Positron emission tomography with ¹¹C CGP-12177 to assess β-adrenergic receptor concentration in idiopathic dilated cardiomyopathy

Background. Positron emission tomography (PET) with ¹¹C-labeled CGP-12177 (CGP) has been shown to have the potential to noninvasively measure β-adrenergic receptor concentration in dog heart. The present study was undertaken to evaluate the clinical value of this technique. Methods and Results. Eight normal subjects and 10 patients with heart failure related to an idiopathic cardiomyopathy were studied. Estimation of β-receptor concentration was based on a graphic method applied on myocardial PET time-concentration curves obtained after an intravenous injection of ¹¹C-CGP followed 30 minutes later by a coinjection of labeled and unlabeled CGP. The clinical tolerance of these injections was good. Left ventricular concentration of β-receptors was decreased in patients compared with controls (3.12±0.51 versus 6.60±1.18 pmol/mL, respectively; p<0.001). This 53% decrease agrees with previous in vitro data. In eight of the 10 patients, the β-receptor concentration obtained from PET was compared with the β-receptor density determined on left ventricular endomyocardial biopsy samples by in vitro binding technique using ³H-CGP-12177. Results obtained with both techniques were correlated (r=0.79, p=0.019). Moreover, decreased β-receptor concentration correlated with the β-contractile responsiveness to intracoronary dobutamine infusion (r=0.83, p=0.003), indicating a direct link between changes in the receptor number and its biological function. Conclusions. PET appears to be a safe and reliable method of assessing in vivo changes in the number of left ventricular β-adrenergk receptor sites of patients with idiopathic cardiomyopathy.