Myocardial β adrenoceptors and left ventricular function in hypertrophic cardiomyopathy

Objective - To assess the relation between left ventricular function and myocardial β adrenoceptor density. Methods - 17 patients with hypertrophic cardiomyopathy, six with and 11 without heart failure, were studied. Left ventricular function was assessed by echocardiography, and myocardial β adrenoceptors by positron emission tomography. Patient data were compared with those obtained in normal controls. Results - Myocardial β adrenoceptor density in the 17 patients was 7.00 (SD 1.90) pmol/g v 11.50 (2.18) pmol/g in normal controls (P <0.01). β Adrenoceptor density in the six patients with left ventricular failure was 5.61 (0.88) pmol/g v 7.71 (1.86) pmol/g in the 11 patients with normal ventricular function (P <0.05), and there was a significant correlation (r = 0.52; P <0.05) between left ventricular fractional shortening and myocardial β adrenoceptor density. A positive correlation (r = 0.51; P <0.05) was also found between myocardial β adrenoceptor density and the E/A transmitral flow ratio, an index of left ventricular diastolic function. Conclusions - There is myocardial β adrenoceptor downregulation in patients with hypertrophic cardiomyopathy with or without signs of heart failure.