title: Bradycardic onset of spiral wave re-entry: structural substrates.
abstract: OBJECTIVE
  The least understood aspect of re-entrant cardiac arrhythmias is how they start spontaneously. The known mechanisms for re-entry induction involve the application of premature electrical stimuli or rapid pacing, whereas in a clinical setting, re-entry often occurs at normal heart rates. Here, we propose a physiological mechanism of re-entry onset at normal and slow heart rates, which is based on structurally determined heterogeneities.
  
  
  RESULTS
  Using a two-dimensional tissue model with Luo-Rudy II kinetics, we study electrical propagation in the presence of macroscopic coupling heterogeneities. We find that spiral wave re-entry occurs if steep and smooth coupling gradients are situated side by side, with the critical steepness depending on the frequency of stimulation. We demonstrate how bradycardia can unmask a slow endogenous pacemaker in a poorly coupled region, subsequently leading to spiral wave re-entry.
  
  
  CONCLUSIONS
  In the presence of coupling heterogeneities, a single excitation coming from the less coupled region may induce spiral wave re-entry.
authors.affiliation: Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, USA. zemlinc@upstate.edu
authors.forename: Christian W
authors.initials: CW
authors.lastname: Zemlin
authors.forename: Arkady M
authors.initials: AM
authors.lastname: Pertsov
mesh_terms: D001281:Atrial Fibrillation / Q000209:etiology / Q000503:physiopathology; D001919:Bradycardia / Q000209:etiology* / Q000503:physiopathology*; D004553:Electric Conductivity; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D008955:Models, Cardiovascular; D010138:Pacemaker, Artificial; D011667:Pulmonary Veins / Q000502:physiology