Preshock phase singularity and the outcome of ventricular defibrillation

Background: Phase singularity (PS) is a topological defect that serves as a source of ventricular fibrillation (VF). Whether or not the quantity of preshock PS determines defibrillation outcome is unclear. Objective: The purpose of this study was to test the hypothesis that the number of PSs at the time of shock is an important factor that determines the shock outcome. Methods: Isolated, perfused rabbit hearts (n = 7) were optically mapped with a potentiometric dye (di-4-ANNEPS). Shocks were delivered during short (10 seconds) and long (1 minute) VF, and the outcome was classified as successful type A (immediate termination), type B (postshock repetitive responses before termination), and unsuccessful. Results: When shock strengths of 50% probability of successful defibrillation (DFT50) ± 50 V were given in short VF, the types A and B and unsuccessful shocks were associated with a preshock PS number of 0.3 ± 0.4, 1.4 ± 0.3, and 1.5 ± 0.4 (P <.01 by analysis of variance) and shock strengths of 205 ± 77, 207 ± 65, and 173 ± 74 V (P <.01), respectively. When the same shocks were applied during long VF, the PS numbers were 1.7 ± 0.5, 3.0 ± 0.5, and 3.5 ± 0.6, respectively (P <.01), and the shock strengths were 282 ± 100, 283 ± 135, and 256 ± 126 V, respectively (P <.01). If we only analyze shocks with strength at DFT50, the preshock PS number was still significantly different for short VF (0.6 ± 0.5, 1.6 ± 0.9, and 1.5 ± 0.8; P <.05) and for long VF (1.4 ± 0.5, 2.7 ± 0.6, and 2.7±1.3; P <.05), respectively. All preshock PSs were eliminated by shocks. However, rapid repetitive activity was then reinitiated in unsuccessful and type B successful shocks but not in type A successful shocks. Conclusions: A low number or an absence of preshock PS was associated with type A successful defibrillation. There was no difference in preshock PS numbers between unsuccessful and type B successful defibrillation. © 2007 Heart Rhythm Society.