‘The electrical spiral of the heart’: its role in the helical continuum.The hypothesis of the anisotropic conducting matrix

Abstract

The study of the dissemination of the electrical impulse throughout the ventricular myocardium, which gave rise to the current theories, was carried out without taking into consideration the complex architecture of the cardiac muscle elucidated by more recent researchers. We propose a novel hypothesis based on the special macroscopic structure of the heart, the anisotropic electrical and mechanical behavior of the myocardium, the characteristics of the intercellular matrix and its very special collagen scaffolding, chemical composition, and biochemistry. The unique properties of the intercellular matrix would make it especially suited to function, in conjunction with the specialized conducting system (His-Purkinje system) as an efficient anisotropic conductor for the spread of electrical activation in the heart in order to allow an optimal sequence of excitation-contraction coupling that results in the coordination of effective myocardial contraction in birds and mammals of the most varied known heart rates. An analysis of certain clinical conditions that raise questions regarding current hypothesis and a review of novel techniques for recording transmembrane and extracellular potentials, which will provide a much firmer basis for the study of cardiac activation and the influence of myofiber architecture and which will allow in depth testing of hypotheses are presented.

The infrahisian conduction system and endocavitary cardiac structures: relevance for the invasive electrophysiologist

“…The clinical relevance of these adaptations is unknown. Purkinje conduction is putatively linked to myocardial extracellular matrix ionic composition and myocardial fiber folding [72], which may also be dynamic, again with unknown clinical consequences. Autonomic influences [30, 73, 74] and antiarrhythmic drugs confer further functional Purkinje plasticity.…”

Arrhythmogenesis by single ectopic beats originating in the Purkinje system

“…Sodium conductance in the DiFrancesco-Nobel model was increased threefold (5) to increase maximum upstroke velocity (‫ץ‬V m/‫ץ‬t) in uncoupled cells from 169 to 380 mV/ms, which is closer to the in vitro value reported by Lu et al (25). Purkinje cell radius was set to 15 m, and intracellular conductivity was set to 1.5 S/m to achieve the conduction velocity (CV) ratio of 4.4 with reference to the myocardium (4), which is within the experimental range (11). Figure 1B shows ventricular excitation by the PS during normal sinus rhythm.…”

Behaviour of the Purkinje System During Defibrillation-Strength Shocks

“…Without modifications to published parameters in both models, the ratio of PS and longitudinal myocardial conduction velocities (Θ PS /Θ myo ) was slightly greater than 1, falling short of accepted values, which range from 2 to 10, depending on species [9]. Model parameters were adjusted to better reflect physiological behaviour:…”

“…In vivo studies have demonstrated inter-species differences in Purkinje endpoint penetration depth [9]. Thus, the effect of defibrillation-strength shocks was assessed for PS structures with surface-coupled fibres, midwall-penetrating fibres (onethird and two-thirds), and fully-penetrating fibres, which nearly reach the epicardium.…”