True regarding myocardial 02 demand
Inversely related to hea rate
Has constant relation to external cardiac work
Directly propoional to duration of systole
Is negligible at rest
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
Cardiovascular system