Morphology of atrial myocardium in human pulmonary veins

OBJECTIVES We report an in-depth postmortem morphologic analysis of atrial myocardium in human pulmonary veins (PVs) from patients with and without atrial fibrillation (AF). BACKGROUND Electrophysiologic studies established the critical role of PVs in the initiation of AF. To date, a paucity of data exists about PV morphology as an arrhythmogenic substrate. METHODS Longitudinal tissue-strips of PVs were excised and histologically analyzed from the distal part to just beyond the atriovenous junction in the left atrium from 20 patients, obtained at autopsy. Anatomical measurements, including diameters, lengths, and wall-thicknesses of PVs, obtained at autopsy, were made. RESULTS Histological analysis revealed extension of atrial myocardium into 89% of all PVs. Prevalence of myocardial extension was significantly higher in veins of 6 patients with compared with 14 patients without AF. Other significant differences in the histology of PVs between the two groups were a higher frequency of discontinuity and hypertrophy and a higher degree of fibrosis of the atrial myocardium in the PVs of patients with AF. A marked variation existed in anatomical dimensions of PVs, although no differences were observed between patients with or without AF. CONCLUSIONS Atrial myocardium was more often present in the PVs of patients with compared with patients without AF. In the first group, the atrial myocardium in the PVs was characterized by more severe discontinuity, hypertrophy, and fibrosis. A marked variation in anatomical dimensions of the PVs existed.