Fig. 1. Outline of the study design. After at least 30 min of rest, baseline measurements were obtained. The Low Dex phase started with the infusion of dexmedetomidine (Dex) to target a plasma concentration of 0.5 ng/ml. After completion of the positron emission tomography (PET) and transthoracic echocardiography (TTE) measurements, High Dex was started by increasing the rate of infusion of dexmedetomidine to target a plasma concentration of 3.2 ng/ml. The infusion of the PET tracer was started exactly 15 min after the infusion of dexmedetomidine was initiated or increased. The PET measurements were followed by the TTE measurements.