Increase of B-type Natriuretic Peptide from Baseline Increases the Risk of Death or Retransplant in Pediatric Cardiac Transplant Patients, Midterm Results

Abstract

BACKGROUND; Several studies have demonstrated the utility of B-type natriuretic peptide (BNP) in the months following cardiac transplant. The purpose of this study was to analyze longitudinal BNP data in pediatric cardiac transplant patients and determine the efficacy of BNP in routine follow-up of transplant to help predict the adverse event of death or re-transplant. From October 2002 to July 2007, 53 pediatric cardiac transplant patients were treated in an unmatched case-control study. Along with routine studies, BNP values were obtained at regular intervals. Six patients were excluded due to recent transplant, and three patients were excluded due to poor compliance. A baseline BNP was established for each subject utilizing the mean of all BNP values during year 2 post-transplant, or the first year of measured BNP in those patients whose transplant preceded the study by more than 1 year (time from transplant to first BNP 7.0 +/- 3.5 years). The median BNP of all data points since transplant was utilized as an additional surrogate baseline. Univariate logistic regression was used to evaluate BNP versus other covariates on cardiac death. Forty-four patients provided 1254 BNP data points spanning 173 patient years. Nine (20.5%) had an adverse event. Patients who experienced an adverse event had a higher baseline BNP (mean 365 +/- 290; median 375 +/- 352)) when compared to patients without an event (mean 128 +/- 78; median 121 +/- 62; p = 0.04 and p = 0.06)). All subjects with adverse events had a BNP value >or= 250 during the 90 days preceding the event compared to 32.4% of those who did not (odds ratio: 23.13, p < 0.01). A log fold increase in the BNP value compared to the baseline median BNP is a risk for cardiac death in the subsequent 90-day period (OR: 6.82, 95% confidence interval: 1.25-37.11, p = 0.03). Routine BNP monitoring in the post-cardiac transplant pediatric patient allows for the determination of a median BNP, which can be used as a baseline. A log fold increase from the median BNP, or a BNP value >or= 250, increases the risk of death or re-transplant and suggests a 90-day period of heightened clinical surveillance, perhaps necessitating increased medication or re-listing for repeat transplant.