Altered humoral control of circulating volume during artificial circulation

Plasma atrial natriuretic polypeptide (ANP) levels and plasma renin activity (PRA) were measured in six left ventricular assist device (LVAD) goats, four single artificial heart (SAH) goats, i.e., LVAD animals with fibrillated hearts, and 3 total artificial heart (TAH) calves. During the 4 week experiment, the ANP levels in the SAH goats increased to 516 pg/ml from the control value of 61.8 pg/ml because of an elevated CVP of 13-21 mmHg, while those of the LVAD goats were near the lower limit of the control values. The TAH calves had slightly decreased ANP levels at 23-46 pg/ml after the third postoperative week, which did not increase after the steep increase in CVP induced by the changes in the driving conditions. The PRA levels were 10-50 times higher than control in the SAH goats and a TAH calf whose CVP rose to 19 mmHg, although the cardiac output was within normal limits.

1) The secretion of ANP secondary to alteration in CVP was preserved in the LVAD recipients and enhanced diuresis, while it was compromised in the TAH cases. 2) The PRA levels in cases with elevated CVPs were high enough to suppress diuresis.