[Electrical aspects of experimental diastolic and mixed ventricular overload]

Hemodynamic and electrical adaptation of ventricular myocardium to progressive diastolic and combined overloads was studied in mongrel dogs weighing between 15 and 20 Kg, anesthetized with intraperitoneal sodium pentobarbital (35 mg/Kg). Unipolar epicardial and intracavitary records as well as corresponding ventricular pressure curves were obtained every 30 mn after infusion was begun. The systolic arterial pressure was followed continuously by a mercury manometer. Right ventricular overload was produced by means of continuous venous infusion of saline solution in a group of 115 dogs with open pericardium (Series A) and in another of 45 dogs with intact pericardium (Series B). In Series A, right proximal and peripheral blocks were present in all the cases, beginning at 180 mn of infusion. In Series B, at 210 mn blocks were not present in 18 dogs (40%), and right peripheral blocks were present in 27 (60%). Left ventricular overload was obtained through continuous infusion of saline serum into left atria of 31 dogs with open pericardium (Series A1) and of another 50 with intact pericardium (Series B1). Only peripheral left blocks appeared in both series. Between 240 and 300 mn of infusion, the percentage of surviving animals was greater in Series B1, with a statistically significant difference at 270 and 300 mn. The pericardium seems to hinder the adaptation of right ventricular myocardium to the overloads evaluated, while it seems to help the response of the left ventricular myocardium to diastolic and combined overload.