Pre-operative risk assessment for coronary artery bypass surgery (CABG) has been evaluated with multiple predictive models; yet none incorporate low cardiorespiratory fitness as a risk factor. The present study evaluates pre-operative metabolic equivalents (METs) and short term morbidity and mortality after CABG.
Patients undergoing CABG from January 2002 to December 2010 at Beaumont Health Systems were reviewed for peak or symptom-limited stress testing < 90 days prior to surgery. METs were estimated from the achieved treadmill speed, grade, and duration, or the cycle ergometer workload corrected for body weight.
596 patients were categorized into 2 groups: those with low aerobic capacity (<5 METs); and those achieving = 5 METs. Fisher's exact tests compared pre-operative aerobic capacity and post-operative morbidity and mortality between the two groups (Table 1). After adjusting for potential confounding variables, we found an inverse relationship between cardiorespiratory fitness and complications after CABG.
Low pre-operative cardiorespiratory fitness was associated with higher operative mortality, 30 day mortality, sternal wound infections, and prolonged ventilation after CABG. These data suggest that pre-operative cardiorespiratory fitness provides an independent and additive marker of prognosis after CABG that has not been previously reported.