Clinical Significance of Postinfarct Fever in ST‐Segment Elevation Myocardial Infarction: A Cardiac Magnetic Resonance Imaging Study

Background Little is known about causality and pathological mechanism underlying association of postinfarct fever with myocardial injury in patients with ST ‐segment elevation myocardial infarction. Methods and Results In 276 patients undergoing primary percutaneous coronary intervention for ST ‐segment elevation myocardial infarction, cardiac magnetic resonance imaging was performed a median of 3.4 days after the index procedure. Forty‐five patients had postinfarct fever (peak body temperature within 4 days after primary percutaneous coronary intervention ≥37.7°C; Fever group) whereas 231 did not (no‐Fever group). Primary outcome was myocardial infarct size as assessed by cardiac magnetic resonance imaging. Secondary outcomes were extent of area at risk, myocardial salvage index, and microvascular obstruction area. In cardiac magnetic resonance imaging analysis, myocardial infarct size (25.6% [19.7–32.4] in the Fever group versus 17.2% [11.8–25.4] in the no‐Fever group; P <0.01), extent of area at risk (43.7% [31.9–54.9] versus 35.3% [24.0–43.7]; P <0.01), and microvascular obstruction area (4.4% [0.0–13.2] versus 1.2% [0.0–5.1]; P =0.02) were greater in the Fever group than in the no‐Fever group. Myocardial salvage index tended to be lower in the Fever group compared to the no‐Fever group (37.7 [28.5–56.1] versus 47.0 [34.1–56.8]; P =0.13). In multivariate analysis, postinfarct fever was associated with larger myocardial infarct (odds ratio, 3.48; 95% CI , 1.71–7.07; P <0.01) and lower MSI (odds ratio, 2.10; 95% CI , 1.01–4.08; P =0.03). Conclusions Postinfarct fever could predict advanced myocardial injury and less salvaged myocardium in ST ‐segment elevation myocardial infarction patients undergoing primary percutaneous coronary intervention.