Changes in ejection fraction after coronary artery bypass grafting for ischemic cardiomyopathy: Impact on survival and determinants of improvement.

Abstract

Coronary artery bypass grafting improves outcomes in patients with ischemic cardiomyopathy, but data on improvement in left ventricular ejection fraction after coronary artery bypass grafting, its impact on late survival, and predictors of left ventricular ejection fraction improvement are limited. We analyzed 679 patients with severe left ventricular dysfunction (≤35%) undergoing isolated coronary artery bypass grafting at our institution (2003-2020). Change in left ventricular ejection fraction after surgery and longitudinal trends in left ventricular ejection fraction over follow-up were analyzed using repeated left ventricular ejection fraction measurements. Using a generalized least squares model, an association of baseline factors with longitudinal changes in left ventricular ejection fraction was evaluated. An extended Cox proportional hazards regression model with serial left ventricular ejection fraction measurements incorporated as a time-dependent covariate was used to assess whether improvements in left ventricular ejection fraction affected long-term outcomes. Median age of the study cohort was 67.6 [interquartile range, 60-76] years, and 79.1% were male. Operative mortality was 2.2% (n = 15). After coronary artery bypass grafting, left ventricular ejection fraction improved by a median of 5 units (interquartile range, 0-12) at the initial prehospital dismissal assessment (P <.001). Over a median follow-up period of 10.5 (interquartile range, 5.7-15.0) years, lower preoperative left ventricular ejection fraction showed a strong initial improvement followed by a steady decline, whereas patients with higher preoperative left ventricular ejection fraction values had smaller initial but more sustained improvements in predicted left ventricular ejection fraction over time. History of revascularization, higher preoperative left ventricular end-diastolic dimension, and mitral valve regurgitation were important risk factors for impaired left ventricular ejection fraction outcomes, whereas younger age and extremes of older age were associated with improved left ventricular ejection fraction. Both male and female patients had early improvements in left ventricular ejection fraction after coronary artery bypass grafting, but only female patients had sustained improvement in predicted left ventricular ejection fraction over time. In adjusted analyses, postoperative improvement in left ventricular ejection fraction was independently associated with a lower risk of mortality (hazard ratio, 0.57 [95% CI, 0.41-0.79]; P <.001). An absolute increase in postoperative left ventricular ejection fraction by 18% was associated with a 43% reduced hazard for late mortality. Early and late outcomes after coronary artery bypass grafting appear satisfactory in patients with ischemic cardiomyopathy. Improvement in left ventricular ejection fraction after coronary artery bypass grafting was associated with significantly lower mortality risk. Younger age and female sex were independently associated with sustained postoperative improvements in left ventricular ejection fraction.