Use of impedance-based catheter tip-to-tissue contact assessment (electroanatomic coupling index, ECI) in typical...

The electrical coupling index (ECI) (Abbott, USA) is a marker of tissue contact and ablation depth developed particularly for atrial fibrillation treatment. We sought to evaluate if these measures can be also a marker of lesion efficacy during cavotricuspid isthmus (CTI) ablation for typical right atrial flutter.

We assessed the ECI values in patients undergoing typical right atrial flutter point-by-point ablation guided by the Ensite Velocity Contact™ (St. Jude Medical, now Abbott St. Paul, MN, USA) electroanatomic mapping system. ECI values were collected before, during (at the plateau), and after radiofrequency (RF) delivery. The physician was blinded to ECI and judged ablation efficacy according to standard parameters (impedance drop, local potential reduction, and/or split in two separate potentials). Patients were followed up at 3 and 12 months.

Fifteen consecutive patients (11 males, mean age 69.2 ± 10.6 years) with a history of typical right atrial flutter were included in this study. A total of 158 RF applications were assessed (mean 10.5 ± 6.6 per patient, range 6-28). The absolute and percentage ECI variations (pre-/post-ablation) were significantly greater when applications were effective (p < 0.001). A 12% drop in the ECI after ablation was identified by the ROC curve as the best cutoff value to discriminate between effective and ineffective ablation (sensitivity 94%, specificity 100%). Acute success was achieved in all patients with no complications and no recurrences during follow-up.

The ECI appeared a reliable index to guide CTI ablation. A 12% drop of ECI during radiofrequency energy delivery was highly accurate in identifying effective lesion.