EXERCISE CAPACITY IN HEART-TRANSPLANT RECIPIENTS - RELATION TO IMPAIRED ENDOTHELIUM-DEPENDENT VASODILATION OF THE PERIPHERAL MICROCIRCULATION

Objectives The aim of this study was to examine the responses to endot helium-dependent and -independent vasodilators on the peripheral micro circulation in heart transplant recipients in relation to exercise cap acity compared with that in healthy controls. Background Impaired endo thelium-dependent vasodilation of the microcirculation may play an imp ortant role in the limitation of exercise capacity after heart transpl antation. Methods Microvascular perfusion responses to four graded lev els of iontophoretically applied 1% acetylcholine (endothelium-depende nt vasodilator) and 1% sodium nitroprusside (SNP) (endothelium-indepen dent) in the forearm skin of 42 transplant recipients and 16 age-match ed controls were determined by laser Doppler perfusion measurements. M aximal exercise capacity was assessed by peak oxygen uptake (peak Vo(2 )) during progressive, symptom-limited, upright bicycle exercise. Resu lts With similar baseline perfusion levels in transplant recipients an d controls (4.2 +/- 0.4 vs 4.6 +/- 0.6 arbitrary units [AU]), the incr eases in perfusion to acetylcholine, but nor to SNP, were significantl y attenuated in the transplant recipients: 7.0 +/- 1.0 vs 11.0 +/- 2.0 , 12.7 +/- 1.5 vs 21.0 +/- 2.8, 21.0 +/- 1.9 vs 32.7 +/- 2.4, and 28.0 +/- 1.6 vs 39.2 +/- 2.4 AU, respectively tall p < 0.01). Peak Vo(2) w as significantly lower in the transplant recipients (22.4 +/- 1.0 vs 3 8.0 +/- 2.9 ml/kg/min; p < 0.01). Furthermore, acetylcholine responses of the transplant recipients correlated closely to their peak Vo(2) i rrespective of level of application (r = 0.63; p < 0.001, all four ace tylcholine responses taken together), whereas no such correlation was found For SNP responses. In the control group, no relation was observe d in acetylcholine/SNP responses to peak Vo(2). Conclusions Exercise l imitation in transplant recipients appears strongly associated with at tenuated endothelium-dependent vasodilation of the peripheral microcir culation.