Histological Study of the Left Atrial Wall —A Consideration of the Compound Myocardial Architecture and Potential Durability with Respect to Catheter Ablation in Pulmonary Vein Isolation Procedures—

Abstract

: Pulmonary vein isolation using radiofrequency energy is performed extensively to treat symptomatic, drug-refractory atrial brillation. However, anatomical knowledge of the left atrial wall surrounding the pulmonary vein PV openings is insuf cient to create an ablation line. Using autopsy hearts from 23 individuals median age of 63 years , we studied the histological nature of anatomical obstacles or related isthmuses near the PV openings. None of the individuals had a history of tachyarrhythmia or other major cardiac abnormalities. After macroscopic measurement of the minimum width of each isthmus, the following areas were excised and histologically prepared: atrial roof-mitral valve annulus MVA , left superior pulmonary vein LSPV -left atrial appendage LAA , LAA-MVA, left inferior pulmonary vein LIPV -MVA, right superior pulmonary vein RSPV -fossa ovalis FO , right inferior pulmonary vein RIPV -FO, and FO-MVA. Within the obstacles near the PV openings, the LSPV-LAA isthmus was found to be the narrowest, whereas the LIPV-MVA was the widest and thickest isthmus. Histological complexity of each isthmus was determined, and the compound architecture of the myocardium was revealed. The further presence of a variety of nerve endings as well as myocardial blood supply enhanced the tissue diversity. Such an insight into the diversity of myocardial architecture or histological complexity in each isthmus might be helpful in creating a reliable ablation line in pulmonary vein isolation procedures.