High-rate pacing reduces variability of repolarization and prevents repolarization-dependent arrhythmias in dogs with chronic AV block

J Cardiovasc Electrophysiol. 2010 Dec;21(12):1384-91. doi: 10.1111/j.1540-8167.2010.01824.x.

Abstract

Introduction: high-rate pacing may have an inhibitory effect on the initiation of Torsade de Pointes arrhythmias (TdP). However, permanent pacing is only indicated in high-risk patients. We performed a proof of concept study into automatic overdrive pacing for prevention of drug-induced TdP, using short-term variability of repolarization (STV) as a feedback parameter of arrhythmic risk.

Methods and results: the minimal signal sampling frequency required for measuring STV was determined through computer simulation. Arrhythmogenic response to dofetilide (25 microg/kg/5 minutes) was tested at two different paced heart rates (60-65 bpm vs 100-110 bpm) in 7 dogs with chronic atrioventricular block, while recording right and left ventricular (LV) monophasic action potential (MAP) and LV electrogram (EGM). Simulations showed a sampling frequency of 500 Hz is sufficient to capture relevant STV values. High-rate pacing prevented dofetilide-induced TdP seen at the low rate (low: 6/7 vs high: 1/7). At the low rate, STV from LV MAP duration increased before occurrence of spontaneous, ectopic activity and TdP (1.7 ± 0.6-3.0 ± 1.8 ms, P < 0.05), but at the high-rate STV did not change significantly (0.9 ± 0.2-1.5 ± 1.4 ms, NS). Regression analysis showed a close relation between STV calculated from LV MAP and from LV EGM (R(2) = 0.71).

Conclusions: high-rate pacing increases repolarization reserve in dogs with chronic atrioventricular block, preventing dofetilide-induced TdP. Changes in repolarization reserve are reflected in values of STV.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arrhythmias, Cardiac / complications
  • Arrhythmias, Cardiac / physiopathology
  • Arrhythmias, Cardiac / prevention & control*
  • Atrioventricular Block / complications
  • Atrioventricular Block / physiopathology*
  • Atrioventricular Block / therapy*
  • Cardiac Pacing, Artificial / methods*
  • Chronic Disease
  • Dogs
  • Torsades de Pointes / complications
  • Torsades de Pointes / physiopathology*
  • Torsades de Pointes / therapy*