B-type natriuretic peptide increases after gastric bypass surgery and correlates with weight loss.

Background: Coronary artery disease is the primary cause of death in the United States, with obesity as a leading preventable risk factor. Previous studies have established the beneficial effect of Roux-en-Y gastric bypass on both weight and cardiac risk factors. Further assessment of cardiac function may be accomplished using B-type natriuretic peptide (BNP), which has demonstrated clinical utility in diagnosing congestive heart failure. This study aimed to assess changes in BNP after intentional weight loss through gastric bypass surgery.

Methods: Plasma volume, weight, and BNP were measured preoperatively and at 3, 6, and 12 months postoperatively for 101 consecutive patients undergoing laparoscopic gastric bypass surgery by a single surgeon in an academic medical setting. Outcomes were compared by matched t-test. Multivariable linear regression and Pearson's correlation were used to examine predictors of pro-B-type natriuretic peptide (NT-proBNP) concentration.

Results: The concentration of BNP increased significantly from a mean preoperative level of 50.5 ng/l to postoperative levels of 73.9 ng/l at 3 months (P=0.013), 74.3 ng/l at 6 months (P<0.001), and 156.3 ng/l at 12 months (P<0.001). In addition, excess weight loss was the only statistically significant predictor of increased BNP concentration (odds ratio, 1.483; P<0.05).

Conclusion: Gastric bypass leads to significant excess weight loss and surprisingly increased BNP concentrations. Correlation of BNP increase with weight loss suggests an additional novel mechanism for surgically induced weight loss.