Ionic bases for electrophysiological distinctions among epicardial, midmyocardial, and endocardial myocytes from the free wall of the canine left ventricle.
Population
Myocytes enzymatically dissociated from discrete layers of the free wall of the canine left ventricle
Design
Preclinical
Authors
Discussion
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Implication
Transmural Ito1 differences may underlie canine repolarization gradients and arrhythmogenesis; leaves open human translation.
Key Points
- To investigate the electrophysiological differences among epicardial, midmyocardial, and endocardial myocytes in canine ventricles.
- Used microelectrode and patch-clamp techniques to measure action potentials and currents in myocytes from canine left ventricle.
- Enzymatically dissociated myocytes were examined from epicardium, midmyocardial (M region), and endocardium.
- Assessed Ito1 and K+ currents among different myocyte layers.
- Epicardial and M region myocytes exhibited a prominent spike and dome in action potentials, while endocardial cells did not.
- Inward rectifier K+ current magnitudes were highest in epicardial cells (392 pA) compared to M region (289 pA) and endocardial (348 pA) cells.
- Ito1 amplitude was significantly greater in epicardial (4,203 pA) and M region (3,638 pA) compared to endocardial (714 pA) myocytes.
Structured PICO
P
Population
Myocytes enzymatically dissociated from discrete layers (epicardium, M region, and endocardium) of the free wall of the canine left ventricle
C
Comparator
Comparison between epicardial, M region, and endocardial myocytes
O
Outcome
Transmembrane action potentials, steady-state current-voltage relations, and the 4-aminopyridine-sensitive transient outward current (Ito1)surrogate
Prominent electrophysiological heterogeneity exists across the canine ventricular wall, driven importantly by differences in the transient outward current (Ito1), which may underlie ECG waveforms and arrhythmogenesis.
Cite This Study
Liu et al. (1993) studied this question.