Gradual Oxygen Exposure During Coronary Bypass for Acute Myocardial Infarction: A Retrospective Cohort Study

This study aimed to analyze the effect of venous vs arterial blood cardioplegia and gradual oxygen exposure during emergency bypass surgery for acute myocardial infarction (MI) and to determine its causal impact on mortality, ventricular function, readmission, and defibrillator requirement in consecutive patients.

This is a retrospective cohort study, reviewing the records of patients with acute MI brought directly to surgery during 8 years at a single center. Tabular analyses were undertaken, followed by logistic regression analysis adjusting for shock, preoperative left ventricular ejection fraction (LVEF), diabetic status, and status of ST-segment MI. Post-acute MI, post-surgery LVEF was analyzed in both groups.

After screening of 113 charts, the analysis included 21 of 66 patients displaying hemodynamic instability or overt shock. Crude mortality was lower in treated vs control patients (2.4% vs 16%; risk ratio [RR], 0.15; 95% CI, 0.02-1.29; P = .049). If cardiogenic shock was present, mortality was (7.1% vs 42.9%; RR, 0.17; 95% CI, 0.018-0.98; P = .015). Readmission for heart failure was 12.2% vs 40.0% (RR, 0.30; 95% CI, 0.12-0.79; P = .009), and requirement for automatic implantable cardioverter-defibrillator was 4.9% vs 20% (RR, 0.24; 95% CI, 0.051-1.16; P =.053). Left ventricle functional profiles showed improvement in LVEF in the treated compared with the untreated patients (+9.5; 95% CI, +2.7-+16.3; P = .007).

Early, purposeful deoxygenated blood cardioplegia administration was safe and led to improved mortality, decreased readmission for any heart failure, the requirement for an implantable defibrillator, and better ventricular recovery.