Abstract P143: Periods of Highly Organized Non-Reentrant Endocardial Activation Can Occur During Long Duration Ventricular Fibrillation
Introduction: Little is known about long duration ventricular fibrillation (LDVF), a time when resuscitation from sudden arrest is still possible.
Methods: 6 beagles (9.5±0.8kg) were anesthetized and instrumented with a 64 electrode mapping basket catheter placed in the LV apex, a RV catheter, and a 12 lead body surface ECG. VF was initiated with pulse stimulation through the RV lead and recorded until spontaneous self termination. The first 15 activations at each 1 min interval after the initiation of VF were identified in the LV and RV electrode recordings. Activation sequences of the 15 cycles of activations on the LV endocardium were compared with the RV activation times and with the ECG during each min of VF.
Results: Early during VF, LV endocardial activation was present throughout most of each cycle 87.8±23.9%) in all animals (Figure A⇓, where each short vertical line represents an activation), consistent with reentry. In 4 of the 6 canines, the activation sequences became highly organized at 4 –7 min after VF onset (Figure B⇓). Activation was only present for a small percentage of each cycle (17.3±5.4%, p=0.02), indicating that reentry was no longer present on the LV endocardium. During this organized period, the RV activation was at a different rate than the LV activation, and the ECG continued to appear irregular, consistent with VF.
Conclusion: During LDVF, a highly organized LV endocardial activation pattern frequently occurs that is not consistent with reentry but is consistent with triggered activity or abnormal automaticity. The ECG continues to appear irregular during this period because of differences in LV and RV cycle lengths.