© 1997 American Heart Association, Inc.
Articles |
Line Stimulation Parallel to Myofibers Enhances Regional Uniformity of Transmembrane Voltage Changes in Rabbit Hearts
From the Department of Biomedical Engineering and the Division of Cardiovascular Disease of the School of Medicine, The University of Alabama, Birmingham.
Abstract The sign of transmembrane voltage (Vm)
change (
Vm) in the heart during unipolar point
stimulation is nonuniform, which introduces dispersion of states of
Vm-dependent ion channels that depends on fiber
orientation. We hypothesized that line stimulation parallel to cardiac
fibers increases regional uniformity of the Vm sign. To
test this, we evaluated electrode current distribution and
Vm produced by unipolar line stimulation in isolated
rabbit hearts. The Vm-sensitive fluorescent dye,
di-4-ANEPPS, and a laser scanner provided Vm
measurements at 63 spots in an 8x8-mm epicardial region. Line
stimulation was tested at specific angles with respect to the fiber
direction. Current peaks occurred at electrode ends. For electrodes
parallel to fibers (0°), epicardium in regions beyond the ends
exhibited a nonuniform Vm sign, whereas epicardium
between the ends exhibited a uniform Vm sign that was
essentially negative (hyperpolarized) during anodal pulses and positive
(depolarized) during cathodal pulses. The Vm sign
between the ends became less uniform when the stimulation angle was
increased relative to the long axis of the fibers. At 90°, the
Vm sign between the ends was nonuniform and was
frequently opposite, near versus away from the electrode. Spatial
distributions of Vm during line stimulation were
qualitatively predictable from anisotropic effects of point stimulation
provided that combined effects of points along the electrode and points
with higher current near ends were considered. For biphasic line
stimulation, Vm during the second phase was weakly
correlated with the temporal sum of effects of phases given
individually, indicating limited ability of summation to predict
Vm. Thus, uniformity of the Vm sign
during stimulation is enhanced in the region between the ends of a line
electrode parallel to fibers. This may lessen arrhythmogenic dispersion
of Vm-dependent ion channel states in the region.
Key Words: transmembrane potential • fluorescent dye • electrical stimulation
This article has been cited by other articles:
 |
|
 |
|
  A. Cheng, T. C. Nguyen, M. Malinowski, G. T. Daughters, D. C. Miller, and N. B. Ingels Jr Heterogeneity of Left Ventricular Wall Thickening Mechanisms Circulation, August 12, 2008; 118(7): 713 - 721. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Qu, L. Li, V. P. Nikolski, V. Sharma, and I. R. Efimov Mechanisms of superiority of ascending ramp waveforms: new insights into mechanisms of shock-induced vulnerability and defibrillation Am J Physiol Heart Circ Physiol, August 1, 2005; 289(2): H569 - H577. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. B. Harrington, F. Rodriguez, A. Cheng, F. Langer, H. Ashikaga, G. T. Daughters, J. C. Criscione, N. B. Ingels, and D. C. Miller Direct measurement of transmural laminar architecture in the anterolateral wall of the ovine left ventricle: new implications for wall thickening mechanics Am J Physiol Heart Circ Physiol, March 1, 2005; 288(3): H1324 - H1330. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Banville, R. A. Gray, R. E. Ideker, and W. M. Smith Shock-Induced Figure<$DOWNLINK>-of-Eight Reentry in the Isolated Rabbit Heart Circ. Res., October 15, 1999; 85(8): 742 - 752. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. B. White, G. P. Walcott, A. E. Pollard, and R. E. Ideker Myocardial Discontinuities : A Substrate for Producing Virtual Electrodes That Directly Excite the Myocardium by Shocks Circulation, May 5, 1998; 97(17): 1738 - 1745. [Abstract] [Full Text] [PDF]
|
|