Usefulness of simultaneous isolation of the coronary sinus and the left atrial inferior wall for persistent atrial fibrillation refractory to box isolation
Authors: Yamauchi Y , Sagawa Y , Murata K , Arai H , Oda A , Suzuki A 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
In patients who are refractory to box isolation (BoxI) and have atrial fibrillation (AF) substrate in left atrial inferior wall (LAIW), LAIW isolation is effective, but the procedure is highly difficult because the connection between LAIW and coronary sinus (CS) is dense. In this study, we report four cases of persistent AF in which simultaneous isolation of LAIW and CS was so effective.

Methods and Results
Case 1 is a 76-year-old female with persistent AF who had undergone BoxI and failed mitral isthmus block (MIB) creation. However, AF and atrial tachycardia (AT) persisted. In the 4th session, chemical ablation of Marshall vein was performed, and AF/AT was terminated, and MIB was created. Thereafter, multiple ATs were still inducible by rapid atrial pacing. Because AT substrate seemed to be confined to LAIW, we attempted to isolate LAIW by performing linear ablation between the right inferior pulmonary vein (RIPV) and posteroseptal mitral annulus (MA) near CS ostium, and linear ablation parallel to CS along posterior MA. However, LAIW isolation could not be achieved. Finally, CS ostial ablation from right atrium (RA) succeeded in simultaneous isolation of LAIW and CS. CS burst pacing could induce AT confined to LAIW and CS although RA maintained sinus rhythm (SR). Rapid RA pacing could not induce AT/AF. Case 2 is a 78-year-old female with persistent AF who completed BoxI and MIB creation. Raid RA pacing induced AF. Because cycle length of LAIW was apparently shorter than RA, we attempted to isolate LAIW. Firstly, we performed linear ablation from RIPV ostium to posterior MA. During linear ablation, AF converted to AT, and finally RA returned to SR while AT was still sustained within LAIW and CS. This tachycardia was a reentrant tachycardia circling LAIW and CS. After this AT returned to SR by linear ablation within LAIW, LAIW and CS were not isolated during SR. CS ostial ablation from RA succeeded in simultaneous LAIW and CS isolation. Case 3 is a 74-year-old female with persistent AF refractory to BoxI. Although non-pulmonary vein (non-PV) trigger was documented in LAIW, the precise origin of non-PV trigger could not be identified due to infrequency. Case 4 is a 64-year-old male with persistent AF refractory to BoxI. He had undergone catheter ablation three times. Fractionation map showed that AF substrate was likely located in LAIW. Therefore, we attempted to isolate LAIW in Case 3 and 4. We performed MI ablation, linear ablation between RIPV ostium and posteroseptal MA, and CS ostial ablation from RA, which succeeded in simultaneous isolation of LAIW and CS in both cases. AF has never recurred in Case 1 and 2. SR could be maintained with antiarrhythmics in Case 3 and 4.

Conclusions
In patients with persistent AF refractory to BoxI, if LAIW has AF/AT substrate or non-PV triggers, simultaneous isolation of LAIW and CS may be a new therapeutic strategy. Simultaneous isolation of LAIW and CS requires ablation at CSos from RA.