[The effect of carvedilol on contrast echocardiography in comparison to metoprolol in conscious dogs].
This animal study was to demonstrate the effect of the betablockers carvedilol (CAS 72956-09-3) and metoprolol (CAS 37350-58-6), respectively, on myocardial perfusion which was quantified by the use of contrast echocardiography. Each of four experimental schemes were applied consecutively to each of six dogs. They were pretreated with oral administration of either carvedilol (2 mg/kg b. wt.) or with metoprolol (4 mg/kg b. wt.), or received no premedication. 2 h later the contrast agent BY963 (0.03 ml/kg)--a new transpulmonary contrast agent for sonography, based on phopspholipid stabilized microbubbles--was injected intravenously three times at intervals of 2.5 min 5 min in advance and 7.5, 10, 20, and 30 min following the first injection 60 digitized echocardiography images were recorded during a time period of each 2.9 s. From these images average grey-scale values at predetermined points of time were derived. Time-intensity curves of the region of interest of the interventricular septum were computed. Changes in intensity were calculated by baseline subtraction. Myocardial opacification was observed with all injections of the contrast agent in each dog. The effects were marked and no non-responder was observed. There was no return to baseline grey-scale values within the observation period (30 min). Pretreatment with carvedilol was followed by a more pronounced contrast intensity than was with metoprolol. All administrations were well tolerated. No changes in ECG were observed. Heart rate decrease was marked on metoprolol. Blood pressure dropped to a greater extent on carvedilol compared to metoprolol.