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The Use of BNP as a Predictor of Morbidity and Long-Term Mortality in CABG and Valve Surgery
Kendal Endicott, Richard Amdur, Michael Greenberg, Gregory Trachiotis.
Veteran's Affairs Medical Center, Washington DC, Washington, DC, USA.
OBJECTIVE: To assess whether B-type natriuretic peptide (BNP) levels are a useful predictor of postoperative morbidity and mortality as well as long term survival in coronary artery bypass graft (CABG) and valve surgery.
METHODS: A retrospective review of patients undergoing CABG and/or valve surgery from 2012 to 2015 at a single center was conducted. 432 patients were identified (295 CABG only, 82 valve only, and 55 CABG and valve cases.) BNP levels were divided into quartiles (quartile 1 BNP <38.5, quartile 2 BNP 38.5-88.5, quartile 3 BNP 88.5-272, quartile 4 BNP >272), and pre-operative, intra-operative, and post-operative variables were collected. Mortality data was available for up to 3.4 years after surgery.
RESULTS: BNP quartile was independently associated with any complication on multivariate analysis with those in the highest quartile of BNP at highest risk (adjusted OR 3.81 (p=0.047)) versus those in the lowest BNP quartile. 30-day mortality was 0.9% with 75% of deaths occurring amongst those patients in the highest quartile of BNP (p=0.015 by Fishers Exact Test). There was a significant association between BNP quartile and time to death (Log-rank chi-square 8.30, p=0.04) with greatest association 9 months after surgery onward (Figure 1). In a Cox regression model for long-term mortality stratified by BNP level, BNP quartile was significantly associated with time to death after adjusting for ejection fraction (EF), procedure (including on versus off pump cases), and other clinical variables in quartile 2 (HR 3.73(1.04-13.44), p=0.044) and quartile 4 (HR 4.33(1.14-16.44), p=0.031). Quartile 3 also had higher risk of death (HR 3.5) however this was only significant at a trend level (p=0.06).
CONCLUSIONS: BNP levels are an independent predictor of morbidity following CABG and/or valve surgery regardless of type of procedure or on/off bypass usage. BNP levels also correlate with time to death highlighting the need for sustained follow-up and heart failure management to attenuate survival in patients with elevated BNP levels presenting for all cardiac surgery. 
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