Key result
Redo AF ablation unmasks unidirectional block with a ~2.4-second pulmonary vein discharge dissociated from sinus rhythm.
Why the study?
Unidirectional conduction during pulmonary vein isolation procedures, including pulmonary vein exit block despite recovery of entrance conduction, requires detailed electrophysiological characterization.
Case Report
Unidirectional PV conduction may occur during isolation; leaves open its prevalence and role in ablation endpoints.
This tracing demonstrates unidirectional conduction during a PV isolation procedure. At onset, there is conduction from the left atrium (LA) into the left superior PV [LSPV; †, far-field atrium (A) followed by PV potentials (PVPs)] interspersed with paced beats demonstrating local PV capture (*) without conduction to the LA. Following the fourth paced impulse, a spontaneous discharge lasting 2.4 s is observed within the PV, dissociated from sinus rhythm (‡). Mechanistically, the small density PV current fails to excite the LA (exit block); however, the larger LA electrical mass is able to activate the injured but viable LA–PV junction (entrance conduction).
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Andrade et al. (2015) conducted a case report in Atrial fibrillation. Redo-ablation (pulmonary vein isolation) was evaluated. Redo-ablation for atrial fibrillation revealed unidirectional conduction where a spontaneous pulmonary vein discharge lasting 2.4 seconds was dissociated from sinus rhythm due to exit block.
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