Association of the portoperative trend of B-Type natriuretic peptinde (BNP) values and cardaic morbidity and mortality

Abstract

BNP is a predictor of cardiac morbidity and mortality prior to cardiac surgery and potentially postoperatively. We hypothesize that the change in BNP concentrations from the first to second postoperative day (“delta BNP”) will differently affect all-cause mortality in patients undergoing on-pump cardiac surgery. In this secondary analysis of prospectively collected data, we included those patients undergoing on-pump cardiac surgery from 08/2008 to 05/2011 with BNP measurements at 6am of both the 1st and 2nd postop. day. Our primary and secondary endpoints were all-cause mortality and mortality and/or major adverse cardiac events (MACE) defined as acute coronary syndrome, cardiac arrest, congestive heart failure, or revascularization at 12 months. ROC analysis was conducted for cut-off determination. We analyzed Kaplan Meier survival curves for increasing and decreasing delta BNP, in addition to a Cox regression adjusting for the EuroSCORE II, surgical factors, and biomarkers. We analyzed 725 patients (72% male; mean age 67±11 years) of whom 351 had decreasing and 374 had increasing delta BNP values, respectively, with a total of 70 deaths occurring. The Kaplan Meier curves (Fig. 1) showed significantly increased survival and MACE-free survival for patients with increasing delta BNP. Multivariate adjustment for the EuroSCORE II, cardiopulmonary bypass time, as well as BNP and TNT on postoperative day 1, continued to show a hazard ratio (HR) of 0.39 (95%CI 0.20 – 0.76) for increasing delta BNP. Stratification of BNP values on the first postop. day above and below 682 ng/L revealed increased mortality in the high BNP group (>682ng/L) for increasing delta BNP (log-rank p=0.010), but decreased mortality in the low BNP group (<682ng/L) for increasing delta BNP (log-rank p =0.001), albeit with a low event rate (21). This preliminary analysis suggests that routine serial BNP measurements may be difficult to interpret. However, for patients with initially high postoperative BNP, a second measurement may contain additional prognostic information Figure 1: Kaplan Meier survival curves for increasing and decreasing postoperative BNP values