Operative Mortality in Coronary Artery Bypass Surgery
The operative mortality for isolated CABG surgery ranges from 1.6% to 2.8% in contemporary practice, with rates varying significantly based on patient age, comorbidities, and institutional volume. 1
Contemporary Mortality Rates
Overall Population
- Isolated CABG mortality: 1.6% to 2.8% for patients aged 50-79 years 1
- 30-day mortality: 1.46% in recent large cohort studies 2
- In-hospital mortality: 2.2% to 2.7% across U.S. hospitals (2008-2012) 3
The Society of Thoracic Surgeons (STS) database reports an average perioperative mortality of 3.0% to 4.0% for isolated AVR and 5.5% to 6.8% for AVR plus CABG, though these figures include valve surgery 1. For isolated CABG specifically, contemporary data demonstrates lower mortality rates of approximately 1.9% 2, 3.
Age-Stratified Mortality
Mortality increases substantially with advancing age 1:
- Ages 50-79 years: 2.8% 1
- Ages 80-89 years: 7.1% 1
- Ages ≥90 years: 11.8% overall, but only 7.2% in nonagenarians without high-risk factors (renal failure, IABP requirement, emergency surgery, or peripheral/cerebrovascular disease) 1
Historical data from Toronto Hospital showed operative mortality declining from 7.2% (1982-1986) to 4.4% (1987-1991) in patients over 70 years, with minimal further improvement through 1996 1.
Risk-Stratified Outcomes
Low-Risk Patients
A multi-institutional STS database analysis identified that patients with predicted risk of mortality (PROM) ≤1.27% can achieve the aspirational goal of 1.0% operative mortality 4. This threshold encompasses approximately 57% of CABG patients 4.
High-Risk Patients
The STS PROM calculator demonstrates limited predictive capacity for patients with estimated risk >25%, where observed mortality begins to diverge from expected mortality 4.
Gender Differences
Women experience significantly higher operative mortality than men (4.60% vs 2.53%, p<0.0001), even after adjustment for preoperative risk factors 5. Multivariate analysis confirms women have an odds ratio of 1.61 (95% CI 1.40-1.84) for operative mortality compared to men 5. This persists despite women being less likely to receive internal mammary artery grafts and more likely to present with diabetes, chronic kidney disease, and nonelective surgery 5.
Emergency CABG After Failed PCI
Emergency CABG following failed PCI carries substantially higher mortality 1:
Risk factors for requiring emergency CABG include cardiogenic shock (OR 11.4), acute MI or emergency PCI (OR 3.2-3.8), multivessel disease (OR 2.3-2.4), and type C lesions (OR 2.6) 1.
Long-Term Mortality Perspective
While operative mortality is the immediate concern, long-term outcomes reveal 6:
- 30-day mortality: 3.2% (13.5-fold higher than general population)
- 1-year mortality: 2.9% (similar to general population at 2.4%)
- 10-year mortality: 30.7% (modestly higher than general population at 25.8%)
- 20-year mortality: 51.1% (substantially higher than general population at 35.6%)
Key Predictors of Mortality
The strongest predictor of post-CABG mortality is preoperative estimated glomerular filtration rate (eGFR) <46.9 mL/min/1.73m², followed by logistic EuroSCORE ≥2.4 2. Additional independent predictors include 2:
- Older age
- Lower body mass index
- Diabetes mellitus
- Chronic obstructive pulmonary disease
- Preoperative renal failure requiring dialysis
- Heart failure
- Lower left ventricular ejection fraction
- NYHA class II-IV symptoms
Institutional Volume Effect
Mortality rates are 33% higher in low-volume centers compared to high-volume centers 1. Medicare data from 684 U.S. hospitals demonstrates average in-hospital mortality of 8.8% for patients over 65 years (13.0% in low-volume vs 6.0% in high-volume centers) 1.
Common Pitfalls
The most common in-hospital complication is postoperative hemorrhage (30.4%), which showed a 35.8% relative increase from 2008 to 2012 despite declining rates of cardiac, respiratory, and infectious complications 3. This necessitates heightened attention to bleeding risk stratification and management strategies.