512 Impact of Nitrate Use in the Emergency Department on Mortality in Patients With Acute Heart Failure

Abstract

Despite the widespread use of nitrates (NTG) in patients with acute heart failure syndromes (AHFS) early after presentation to hospital, there is limited evidence of any beneficial effect on clinical outcomes. To identify whether early NTG exposure is associated with improved survival in patients with AHFS. We examined patients who presented to an emergency department (ED) in Ontario between 2004-2007, who were enrolled in either the Enhanced Feedback For Effective Cardiac Treatment study or the Emergency Heart failure Mortality Risk Grade study. We compared the clinical characteristics of patients who were treated with vs. without NTG as oral, transdermal, or intravenous routes of delivery, in the ED. We performed a propensity-matched analysis to evaluate mortality at 7, 30, 90 and 365 days in those who were administered early NTG vs. no acute therapy. Sensitivity analyses were performed in 4 subgroups: those with vs. without elevated serum troponin, and those with vs. without prior history of coronary artery disease. A total of 11,078 patients (mean age 75±12 years, 52% men) were studied, of whom 28.5% received NTG in the ED. Patients who were prescribed NTG in the ED were more likely to have presented with chest pain (22.3 vs. 16.5%, p<0.001) and more often had a history of coronary artery disease (58.1 vs. 47.6%, p<0.001). Patients prescribed NTG in the ED had higher heart rate (95±25 vs. 89±23 beats/min), higher respiratory rate (26±8 vs. 23±6 breaths/min), and lower oxygen saturation (92±8 vs. 94±6%), but had higher systolic blood pressure (160±31 vs. 148±27 mmHg) [all p<0.001]. The 30-day mortality rate was 5.9 vs. 4.8% (p=0.016) for those prescribed NTG vs. no NTG. In a propensity analysis of 2589 matched pairs, matching on 45 covariates, the adjusted hazards ratio [HR] for death was 1.11 (95%CI; 0.88-1.39, p=0.39) for no NTG vs. NTG. There was no effect of NTG in propensity-matched analyses stratified by troponin elevation present (HR 0.87, 95%CI; 0.41-1.82, p=0.71) or absent (HR 1.19, 95%CI; 0.87-1.61, p=0.28). Similarly, NTG effect was not significant in propensity-matched analyses stratified by known coronary artery disease present (HR 1.17, 95%CI; 0.79-1.74, p=0.42) or absent (HR 1.32, 95%CI; 0.79-2.22, p=0.30). In patients presenting to the ED with AHFS, early nitrate exposure was not associated with a reduction in mortality compared with no NTG. Stratification by serum troponin value or history of coronary artery disease did not yield different results.