January 2, 2003
View Full PaperSimulation of the electrocardiographic U wave in heterogeneous myocardium: effect of local junctional resistance
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.
Structured PICO
P
Population
Simulated 2-cm linear cable comprising 200 myocardial cells coupled through gap junctions
I
Intervention
Imposing a resistive barrier on either side of the M region by increasing gap junction resistance to levels 3-30 times normal
C
Comparator
Globally homogeneous medium (no resistive barrier)
O
Outcome
Generation of a distinct U wave in the simulated ECGsurrogate
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.
Abstract
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.>