Is the Vein Truly Isolated?
A 52-year-old male with drug-refractory and highly symptomatic paroxysmal atrial fibrillation was brought to the electrophysiology laboratory for a first attempt at ablation of his atrial fibrillation. A pre-operative CT scan confirmed the presence of four pulmonary veins with separate ostia.A decapolar spiral mapping catheter and irrigated ablation catheter were each introduced into the left atrium (LA) via transseptal puncture. A further steerable decapolar catheter was placed in the coronary sinus (CS).
Exit block of the LSPV was then confirmed with high output (10 mA, 2.0ms) pacing around the spiral catheter (representative pacing from Ls 6,7 is shown in Figure 1b). The left inferior pulmonary vein was also confirmed to be isolated (entrance and exit block) with the same lesion set.After subsequent isolation of the right pulmonary veins, the spiral catheter was replaced in the LSPV to assess for acute reconnection. Although the LSPV EGMs remained largely unchanged (Figure 2a), high output pacing (10mA, 2.0ms) from electrodes on the anterior margin of the vein now captured the LA, shown in Figure 2b. No spontaneous pulmonary vein potentials were seen in the LSPV.
The differential diagnosis for LA capture after apparent successful isolation of the LSPV includes: 1) subtle or unidirectional acute reconnection, 2) far-field capture of the left atrial appendage or 3) connection of the left pulmonary veins to the LA via the ligament of Marshall.
What is the appropriate next step in assessing the LSPV?