Catheter Ablation of Posterior LA Isolation: Box Isolation

Both pulmonary veins (PVs) and the posterior left atrium (LA) are developed from the sinus venosus, where there are many pacemaker cells with spontaneous rhythmic activity. Non-PV foci originated mainly from the PV ostium or the posterior LA, and the posterior LA and the LA roof serve as a substrate for maintenance of AF in the patients with AF. It has been proposed that the surgical procedures for isolating the posterior LA and PVs could cure AF in 93% of patients with lone AF. These findings support that isolation of not only PVs but also the whole posterior LA can result in a much better cure rate in the patients with paroxysmal and persistent AF. Therefore, we developed a new approach for complete isolation of the posterior LA including all PVs, namely Box isolation. In the posterior LA, there are many arrhythmogenic substrates for AF, including the ganglionated plexi, reentries, triggers, and low-voltage areas. Box isolation can contain these abnormal substrates in the posterior LA and reduce the critical mass for maintenance of AF. Additional posterior LA isolation to PV isolation facilitates AF termination and non-inducibility. Previous studies reported that box isolation is an effective and safe treatment for paroxysmal or persistent AF. A meta-analysis showed that box isolation reduced AF recurrence with comparable recurrence rates of atrial tachycardia/flutter, complications, and procedure time compared with PV isolation alone.