Histological evaluation of atrial muscle sleeve of pulmonary veins as relevant to trigger mapping and ablation.

BACKGROUND

The atrial myocardial sleeve of the pulmonary vein is the most common source of arrhythmogenic triggers in atrial fibrillation. The present study was designed to study the atrial muscle sleeve in detail, to help in planning and execution of "trigger mapping and ablation" procedure, used for treating resistant atrial fibrillation.

METHODS

A longitudinal tissue section was taken along the length of each pulmonary vein including the posterior wall of the left atrium, from 15 normal human formalin fixed hearts. The histological and micro-morphometric details of the atrial muscle sleeve were studied.

RESULTS

A muscle sleeve composed of cardiac muscle was found in each pulmonary vein, situated between adventitia and media, and separated from media by clearly defined connective tissue. The fiber arrangement was non uniform and angular changes in the fiber direction were frequent. Autonomic ganglia were found in the adventitia. The sleeve was tapering distally but reduction was not circumferentially uniform, minimum thickness was more for right (~ 0.2 mm) than for left veins (0.1 mm). The mean atrial sleeve length was 6.3 mm; the left veins had longer sleeve then right while left inferior veins had the maximum mean length.

CONCLUSION

The trigger mapping should be done for 2 cm on pulmonary veins to fully cover the atrial muscle sleeve. The gradual tapering of the atrial sleeve indicates that the maximum intensity ablative lesions would be needed at the veno-atrial junction while the ablation power should be reduced distally. Distal triggers on right veins would need more ablation then on the left veins.