Computer-simulated alternative modes of U-wave genesis.

OBJECTIVE Several hypotheses for the origin of the U wave in electrocardiograms have been proposed. We have set out to explore and test alternative modes for U-wave genesis via computer simulations. METHODS AND RESULTS A spatial model of a left ventricle has been constructed from 12 layers composed of cubic cells. Each cell is assigned its own time-dependent action potential with its own contribution to the electrical potential at arbitrary points where ECGs are measured. Simulated ECGs show that U waves can be generated using various combinations of action potentials (APs) across the different layers of the ventricular wall. We demonstrate a new mode of U-wave genesis, even with small differences in the repolarization. CONCLUSION The U wave can be generated in the presence of strong intercellular coupling. Myocardial layers with prolonged action potentials, like M cells, are not necessarily needed for U-wave genesis.