. The energy cost of drug-induced contractility enhancement was assessed by myocardial oxygen consumption related to the mechanical indexes tension-time index, pressure-volume area, and total mechanical energy. ANCOVA did not reveal any increased oxygen cost of contractility for either drug in these doses. However, both dobutamine and levosimendan at supratherapeutic levels (10 microg x kg(-1) x min(-1) and 48 microg/kg loading with 0