Exercise capacity in heart transplant recipients: relation to impaired endothelium-dependent vasodilation of the peripheral microcirculation.
OBJECTIVE
The aim of this study was to examine the responses to endothelium-dependent and -independent vasodilators on the peripheral microcirculation in heart transplant recipients in relation to exercise capacity compared with that in healthy controls.


BACKGROUND
Impaired endothelium-dependent vasodilation of the microcirculation may play an important role in the limitation of exercise capacity after heart transplantation.


METHODS
Microvascular perfusion responses to four graded levels of iontophoretically applied 1% acetylcholine (endothelium-dependent vasodilator) and 1% sodium nitroprusside (SNP) (endothelium-independent) in the forearm skin of 42 transplant recipients and 16 age-matched controls were determined by laser Doppler perfusion measurements. Maximal exercise capacity was assessed by peak oxygen uptake (peak VO2) during progressive, symptom-limited, upright bicycle exercise.


RESULTS
With similar baseline perfusion levels in transplant recipients and controls (4.2 +/- 0.4 vs 4.6 +/- 0.6 arbitrary units [AU]), the increases in perfusion to acetylcholine, but not to SNP, were significantly 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 (all p < 0.01). Peak VO2 was significantly lower in the transplant recipients (22.4 +/- 1.0 vs 38.0 +/- 2.9 ml/kg/min; p < 0.01). Furthermore, acetylcholine responses of the transplant recipients correlated closely to their peak VO2, irrespective of level of application (r = 0.63; p < 0.001, all four acetylcholine responses taken together), whereas no such correlation was found for SNP responses. In the control group, no relation was observed in acetylcholine/SNP responses to peak VO2.


CONCLUSIONS
Exercise limitation in transplant recipients appears strongly associated with attenuated endothelium-dependent vasodilation of the peripheral microcirculation.
Department of Cardiology, Rikshospitalet, Oslo, Norway.
A K
AK
Andreassen
K
K
Kvernebo
B
B
Jørgensen
S
S
Simonsen
J
J
Kjekshus
L
L
Gullestad
D000109:Acetylcholine; D000328:Adult; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D016027:Heart Transplantation / Q000502:physiology*; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008875:Middle Aged; D009569:Nitric Oxide / Q000502:physiology*; D009599:Nitroprusside; D010100:Oxygen / Q000097:blood; D011183:Postoperative Complications / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012867:Skin / Q000098:blood supply*; D014664:Vasodilation / Q000502:physiology*
D009599:Nitroprusside; D009569:Nitric Oxide; D000109:Acetylcholine; D010100:Oxygen