The beta-adrenoceptor (beta-AR) plays an important role in the regulation of heart function and has been extensively studied in recent decades. In vitro studies have shown down-regulation of beta-AR density in heart failure and cardiac conditions that may lead to heart failure. As in vitro measurements on cardiac tissue samples do not allow longitudinal and regional assessment of myocardial beta-ARs in humans, new methods are being developed to measure beta-ARs in vivo using positron emission tomography (PET). Studies using PET and the radioligand [(11)C]CGP 12177 have shown promising results that are in agreement with those of in vitro studies. However, the radiochemical synthesis of [(11)C]CGP 12177 is very demanding, preventing its widespread use. Hence, new radioligands are being developed using simpler methods of radiochemical synthesis. ( S)-[(11)C]CGP 12388 has been presented as a promising new radioligand. So far, in vivo measurements of beta-AR density using PET have mainly been performed to confirm in vitro studies. Using the full potential of PET, performance of regional measurements and longitudinal studies might add further knowledge on the pathophysiological role of the beta-AR in cardiac disease and the effect of interventions. Furthermore, PET might gain a role in the clinical management of patients with abnormalities of cardiac contractile function.

Background: In chronic heart failure augmented wall stress leads to increased energy demand. Supply, however, may be reduced due to coronary vasoconstriction and endothelial dysfunction. This might lead to a mismatch between demand and supply. In the present study we further explored the effect of increased demand during dobutamine stress echocardiography. Ž Methods and results: Sixteen patients with idiopathic dilated cardiomyopathy mean age 44 " 13 years, New York Heart . Association class II᎐III, mean left ventricular ejection fraction 0.27" 0.10 underwent dobutamine stress echocardiography Ž . 5᎐40 grmin per kg bodyweightq atropine if required . Wall motion and thickening was assessed in 16 segments using a Ž . four-point scale. Eleven patients 69% showed regions with worsening of wall motion or a biphasic response during dobutamine infusion. Of the remaining five patients one patient did not show any wall motion changes and one patient showed a partial improvement while only in three patients wall motion improvement in the whole heart was found. Conclusion: A majority of patients with idiopathic dilated cardiomyopathy showed decreased wall motion during increased demand, i.e. ischemia-like myocardial contractile responses during dobutamine stress echocardiography. These findings further support the concept that an energy mismatch between demand and supply might play a pathophysiological role in idiopathic dilated cardiomyopathy. ᮊ