Background: Patients with a history of occlusion myocardial infarction (prior-OMI) are at increased risk of recurrent cardiovascular events, including reinfarction and sudden cardiac death. These outcomes may be influenced by the prior myocardial injury (“pre-conditioning”) as well as suboptimal secondary prevention. However, data on long-term mortality and outcomes in patients presenting with ST-segment elevation myocardial infarction (STEMI) who have a history of OMI remain limited.
Objective: To determine the impact of prior-OMI on long-term mortality in STEMI patients.
Methods and Results: This retrospective study included 1,787 STEMI patients treated with primary percutaneous coronary intervention (PPCI) in a clinical cohort and 21,075 STEMI patients from health insurance claims data. In the clinical cohort, 241 patients (11.9%) had a prior-OMI, while in the insurance claims cohort 1,822 patients (8.7%) had prior-OMI. In the latter cohort, the prior-OMI patients (1,232 STEMI and 590 non-ST-segment elevation myocardial infarction [NSTEMI] as index events) were propensity-score matched to 1,822 STEMI patients without a history of OMI for the analysis.
In the clinical cohort, patients with prior-OMI were older, had worse renal function, a higher prevalence of hypertension, reduced systolic left ventricular ejection fraction, and showed an increased risk of 3-year mortality (Hazard Ratio [HR]=2.04; 95% Confidence Interval [CI] 1.45–2.86; p<0.005). In a subset of patients (n=1,206 patients), serial single-photon emission computed tomography imaging was available. Prior-OMI patients had a larger final infarct size (median of the left ventricle (%): 16.7%, Interquartile Range [IQR 6.0–28.0%] vs. 9.0% [IQR 2.0–22.0%], p<0.005) and a lower myocardial salvage index (median: 0.35 [IQR 0.11–0.63] vs. 0.53 [IQR 0.27–0.82], p<0.005).
Consistent with the clinical cohort, health insurance claims data revealed that patients with prior-OMI had a higher risk of 3-year mortality (HR=1.19; 95% CI 1.06–1.34; p<0.005). Subgroup analysis revealed that STEMI patients with a history of prior STEMI did not have increased mortality compared to first-MI patients (HR=0.98; 95% CI 0.84–1.15; p=0.83), while STEMI patients with a history of NSTEMI presented higher mortality (HR=1.60; 95% CI 1.32–1.95; p<0.005). A direct comparison between STEMI patients with prior-NSTEMI and prior-STEMI further confirmed worse outcomes in prior-NSTEMI patients (HR=1.46; 95% CI 1.20–1.77; p<0.005).
Conclusion: STEMI patients with a history of OMI had larger infarcts, reduced myocardial salvage, and higher 3-year mortality. Notably, patients with a prior NSTEMI experienced worse outcomes after STEMI than those with a prior STEMI, highlighting the need for further investigation of this high-risk subgroup.
