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 u003e5 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 per...