The myocardial sleeves of the pulmonary veins: potential implications for atrial fibrillation.

Atrial fibrillation (AF) is the most common abnormal heart rhythm and contributes to cardiac morbidity and mortality. Electrophysiological studies with pacing have shown that AF is initiated by ectopic beats localized in the pulmonary vein (PV) walls. The aim of this work was to look for some anatomical or histological particularities to explain these ectopic beats. Ten autopsied hearts were examined (6 males, 4 females). The myocardium was studied from the left atrium to the PV. Histological sections were made from 39 PVs. Myocardial cells were localized to PV between 9 and 38 mm from the PV-atrial junction. The sleeve was composed of circularly and longitudinally oriented bundles of cardiomyocytes. The peripheral end of the myocardial sleeve was irregular. The longest myocardial sleeves were found in the superior veins and were longitudinally oriented. At the PV-atrial junction, the circular bundles were not often circumferential. PV myocardial architecture confirmed the possibility of initiating AF. This fact is important for therapeutic radiofrequency ablation and explains why PV disconnection is essential.