B-type natriuretic peptide predicts disease severity in children with hypertrophic cardiomyopathy

Background: In adults with hypertrophic cardiomyopathy ( HCM), plasma B-type natriuretic peptide ( BNP) levels correlate with dyspnoea class and other markers of disease severity. In children with HCM, symptoms are a poor guide to disease severity and no studies have evaluated the clinical utility of BNP testing. Objective: To assess the relation of BNP levels to symptoms and markers of disease severity in children with HCM. Methods: Forty-four consecutive patients with HCM (27 male, age <= 17 years (median 13.6) underwent assessment of plasma BNP. Clinical evaluation of patients was carried out, including ECG, echocardiography and tissue Doppler imaging. Results: BNP levels correlated with maximal left ventricular (LV) wall thickness (r(s)= 0.631, p<0.001), resting LV outflow tract gradient (r(s)=0.611, p<0.001), transmitral E/septal Ea (E/Ea(s)) ratio (r(s)=0.770, p<0.001) and percentage predicted maximum VO2 (r(s)=-0.390, p=0.025); there was no relation between BNP and heart failure symptoms. BNP levels were higher in patients who had undergone implantation of an internal cardioverter-defibrillator than in those who had not (309 (interquartile range (IQR) 181 -391) vs 50 (IQR 18 -188) pg/ml, p= 0.001). BNP was independently associated with E/Ea(s) (rs= 0.632, p, 0.001) and maximal LV wall thickness (rs= 0.412, p= 0.008) on multivariate analysis. At a cutoff point of 50 pg/ ml, BNP had a positive predictive value of 93% and a negative predictive value of 80% for predicting E/Ea(s)>10 (area under the receiver operator characteristic curve = 0.875 (p<0.001)). Conclusions: BNP levels correlate with non-invasive parameters of disease severity in children with HCM, including measures of raised LV filling pressures. For patients in whom evaluation of symptoms is difficult, BNP may be a useful additional tool in the assessment of disease severity.