title: Long-term Intrinsic Rhythm Evaluation in Dogs with Atrioventricular Block.
abstract: BACKGROUND
  Atrioventricular block (AVB) is a conduction abnormality along the atrioventricular node that, depending on etiology, may lead to different outcomes.
  
  
  OBJECTIVE
  To evaluate variations of intrinsic rhythm (IR) in dogs that underwent pacemaker implantation (PMI).
  
  
  METHODS
  Medical records of 92 dogs affected by 3rd degree atrioventricular block (3AVB), advanced 2nd degree AVB (2AVB), paroxysmal 3AVB, 2:1 2AVB, or 3AVB with atrial fibrillation (AF) were retrospectively reviewed.
  
  
  METHODS
  The patient IR was documented with telemetry on the day of 1--(95% CI, 1-2), 33--(95% CI, 28-35), 105--(95%CI, 98-156), and 275 days (95%CI, 221-380) after PMI. According to AVB grade at different examinations, AVB was defined as progressed, regressed, or unchanged.
  
  
  RESULTS
  In 48 dogs, 3AVB remained unchanged, whereas in 7 it regressed. Eight cases of 2AVB progressed, 3 regressed and 2 remained unchanged. Eight cases of paroxysmal 3AVB progressed and 3 remained unchanged. Four dogs affected by 2:1 2AVB progressed, 2 regressed, and 1 remained unchanged. All cases with 3AVB with AF remained unchanged. Regression occurred within 30 days after PMI, whereas progression was documented at any time. Variations in IR were associated with type of AVB (P < .03) and time of follow-up (P < .0001).
  
  
  CONCLUSIONS
  The degree of AVB assessed at the time of PMI should not be considered definitive because more than one-third of the cases in this study either progressed or regressed. Additional studies would be necessary to elucidate possible causes for transient AVB in dogs.
authors.affiliation: Clinica Veterinaria Malpensa, Samarate, Varese, Italy.
authors.forename: R A
authors.initials: RA
authors.lastname: Santilli
authors.affiliation: Clinica Veterinaria Malpensa, Samarate, Varese, Italy.
authors.forename: D M
authors.initials: DM
authors.lastname: Porteiro Vázquez
authors.affiliation: Ospedale Didattico Veterinario "Mario Modenato", Dipartimento di Scienze Veterinarie, Università di Pisa, San Piero a Grado (Pisa), Italy.
authors.forename: T
authors.initials: T
authors.lastname: Vezzosi
authors.affiliation: Clinica Veterinaria Malpensa, Samarate, Varese, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Perego
mesh_terms: D000818:Animals; D054537:Atrioventricular Block / Q000473:pathology / Q000662:veterinary*; D004283:Dog Diseases / Q000473:pathology*; D004285:Dogs; D005260:Female; D008297:Male; D010138:Pacemaker, Artificial; D012189:Retrospective Studies; D013997:Time Factors
keywords: Arrhythmias; Dog; Myocarditis; Pacemaker