Impact of preoperative intravenous nitroglycerin on in-hospital outcomes after coronary artery bypass grafting for unstable angina

Abstract

Background Intravenous nitroglycerin (NTG) is an effective therapy for unstable angina (UA), but it may induce endothelial dysfunction and impair vascular nitric oxide signaling. We sought to determine whether preoperative intravenous NTG administration alters in-hospital outcomes in patients undergoing coronary artery bypass grafting (CABG) for UA. Methods and results All in-hospital patients with Canadian Cardiovascular Society class IV angina who had isolated CABG between March 1995 and July 2002 at two Canadian centers were identified (n = 3976). Of these, 2506 were not receiving intravenous NTG and 1470 were receiving intravenous NTG at the time of CABG. Outcomes assessed were in-hospital mortality (IHM), intraoperative or postoperative aortic balloon pump use, perioperative myocardial infarction, prolonged (≥24 hours) ventilation (p-vent), and a composite outcome, defined as any one or more of the above. Unadjusted IHM (5.9% vs 4.2%, P = .02), p-vent (22.2% vs 10.5%, P = .0001), and composite outcome (26.5% vs 15.2%, P = .0001) were higher in patients receiving intravenous NTG. Logistic regression showed that preoperative intravenous NTG was not an independent predictor of composite outcome (OR, 1.1; P = .49) or IHM (OR, 0.94; P = .69). Propensity score analysis was used to match two subgroups of patients (group 1, intravenous NTG, n = 1176; group 2, no intravenous NTG, n = 1176) on multiple factors. After adjustment with the propensity score, preoperative intravenous NTG use had no significant effect on any of the outcomes assessed. Conclusions Despite its potential to induce endothelial dysfunction and impair vascular nitric oxide signaling, preoperative intravenous NTG administration is not associated with altered in-hospital outcomes after CABG for UA.