Prognostic implications of procedural vs spontaneous myocardial infarction: Results from the Evaluation of Drug Eluting Stents and Ischemic Events (EVENT) registry

Background In randomized clinical trials, procedural myocardial infarction (MI) or spontaneous MI is often weighted equally as a component of a composite clinical end point. An underlying assumption of this approach is that procedural and spontaneous MIs have similar prognostic impact. Our aim was to evaluate the prognostic impact of procedural vs spontaneous MI in patients undergoing percutaneous coronary intervention (PCI). Methods We used data from the EVENT registry to examine the relative prognostic impact of procedural vs spontaneous MI. For the purposes of this study, patients undergoing initial PCI were stratified into 3 groups-no MI, procedural MI, or spontaneous MI-based on standard definitions applied at the time of the index procedure and followed for 1 year for outcomes of all-cause mortality and cardiovascular mortality. Multiple propensity score adjustment analysis was used to adjust for differences in baseline covariates among the 3 groups. Results Among 7,380 patients included in this analysis, 4,568 (62%) patients had no MI, 580 (8%) patients had procedural MI at the time of their index procedure, and 2,232 (30%) patients presented with a spontaneous MI before PCI. In unadjusted analyses, there was a graded increase in risk of 1-year mortality (1.9% vs 3.1% vs 3.9%; P < .0001) and cardiovascular death (0.5% vs 1.0% vs 1.7%; P < .0001) across the 3 groups. After adjusting for propensity scores, spontaneous MI (adjusted hazard ratio [HR] 1.62, 95% CI 1.11-2.37, P = .01) but not procedural MI (adjusted HR 1.51, 95% CI 0.89-2.54, P = .12) was independently associated with death at 12 months when compared with the no-MI group. Findings were similar when the analysis was limited to cardiovascular death (adjusted HRs 3.14 [95% CI 1.68-5.90, P < .001] and 1.74 [95% CI 0.69-4.40, P = .24], respectively). Conclusions Among patients undergoing PCI, spontaneous but not procedural MI was independently associated with death and cardiovascular death at 1 year. These finding suggest that the prognostic impact of procedural MI may be less than that of spontaneous MI and should be considered in designing end points for future studies of coronary revascularization.