Coronary microvascular endothelial dysfunction in transplanted children.
AIMS: To assess the response of the coronary microcirculation to acetylcholine (endothelium-dependent vasodilator) and of adenosine (endothelium-independent vasodilator) in children after heart transplantation and to verify whether endothelial dysfunction is time-dependent. METHODS AND RESULTS: We studied the endothelial function of 26 asymptomatic children previously submitted to heart transplantation, with normal transplanted hearts and epicardial coronary arteries. Ten untransplanted children served as controls. The response of coronary blood flow velocity to intracoronary infusion of acetylcholine (1.8 microg x min(-1)) and adenosine (270 microg x min(-1)) was assessed using a Doppler wire positioned in an epicardial coronary branch. In the study group, coronary blood flow velocity increased slightly during acetylcholine infusion (peak/baseline ratio=1.17+/-0.22). The ratio was inversely correlated with the length of follow-up (r=-0.50;P=0.0078). The peak/baseline ratio in control children was 1.76+/-0.73 (P<0.0002 vs. study group). After adenosine infusion, the coronary blood flow velocity peak/baseline ratio was 3.75+/-1.54 in transplanted children and 3.72+/-1.34 in controls (P=ns). CONCLUSIONS: Endothelial dysfunction in paediatric transplanted patients becomes more evident in patients with longer follow-up. This finding could prove useful in the prevention of accelerated arteriosclerosis.