Abstract P139: Rates of Low Output Failure After Cardiac Surgery Cannot Be Explained Solely by Preoperative Characteristics

Abstract

Background: Post-operative low output failure (LOF) is an important contributor to morbidity and mortality during coronary artery bypass grafting (CABG) surgery, and may result from poor myocardial protection. We hypothesized that rates of LOF would vary across surgeons, in part attributed to their myocardial protective strategy. Methods: We identified 11,838 patients undergoing non-emergent, isolated CABG surgery utilizing cardiopulmonary bypass (CPB) at 8 centers in northern New England from 2001-2009. Our cohort included patients with preoperative ejection fractions 40+% and patients operated on by surgeons who performed 80+ CABG procedures during the time period. Patients with preoperative balloon pumps were excluded. LOF was defined as the need for an intra- or post-operative balloon pump, or return to CPB or 2+ inotropes at 48 hours. Predicted rates of LOF were estimated using logistic regression. Results: Case volume varied across surgeons (range: 80-766, median: 344). Overall rate of LOF was 5.3% (return to CPB: 3.2%, balloon pump: 1.8%, inotrope usage: 1.3%). While predicted risk of LOF did not differ across surgeons, p=0.381, observed rates varied from 1.1% to 15.6%, p=0.003 (Figure). Post-operative outcomes, including death (ptrend=0.03) or stroke (ptrend =0.02), significantly increased across surgical LOF strata (low: <2%, medium: 3-9%, high: 10+%). Conclusions There was a 14-fold variability in rates of LOF across surgeons among patients with ejection fractions 40+%. This variability could not be explained by patient case mix. Future work should focus on understanding the relationship between myocardial protective strategy and risk of LOF.