Clinical and computational studies reveal that quantitative criteria of ECG voltage variation differ significantly between VF-sustaining rotors and focal sources, and provide insight into the mechanisms of such variation. Future studies should prospectively evaluate if these criteria can separate clinical VF mechanisms and guide therapy.

Introduction: Recent work has shown that rotor characteristics can distinguish sustained versus non-sustained ventricular fibrillation (VF). However, the significance of functional VF substrates on patient outcomes is not studied. Methods: In 26 consecutive patients presenting for ventricular arrhythmia ablation procedures, 64-electrode basket catheters were inserted into both the left and right ventricles and VF was induced and defibrillated at 11±3 seconds. Computational phase analysis was performed and each VF cycle was characterized as rotor, focal, or disorganized activation. Follow-up data were analyzed for arrhythmia recurrence and compared to rotor stability. Forward stepwise regression analysis incorporating age, history of CHF, history of a-fib, history of prior MI, number of VTs induced, and presence of post-procedure inducible VT was performed to determine the strongest predictor of procedural outcome. Results: Of 26 patients, 19 had sustained VF, and 16 underwent attempted ablation (7 VT, 9 PVC). Optimization of the Youden index for the ROC analysis regarding rotor stability and procedural outcome demonstrated that maximum rotor stability of > 14.5 rotations (corresponding to total rotor prevalence of 71%) provided optimal sensitivity of 85% and specificity of 87% for arrhythmia recurrence. Among these, greater rotor stability was significantly associated with ventricular arrhythmia recurrence (86% versus 11%, p = 0.01) (Table 1), and was the strongest predictor of outcomes. Recurrence was independent of presenting arrhythmia. Conclusions: Functional VF/VT metrics were the strongest predictor of ventricular arrhythmia outcomes compared to traditional predictors in this series of patients. This suggests that functional substrate characteristics may provide added insight into recurrence mechanisms. Whether they may identify a target for future interventions requires further study.

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