Thirty years ago my boss had told me of an aortic valve replacement he had performed. The heart came off bypass well with a good output, but later it was apparent that, although the patient’s legs were warm to the touch, there was no pulsatile flow. “It was as if,” he said, “there was a sponge in the aorta.” And then the penny dropped. During the operation, it was customary to put a sponge in the left ventricular cavity …