title: Remodeling of cardiac passive electrical properties and susceptibility to ventricular and atrial arrhythmias.
abstract: Coordinated electrical activation of the heart is essential for the maintenance of a regular cardiac rhythm and effective contractions. Action potentials spread from one cell to the next via gap junction channels. Because of the elongated shape of cardiomyocytes, longitudinal resistivity is lower than transverse resistivity causing electrical anisotropy. Moreover, non-uniformity is created by clustering of gap junction channels at cell poles and by non-excitable structures such as collagenous strands, vessels or fibroblasts. Structural changes in cardiac disease often affect passive electrical properties by increasing non-uniformity and altering anisotropy. This disturbs normal electrical impulse propagation and is, consequently, a substrate for arrhythmia. However, to investigate how these structural changes lead to arrhythmias remains a challenge. One important mechanism, which may both cause and prevent arrhythmia, is the mismatch between current sources and sinks. Propagation of the electrical impulse requires a sufficient source of depolarizing current. In the case of a mismatch, the activated tissue (source) is not able to deliver enough depolarizing current to trigger an action potential in the non-activated tissue (sink). This eventually leads to conduction block. It has been suggested that in this situation a balanced geometrical distribution of gap junctions and reduced gap junction conductance may allow successful propagation. In contrast, source-sink mismatch can prevent spontaneous arrhythmogenic activity in a small number of cells from spreading over the ventricle, especially if gap junction conductance is enhanced. Beside gap junctions, cell geometry and non-cellular structures strongly modulate arrhythmogenic mechanisms. The present review elucidates these and other implications of passive electrical properties for cardiac rhythm and arrhythmogenesis.
authors.affiliation: Clinic for Cardiac Surgery, Heart Center Leipzig, University Leipzig Leipzig, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Dhein
authors.affiliation: Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah Salt Lake City, UT, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Seidel
authors.affiliation: Clinic for Pediatric Cardiology, Heart Center Leipzig, University Leipzig Leipzig, Germany.
authors.forename: Aida
authors.initials: A
authors.lastname: Salameh
authors.affiliation: Clinic for Cardiology, Heart Center Leipzig, University Leipzig Leipzig, Germany.
authors.forename: Joanna
authors.initials: J
authors.lastname: Jozwiak
authors.affiliation: Hospital for Children and Adolescents, University of Leipzig Leipzig, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Hagen
authors.affiliation: Clinic for Cardiac Surgery, Heart Center Leipzig, University Leipzig Leipzig, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kostelka
authors.affiliation: Clinic for Cardiology, Heart Center Leipzig, University Leipzig Leipzig, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Hindricks
authors.affiliation: Clinic for Cardiac Surgery, Heart Center Leipzig, University Leipzig Leipzig, Germany.
authors.forename: Friedrich-Wilhelm
authors.initials: FW
authors.lastname: Mohr
keywords: anisotropy; cable theory; cardiac tissue; connexin; electrical propagation; gap junction; inhomogeneity; passive electrical properties