Early and late predictors of mortality following on-pump coronary artery bypass graft surgery in the elderly as compared to a younger population

Abstract

To identify independent factors associated with early (30-day) mortality and in surviving patients, identify factors for late (1-year) mortality following primary coronary artery bypass graft (CABG) surgery and to test the interaction with age. An analysis of a single centre's data contribution to the Society for Cardiothoracic Surgery in Great Britain and Ireland database was performed. Data on consecutive patients aged > or =75 years (n=659) and aged 60-74 years (n=3024) undergoing primary CABG surgery (1999-2005) were analysed. One-year mortality data were collected using the Office of National Statistics (ONS) tracking system. Factors associated with early and late mortality were identified using Cox regression; hazard ratios (HRs) and 95% confidence intervals (CIs) are presented. The proportion of patients aged > or =75 years increased by 10% over 5 years (2000-2005). One-year mortality in the elderly showed a significant linear decrease from 15% to 7% (p=0.01) while mortality in the younger cohort remained static at 2-4%. Early mortality in the elderly group was 5% compared to 1.8% in the younger group (p<0.001), while late mortality was 4.1% vs 1.8%, respectively (p<0.001). Factors independently associated with early mortality were age > or =75 years, HR 2.0 (95% CI 1.28, 3.11); female gender; angina (CSS III-IV); and cardiopulmonary bypass duration >97 minutes. Arrhythmia and renal impairment were risk factors common in both early and late mortality models. Risk factors for late mortality also included ventricular ejection fraction <30%, non-elective surgery and arteriopathy. Age was not an independent risk factor for late mortality. Mortality in elderly patients showed a substantial improvement, but remained over twice that of younger patients. The difference in factors associated with early and 1-year morality suggests the need for effective short- and long-term strategies, particularly in the management of chronic diseases such as heart and renal failure.