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Aims: Presentation with an acute coronary syndrome (ACS) on chronic aspirin therapy is an independent predictor of adverse short-term outcomes. Whether this finding applies to chronic thienopyridine use, and with the contemporary invasive management of ACS, is unknown., Methods and Results: In ACUITY, 13819 patients with moderate and high-risk ACS were studied; patients transferred from an outside hospital were excluded from the present analysis, given uncertain preadmission antiplatelet status. Endpoints included major adverse cardiovascular events (MACE: death, myocardial infarction, or unplanned revascularization), major bleeding, and net adverse clinical events (NACE). Among 11313 study patients, 31 % were naive for antiplatelet agent, 49% were receiving aspirin alone, and 20% were on dual antiplatelet therapy. Chronic antiplatelet users were older and had a higher risk profile. After adjusting for baseline differences, chronic antiplatelet therapy (single or dual) was not associated with an increased incidence of 30-day MACE, bleeding, or NACE. However, patients on chronic aspirin or dual antiplatelet therapy at presentation had significantly higher 1-year rates of MACE [odds ratio (95% confidence interval) = 1.17 (1.01–1.36), P = 0.03 and 1.29 (1.02–1.64), P = 0.03, respectively]. Patients presenting on dual antiplatelet therapy had significantly greater adjusted MACE at 1-year than those on aspirin alone [odds ratio (95% confidence interval) = 1.34 (1.15–1.56), P < 0.0001]., Conclusion: Contrary to earlier studies, prior antiplatelet therapy was not associated with an increased risk of adverse outcomes at 30 days in invasively managed patients. Such use did, however, independently predict 1-year ischemic MACE, with outcomes worse for patients presenting on chronic dual antiplatelet therapy compared with aspirin alone.

Aims: Brief episode(s) of ischaemia may increase cardiac tolerance to a subsequent major ischaemic insult ('preconditioning'). Nitrates can pharmacologically mimic ischaemic preconditioning in animals. In this study, we investigated whether antecedent nitrate therapy affords protection toward acute ischaemic events using data from the Global Registry of Acute Coronary Events., Methods and Results: The dataset comprised 52,693 patients from 123 centres in 14 countries: 42,138 (80%) were nitrate-naïve and 10,555 (20%) were on chronic nitrates at admission. In nitrate-naïve patients, admission diagnosis was ST-segment elevation myocardial infarction (STEMI) in 41%, whereas 59% presented with non-ST-segment elevation acute coronary syndrome (NSTE-ACS). In contrast, only 18% nitrate users showed STEMI, whereas 82% presented with NSTE-ACS. Thus, among nitrate users clinical presentation was tilted toward NSTE-ACS by more than four-fold, STEMI occurring in less than one of five patients (P < 0.0001). After adjustment (age, sex, medical history, prior therapy, revascularization, previous angina), chronic nitrate use remained independent predictor of NSTE-ACS (OR 1.36; 95% CI 1.26-1.46; P < 0.0001). Furthermore, regardless of presentation, within both STEMI and NSTEMI populations, antecedent nitrate use was associated with significantly lower levels of CK-MB and troponin (P < 0.0001 for all)., Conclusion: In this large multinational registry, chronic nitrate use was associated with a shift away from STEMI in favour of NSTE-ACS and with less release of markers of cardiac necrosis. These findings suggest that in nitrate users acute coronary events may develop to a smaller extent. Randomized, placebo-controlled trials are warranted to establish whether nitrate therapy may pharmacologically precondition the heart toward ischaemic episodes.