Myocardial beta-Adrenergic Receptor Density Assessed by 11C-CGP12177 PET Predicts Improvement of Cardiac Function After Carvedilol Treatment in Patients with Idiopathic Dilated Cardiomyopathy

We evaluated whether myocardial β-adrenergic receptor (β-AR) density, as determined by 11 C-CGP12177 PET, could predict improvement of cardiac function by β-blocker carvedilol treatment in patients with idiopathic dilated cardiomyopathy (IDC). Methods: Ten patients with IDC (left ventricular ejection fraction [LVEF] < 45%) were studied. Myocardial β-AR density was estimated using 11 C-CGP12177 PET before treatment with carvedilol. Changes of LVEF in response to dobutamine infusion (ALVEF-dobutamine) were also measured by echocardiography. Changes of LVEF (ALVEF-carvedilol) were evaluated after 20 mo of carvedilol treatment. Results: Baseline myocardial β-AR density significantly correlated with ALVEF-carvedilol (r = -0.88, P < 0.001). In contrast, ALVEF-dobutamine did not correlate with ALVEF-carvedilol (P = 0.65). Myocardial β-AR density was the significant multivariate independent predictor of ALVEF-carvedilol (β = -0.88, P < 0.001) among univariate predictors, including functional class (r = 0.76, P < 0.05), plasma norepinephrine (r = 0.85, P < 0.01), LVEF (r = -0.64, P < 0.05), and age as confounding factors. Furthermore, myocardial β-AR density was significantly correlated with plasma norepinephrine (r = -0.79, P < 0.01) and LVEF (r = 0.70, P < 0.05). Conclusion: Myocardial β-AR density is more tightly related to improvement of LVEF-carvedilol than is cardiac contractile reserve in patients with IDC. Patients with decreased myocardial β-AR have higher resting adrenergic drive, as reflected by plasma norepinephrine, and may receive greater benefit from being treated by antiadrenergic drugs.