Differences in the activation patterns between sustained and self-terminating episodes of human ventricular fibrillation.

BACKGROUND: Experimental studies have suggested that R-R interval dynamics during ventricular fibrillation (VF) have organized features, but whether dynamic behavior of non-sustained VF differs from sustained VF is unknown. AIM: The purpose of this study was to investigate whether the dynamics of R-R intervals during non-sustained VF differs from the dynamics during sustained VF.
METHODS: A group of 67 patients undergoing routine implantable cardioverter defibrillator (ICD) testing was studied. Forty-three VF events containing mean of 38 local cardiac activation intervals before the termination by ICD shock were analyzed. From intracardiac electrogram recordings, the ratio between the short and long term variability (SD1/SD2) and fractal scaling exponent (alpha) were analyzed. After the initial analyses, data sets were randomized and reanalyzed. Local activation dynamics were then also compared in seven patients with both sustained and spontaneously terminating VF episodes.
RESULTS: Randomization caused a change in the VF dynamics from organized toward less organized dynamics (alpha) from 1.08 +/- 0.57 to 0.81 +/- 0.45, P < 0.05 and SD1/SD2 from 0.80 +/- 0.23 to 1.04 +/- 0.20, P < 0.01). Spontaneously terminating VF showed more organized dynamics than sustained VF terminated by shock (P < 0.05).
CONCLUSIONS: Local cardiac activation dynamics during initial phase of human VF shows organized dynamics. Spontaneously terminating VF episodes have more structured dynamics than sustained VF. Thus, the dynamic behavior of local cardiac activation intervals may be related to the maintenance of ventricular tachyarrhythmias.