It has been suggested that volume displaced by the intraaortic balloon is more significant than any other IAB (intraaortic balloon) factors (such as timing and speed), especially during the low cardiac output states. To investigate the operation of the balloon in the aorta during such conditions, a refined mathematical model of the balloon system was incorporated into a cardiovascular model. The model describes the balloon inflations as a pressure-dependent wavefront. This results in cardiac ouptut that is not linearly proportional to IAB volume. Thus for example under typical condition a single-chamber 4-cm3 IAB has the same effect on cardiac output as a 60-cm3 IAB