Phase Angle as a Reliable Biomarker of Frailty to Predict Postoperative Outcomes in Patients Undergoing Off-Pump Coronary Artery Grafting: A Prospective Observational Study

Objective: To elucidate the association between phase angle (PA) and a composite adverse outcome in patients requiring off-pump coronary artery bypass grafting (OPCAB). Design: A prospective observational study. Setting: High-volume single center. Participants: A total of 229 adult patients who underwent OPCAB from May 2019 to October 2020. Interventions: Each patient underwent bioelectrical impedance analysis, including PA assessment before surgery (PA_pre), immediately postoperatively (PA_post), and 1 day postoperatively (PA_POD1), using an Inbody S10. Frailty index and nutritional assessments also were obtained before surgery. Measurements and Main Results: Patient outcomes were assessed using a composite adverse outcome comprising death, myocardial infarction, revascularization, new-onset atrial fibrillation, acute kidney injury, stroke, postoperative pulmonary complications, wound complications, sepsis, reoperation, and/or delirium occurring during hospitalization and over the following year. Patients for whom composite adverse outcomes were reported had lower PA_pre than those without complications (5.4 ± 0.9 v 6.0 ± 0.9, p < 0.001). The PA was significantly associated with in-hospital and 1-year composite postoperative outcomes. The odds ratios (OR, [95% confidence interval]) for PA_pre by time were in-hospital complications (0.435 [0.314, 0.604], p < 0.001; 1-year complications: 0.459 [0.330, 0.638], p < 0.001) and PA_POD1 (OR, in-hospital complications: 0.400 [0.277, 0.576], 1-year complications: 0.429 [0.298, 0.619], p < 0.001). The PA_pre was significantly associated with days alive and out of hospital until 1 year. The cut-off value of PA_pre for optimal prediction of in-hospital complications was 6.0 (area under the curve: 0.691 [0.623-0.758], p < 0.001). Conclusion: Low PA as an indicator of frailty is associated with adverse postoperative outcomes after OPCAB. Low PA may be employed as a noninvasive and practical tool for the prediction of prognosis in patients with coronary artery disease.