Tridimensional activation patterns of acquired torsade-de-pointes tachycardias in dogs with chronic AV-block

Basic Research in Cardiology
Kirsten D SchreinerWolfgang Schoels

Abstract

Dogs with chronic AV block exposed to type-III antiarrhythmic agents develop polymorphic ventricular tachycardias (PVT). Controversy exists regarding PVT mechanism and underlying pathophysiology. 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 on...Continue Reading

Citations

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