Abstract 16022: Failed Defibrillation Shocks Change Activation Patterns Following Prolonged but Not Short Duration Ventricular Fibrillation
Introduction: Recent studies have demonstrated that as ventricular fibrillation (VF) persists past the first 1-2 minutes, 3 distinct patterns of activity can be present subendocardially: chaotic, regular, and synchronous.
Hypothesis: Failed defibrillation shocks change activation patterns even though they are not successful in terminating VF.
Methods: A 64 electrode basket catheter was inserted into the LV of 6 dogs. Ten sec after VF was induced electrically, short duration VF (SDVF), shocks of increasing strength were delivered between coils in the right ventricle and the superior venae cava every 10 s until VF was terminated. After a >5 min recovery period, the procedure was repeated following 7 min of VF, (long duration VF, LDVF. An automated algorithm was used to categorize endocardial activation patterns as chaotic (varying cycle lengths and non-synchronous activations), regular (highly repeatable cycle lengths), and synchronous (activation that spreads rapidly over the endocardium with diastolic periods between activations).
Results: The defibrillation threshold was 37±31 J for SDVF and 16±11 J for LDVF (p=0.09). In SDVF, the chaotic pattern was predominant before and after failed shocks. The synchronous pattern only emerged after one shock. Following LDVF, however, the synchronous pattern either preceded (n=2) or emerged after failed shocks (n=4), so that all successful shocks (6/6) were delivered during the synchronized pattern (p<0.05 by Fisher’s exact test for incidence of synchronous pattern in LDVF vs. SDVF preceding successful shocks).
Conclusions: Failed defibrillation shocks significantly change activation patterns in LDVF but not in SDVF. Further investigation is warranted to determine if defibrillation for LDVF is more likely to succeed if the shock is delivered when the synchronous pattern is present.
Author Disclosures: L. Li: None. J. Huang: None. N. Panitchob: None. R.E. Ideker: Research Grant; Significant; NIH. D.J. Dosdall: Research Grant; Significant; NIH.
- © 2016 by American Heart Association, Inc.