VENTRICULAR EXPRESSION OF BRAIN NATRIURETIC PEPTIDE IN HYPERTROPHIC CARDIOMYOPATHY

Background. Brain natriuretic peptide (BNP), as a cardiac hormone, is expressed together with atrial natriuretic peptide (ANP) in the ventri cles in congestive heart failure. However, the ventricular expression of BNP in hypertrophic cardiomyopathy (HCM) with normal systolic funct ion is still unclear. Methods and Results. The study population consis ted of 39 HCM patients with asymmetric septal hypertrophy and 10 contr ol subjects without any specific cardiac disease. Eleven cases of HCM were obstructive (HOCM), and the other 28 cases were nonobstructive (H NCM). All of these patients had a normal ejection fraction. Immunohist ochemical analysis of endomyocardial biopsy specimens with specific mo noclonal antibodies showed BNP immunoreactivity in the HOCM group (5/1 0,50%) but not in the HNCM group (0/22) or in control subjects (0/5). In HOCM, left ventricular end-diastolic pressure was significantly hig her in the BNP-positive patients than the BNP-negative patients. Histo logical changes such as myocardial fiber disarray, hypertrophy of myoc ytes, and fibrosis were greater in BNP-positive patients than BNP-nega tive patients in HCM. However, the expression had no significant relat ion with other clinical parameters. The elevation of the BNP plasma le vel versus control subjects was marked in both HOCM (85-fold) and HNCM (23-fold). By contrast, the elevation of the ANP plasma level versus control subjects was mild in HOCM (5.7-fold) and HNCM (4.2-fold). The ratio of BNP level to ANP level was higher in HOCM (4.16) than in HNCM (1.46) and control subjects (0.28), and it was higher than the ratio previously reported for severe congestive heart failure (1.72). Conclu sions. These findings suggest that BNP is expressed in the ventricular myocytes of HCM with normal systolic function. In HOCM, ventricular e xpression of BNP may be augmented in response to both obstruction and diastolic dysfunction.