心房細動における肺静脈隔離時の伝導ギャップを推定する平均インピーダンス低下

EnSite X provides a module to filter oscillated generator impedance signals due to cardiac beating/respiration (averaged impedance drop, AID). TactiFlex ablation catheter Sensor Enabled (TFSE) is the latest product to incorporate a contact-force sensor with a flexible tip but without lesion-estimating parameters.

To examine if AID estimates lesion formation, AID were compared between ablated lesions (n = 1687) with and without conduction gaps (CGs) after first-pass pulmonary vein isolation (PVI) using TFSE in atrial fibrillation (AF) patients (n = 20). The clinical efficacy of AID-guided PVI was evaluated in another subset of AF patients (n = 30).

CGs were observed in 45 points (CG[+]) but not in 1642 points (CG[-]). CG[+] had lower %AID (=absolute AID/initial impedance, p < 0.0001) than CG[-]. Decrease of bipolar voltage amplitude during radiofrequency application was linearly correlated with %AID (R²= 0.785, p < 0.05). In receiver operating curve analysis, the cutoff values of %AID and unfiltered generator impedance drop for predicting CG was 9.33% and 11.0 Ω, respectively; %AID had significantly higher area under the curve than unfiltered generator impedance drop (0.761 vs. 0.627, p < 0.05). In swine heart experiments, %AID was correlated with lesion volume (R² = 0.711, p < 0.05). In another subset of AF patients, success rate of first-pass isolation in %AID ( ≥ 9%)-guided PVI was 90% for LPV and 90% for RPV. The 1-year event-free rate of atrial tachyarrhythmias was 82%.

AID would improve the usability of impedance drop as an end point for RF　application. %AID-guided PVI using TFSE would be effective in AF patients.