Age is a strong predictor of spontaneous myocardial infarction in medically managed patients

Renato Lopes
Renato Lopes

Renato D Lopes (Division of Cardiology, Department of Medicine, Duke University School of Medicine, Duke Clinical Research, Durham, USA) and others report in the Journal of the American College of Cardiology that certain baseline characteristics, such as age, can be used to predict the risk of spontaneous myocardial infarction in patients with non-ST-segment elevation acute coronary syndrome who have not undergone revascularisation.

Lopes et al report that medically managed patients with non-ST-segment elevation acute coronary syndrome are at increased risk of subsequent spontaneous myocardial infarction compared with those who have received revascularisation. They add: “A study observed spontaneous myocardial infarction is perceived by patients as being equally important as death or stroke.” However, they note that the “frequency and predictors of such events in this setting have not been delineated”. Therefore, the authors comment: “We sought to comprehensively characterise patients with spontaneous myocardial infarction events during long-term follow-up through 30 months to develop a prediction model for time to first spontaneous myocardial infarction event.”

Using data from the TRILOGY ACS (Targeted antiplatelet inhibition to clarify the optimal strategy to medically manage acute coronary syndrome), which compared the use of aspirin plus prasugrel (Efient, Daiichi Sankyo) with aspirin plus clopidogrel (Plavix, Bristol-Myers Squibb and Sanofi Aventis) for the medical management of acute coronary syndromes, Lopes et al assessed the time to first spontaneous myocardial infarction during 30 months of follow-up and used these results to develop a prediction model. They report that among 9,294 patients in the study, 695 spontaneous myocardial infarction events occurred over a median 17 months which they say represented “94% of adjudicated myocardial infarction events” (737 events in total). “Our results add to a growing body of evidence indicating that spontaneous myocardial infarction is a common and clinically important event following acute coronary syndrome,” Lopes et al comment. They add that a registry study of 8,582 patients who underwent successful percutaneous coronary intervention (PCI) with a drug-eluting stent reported an incidence of spontaneous myocardial infarction of 4.1% among the 4,205 patients who presented with acute coronary syndrome—“much lower than the incidence than we observed in our analysis”.

The authors state: “In general, patients who developed subsequent myocardial infarction were older, had more comorbidities, presented more commonly with non-ST-segment elevation myocardial infarction (NSTEMI)—rather than unstable angina—and received more medications at discharge, suggesting a perceived higher risk of cardiovascular events.” However, the final multivariable prediction model for a first spontaneous myocardial infarction event included 17 variables (with age, NSTEMI, and diabetes being the top three variables). According to Lopes et al, the model’s ability to distinguish patients who had an event from those who did not was good, with a Harrell’s c index of 0.732. “Meaning that the probability of concordance between predicted and observed response is 73.2%,” they explain.

Lopes et al conclude: “Our findings provide unique insights into the long-term natural history of medically managed unstable angina/NSTEMI patients and may help inform clinical practice and the design of clinical trials evaluating novel acute coronary syndromes for this under-studied populatuion.”

Lopes told Cardiovascular News: “We were able to construct a new predictive model for physicians that provides real-time and individualised time-varying risk estimates on the basis of key variables. This is a well-developed, very good predictive model, not just for patients who are at high risk of a heart attack, but particularly for low- and intermediate-risk patients. Now it is just a question of familiarising physicians with the tool.”