Attenuated severity of new acute ischemic events in patients with previouscoronary heart disease receiving long-acting nitrates

Background: Platelet aggregation and secondary vasoconstriction are key eve nts in the genesis of acute coronary syndromes. Hypothesis: Since nitrates have vasodilatory and antiaggregant effects, tre atment with long-acting nitrates at the time of onset of acute coronary syn dromes could be associated with attenuation of their severity. Methods: A consecutive series of 533 patients with acute coronary syndrome and past history of coronary artery disease admitted to the Cardiology Serv ice of a general hospital was studied. A specific questionnaire assessed th e use of nitrates and other relevant drugs, as well as other clinical varia bles. The diagnosis of unstable angina or acute myocardial infarction (MI) was established according to clinical, electrocardiographic, and enzymatic criteria. Results: In the whole cohort, 169 patients had MI and 364 had unstable angi na. Previous use of long-acting nitrates was significantly more common in p atients with unstable angina (56%) than in those with MI (37%) (p < 0.0001) . Multivariate analysis identified being a nonsmoker [odds ratio: 95%, conf idence limits (CL) 0.37, 0.23-0.59], previous unstable angina (CL 0.62, 0.4 1-0.92), use of aspirin (CL 0.58, 0.41-0.92), and use of long-acting nitrat es (CL 0.61, 0.4-0.93) as the independent predictors of the development of unstable angina rather than MI; of these the combination of nitrates and as pirin was the strongest predictor. Conclusions: Long-acting nitrates as well as aspirin are suggested to have a protective or modifying effect on the development of acute coronary syndr omes, favoring unstable angina rather than acute MI.