In most dogs the formation of the signs of the overstrain of the left and right cardiac regions over time was accompanied by clear-cut changes in the position of the heart. A significant disorder of myocardial function in the irradiated animals showed evidence for the appearance of the coronary T wave in leads II and III and aVF lead.