Anatomic characteristics of extensions of atrial myocardium into the pulmonary veins in subjects with and without atrial fibrillation.

Myocardial extensions around pulmonary veins (PVs) have been recognized as the most important sites of origin for arrhythmogenic foci that trigger atrial fibrillation. The aim of this study was to evaluate the characteristics of atrial myocardium in pulmonary veins from subjects with and without a history of atrial fibrillation. A total number of 43 human hearts obtained at autopsy were studied (27 men, 16 women, mean age 67 +/- 8 years). Sixteen subjects (group 1) had a history of atrial fibrillation (11 men, mean age 66 +/- 10 years). The remaining 27 subjects (group 2) were without arrhythmia (16 men, mean age 68 +/- 8 years). The presence and morphology of the myocardial extensions were studied microscopically. Of the total number of 172 PVs evaluated, myocardial extensions were revealed in 117 (68%) cases. Myocardial fibers were arranged in a variable manner with the most prevailing circular pattern. Continuous extensions were present in 74, while a discontinuous pattern was revealed in 29 PVs. Maximum extension of the sleeves reached 48 mm (mean 7.7-10 mm) and their maximum thickness was 5 mm. Myocardial extensions were longer and thicker in the upper PVs from subjects with previous atrial fibrillation. In conclusion, a significant interindividual variability in the presence, arrangement, and thickness of atrial myocardial sleeves into PVs was revealed. Patients with a history of atrial fibrillation were found to have longer and thicker myocardial extensions into the upper PVs, and this finding may have implications for the catheter ablation technique.