Myocardial O2 consumption in stunned cor is relatively high compared with the rduced ventricular function.The metabolism of this "oxygen paradox" could occur at different levels: basal metabolism, excitation-contraction coupling, and energy production. Although ventricular function is substantialy depressed, O2 consumption in the stunned myocardium is normal or close to normal.Hence, the stunned myocardium is inefficient.The reason of this inefficiency could be due to high myocardial O2 consumption for excitation-contraction coupling, uncoupling between substrate metabolism and energy production, accelerated but useless energy drainage, some impairment between energy transfer and function of contractile proteins, or increased ATP requirments for force generation by the myofilaments. The relatively high O2 consumption has also been attributed to repair processes taking place in stunned myocardium.