© 1995 American Heart Association, Inc.
Articles |
Optical Mapping Reveals That Repolarization Spreads Anisotropically and Is Guided by Fiber Orientation in Guinea Pig Hearts
From the University of Pittsburgh (Pa) School of Medicine, Department of Cell Biology and Physiology.
Correspondence to Dr Anthony J. Kanai, Department of Pharmacology, Box 3845, Duke University Medical Center, Durham, NC 27710.
Abstract Guinea pig hearts were stained with a
voltage-sensitive dye and imaged on a photodiode array to
record fluorescent action potentials (APs) from 124 sites.
Activation and repolarization patterns were recorded from the
epicardium during stimulation at different loci and correlated with the
underlying fiber architecture. Endocardial APs were recorded by
inserting a light guide into the ventricular cavity or by
dissecting out the ventricular free wall to expose the
endocardium. In hearts paced on the right atrium to simulate sinus
rhythm, activation emerged synchronously over a large area of the
ventricular epicardium and spread laterally in 5 to 7 ms.
The apparent longitudinal and transverse velocities were 2.66±0.11 and
1.65±0.09 m/s (n=12). In contrast, repolarization began near the apex
on the endocardium and spread transmurally in 6±1.3 ms (n=12) and then
anisotropically along the epicardium in 25 to 30 ms with apparent
maximum (0.53±0.11 m/s) and minimum (0.31±0.10 m/s) repolarization
velocities that aligned with the longitudinal and transverse axes of
epicardial fibers. When paced on the epicardium, activation of intact
hearts (n=12) and perfused sheets (n=8) was anisotropic, with
longitudinal (0.85±0.05 m/s) and transverse (0.44±0.04 m/s)
conduction velocities that aligned with the epicardial fiber
orientation. When activation was initiated at different sites on the
epicardium, repolarization always began near the apex and exhibited
patterns similar to those obtained under right atrial pacing, but with
slower longitudinal (0.41±0.09 m/s) and transverse (0.23±0.07 m/s)
repolarization velocities (n=18). In sheets stretched parallel to the
longitudinal axis of surface fibers, AP durations (APDs) increased as a
function of fiber length, from the length at zero developed tension to
120% of the length at maximum developed tension
(Lmax). Spatial distributions of APDs did not change
during stretches along the rising phase of the length-tension
curve. In sheets stretched to 50% of Lmax, APDs
were shorter and more homogeneous on the endocardium (mean
APD, 188 ms; 
APD, 195-186=9 ms) than on the epicardium (mean APD,
204 ms; APD, 212-186=26 ms; n=8). In guinea pig hearts, activation
is rapid; therefore, repolarization depends primarily on intrinsic
spatial heterogeneities of APDs. Consequently, repolarization begins at
endocardial cells with the shortest APDs and spreads transmurally and
then anisotropically on the surface according to the epicardial cell
orientation.
Key Words: myocardial fiber orientation • action potential duration • optical mapping • repolarization patterns • activation patterns
This article has been cited by other articles:
 |
|
 |
|
  R. Weber dos Santos, A. Nygren, F. Otaviano Campos, H. Koch, and W. R. Giles Experimental and theoretical ventricular electrograms and their relation to electrophysiological gradients in the adult rat heart Am J Physiol Heart Circ Physiol, October 1, 2009; 297(4): H1521 - H1534. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Sims, S. Reisenweber, P. C. Viswanathan, B.-R. Choi, W. H. Walker, and G. Salama Sex, Age, and Regional Differences in L-Type Calcium Current Are Important Determinants of Arrhythmia Phenotype in Rabbit Hearts With Drug-Induced Long QT Type 2 Circ. Res., May 9, 2008; 102(9): e86 - e100. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Mantravadi, B. Gabris, T. Liu, B.-R. Choi, W. C. de Groat, G. A. Ng, and G. Salama Autonomic Nerve Stimulation Reverses Ventricular Repolarization Sequence in Rabbit Hearts Circ. Res., April 13, 2007; 100(7): e72 - e80. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. London, L. C. Baker, P. Petkova-Kirova, J. M. Nerbonne, B.-R. Choi, and G. Salama Dispersion of repolarization and refractoriness are determinants of arrhythmia phenotype in transgenic mice with long QT J. Physiol., January 1, 2007; 578(1): 115 - 129. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. L. Riess, A. K. S. Camara, S. S. Rhodes, J. McCormick, M. T. Jiang, and D. F. Stowe Increasing Heart Size and Age Attenuate Anesthetic Preconditioning in Guinea Pig Isolated Hearts Anesth. Analg., December 1, 2005; 101(6): 1572 - 1576. