NT-proBNP values and Weber functional class in patients with chronic heart failure

To assess the correlation between NT-proBNP values and Weber functional class as determined by cardiopulmonary exercise testing (CPET) in patients with chronic heart failure (CHF).

We studied 95 patients, 68 male, mean age 50.4 +/- 10.5 years, with CHF due to dilated cardiomyopathy (DCM), 65% of non-ischemic etiology, classified by symptom-limited treadmill CPET (modified Bruce protocol) as follows: 48 Weber class A, 27 class B, 16 class C and 4 class D. NT-proBNP values (pg/ml) were determined after 15 minutes rest immediately prior to CPET. There were no significant differences between the groups in gender, age or percentage of patients taking ACE inhibitors or ARBs and beta-blockers. Left ventricular ejection fraction was higher in class A and B (27.6+/-8.3%) than in class C and D (19.7+/-6.2%, p=0.001). Serum creatinine was lower in class A (0.97+/-0.22 mg/dl) than in classes C or D (1.16+/-0.26, p=0.006).

NT-proBNP was: class A=1325.8+/-1500.3, class B=3473.0+/-2575.3 (p<0.001 vs. class A), class C=6193.1+/-2066.8 (p<0.001 vs. A and B), while in class D it was 11821.8+/-5489.7. There was an overall significant correlation between NT-proBNP and peak oxygen uptake (r=-0.66, p<0.001). On ROC curve analysis, an NT-proBNP value of 1766.5 pg/ml was found to be the best cut-off to discriminate class A vs. non-A (AUC=0.896, p<0.001, 95% CI 0.834 to 0.957, sensitivity=79%, specificity=83%), while a value of 5029.0 was the best discriminator of class B vs. class C or D (AUC=0.865, p<0.001, 95% CI 0.760 to 0.970, sensitivity=82%, specificity=80%).

In patients with CHF due to DCM, NT-proBNP values correlate with Weber class as determined by CPET, and this study presents discriminative values.