This study was performed at the Renmin Hospital of Wuhan University and was to assess the feasibility and clinical success rate of pulmonary veins isolation (PVI) combined with AI‐guided high‐power linear ablation of LA roof and posterior inferior(LA posterior wall isolation)and MI for PAF patients. The protocol of this retrospective study was approved by the Ethics Committee of the Renmin Hospital of Wuhan University. All methods were performed in accordance with the relevant guidelines and regulations. All the patients met the diagnostic criteria of AF and written informed consent to undergo RFCA. 200 consecutive patients with PAF from March 2019 to December 2019 were enrolled. PAF was defined as a sustained episode lasting ≥7 days .Exclusion criteria included valvular AF, history of cardiac surgery, dialysis or heart failure (LVEF < 30% and New York Heart Association classification III or IV), left atrial thrombus and age ≥80 years.
The study protocol was approved by the ethics committee of the Renmin Hospital of Wuhan University
Pre-procedural
Before the ablation procedure, blood tests, transthoracic echocardiogram, transesophageal echocardiography,cardiac contrast-enhanced CT, 12-lead electrocardiogram (ECG) and 24 hours electrocardiogram (Holter) were obtained. The absence of any LA thrombi was confirmed by transesophageal echocardiography.
General principles of ablation:
The procedure was performed under general anesthesia using the CARTO-3 mapping system (Biosense Webster, Diamond Bar, CA). A decapolar coronary sinus (CS) catheter was introduced via left subclavian vein. And then double transseptal punctures was performed under fluoroscopic guidance. Intravenous heparinization was performed when two atrial septal punctures were completed. Two catheters were introduced via the femoral vein: (1) an irrigated-tip radiofrequency (RF) ablation catheter (ThermoCool SmartTouch STSF; Biosense Webster); (2) a multipolar mapping catheter (Pentaray; Biosense Webster). The target activated clotting time was 300 to 350 seconds. a LA 3D electroanatomical map using the CARTO 3 System was performed using a Pentaray catheter. Point-by-point ablation was performed in power-control mode (temperature 43℃; saline irrigation 15mL/min). Ablation with high power and RF current was delivered for 10–30 seconds (power 45W). Automated lesion annotation was performed using the VisiTag module (catheter stability range of motion 3 mm for 5 seconds; force ranges 10-15g for 70% of time; Biosense Webster). The AI targets were 400 for the LA roof and posterior inferior line, PVI (ridge 500; inferior 450; superior 450; posterior 400), and 450 for the MI line (Figure 1A). Serious procedure-related complications were defined as cardiac tamponade, thromboembolic complications, phrenic palsy, PV stenosis, or atrioesophageal fistula. Post-procedure, the patients were maintained under oral anticoagulation(Rivaroxaban, Dabigatran, Edoxaban) for at least 3 months and using 1 to 2 antiarrhythmic drugs(Betaloc, Amiodarone, Dronedarone)for generally 3 months at a heart rate no less than 55 beats / min.
The strategy of ablation:
- PVI: PVI was performed and verified as previously described[7].
- MI linear ablation:linear ablation was performed across the MI between the left inferior PV and mitral annulus. AI guided high power ablation was used with the ablation energy of 45W and the target AI of 450 (Figure 1A-B).
- PWI: LA roof linear ablation was performed across the LA roof joining the two superior isolated PV and LA. LA posterior inferior linear joining the two inferior isolated PV and LA. AI guided high power ablation was used with the ablation energy of 45W and the target AI of 400 (Figure 1A-B).
- Electrical cardioversion: If AF has not been terminated after the completion of PVI and linear ablation, the electrical cardioversion (bi-phase 150-200J) would be performed to stop AF.
- If AF was converted to AFL (atrial flutter) during ablation, reentrant circus was determined by high density activation mapping activation mapping, then linear ablation of the key isthmus was performed, including tricuspid isthmus. Whenever AF terminated to one or more atrial tachycardias (ATs), these were targeted for ablation until sinus rhythm(SR)was achieved.
Ablation line block examination:
- MI ablation line conduction block: Bidirectional block established by pacing in the LAA and high-density activation mapping by Pentaray catheter (Figure1C). Ablation was performed within the CS vein if the MI ablation line was not blocked[8, 9] (Figure 2).
- LA roof and posterior inferior ablation line conduction block : When we finished the roof and posterior inferior ablation line, the PWI was illustrated by applying Pentaray catheter to the posterior wall with no electrical potential,and pacing the Pentaray Catheter, conduction delayed when pacing at the LA posterior wall. (Figure 3). If the posterior wall is not isolated then continue ablation until PWI.
Inducing the tachycardia: After the lesion set was completed, burst pacing was delivered from the LAA and proximal CS at decreasing pacing cycle lengths down to 200 ms (or to the local refractory period) for 3 times at each site to induce atrial tachycardia (AT). If atrial flutter was induced, we used high-density activation mapping by Pentaray catheter, and then ablation was performed until SR was achieved. If AF was induced, the electric cardioversion or intravenous ibutilide cardioversion was applied to terminate it.
Follow-up
Follow-up at 1, 3, 6, 12 ,24 months and beyond was performed. 12-lead electrocardiogram(ECG) was routinely reviewed 1 month after the operation. A 7-days Holter ECG and transthoracic echocardiogram was acquired at 3 months. A 24-h Holter ECG was acquired at 6 ,12 and 24 months. In addition to the scheduled follow-up, the telephone follow up has been carried out by dedicated follow-up commissioners. Patients were strongly recommended to visit a healthcare provider if they felt symptoms possibly due to an arrhythmia or noticed any irregularity of their peripheral pulse by self-measurement. An ECG was performed at every additional visit, and cases with symptoms or findings suggestive of recurrence underwent Holter ECG monitoring. Arrhythmia recurrence was defined as any episode of AF/AT lasting>30 seconds after a 3-month blanking period post-ablation.
Statistical analysis
Continuous data are given as mean ± SD, comparisons between groups were made using Student t tests. Categorical variables are given as absolute number (percentage). Freedom from atrial arrhythmia recurrence during follow-up of up to 24 months was analyzed by using survival analysis for cumulative event rates including Kaplan–Meier estimates and Cox regression for calculation of odds ratios. Odds ratios are presented with 95% Cl. P-value of P<0.05 was deemed statistically significant. All statistical analysis was done using SPSS (Version 26, IBM Corp., Armonk, NY, USA).