Key result
Imposing a resistive barrier by increasing gap junction resistance to 3-30 times normal generated a distinct U wave following the T wave in simulated electrocardiograms.
Computational modeling suggests that a distinct U wave on the ECG can be generated by sharp action potential duration transitions caused by increased local junctional resistance around the M region.
Hypothesis-generating for M-region resistance in U-wave genesis; requires in vivo and clinical validation before any interpretive change.
The electrocardiogram (ECG) was reconstructed from extracellular fields generated by action potentials propagating along a 2-cm linear cable comprising 200 myocardial cells coupled through gap junctions (GJs). Intrinsic APD was varied by altering the maximal conductance of the delayed rectifier (G/sub x/). A longer APD was simulated in the M region by a uniform decrease of G/sub x/. APD prolongation in the M region, no matter how great, failed to yield a distinct U wave in the ECG, as expected for a globally homogeneous medium. To account for the sharp APD transitions observed experimentally, the authors imposed a resistive barrier on either side of the M region by increasing GJ resistance to levels 3-30 times normal. Conduction was little affected under these conditions, yet a separate U wave was seen to follow the T wave. U wave amplitude was directly proportional to the size of the M region and displayed sigmoid dependence of the log of the barrier resistance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
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Nesterenko et al. (2003) studied Electrocardiographic U wave simulation. Increased gap junction resistance (resistive barrier) vs. Globally homogeneous medium was evaluated on Generation of a distinct U wave in the ECG. Imposing a resistive barrier by increasing gap junction resistance to 3-30 times normal generated a distinct U wave following the T wave in simulated electrocardiograms.
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