A 74-year-old male patient's circulation was supported by an intra-aortic balloon for a period of six days following multiple cardiac infarcts. On the sixth day, several 'leak in IAB circuit' alarms appeared. The nursing staff checked the tubing and refilled the balloon, as described in the manual, without notifying the medical staff or perfusionist. A few hours later, the balloon showed a leak, as blood was seen in the catheter tubing. This leak resulted in considerable damage to the device caused by a large amount of blood migrating back to the tubing and flooding the internal drive system, due to a failing 'blood detection' sensor. The balloon catheter was removed percutaneously and intra-aortic counterpulsation was discontinued. The patient died 20 days later of heart failure. This raises doubts over the adequacy of the protective sensors of such devices and, importantly, how to interpret the present user manuals and the instructions for troubleshooting.