Intra-aortic balloon pump (IABP) technology is an established treatment modality for patients with acute cardiac failure. Advances in IABP technology have simplified use and reliability such that electromechanical malfunctions are relatively rare. We present a case of an unanticipated pressure output signal from a powered off Cardiosave IABP console resulting in an erroneous mean arterial blood pressure waveform being displayed during cardiopulmonary bypass. The patient suffered no ill effects and made a full recovery. As a result of this incident, our policies have been revised to ensure that all patients with an IABP brought to the operating room for surgery have at least two arterial lines, one of which is not off the IABP, to prevent future occurrences.