Architecture of the pulmonary veins: relevance to radiofrequency ablation

Background-Radiofrequency ablation of tissues in pulmonary veins can elimin ate paroxysmal atrial fibrillation. Objective-To explore the characteristics of normal pulmonary veins so as to provide more information relevant to radiofrequency ablation. Methods-20 structurally normal heart specimens were examined grossly. Histo logical sections were made from 65 pulmonary veins. Results-The longest myocardial sleeves were found in the superior veins. Th e sleeves were thickest at the venoatrial junction in the left superior pul monary veins. For the superior veins, the sleeves were thickest along the i nferior walls and thinnest superiorly. The sleeves were composed mainly of circularly or spirally oriented bundles of myocytes with additional bundles that were longitudinally or obliquely oriented, sometimes forming mesh-lik e arrangements. Fibrotic changes estimated at between 5% and 70% across thr ee transverse sections were seen in 17 veins that were from individuals age d 30 to 72 years. Conclusions-The myocardial architecture in normal pulmonary veins is highly variable. The complex arrangement, stretch, and increase in fibrosis may p roduce greater non-uniform anisotropic properties.