Delayed reconnection of the posterior wall inferior line after biatrial Cox-Maze IV despite previously confirmed bidirectional block

Figures

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  Figure 1. Surgical lesion set created during biatrial Cox-Maze IV surgery. Schematic illustration of the biatrial Cox-Maze IV lesion set performed 10 years earlier. Posterior wall box isolation was performed as part of the left atrial lesion set, with the inferior posterior wall line created by cryoablation (highlighted). The site of late reconnection identified on repeat mapping is indicated by a red arrow. IVC = inferior vena cava; LAA = left atrial appendage; PVs = pulmonary veins; RAA = right atrial appendage; SVC = superior vena cava.

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  Figure 2. Documented complete posterior wall isolation at intermediate follow-up. A high-density left atrial voltage map was obtained 5 years postoperatively using the CARTO 3 system (Biosense Webster) with a PentaRay (Biosense Webster) mapping catheter during high right atrial pacing. Bipolar voltage scale: 0.1–0.5 mV. A dense scar (<0.1 mV) was observed across the posterior wall, consistent with complete posterior wall box isolation. Bidirectional block was confirmed by both entrance and exit block assessment using pacing from multiple sites within the pulmonary veins and posterior wall.

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  Figure 3. Conduction across the posterior wall identified at repeat evaluation. High-density left atrial voltage map obtained 10 years postoperatively using the CARTO 3 system with an OCTARAY mapping catheter. Identical bipolar voltage thresholds were applied (dense scar < 0.1 mV; low voltage: 0.1–0.5 mV). Electrical activity within the posterior wall, compared with prior mapping, indicates late manifestation of conduction across the posterior wall. The roof, anterior, and right atrial maze lines remained electrically intact.

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  Figure 4. Inferior posterior wall breakthrough during activation mapping. Left atrial activation map during proximal coronary sinus pacing at repeat evaluation. The earliest activation was observed at the inferior posterior wall, corresponding to the prior inferior cryoablation line, consistent with a localized breakthrough across the inferior line of the posterior wall box. Activation subsequently propagated across the posterior wall toward the pulmonary veins. See Supplemental Video 1 for the dynamic activation mapping.