title: Local Heterogeneous Electrical Restitution Properties of Rabbit Atria.
abstract: This study aims to characterize the regional variability in rate-adaptation in the atria.
  
  
  
  Action potential (AP) responses to pulses with uniform as well as pseudo-random non-uniform pacing intervals were recorded from rabbit sino-atrial node, right and left atrial pectinate as well as pulmonary vein antrum tissue preparations using conventional intracellular glass microelectrodes. Steady-state restitution curves were reconstructed for various AP waveform metrics. We observed significant variability between the four regions under basal pacing representing the rabbit resting heart rate as well as regional variability in rate-adaptation to increased pacing frequencies. Right-left atrial restitution differences were further confirmed using the non-uniform pacing protocol, with significant differences in AP amplitude, duration (APD) as well as maximum phase 0 depolarization rate restitution curves in response to an identical sequence of non-uniform pacing intervals. In addition, we report regional differences in alternans of AP waveform metrics, over a wide range of pacing frequencies and not simply prior to 1:1 entrainment being lost. We also observed an increase in APD90 along the conduction pathway from the left atrium to pulmonary vein junction.
  
  
  
  Our results identified significant regional differences in electrical restitution in the rabbit atria and suggest their dependency on both baseline AP morphology and local intrinsic differences in rate-adaptation. We propose that the atrial heterogeneity in rate-adaptation could contribute to arrhythmogenesis and the greater susceptibility of pulmonary vein myocardial sleeves to ectopic foci and reentrant activity.
authors.affiliation: Graduate School of Biomedical Engineering, University of New South Wales Australia, Sydney, Australia.
authors.forename: Amr
authors.initials: A
authors.lastname: Al Abed
authors.affiliation: Graduate School of Biomedical Engineering, University of New South Wales Australia, Sydney, Australia.
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Lovell
authors.affiliation: Graduate School of Biomedical Engineering, University of New South Wales Australia, Sydney, Australia.
authors.forename: Socrates
authors.initials: S
authors.lastname: Dokos
mesh_terms: D000200:Action Potentials; D000222:Adaptation, Physiological; D000818:Animals; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D016275:Atrial Function; D002304:Cardiac Pacing, Artificial / Q000379:methods; D004195:Disease Models, Animal; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006325:Heart Atria / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D000067268:Isolated Heart Preparation; D008297:Male; D011667:Pulmonary Veins / Q000503:physiopathology; D011817:Rabbits; D013997:Time Factors
keywords: action potential; atria; electrical restitution; heterogeneity; pulmonary veins