To investigate the ventricular expression of
atrial natriuretic peptide (
ANP) in human hypertrophic hearts, we conducted an immunohistochemical study of 130 endomyocardial biopsy specimens obtained from the right side of the ventricular septum (RVB), left ventricular free wall (LVB), or both from a total of 80 patients: 44 patients with
hypertrophic cardiomyopathy (HCM), 14 with
apical hypertrophic cardiomyopathy (APH), 13 with hypertensive hearts (HHD), and nine without
hypertrophy (controls). No patients had apparent
congestive heart failure.
ANP was not seen in ventricular myocytes in controls but was identified in biopsy specimens of hypertrophic hearts, and its distribution was characteristic in each hypertrophic group: 15 RVB (37%) and two LVB (7%) of the HCM group, one RVB (7%) and two LVB (18%) of the APH group, and zero RVB (0%) and five LVB (46%) of the HHD group. Clinical data (including echocardiographic, hemodynamic, and angiographic data) were not directly related to ventricular
ANP expression in HCM, APH, or HHD with one exception. In HHD patients, LVB specimens with
ANP showed greater ventricular wall thickness than LVB specimens without
ANP. According to histological data, however, the
ANP-present RVB specimens of HCM or
ANP-present LVB specimens of HHD had greater myocyte size than did the
ANP-absent specimens. In addition, in HCM patients, the
ANP-present RVB specimens showed more severe
fibrosis and myofiber disarray than did the
ANP-absent specimens. We conclude that a failing state and hemodynamic overload are not likely to be indispensable for
ANP expression in human hypertrophic ventricles and that ventricular
ANP expression occurs as a response to disease-specific changes: hemodynamic overload in HHD and histological changes such as myocardial fiber disarray,
hypertrophy of myocytes, and
fibrosis in HCM, which may reflect the characteristic distribution of intraventricular
ANP.