Influence of smoking status on angiotensin-converting enzyme inhibition-related improvement in coronary endothelial function

Our study evaluated the influence of smoking status on coronary endothelial function in normotensive patients with coronary artery disease who received placebo or the angiotensin-converting enzyme inhibitor quinapril in the TREND study (Trial on Reversing Endothelial Dysfunction). In this retrospective analysis of data from the previously published study, patients were classified as either smokers (n = 23) or nonsmokers (n = 82). Patients underwent coronary angiography at baseline and again after 6 months follow-up. The primary response variable was the net change in acetylcholine-induced diameter of the target coronary artery segments (n = 105) between the baseline and 6-month follow-up angiograms. The secondary response variables were based on analysis of all segments (n = 300) and the mean diameter responses of target and all segments at 6 months. At baseline, coronary artery vasomotor responses were similar in smokers and nonsmokers in the placebo and quinapril groups. There was a significant improvement in the primary response variable for both smokers (P = 0.008) and nonsmokers (P = 0.047) randomized to quinapril compared with placebo. At 6 months follow-up, nonsmokers in the placebo group showed no significant change in the mean vasoconstrictor responses (8.3% vs. 8.0% at acetylcholine 10(-4) mol/L), whereas nonsmokers in the quinapril-treated group showed significantly less vasoconstriction (2.7% vs. 13.2%; P = 0.003). Among smokers in the placebo group, vasoconstriction increased nonsignificantly (21.7% vs. 17.2% at baseline) but decreased significantly in the quinapril group (0.5% vs. 17.9%; P = 0.002). These results indicate that ACE inhibition improves the coronary vasomotor response in both smokers and nonsmokers, but that smokers apparently derive greater benefit.