SUPERSENSITIVITY MISMATCH OF ADENOSINE IN THE TRANSPLANTED HUMAN HEART - CHRONOTROPY AND DROMOTROPY VERSUS INOTROPY

Supersensitive negative chronotropic and dromotropic effects have been described for adenosine after human heart transplantation. The presen t study investigated a potential antiadrenergic negative inotropic eff ect of adenosine in heart transplant recipients compared to normal sub jects. Sinus cycle length, PR interval, blood pressure, and inotropic response in vivo were compared in seven orthotopic heart transplant re cipients and seven healthy volunteers (controls). Fractional shortenin g, velocity of circumferential fiber shortening, and systolic pressure /dimension ratio were calculated using M-mode echocardiography. Baseli ne ventricular contractility was normal in both groups. Although adeno sine induced a significant exaggeration of the negative chronotropic a nd dromotropic effect in the transplant group, the positive inotropic effect of 20 ng/kg x min isoproterenol (FS 53.2 +/- 8.8 vs 51.0 +/- 4. 6%, PID 5.8 +/- 1.9 vs 6.0 +/- 0.8 mm Hg/mm, V-cf 0.21 +/- 0.04 vs 0.2 0 +/- 0.02 %/ms for heart recipients vs controls) was not reduced by t he additional administration of 150 mu g/kg adenosine (FS 52.2 +/- 8.6 vs 51.7 +/- 5.6%, PID 5.5 +/- 1.5 vs 5.4 +/- 0.8 mm Hg/mm, V-cf 0.24 +/- 0.07 vs 0.21 +/- 0.02 %/ms for transplant recipients vs controls). In contrast to a chronotropic and dromotropic supersensitivity, adeno sine does not attenuate the catecholamine-induced increase in contract ility in the human ventricle in vivo after heart transplantation.