EFFICAS II: optimization of catheter contact force improves outcome of pulmonary vein isolation for paroxysmal atrial fibrillation

Abstract

Aims: A challenge of pulmonary vein isolation (PVI) in catheter ablation for paroxysmal atrial fibrillation (PAF) is electrical reconnection of the PV. EFFICAS I showed correlation between contact force (CF) parameters and PV durable isolation but no prospective evaluation was made. EFFICAS II was a multicentre study to prospectively assess the impact of CF guidance for an effective reduction of PVI gaps.

Methods and results: Pulmonary vein isolation using a radiofrequency (RF) ablation catheter with an integrated force sensor (TactiCath™) was performed in patients with PAF. Operators were provided EFFICAS I-based CF guidelines [target 20 g, range 10-30 g, minimum 400 g s force-time integral (FTI)]. Conduction gaps were assessed by remapping of PVs after 3 months, and gap rate was compared with EFFICAS I outcome. At follow up, 24 patients had 85% of PVs remaining isolated, compared with 72% in EFFICAS I (P = 0.037) in which CF guidelines were not used. The remaining 15% of gaps correlated to the number of catheter moves at creating the PVI line, quantified as Continuity Index. For PV lines with contiguous lesions and low catheter moves, durable isolation was 81% in EFFICAS I and 98% in EFFICAS II (P = 0.005). At index procedure, the number of lesions was reduced by 15% in EFFICAS II vs. EFFICAS I.

Conclusion: The use of CF with the above guidelines and contiguous deployment of RF lesions in EFFICAS II study resulted in more durable PVI in catheter ablation of PAF.

Keywords: Atrial fibrillation; Catheter ablation; Conduction gaps; Contact force; Pulmonary vein isolation.

Figure 1

Positions and segments around pulmonary veins. (A) Sixteen numbered positions: 1, 9: superior; 2, 16: anterior-superior; 3, 15: anterior-middle; 4, 14: anterior-inferior; 5, 13: inferior; 6, 12: posterior-inferior; 7, 11: posterior-middle; 8, 10: posterior-superior. (B) Positions 2–4 and 14–16 were grouped respectively into left and right anterior segments and positions 6–8 and 10–12 were grouped into respectively left and right posterior segments.

Figure 2

Continuity Index assessment. Continuity Index calculation for two examples of consecutive ablations. Arrow and numbers show order of RF applications.

Figure 3

Pulmonary vein isolation at 3-month remapping. (A) Comparison of durable isolation rates per vein in EFFICAS I, without CF guidelines, and EFFICAS II, with CF guidelines. n PVs, total number of veins. (B) The number of conduction gaps is given per PV segment for both studies.

Figure 4

Evolution of CI from EFFICAS I to EFFICAS II. Continuity Index for ‘Success’ and ‘Gap’ segments is represented with average, standard deviation, and median values. (A) In EFFICAS I, besides minimum FTI, CI was also a significant predictive factors for ‘Gap’ or ‘Success’ in the pulmonary vein isolation line. (B) In EFFICAS II, guidance was prospectively given on CF and FTI, whereas no guidance on CI was given to operators. As a result, CI for ‘Gap’ and ‘Success’ remained unaffected and CI appeared to be the only remaining predictive factor for gaps in EFFICAS II.

Figure 5

Distribution of CF and FTI. (A) Comparison of CF distribution in EFFICAS I (1856 ablations) and EFFICAS II (1372 ablations). Red dots highlight the global percentage of ablations within EFFICAS II recommended CF range (10–30 g). This percentage significantly increased from 49 to 68% between both trials (P < 0.001). Proportion of low CF ablations (<10 g) reduced from 33 to 14%, and high CF ablations (>30 g) was 18% for both trials. (B) Analogous distribution of FTI. The red dots segregate low FTI (<400 g s) vs. EFFICAS II recommended range (>400 g s). Proportion of low FTI decreased from 45 to 22% of ablations between both trials (P < 0.001).