Uncoupling endocardial bundles coupled by an epicardial bundle in the left atrium and pulmonary veins.

Uncoupling of the endocardial bundles in the left atrium was suggested during modified posterior wall isolation. Although this fact may not be observed because of the possible bridging conduction by epicardial bundles in humans, partially failed transmural ablation in the atrial roof may have iatrogenically unveiled this fact.