Deficient acceleration of left ventricular relaxation during exercise after heart transplantation.

The exercise-induced rise in left ventricular filling pressures after cardiac transplantation is considered to be the result of a blunted heart rate response, of elevated venous return, and of unfavorable passive late-diastolic properties of the cardiac allograft. In contrast to passive late-diastolic left ventricular properties, the effect of left ventricular relaxation on the exercise-induced rise in left ventricular filling pressures of the cardiac allograft has not yet been studied. In the present study, the response of left ventricular relaxation to exercise was investigated in transplant recipients and compared with left ventricular relaxation observed in normal control subjects exercised to the same heart rate. Moreover, the response of left ventricular relaxation of the cardiac allograft to beta-adrenoreceptor stimulation, to reduced left ventricular afterload, and to increased myocardial activator calcium was investigated by infusion of dobutamine and of nitroprusside and by postextrasystolic potentiation.