Determinants of Improvement in Ejection Fraction and Impact on Mortality After Coronary Artery Bypass Grafting for Ischemic Cardiomyopathy

Purpose: Coronary artery bypass grafting (CABG) has been shown to improve outcomes in patients with ischemic cardiomyopathy. Data on improvement in left ventricular ejection fraction (LVEF) after CABG, its impact on late survival, and preoperative predictors of LVEF improvement are limited.

Methods: We reviewed and analyzed a total of 839 patients with severe left ventricular dysfunction (≤35%) undergoing isolated CABG at our institution between January 2003 and December 2020. Late survival was estimated using Kaplan-Meier analysis and competing risk analysis accounting for risk of death was used to estimate incidence of revascularization over follow-up. Logistic regression was used to determine independent predictors associated with LVEF improvement postoperatively. Cox proportional hazards regression models were used to identify factors associated with late mortality and evaluate the association of mortality with increase in LVEF postoperatively by at least 25% of preoperative LVEF.

Results: Median age of the study cohort was 68 [IQR 60-76] years, and 79.7% (n=669) were male. Prior history of CABG was seen in 4.9% (n=41) and a prior PCI in 26% (n=218) patients. Operative mortality was 3.9% (n=33). Over a median follow-up period of 10.6 [IQR 5.7-15.2] years, there were a total of 455 deaths. Survival at 1, 5, and 10 years was 89.6%, 72.3%, and 43.5% respectively. Over follow-up, 72 patients required repeat revascularization (PCI or CABG) and cumulative incidence of revascularization accounting for risk of death at 5 and 10 years was 7.7% and 10.4% respectively. A total of 405 (48.3%) patients had post-dismissal echocardiographic evaluation within one-year (median [IQR] 146 [93-259] days) and follow-up of more than one-year; among these 227 (56%) showed an increase in LVEF by at least 25% of preoperative LVEF within the first year. Increase by at least 25% of preoperative LVEF within one-year was independently associated with significantly lower long-term mortality risk (adjusted HR 0.49 [95% CI 0.35-0.72]; p< 0.001, Table). Lower preoperative LVEF and female sex were independently associated with postoperative improvement in LVEF whereas history of revascularization, and preoperative moderate/severe LV dilatation were associated with lower odds of LVEF improvement.

Conclusion: Early and late outcomes after CABG appear satisfactory in patients with ischemic cardiomyopathy. An improvement in LVEF within one-year after CABG by at least 25% of preoperative LVEF was associated with significantly lower long-term mortality risk. Lower preoperative LVEF and female sex were independently associated with postoperative improvement in LVEF.

Identify the source of the funding for this research project: No funding.