Comparative effectiveness of high-density mapping-guided versus empirical linear ablation in left atrial flutter: interim analysis of the FLUTMALINE clinical trial

Introduction Left atrial flutter (LAF) is a complex macro-reentrant arrhythmia associated with significant morbidity and suboptimal response to antiarrhythmic drugs. While catheter ablation is recommended (ESC guidelines Class I, Level B), the optimal ablation strategy remains debated. High-density activation mapping (HDM) enables precise localization of reentrant circuits and targeted radiofrequency application, but an alternative wolud be empirical linear ablation (ELA), that aims to simplify the procedure by creating predefined anatomical lines. The FLUTMALINE clinical trial was designed to compare the efficacy of HDM-guided ablation versus ELA in preventing recurrent sustained LAF (≥30 seconds) at one year. We present the interim analysis of this trial. Methods This is a single-center, prospective, randomized, open-label superiority trial. Patients ≥18 years with confirmed LAF were eligible. Exclusion criteria included prior LAF ablation or prior left atrial lines (except for pulmonary vein isolation). Patients were randomized to HDM-guided ablation or ELA. ELA included the following lesions: anteroseptal and anterolateral mitral lines, roof line, posterior line (between pulmonary veins), anterosuperior wall line, and the cavotricuspid isthmus line. Daily ECG rhythm monitoring was conducted during a 1-year follow-up using event recorders. Results Of 74 patients screened, 56 were randomized (29 HDM, 27 ELA). Baseline characteristics were similar between groups (see Figure 2 for graphical summary). Mean age was 72.8 ± 14.0 years (HDM) and 75.3 ± 8.2 (ELA). Ablation procedural success—absence of inducible sustained LAF at procedure end—was comparable in both arms: 65.5% in HDM vs 66% in ELA. No significant differences were observed in procedure duration or total fluoroscopy time, but RF time was significantly longer in the ELA group (49.9 ± 18.9 min vs 26.1 ± 13.6 min for HDM, p=0.05).At 1-year follow-up, the rate of documented recurrence of sustained LAF was numerically lower for HDM (cumulative freedom from sustained LAF: 71.3% [95%CI, 55.3–91.9] vs 50.5% [33.8–75.6] for ELA; p=0.248—Figure 1). Stratified analysis according to LAF cycle length and number of induced flutters showed no significant efficacy differences between strategies. The overall complication rate was low and without group differences: two pseudoaneurysms and two respiratory complications in HDM, versus one vascular hematoma and one high-grade AV block in ELA (p=0.67). No cases of cardiac tamponade occurred. Conclusion High-density mapping-guided ablation shows a trend toward greater efficacy in preventing recurrence of left atrial flutter at 1 year compared to empirical linear ablation, although the differences do not reach statistical significance, likely due to the limited sample size of this interim analysis. Ongoing recruitment is needed to confirm these findings and identify subgroups who may benefit from a tailored ablation approach.Baseline characteristics