IK1 modulates the U-wave: insights in a 100-year-old enigma.

n 1906, 11 years after Einthoven's first description of the P-QRS-T complex in a human electrocardiogram in 1895,1 he reported the existence of a wave after the T-wave, accordingly named U-wave, in a patient with “degenerative myocardial disease.” In the following years, Einthoven and Lewis noted the existence of a U-wave in the majority of their tracings. Recently, the unresolved problem of the U-wave genesis attracted renewed attention. These contradictory results prompted us to further investigate this phenomenon.