The Double U Wave—Should the Electrocardiogram be Interpreted Echocardiographically?

The U wave is still an electrocardiographic deflection of enigmatic origin. Numerous hypotheses on its origin have been formulated, but to date none has been conclusively proven. Recently, a report described the first case of bifid (or notched) U waves. Until then this phenomenon has only been described in the T wave. This is the first report of double U waves-two separate deflections, ascribed to an accessory papillary muscle.