Directional differences in excitability and margin of safety for propagation in sheep ventricular epicardial muscle
- PMID: 2364498
- DOI: 10.1161/01.res.67.1.97
Directional differences in excitability and margin of safety for propagation in sheep ventricular epicardial muscle
Abstract
Computer simulations and isolated tissue experiments were used to characterize the relation between excitability and margin of safety for propagation in anisotropic ventricular myocardium. Longitudinal, uniform transverse, and nonuniform transverse tissue directions were modeled in a one-dimensional Beeler-Reuter based cable. Stimulation threshold was smallest in the nonuniform transverse direction. The safety factor for propagation was determined in the model as the total axial charge that was available for depolarizing downstream tissue divided by the threshold charge that was just sufficient for continued propagation and was largest in the longitudinal direction. The strength-interval plot for the junction between simulated longitudinal and nonuniform transverse directions identified a range of stimulus strengths and intervals that resulted in nonuniform transverse but not longitudinal propagation. When high values of transverse resistance were used, higher stimulus strengths during premature stimulation resulted in longitudinal but not nonuniform transverse propagation. The experimental strength interval plots from 17 L-shaped preparations of isolated sheep epicardial muscles had similar characteristics. In nine additional L-shaped tissue experiments, changing extracellular K+ concentrations from 4 to 20 mM resulted in progressive membrane depolarization and conduction impairment in both directions. However, in eight of nine experiments, complete block occurred first in the transverse direction. In one experiment, block was simultaneous in both directions. We conclude that, under normal conditions, threshold requirements for active propagation are lower for transverse than for longitudinal propagation. In addition, when active membrane properties are impaired, the safety factor for propagation is larger in the direction along the longitudinal axis of the cells.
Similar articles
-
Effects of increasing intercellular resistance on transverse and longitudinal propagation in sheep epicardial muscle.Circ Res. 1987 May;60(5):780-5. doi: 10.1161/01.res.60.5.780. Circ Res. 1987. PMID: 3594750
-
Wave-front curvature as a cause of slow conduction and block in isolated cardiac muscle.Circ Res. 1994 Dec;75(6):1014-28. doi: 10.1161/01.res.75.6.1014. Circ Res. 1994. PMID: 7525101
-
Computer simulations of three-dimensional propagation in ventricular myocardium. Effects of intramural fiber rotation and inhomogeneous conductivity on epicardial activation.Circ Res. 1993 Apr;72(4):744-56. doi: 10.1161/01.res.72.4.744. Circ Res. 1993. PMID: 8443866
-
Anisotropic activation spread in heart cell monolayers assessed by high-resolution optical mapping. Role of tissue discontinuities.Circ Res. 1996 Jul;79(1):115-27. doi: 10.1161/01.res.79.1.115. Circ Res. 1996. PMID: 8925559 Review.
-
[Anisotropic impulse conduction characteristics in chronic myocardial infarct. The importance for initiation and perpetuation of ventricular tachycardia].Z Kardiol. 1993 Apr;82(4):229-36. Z Kardiol. 1993. PMID: 8506717 Review. German.
Cited by
-
Coupling between cardiac cells-An important determinant of electrical impulse propagation and arrhythmogenesis.Biophys Rev (Melville). 2021 Sep;2(3):031301. doi: 10.1063/5.0050192. Epub 2021 Jul 13. Biophys Rev (Melville). 2021. PMID: 34296210 Free PMC article. Review.
-
Anisotropic Cardiac Conduction.Arrhythm Electrophysiol Rev. 2020 Dec;9(4):202-210. doi: 10.15420/aer.2020.04. Arrhythm Electrophysiol Rev. 2020. PMID: 33437488 Free PMC article. Review.
-
Direction- and rate-dependent fractionation during atrial fibrillation persistence: Unmasking cardiac anisotropy?J Cardiovasc Electrophysiol. 2020 Aug;31(8):2206-2209. doi: 10.1111/jce.14597. Epub 2020 Jun 11. J Cardiovasc Electrophysiol. 2020. PMID: 32478928 Free PMC article.
-
Strength-duration relationship as a tool to prioritize cardiac tissue properties that govern electrical excitability.Am J Physiol Heart Circ Physiol. 2019 Jul 1;317(7):H13-H25. doi: 10.1152/ajpheart.00161.2019. Epub 2019 Mar 29. Am J Physiol Heart Circ Physiol. 2019. PMID: 30925072 Free PMC article.
-
New insights on the cardiac safety factor: Unraveling the relationship between conduction velocity and robustness of propagation.J Mol Cell Cardiol. 2019 Mar;128:117-128. doi: 10.1016/j.yjmcc.2019.01.010. Epub 2019 Jan 22. J Mol Cell Cardiol. 2019. PMID: 30677394 Free PMC article.
Publication types
MeSH terms
Grants and funding
LinkOut - more resources
Full Text Sources