Multiple monophasic shocks improve electrotherapy of ventricular tachycardia in a rabbit model of chronic infarction

Heart Rhythm. 2009 Jul;6(7):1020-7. doi: 10.1016/j.hrthm.2009.03.015. Epub 2009 Mar 11.


Background: We previously showed that the cardioversion threshold (CVT) for ventricular tachycardia (VT) is phase dependent when a single monophasic shock (1MP) is used.

Objective: The purpose of this study was to extend these findings to a biphasic shock (1BP) and to compare the efficacy of phase-independent multiple monophasic (5MP) and biphasic shocks (5BP).

Methods: Panoramic optical mapping with blebbistatin (5 microM) was performed in postmyocardial infarction rabbit hearts (n = 8). Flecainide (1.64 +/- 0.68 microM) was administered to promote sustained arrhythmias. 5MP and 5BP were applied within one VT cycle length (CL). Results were compared to 1BP and antitachycardia pacing.

Results: We observed monomorphic VT with CL = 149.6 +/- 18.0 ms. Similar to 1MP, CVTs of 1BP were found to be phase dependent, and the maximum versus minimum CVT was 8.6 +/- 1.7 V/cm versus 3.7 +/- 1.9 V/cm, respectively (P = .0013). Efficacy of 5MP was higher than that of 1BP and 5BP. CVT was 3.2 +/- 1.4 V/cm for 5MP versus 5.3 +/- 1.9 V/cm for 5BP (P = .00027). 5MP versus averaged 1BP CVT was 3.6 +/- 2.1 V/cm versus. 6.8 +/- 1.5 V/cm, respectively (P = .00024). Antitachycardia pacing was found to be completely ineffective in this model.

Conclusion: Maintenance of shock-induced virtual electrode polarization by multiple monophasic shocks over a VT cycle is responsible for unpinning of reentry leading to self-termination. Elimination of virtual electrode polarization by shock polarity reversal during multiple biphasic shocks proved ineffective. A significant reduction in CVT can be achieved by applying multiple monophasic shocks within one VT CL or one single shock at the proper coupling interval.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Disease Models, Animal
  • Electric Countershock / methods*
  • Female
  • Male
  • Myocardial Infarction / complications*
  • Myocardial Infarction / physiopathology
  • Rabbits
  • Tachycardia, Ventricular / etiology
  • Tachycardia, Ventricular / physiopathology
  • Tachycardia, Ventricular / therapy*