Myocardial hypertrophy in guinea-pig hearts altered conduction velocity and anisotropy, corresponding to more cell contacts per cell (8.1 vs 5.7) and side-to-side coupling disks (10.2 vs 8.2).
Does left ventricular hypertrophy alter action potential conduction velocity and anisotropy through changes in gap-junction coupling and intracellular conductance in guinea-pig hearts?
Left ventricular hypertrophy alters myocardial conduction velocity and anisotropy due to changes in intracellular conductance and the topography of cell-cell coupling.
BACKGROUND: We tested the hypothesis that alterations to action potential conduction velocity (CV) and conduction anisotropy in left ventricular hypertrophy are associated with topographical changes to gap-junction coupling and intracellular conductance by measuring these variables in the same preparations. METHODS AND RESULTS: Left ventricular papillary muscles were excised from aortic-banded or sham-operated guinea-pig hearts. With intracellular stimulating and recording microelectrodes, CV was measured in 3 dimensions with simultaneous conductance mapping with subthreshold stimuli and correlated with quantitative histomorphometry of myocardial architecture and connexin 43 distribution. In hypertrophied myocardium, CV in the longitudinal axis was smaller and transverse velocity was greater compared with control; associated with similar differences of intracellular conductance, consistent with more cell contacts per cell (5.7 ± 0.2 versus 8.1 ± 0.5; control versus hypertrophy), and more intercalated disks mediating side-to-side coupling (8.2 ± 0.2 versus 10.2 ± 0.4 per cell). Intercalated disk morphology and connexin 43 immunolabelling were not different in hypertrophy. Hypertrophied preparations showed local submillimeter (≈250 μm) regions with slow conduction and low intracellular conductance, which, although not affecting CV on the millimeter scale, were consistent with discontinuities from increased microscopical connective tissue content. CONCLUSIONS: With myocardial hypertrophy, altered longitudinal and transverse CV, and greater nonuniformity of CV anisotropy correspond to changes of intracellular conductance. These are associated with alteration of myocardial architecture, specifically the topography of cell-cell coupling and gap-junction connectivity.
Fry et al. (Tue,) conducted a other in Left ventricular hypertrophy. Aortic banding (hypertrophy) vs. Sham operation (control) was evaluated on Action potential conduction velocity and intracellular conductance. Myocardial hypertrophy in guinea-pig hearts altered conduction velocity and anisotropy, corresponding to more cell contacts per cell (8.1 vs 5.7) and side-to-side coupling disks (10.2 vs 8.2).