CORONARY ENDOTHELIAL FUNCTION IN CARDIAC TRANSPLANT RECIPIENTS WITH ACCELERATED CORONARY-DISEASE

Background: Previous studies with the endothelium-dependent vasodilato r substance P have shown a preserved vasodilator response in cardiac t ransplant recipients with angiographically normal coronary arteries. A lthough endothelial dysfunction is known to occur in cardiac transplan t recipients with accelerated coronary disease, the degree to which th e endothelium is affected is not known precisely. The aim of the prese nt study was to examine endothelial function in accelerated coronary d isease following cardiac transplantation. Methods: Thirteen cardiac tr ansplant recipients with epicardial coronary disease underwent substan ce P infusion. The response to incremental doses of substance P was me asured in smooth segments of affected coronary arteries. Substance P w as infused over 2 min with a starting dose of 1.4 pmol/min and a maxim um of 22.4 pmol/min, reached by doubling the dose in steps, followed b y an infusion of 2mg isosorbide dinitrate over 2 min. Results: Substan ce P caused less vasodilation at lower concentrations, with a signific antly higher dose required to achieve half maximal dilation compared w ith cardiac transplant recipients with no coronary disease. The mean m aximal dilation achieved with substance P was 22.98+/-4.62% compared t o 21.95+/-4.9% with isosorbide dinitrate; the latter value was not sig nificantly different from the maximal dilation achieved in cardiac tra nsplant recipients without coronary disease. Conclusions: In cardiac t ransplant recipients with accelerated coronary disease the functional vasodilatory ability of the coronary endothelium is impaired in segmen ts of apparently unaffected epicardial arteries, which may lead to an increase in the resting vasoconstrictor tone and have important functi onal and therapeutic implications.