Beyond all-cause mortality: reduction of coronary deaths after CABG - MASS Registry analysis

Background In clinical studies, the selection of endpoints faces challenges and indirect results may mislead their interpretation The use of all-cause mortality for the comparison of therapies in chronic coronary syndrome (CCS) patients have shown similar results, however, when mortality causes are depicted, noncardiac ones, that are not related to therapies, may interfere in the final results. Thus, a specific analysis of mortality causes in this population is needed to compare therapeutic strategies. Purpose The aim of this study is to analyze the cardiac and noncardiac mortalities in a CCS population with preserved left ventricular ejection fraction (LVEF) in a 10-year follow-up of medical (MT), percutaneous (PCI) or surgical (CABG) treatments. Methods Retrospective cohort of patients with multivessel CCS, preserved LVEF and presence of myocardial ischemia, treated by MT, PCI or CABG. The primary endpoint was cardiac or noncardiac death in 10 years, with all deaths revised and reclassified using hospitalization summaries, death certificates, autopsies, access to federal government database and family information, with deaths adjudication made by a blinded medical committee. Results The population comprised 1729 patients, 460 (27%) MT, 468 (27%) PCI, and 801 (46%) CABG. There were 558 deaths, 43% of them cardiac causes, while 47% of noncardiac ones. Regarding all-cause mortality, MT presented with 40%, PCI 28% and CABG 30% (p = 0.007). A trend of less cardiac mortality was observed in the CABG group (12%), while in the PCI and MT arms it was 14% and 17%, respectively (p = 0.1). In relation to noncardiac deaths, the MT group presented 19%, PCI 11% and CABG 15% (p = 0.01). In the multivariate analysis, only CABG was associated with a 31% reduction in cardiac mortality comparing to the MT arm – HR 0.69 (CI 95%, 0.50-0.94, p = 0.02), with a 53% reduction of fatal myocardial infarction (MI) – HR 0.47 (CI 95%, 0.31-0.72, p < 0.001). Surgery was associated with a 27% reduction of all-cause mortality – HR 0.73 (CI 95%, 0.60-0.89, p = 0.002); while PCI with a 28% reduction comparing to the MT arm – HR 0.72 (CI 95%, 0.57-0.90, p = 0.005), the last one due to a 39% of reduction in noncardiac deaths – HR 0.61 (CI 95%, 0.43-0.86, p = 0.005). Conclusion Coronary artery bypass surgery was associated with a reduction of cardiac mortality in CCS patients during a 10-year follow-up due to the reduction of fatal MI. The predominancy of noncardiac mortality, in the MT arm, enforces the complexity of mortality analysis to compare coronary treatment strategies.1