Previous studies with the endothellum-dependent vasodilator substance P have shown a preserved vasodilator response in cardiac transplant recipients with angiographically normal coronary arteries. Although endothelial dysfunction is known to occur in cardiac transplant recipients with accelerated coronary disease, the degree to which the endothellum is atlected is not known precisely. The aim of the present study was to examine endothelial function in accelerated coronary disease following cardiac transplantation.Methods
Thirteen cardiac transplant recipients with epicardial coronary disease underwent substance P infusion. The response to incremental doses of substance P was measured in smooth segments of affected coronary arteries. Substance P was infused over 2 mm with a starting dose of 1.4 pmol/min and a maximum of 22.4 pmol/mm, reached by doubling the dose in steps, followed by an infusion of 2 mg isosorbide dmitrate over 2 mm.Results
Substance P caused less vasodilation at lower concentrations, with a significantly higher dose required to achieve half maximal dilation compared with cardiac transplant recipients with no coronary disease. The mean maximal dilation achieved with substance P was 22.98 ± 4.62% compared to 21.95 ± 4.9% with isosorbide dmitrate; the latter value was not significantly different from the maximal dilation achieved in cardiac transplant recipients without coronary disease.Conclusions
In cardiac transplant recipients with accelerated coronary disease the functional vasodilatory ability of the coronary endothelium is impaired in segments of apparently unaffected epicardial arteries, which may lead to an increase in the resting vasoconstrictor tone and have important functional and therapeutic implications.