The Molar Ratio of N-terminal pro-B-type Natriuretic Peptide/B-type Natriuretic Peptide for Heart Failure-related Events in Stable Outpatients with Cardiovascular Risk Factors

OBJECTIVE: B-type natriuretic peptide (BNP) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) should be secreted from cardiomyocytes in response to increased myocardial wall stress in a molar ratio of 1.00; however, the calculated molar blood levels of NT-proBNP are often greater than those of BNP in routine clinical practice. The purpose of this study was to investigate the hypothesis that the molar ratio of NT-proBNP/BNP provides useful clinical information in stable outpatients with cardiovascular risk factors. METHODS: We measured both the BNP and NT-proBNP levels simultaneously in 551 consecutive, stable outpatients with at least one cardiovascular risk factor and then calculated the molar ratio of NT-proBNP/BNP. All patients were prospectively followed-up for the occurrence of heart failure (HF)-related events. RESULTS: Of those patients, 38 patients had an HF-related event. A multivariate Cox hazards analysis showed that the log (molar ratio of NT-proBNP/BNP) was an independent predictor of future HF-related events (p=0.039). A Kaplan-Meier analysis showed a significantly higher probability of HF-related events in patients with a higher molar ratio of NT-proBNP/BNP (≥1.70) (p<0.001). The area under the curve (AUC) of the receiver operating characteristic curve (ROC) for the molar ratio of NT-proBNP/BNP to predict HF-related events was 0.75 (p<0.001). The AUC of the ROC curve analysis with the molar ratio of NT-proBNP/BNP for the prediction of HF-related events was not significantly greater than that of BNP or NT-proBNP. CONCLUSION: The molar ratio of NT-proBNP/BNP may be a significant prognostic factor for HF-related events.