Usefulness of B-Type Natriuretic Peptide Assay in the Assessment of Symptomatic State in Hypertrophic Cardiomyopathy

Background - Hypertrophic cardiomyopathy (HCM) has a diverse clinical spectrum that often includes progressive heart failure symptoms and disability. Assessment of symptom severity may be highly subjective, encumbered by the heterogeneous clinical presentation. Plasma B-type natriuretic peptide (BNP) has been used widely as an objective marker for heart failure severity and outcome, predominantly in coronary heart disease with ventricular dilatation and systolic dysfunction. Methods and Results - We prospectively assessed plasma BNP as a quantitative clinical marker of heart failure severity in 107 consecutive HCM patients. BNP showed a statistically significant relationship to magnitude of functional limitation, assessed by New York Heart Association (NYHA) functional class: I, 136±159 pg/mL; II, 338±439 pg/mL; and III/IV, 481±334 pg/mL (P<0.001). Multivariable analysis showed that BNP was independently related to NYHA class as well as age and left ventricular wall thickness (each with a value of P=0.0001). BNP ≥200 pg/mL was the most reliable predictor of heart failure symptoms, with positive and negative predictive values of 63% and 79%, respectively. BNP power in distinguishing patients with or without heart failure symptoms was less than that for differentiating between no (or only mild) and severe symptoms (area under receiver operating characteristic curve=0.75 and 0.83, respectively). Conclusions - Plasma BNP is independently related to the presence and magnitude of heart failure symptoms in patients with HCM. As a clinical marker for heart failure, BNP is limited by considerable overlap in values between categories of heart failure severity as well as confounding variables of left ventricular wall thickness and age.