The U wave and papillary muscle variants: revisiting an old association.

One of the earliest hypotheses on the origin of the U wave was that these waves represent repolarisation of the papillary muscles and their neighboring structures. Various U-wave and TU-segment abnormalities have been described and ascribed to certain cardiac pathological conditions. In this case report it is hypothesised that prominent U waves in the inferior leads are caused by an accessory papillary muscle. Any possible long-term consequences are not known.