Morphine and P2Y12 Inhibitors in ST-Elevation Myocardial Infarction: An Updated Meta-Analysis

Background: Morphine is used to control pain in ST-elevation myocardial infarction but reduces P2Y12 inhibition. It is not known if this modulation of platelet inhibition appreciably affects clinical outcomes. Methods: We screened 979 articles and identified seven studies that met the eligibility criteria for meta-analysis. Outcomes included 11 metrics across angiographic and clinical domains. A random effects model assessed heterogeneity between studies. Results: The opiate group showed decreased achievement of postprocedural thrombolysis in myocardial infarction (TIMI) 2 flow relative to placebo [risk ratio (RR) 0.71, 95% confidence interval (CI) 0.52–0.97, p = 0.03, I² = 0.0%]. All other metrics listed below showed no statistically significant difference between groups: infarct size, microvascular obstruction, microvascular/salvage index, absence of pre- percutaneous coronary intervention (PCI) TIMI 3 flow, postprocedural TIMI 2 flow, postprocedural TIMI 3 flow, all-cause mortality, stroke, repeat MI, unstable angina, and left ventricular ejection fraction. However, there were no statistically significant differences in infarct size [odds ratio (OR) − 0.12, 95% CI − 0.37 to 0.17, p = 0.42], microvascular obstruction [standard mean difference (SMD) = 0.02, 95% CI − 0.12 to 0.16, p = 0.82], microvascular obstruction/salvage index (SMD = − 0.05, 95% CI − 0.24 to 0.13, p = 0.57), absence of pre-PCI TIMI 3 flow (OR 0.98, 95% CI 0.79–1.22, p = 0.87), and postprocedural TIMI 3 flow (OR 1.23, 95% CI 0.84–1.79, p = 0.28) between the two groups. Conclusions: In STEMI, opiates correlate with worse angiographic outcomes, specifically postprocedural TIMI 2 flow. However, this observation does not appear to be clinically consequential.