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Lakireddy, P. Baweja, A. Syed, G. Bub, M. Boutjdir, and N. El-Sherif Contrasting effects of ischemia on the kinetics of membrane voltage and intracellular calcium transient underlie electrical alternans Am J Physiol Heart Circ Physiol, January 1, 2005; 288(1): H400 - H407. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. R. Efimov, V. P. Nikolski, and G. Salama Optical Imaging of the Heart Circ. Res., July 9, 2004; 95(1): 21 - 33. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. L. Riess, A. K. S. Camara, E. Novalija, Q. Chen, S. S. Rhodes, and D. F. Stowe Anesthetic Preconditioning Attenuates Mitochondrial Ca2+ Overload During Ischemia in Guinea Pig Intact Hearts: Reversal by 5-Hydroxydecanoic Acid Anesth. Analg., December 1, 2002; 95(6): 1540 - 1546. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B.-R. Choi, F. Burton, and G. Salama Cytosolic Ca2+ triggers early afterdepolarizations and torsade de pointes in rabbit hearts with type 2 long QT syndrome J. Physiol., September 1, 2002; 543(2): 615 - 631. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. W. Cates, W. M. Smith, R. E. Ideker, and A. E. Pollard Purkinje and ventricular contributions to endocardial activation sequence in perfused rabbit right ventricle Am J Physiol Heart Circ Physiol, August 1, 2001; 281(2): H490 - H505. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Restivo, D. O. Kozhevnikov, and M. Boutjdir Optical mapping of activation patterns in an animal model of congenital heart block Am J Physiol Heart Circ Physiol, April 1, 2001; 280(4): H1889 - H1895. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. L Burton and S. M Cobbe Dispersion of ventricular repolarization and refractory period Cardiovasc Res, April 1, 2001; 50(1): 10 - 23. [Full Text] [PDF]
|
|
|
|
|
|
B.-R. Choi, T. Liu, and G. Salama The Distribution of Refractory Periods Influences the Dynamics of Ventricular Fibrillation Circ. Res., March 16, 2001; 88 (5): e49 - e58. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B.-R. Choi and G. Salama Simultaneous maps of optical action potentials and calcium transients in guinea-pig hearts: mechanisms underlying concordant alternans J. Physiol., November 15, 2000; 529(1): 171 - 188. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. C. Baker, B. London, B.-R. Choi, G. Koren, and G. Salama Enhanced Dispersion of Repolarization and Refractoriness in Transgenic Mouse Hearts Promotes Reentrant Ventricular Tachycardia Circ. Res., March 3, 2000; 86(4): 396 - 407. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Salama and B.-R. Choi Images of Action Potential Propagation in Heart Physiology, February 1, 2000; 15(1): 33 - 41. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. F. Scollan, A. Holmes, R. Winslow, and J. Forder Histological validation of myocardial microstructure obtained from diffusion tensor magnetic resonance imaging Am J Physiol Heart Circ Physiol, December 1, 1998; 275(6): H2308 - H2318. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. R. Efimov; and B.-R. Choi Letters to the Editor Am J Physiol Heart Circ Physiol, November 1, 1998; 275(5): H1905 - H1909. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. A. Gray and J. Jalife Effects of Atrial Defibrillation Shocks on the Ventricles in Isolated Sheep Hearts Circulation, April 28, 1998; 97(16): 1613 - 1622. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. M Bryant, S.J. Shipsey, and G. Hart Regional differences in electrical and mechanical properties of myocytes from guinea-pig hearts with mild left ventricular hypertrophy Cardiovasc Res, August 1, 1997; 35(2): 315 - 323. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. El-Sherif, E. B. Caref, H. Yin, and M. Restivo The Electrophysiological Mechanism of Ventricular Arrhythmias in the Long QT Syndrome: Tridimensional Mapping of Activation and Recovery Patterns Circ. Res., September 1, 1996; 79(3): 474 - 492. [Abstract] [Full Text]
|
|
|
|
|
|
K. R. Laurita, S. D. Girouard, and D. S. Rosenbaum Modulation of Ventricular Repolarization by a Premature Stimulus: Role of Epicardial Dispersion of Repolarization Kinetics Demonstrated by Optical Mapping of the Intact Guinea Pig Heart Circ. Res., September 1, 1996; 79(3): 493 - 503. [Abstract] [Full Text]
|
|