Introduction: Pulmonary vein isolation (PVI) has been proven to be efficacious for ablation of paroxysmal atrial fibrillation. Several advances have been made in PVI techniques to lower the rate of recurrences while ensuring the accuracy and adequacy of lesion formation. In addition to using optimal contact force as per the TOCCATA trial, it was shown in another multicenter trial (EFFICAS I) that using a minimal “Force Time Interval” (FTI) of 400gs for all segments of the pulmonary veins (PV) further improves the ablation outcomes with less gaps and gap reconnections evident with invasive re-evaluation of PVI at 3 months.
Hypothesis: We assessed the hypothesis that, in contrast to EFFICAS I, the different segments of PV require different contact force parameters, particularly FTI.
Methods: By using the high output pacing module (10 mA at 2 ms) during the PVI of 13 patients, the values of FTI were collected. The digital records of 458 lesions were correlated with catheter position in each of the 4 anatomical segments (anterior, posterior, superior and inferior) surrounding both right and left pulmonary veins. Average FTI values were compared for each segment.
Results: The results showed that the right anterior segment of the PV requires the highest FTI value of (553+/-81) compared to the right posterior (291+/-38.6), inferior (403+/-32) and superior (343+/-13) prior to losing capture at high output pacing. Similarly, the left anterior segment requires a higher FTI (367+/-31) compared to the left posterior (323+/-24), left inferior (203 +/- 27) and left superior (309+/-32). It was also apparent that when power is incorporated to the equation; the LSI (Lesion Stability Index) values are much less variable than FTI.
Conclusion: When using loss of capture at high output pacing as a surrogate for transmural lesions, variable FTI and LSI values are seen in different segments of the pulmonary vein. Based on our finding, higher FTI should be applied to the right and left anterior segments to provide durable lesion formation, whereas lower FTI can be applied in posterior and inferior segments to reduce procedure time and complication related to collateral organ damage.