Background: Contact force (CF) guided catheter ablation (CA) is a novel technology developed to improve efficacy and reduce complications. In a randomised controlled trial (RCT), we previously documented that after three months, rate of persistent conduction block was similar with and without using CF while performing CA for typical atrial flutter (AFL). Clinical effect of CF on recurrent arrhythmia is unknown. Objective: To study recurrent atrial arrhythmia during 12-months follow-up in a RCT investigating whether CF-guided CA for typical AFL is superior to CF-blinded CA. Method: Patients were randomized 1:1 to CA guided by CF (intervention group) or blinded to CF (control group). After 12 months, patients attended clinical check-up preceded by a 5-day ambulatory Holter monitor recording. Primary outcome was any recurrent atrial arrhythmia ≥30 seconds within 12 months, symptomatic or asymptomatic and documented in 12-lead ECG or Holter monitor recording. We did intention-to-treat (ITT) analysis. Results: We included and randomized 156 patients, four patients withdrew consent and two died during follow-up. Thus, 150 patients were included in ITT-analysis, in which recurrent arrhythmia was detected in 47 (31%) patients, 25 in the intervention group and 22 in the control group (p = 0.25). Atrial fibrillation was detected in 38 patients (18 versus 20 patients), and AFL in the remaining 9 patients (7 versus 2 patients). Conclusion: Contact force guided ablation for typical atrial flutter does not reduce recurrent atrial arrhythmia after 12-months follow-up as compared with ablation blinded for contact force.

Introduction: Studies have shown an association between outcome in cardiac resynchronization therapy (CRT) and longer interventricular delay at the site of the left ventricular (LV) lead. Targeted LV lead placement at the latest electrically activated segment increases LV function further as compared with standard treatment. We aimed to determine reproducibility and repeatability of identifying latest electrically activated segment during mapping of all available CS branches in patients receiving CRT. Methods: We included 35 patients who underwent CRT implantation with protocolled mapping guided LV lead implantation aiming for the site of latest electrical activation. Three different doctors experienced in electrophysiology and implantation of CRT devices independently measured time interval from the local bipolar right ventricular (RV) electrogram (EGM) to the local unipolar LV EGM at all mapped sites (RV-LV). The segment with the latest electrical activation was defined as target segment (TS) and the CS tributary containing TS was defined as target vein (TV). Weighted Kappa statistics with 95% confidence intervals were computed to assess intra-and inter-observer agreement for TS and TV. Results: We mapped 258 segments within 131 veins. Weighted kappa values for repeatability were 0.85 (0.81-0.89) for TS and 0.92 (0.89-0.93) for TV, and weighted kappa values of inter-observer agreement ranged from 0.70 (0.61-0.73) to 0.80 (0.76-0.83) for TS and 0.73 (0.64-0.78) to 0.86 (0.83-0.89) for TV among all three observers. Conclusion: The reproducibility and repeatability of identifying latest electrically activated segment during mapping of all available CS branches in patients receiving CRT ranges from good to very good.