Impairments of myocardial sympathetic activity may reflect the progression of myocardial damage or dysfunction in hypertrophic cardiomyopathy.

BACKGROUND: Abnormalities of myocardial sympathetic nerve function have been reported in hypertrophic cardiomyopathy (HCM). However, the mechanism of such abnormalities remains unknown. In part, the high plasma level of B-type natriuretic peptide (BNP) reportedly reflects myocardial damage in addition to hemodynamic disorder.

METHODS AND RESULTS: To assess myocardial sympathetic nerve function, we obtained metaiodobenzylguanidine (MIBG) images 15 and 180 minutes after the injection of iodine 123-MIBG at a dose of 111 MBq and calculated the heart-mediastinum count ratio (H/M) and the washout rate (WR) in 59 consecutive patients with HCM and age-matched normal control subjects (C, n = 23). The plasma levels of atrial natriuretic peptide (ANP), BNP, and norepinephrine (NE) were also measured. The left ventricular mass index (LVMI) and left ventricular ejection fraction (LVEF) were measured by echocardiographic study. H/M was significantly lower in patients with HCM (2.1 +/- 0.3) than in control subjects (2.6 +/- 0.4) (P <.01). WR was higher in patients with HCM (35 +/- 6) than in control subjects (28 +/- 3) (P <.01). H/M had a significant negative correlation with LVEF, LVMI, ANP, BNP, and NE. WR also had a significant positive relationship with the plasma levels of NE and BNP. Multivariate regression analysis was used with 5 variables (LVEF, LVMI, ANP, BNP, and NE). BNP (P =.0001) and LVMI (P =.0009) were independent and significant predictors of H/M. NE was an independent and significant predictor of WR (P =.0018).

CONCLUSIONS: These findings indicate that impairments of myocardial sympathetic function may reflect the progression of myocardial damage or dysfunction in HCM.