Physiology Heart, Circulation, and Blood a9dfa972 True about cardiac O2 demand is- A Directly proportional to mean arterial pressure B Inversely proportional to heart rate C Inversely proportional to cardiac work D Has a constant relation to the external work done by the heart High-Yield Explanation Ans. (a) Directly proportional to mean arterial pressureRef: Ganong, 25th ed/p.612Myocardial oxygen consumption is directly proportional to mean arterial pressure