Date Published: April 3, 2019
Publisher: Public Library of Science
Author(s): Gordon A. Begg, James O’Neill, Afzal Sohaib, Ailsa McLean, Chris B. Pepper, Lee N. Graham, Andrew J. Hogarth, Stephen P. Page, Richard G. Gillott, Nicola Hill, Jacqueline Walshaw, Richard J. Schilling, Prapa Kanagaratnam, Muzahir H. Tayebjee, Giuseppe Andò.
Electrical coupling index (ECI) and contact force (CF) have been developed to aid lesion formation during catheter ablation. ECI measures tissue impedance and capacitance whilst CF measures direct contact. The aim was to determine whether the presence of catheter / tissue interaction information, such as ECI and CF, reduce time to achieve bidirectional cavotricuspid isthmus block during atrial flutter (AFL) ablation.
Patients with paroxysmal or persistent AFL were randomised to CF visible (range 5-40g), CF not visible, ECI visible (change of 12%) or ECI not visible. Follow-up occurred at 3 and 6 months and included a 7 day ECG recording. The primary endpoint was time to bidirectional cavotricuspid isthmus block.
114 patients were randomised, 16 were excluded. Time to bidirectional block was significantly shorter when ECI was visible (median 30.0 mins (IQR 31) to median 10.5mins (IQR 12) p 0.023) versus ECI not visible. There was a trend towards a shorter time to bidirectional block when CF was visible. Higher force was applied when CF was visible (median 9.03g (IQR 7.4) vs. 11.3g (5.5) p 0.017). There was no difference in the acute recurrence of conduction between groups. The complication rate was 2%, AFL recurrence was 1.1% and at 6 month follow-up, 12% had atrial fibrillation.
The use of tissue contact information during AFL ablation was associated with reduced time taken to achieve bidirectional block when ECI was visible. Contact force data improved contact when visible with a trend towards a reduction in the procedural endpoint.
Until recently, catheter contact during ablation was determined using surrogates such as lack of catheter motion, electrogram attenuation and electrical impedance drops [1,2]. However, the importance of being able to quantify the catheter-tissue interface has become increasingly clear  and there are now technologies available which allow the direct measurement of tissue catheter contact and tissue impedance and capacitance.
A total of 114 patients were randomised into the trial between April 2015 and February 2017 (Fig 1). Of these, 16 patients were excluded from the study, either due to the finding of AF or atypical (non-isthmus dependent) atrial flutter at the time of the procedure or due to equipment failure. A further 9 patients were lost to follow-up. One patient was excluded from analysis due to a discrepancy between the case report form and source documentation whereby activation mapping had been used during the case but this had not been recorded in the case report form. It was not possible to ascertain whether the time to bidirectional block included activation mapping and so the data was removed from analysis.
This study is the first head to head comparison of two different technologies that provide information on the interaction between the ablation catheter and cardiac tissue in flutter ablation. The use of contact technology (in this study, ECI) increases catheter/tissue contact, reduces the time to achieve the primary endpoint of bidirectional block when ECI is visible and reduces the need for X-ray.
The use of tissue contact information during AFL ablation was associated with a reduction in the time taken to achieve bidirectional block when ECI was unblinded. Contact force data improved contact when visible with a trend towards a reduction in the procedural endpoint. Information on catheter tissue interaction however, does not seem to improve outcomes of flutter ablation.