Ablation procedure
AF ablations were performed by a standardized approach: Patients underwent the procedure in deep analgosedation with midazolam, fentanyl and propofol under invasive radial blood pressure monitoring. Groin-access was achieved using two 6 french and one 12 french venous sheaths. Diagnostic right ventricle and coronary sinus catheters were placed in all patients. A single transseptal puncture was guided by fluoroscopy using Abbott agilis medium curve sheaths and a Abbott BRK needle, followed by ACT-guided heparin treatment.
All procedures were guided by the Biosense Webster Inc. Carto3 v7 mapping system with univu-fluoroscopy integration. Left atrial angiograms were recorded under rapid pacing. Left atrial electro-anatomical reconstruction was done using Biosense Lasso catheters and the Carto3 V7 confidense module, with low-voltage settings for substrate mapping as previously described 8,9.
PVI was performed in all patients. Additional lesion sets based on substrate homogenisation and block-isolation were performed when deemed necessary as previously described 10. Ablation of the cavo-tricuspid isthmus was performed when right-atrial flutter was previously documented or induced during the procedure. All ablations were performed using the Biosense Webster SmartTouch SurroundFlow (ST-SF) ablation catheter and the Biosense Webster Smart-Ablate RF generator. Saline irrigations was performed as recommended by the manufacturer (<30W 8 ml/s, >30W 15 ml/s).
Ablation lesions were guided by the ablation-index module, with procedural guidelines and tag-settings previously described and validated in the CLOSE protocol 4. Briefly, AI targets of 400 and 550 were used for posterior and anterior lesions, respectively, with an inter-lesion-distance (ILD) of <6 mm and VisiTag size of 3 mm. Catheter stability was set to 10 mm, with force above threshold for >25% of the time, and minimal stability for 3 seconds. In the control group the AI was reached with variable power in dependence of the anatomy (posterior and inferior wall 20W, roof and anterior wall 40W). In the HPSD group the AI was reached with a fixed high power of 50W independently of the anatomical location.
After completion of all ablation sets and documented entrance and exit blocks, as well as bidirectional block of all additional lines, inducibility of sustained atrial tachycardia was tested by atrial high-rate burst and ramp stimulation.
CTI lesions were formed with 40W in both groups. Periprocedural oesophageal temperature monitoring was not performed.