Journal
CIRCULATION
Volume 112, Issue 16, Pages 2386-2396Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/CIRCULATIONAHA.105.534784
Keywords
myocardial infarction; ion channels; reentry; arrhythmia; electrophysiology
Funding
- NHLBI NIH HHS [R01 HL066140-04, P01 HL030557, P01 HL030557-180009, HL-30557, R01 HL066140, HL-66140] Funding Source: Medline
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Background - Anisotropic reentrant excitation occurs in the remodeled substrate of the epicardial border zone (EBZ) of the 5-day infarcted canine heart. Reentry is stabilized because of the formation of functional lines of block. We hypothesized that regional differences of ionic currents in cells of the EBZ form these lines of block. Therefore, we first mapped reentrant circuits of sustained tachycardias, then dispersed cells ( infarct zone cells, IZs) from the central common pathway of the circuit (IZc) as well as from the other side of the line of block ( outer pathway, IZo) for study. Methods and Results - We mapped reentrant circuits in the EBZ of infarcted hearts during sustained ventricular tachycardias (> 30 seconds, n = 17 episodes, cycle lengths = 218 +/- 7.9 ms). I-Na density was reduced in both IZc and IZo, and the kinetic properties of IZc INa were markedly altered versus IZo. Structural remodeling of the sodium channel protein Na(v)1.5 occurred in IZs, with cell surface localization differing from normal cells. Both IZc and IZo have similar but reduced I-CaL, whereas IZc showed changes in Ca2+ current kinetics with an acceleration of current decay. Computer simulations of the 2D EBZ showed that incorporating only differences between INa in IZc and IZo prevented stability of the reentrant circuit. Incorporating only differences between I-CaL in the IZc and IZo cells also prevented stability of the circuit. However, incorporating both I-Na and I-CaL current differences stabilized the simulated reentrant circuit, and lines of block formed between the 2 distinct regions. Conclusions - Despite differences in I-Na and I-CaL properties in cells of the center and outer pathways of a reentrant circuit, the resulting changes in effective refractory periods tend to stabilize reentry in this remodeled substrate.
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