The APEX trial: Effects of allopurinol on exercise capacity, coronary and peripheral endothelial function, and natriuretic peptides in patients with cardiac syndrome X

Abstract

This study was a randomized, double-blind, placebo-control crossover trial. Nineteen patients (mean age 59±10years, 11 women and 8 men) with cardiac syndrome X were randomized to a 6-week treatment with either allopurinol (600mg/day) or placebo. After 4weeks of washout period, they were crossed over to the other arm. Outcomes measured at baseline and after treatment were maximum exercise time (ET) derived from Bruce protocol exercise treadmill test, serum BNP measurement, coronary flow reserve (CFR) as assessed by measuring the response of flow velocity in the left anterior descending artery to adenosine, and flow-mediated vasodilatation of the brachial artery (FMD). Allopurinol significantly reduced serum uric acid levels when compared with placebo (-48±24% vs 1.9±11%, P<.001). There was no significant difference in maximum ET, CFR, and FMD between allopurinol and placebo. However, there was a trend that allopurinol reduced serum BNP when compared to placebo (-8% [interquartile range -22% to 65%] vs 44% [interquartile range -18% to 140%]; P=.07). In patients with cardiac syndrome X, high-dose allopurinol did not improve exercise capacity, and coronary or peripheral endothelial function.