Adaptive frequency tracking of the baseline ECG identifies the site of atrial fibrillation termination by catheter ablation
Multiple organization indices have been used to predict the outcome of stepwise catheter ablation in long-standing persistent atrial fibrillation (AF), however with limited success. Our study aims at developing innovative organization indices from baseline ECG (i.e. during the procedure, before ablation) in order to identify the site of AF termination by catheter ablation. Seventeen consecutive male patients (age 60±5 years, AF duration 7±5 years) underwent a stepwise catheter ablation. Chest lead V6 was placed in the back (V6b). QRST cancellation was performed from chest leads V1 to V6b. Using an innovative adaptive harmonic frequency tracking, two measures of AF organization were computed to quantify the harmonics components of ECG activity: 1) the adaptive phase difference variance (APD) between the AF harmonic components as a measure of AF regularity, and 2) and adaptive organization index (AOI) evaluating the cyclicity of the AF oscillations. Both adaptive indices were compared to indices computed using a time-invariant approach: 1) ECG AF cycle length (AFCL), 2) the spectrum based organization index (OI), and 3) the time-invariant phase difference TIPD. Long-standing persistent AF was terminated into sinus rhythm or atrial tachycardia in 13/17 patients during stepwise ablation, 11 during left atrium ablation (left terminated patients – LT), 2 during right atrium ablation (right terminated patients – RT), and 4 were non terminated (NT) and required electrical cardioversion. Our findings showed that LT patients were best separated from RT/NT before ablation by the duration of sustained AF and by AOI on chest lead V1 and APD from the dorsal lead V6b as compared to ECG AFCL, OI and TIPD respectively. Our results suggest that adaptive measures of AF organization computed before ablation perform better than time-invariant based indices for identifying patients whose AF will terminate during ablation within the left atrium. These findings are indicative of a higher baseline organization in these patients that could be used to select candidates for the termination of AF by stepwise catheter ablation.