Myocardial oxygen demand depend upon

Oxygen consumption has also been shown to be nearly propoional to the tension that occurs in the hea muscle during contractionOxygen consumption has also been shown to be nearly propoional to the tension that occurs in the hea muscle during contraction multiplied by the duration of time that the contraction persists, called the tension-time indexRef: Guyton and Hall Textbook of Medical Physiology (12th Edn) page No:209