title: Tridimensional activation patterns of acquired torsade-de-pointes tachycardias in dogs with chronic AV-block.
abstract: BACKGROUND
  Dogs with chronic AV block exposed to type-III antiarrhythmic agents develop polymorphic ventricular tachycardias (PVT). Controversy exists regarding PVT mechanism and underlying pathophysiology.
  
  
  RESULTS
  In dogs with acute (n = 10, AAVB) or chronic AV block (n = 14, CAVB, 62 +/- 5 days after AV-node ablation) 60 pins (12 mm long, 4 bipolar electrodes) were inserted into both ventricles. QT intervals and effective refractory periods (ERP) at 56 +/- 22 randomly selected sites (extrastimulus technique, 800 ms basic cycle length) were determined before and after Almokalant (0.34 micromol/kg). A multiplexer mapping system was used to reconstruct 3D activation patterns. The heart-to-body-weight index (HBWI) was obtained after the experiments. CAVB led to a significant increase in HBWI (11.3 +/- 1.5 vs. 9 +/- 1.2 g/kg BW, p < 0.001), and a significant increase in ERP (280 +/- 28 ms vs. 260 +/- 37 ms, p < 0.05) and QT interval (339 +/- 16 vs. 288 +/-12 ms, p < 0.05). Dispersion (DISP) of ERP was similar for AAVB and CAVB dogs. No AAVB dog, but 9 of 14 CAVB dogs developed PVTs in response to Almokalant. All PVTs originated from an endocardial focus. Consecutive beats continued to reveal centrifugal activation patterns in 8 of 10 episodes. In only 2 episodes was reentrant activation evident.
  
  
  CONCLUSIONS
  Myocardial hypertrophy associated with CAVB predisposes the canine heart to drug induced PVTs. This seems to be primarily linked to prolonged repolarization. PVTs in this model are not only initiated, but also perpetuated by a centrifugal spread of activation.
authors.affiliation: University of Heidelberg, Department of Cardiology, Bergheimerstr 58, 69115, Heidelberg, Germany. Dr.Mark.Schreiner@telemed.de
authors.forename: Kirsten D
authors.initials: KD
authors.lastname: Schreiner
authors.forename: Frederik
authors.initials: F
authors.lastname: Voss
authors.forename: Julia C
authors.initials: JC
authors.lastname: Senges
authors.forename: Ruediger
authors.initials: R
authors.lastname: Becker
authors.forename: Patrizia
authors.initials: P
authors.lastname: Kraft
authors.forename: Alexander
authors.initials: A
authors.lastname: Bauer
authors.forename: Kamilla
authors.initials: K
authors.lastname: Kelemen
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kuebler
authors.forename: Marc A
authors.initials: MA
authors.lastname: Vos
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schoels
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects*; D006332:Cardiomegaly / Q000150:complications / Q000503:physiopathology; D004285:Dogs; D004562:Electrocardiography; D006327:Heart Block / Q000150:complications / Q000503:physiopathology; D006329:Heart Conduction System / Q000503:physiopathology*; D023421:Models, Animal; D011412:Propanolamines / Q000009:adverse effects*; D016171:Torsades de Pointes / Q000139:chemically induced* / Q000503:physiopathology*
chemical_list: D000889:Anti-Arrhythmia Agents; D011412:Propanolamines; C074334:almokalant