True regarding myocardial 02 demand: (A) Inversely related to hea rate, (B) Has constant relation to external cardiac work, (C) Directly propoional to duration of systole, (D) Is negligible at rest
Answer is B. Experimental studies have shown that oxygen consumption of the hea and the chemical energy expended during contraction are directly related to the external work Ref: Guyton and Hall Textbook of Medical Physiology (12th Edn) page No:209