Thoracic sarcopenia measured by Hounsfield unit average calculation predicts morbidity and mortality in coronary artery bypass grafting

OBJECTIVES The aim of the study was to investigate the potential prognostic role of preoperative measurement of erector spinae myosteatosis with Hounsfield unit average calculation as a marker for sarcopenia and frailty in patients undergoing coronary bypass surgery. METHODS Preoperative computer tomography-derived measurements of 479 consecutive patients undergoing coronary bypass surgery between January 2017 and December 2019 were retrospectively performed. The erector spinae muscle at the level of the 12th vertebra was manually outlined bilaterally on the axial computer tomography slices and Hounsfield unit average calculation was performed. The lower quartile of muscle density values was defined as myosteatotic and thus sarcopenic. Sarcopenic (n = 121) versus non-sarcopenic patients (n = 358) were compared regarding postoperative morbidity and short- and long-term mortality. Results were adjusted for age, body mass index, atrial fibrillation and hypertension using inverse probability weighting. RESULTS Sarcopenia was associated with higher 30-day mortality (4.1% vs 0.8%; P = 0.012), mid-term mortality after 1 year (9.3% vs 3.1%; P = 0.047) and 2 years (10.8% vs 4.2%; P = 0.047). Long-term mortality (5 years) was 20.8% for sarcopenic and 13.0% for non-sarcopenic patients but was not found to be significantly different (P = 0.089). Sarcopenia was associated with higher rates of reintubation (7.5% vs 1.1%; P < 0.001), sternal wound infections (7.5% vs 2.8%; P = 0.039) and acute kidney injury requiring haemodialysis (2.5% vs 0.4%; P = 0.021). CONCLUSIONS In patients undergoing coronary bypass surgery, sarcopenia was associated with increased short-term mortality, mid-term mortality and morbidity. The measurement of erector spinae myosteatosis could be an easy and useful parameter in preoperative risk assessment.