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Effect of Strength and Timing of Transmembrane Current Pulses on Isolated Ventricular Myocytes
Author(s) -
GRAY RICHARD A.,
HUELSING DELILAH J.,
AGUEL FELIPE,
TRAYANOVA NATALIA A.
Publication year - 2001
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1046/j.1540-8167.2001.01129.x
Subject(s) - depolarization , repolarization , membrane potential , myocyte , biophysics , medicine , plateau (mathematics) , transmembrane protein , cardiology , electrophysiology , biology , mathematical analysis , receptor , mathematics
Cellular Response to Premature Stimuli.Introduction: Little is known about how the amplitude and timing of transmembrane current pulses affect transmembrane potential ( V m ) and action potential duration (APD) in isolated myocytes. Methods and Results: Ten ventricular myocytes were isolated from five rabbit hearts. Each cell was paced at an S1 cycle length of 250 msec, and S2 pulses of 10‐msec duration were delivered at various strengths and time intervals. For all S2 strengths (0.2 to 1.5 nA), the magnitude of changes in V m did not depend on polarity during the plateau, but were larger for depolarizing pulses during phase 3 repolarization. However, the magnitude of changes in APD varied with polarity during the entire action potential for strengths ranging from 0.5 to 1.5 nA. Greater changes in APD occurred for hyperpolarizing pulses during the plateau and depolarizing pulses during phase 3. In addition, we used a cardiac phase variable to quantify the current threshold for regenerative depolarization and repolarization as a function of prestimulus V m . Regenerative depolarization occurred during phase 3 repolarization, and its current threshold was less than that required for regenerative repolarization that occurred during the plateau. These data were compared to computer simulations in a patch of membrane represented by Luo‐Rudy dynamic kinetics, and the results were qualitatively similar, including the higher threshold for regenerative repolarization compared to regenerative depolarization. Conclusion: This characterization of the nonlinear response of isolated cells to transmembrane current, including phase resetting, should aid in understanding the mechanisms of defibrillation because shockinduced changes in V m and APD have been implicated as important factors in determining defibrillation success.