Richard J. Cleveland

Hemodynamic Effects of Volume Loading in Dogs Following Cardiac Homotransplantation

The response to an acute volume load of 25 cc/kg of homologous whole blood was evaluated in ten control dogs and five dogs with orthotopic cardiac transplants at the time of combined hemodynamic-cineangiographic study 7 to 12 days after thoracotomy or transplantation. Both groups elevated their mean left ventricular end-diastolic pressures to similar levels. Cardiac output, mean systemic aortic pressure, systemic vascular resistance, and stroke work did not differentiate the two groups.The following abnormalities in diastolic filling of the transplants were noted: (1) the maximum rate of change of left ventricular area during early rapid diastolic filling was lower (P = 0.01); (2) the baseline left ventricular end-diastolic area was smaller (P = 0.15), although the left ventricular end-diastolic pressure was elevated and the heart rate lower; and (3) the increase in left ventricular end-diastolic area was less with volume loading. Decreased distensibility of the left ventricle and a lower baseline heart rate with absence of effective atrial contractions are possible explanations for this difference. Multiple factors may account for the decrease in distensibility.