title: Isorhythmic atrioventricular dissociation in Labrador Retrievers.
abstract: BACKGROUND
  Isorhythmic atrioventricular dissociation (IAVD) is a rhythm disturbance in which atria and ventricles are driven by independent pacemakers at equal or nearly equal rates.
  
  
  OBJECTIVE
  To describe electrocardiographic and electrophysiologic features of IAVD in a group of 11 Labrador Retrievers and its possible correlation with focal junctional tachycardia (FJT).
  
  
  METHODS
  Between December 2004 and October 2010, medical records of 11 Labrador Retrievers with surface electrocardiographic findings compatible with IAVD were retrospectively analyzed.
  
  
  METHODS
  Twelve-lead surface electrocardiograms, thoracic radiographs, and echocardiographic findings of each dog and electrophysiologic mapping results of 3 dogs were retrospectively analyzed.
  
  
  RESULTS
  In 10 of 11 dogs, the ECG pattern revealed the presence of IAVD with type I synchronization. In 5 of 10 dogs, IAVD with type I synchronization was interrupted by periods of junctional tachycardia with 1 : 1 ventriculo-atrial conduction. One of 11 dogs presented IAVD with type II synchronization. The ECG diagnosis of IAVD with type I and type II synchronization, and junctional rhythm with 1 : 1 ventriculo-atrial conduction was confirmed in 3 of 11 dogs with endocardial mapping in which the diagnosis of focal junctional tachycardia was made.
  
  
  CONCLUSIONS
  IAVD with type I synchronization is more common than IAVD with type II synchronization in Labrador Retrievers, and a correlation between IAVD and FJT can be hypothesized.
authors.affiliation: Clinica Veterinaria Malpensa, Samarate, Varese, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Perego
authors.forename: L
authors.initials: L
authors.lastname: Ramera
authors.forename: R A
authors.initials: RA
authors.lastname: Santilli
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000662:veterinary*; D001283:Atrioventricular Node / Q000000981:diagnostic imaging / Q000503:physiopathology*; D004283:Dog Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D004285:Dogs; D004452:Echocardiography / Q000662:veterinary; D004562:Electrocardiography / Q000662:veterinary; D005260:Female; D008297:Male; D011859:Radiography; D012189:Retrospective Studies; D013613:Tachycardia, Ectopic Junctional / Q000000981:diagnostic imaging / Q000503:physiopathology*