Myocardium extending from the left atrium onto the pulmonary veins: A comparison between subjects with and without atrial fibrillation

Rapid discharges from the myocardium extending from the left atrium onto th e pulmonary vein (PV) have been shown to initiate AF, and AF may be eradica ted by the catheter ablation within the PV. However, if there is any differ ence in the distribution patterns of the myocardial sleeve onto the PV betw een the subjects with and without AF is to be determined. Twenty-one autops ied hearts were examined. Eleven patients previously had AF before death an d another 10 patients had normal sinus rhythm as confirmed from the medical records including ECGs before death. After exposing the heart, the distanc e to the peripheral end of the myocardium was measured from the PV-atrial j unction in each PV. Then, the PVs were sectioned and stained and the distal end of myocardium and the distribution pattern were studied. The anteropos terior diameter of the left atrium was also measured. In 74 of 84 PVs, the myocardium extended beyond the PV-atrial junction. The myocardium was local ized surrounding the vascular smooth muscle layer forming a myocardial slee ve. The peripheral end of the myocardial sleeve was irregular and the maxim al and minimal distances were measured in each PV, The myocardium extended most distally in the superior PVs compared to the inferior ones and the max imal distance to the peripheral end was similar between the AF and non-AF s ubjects (8.4 +/- 2.8 vs 8.7 +/- 4.4 mm for the left superior and 6.5 +/- 3. 5 vs 5.1 +/- 3.9 mm for the right superior PV, respectively). A significant difference was found in the maximal distance in the inferior PVs: 7.3 +/- 4.6 vs 3.3 +/- 2.8 mm for the left (P < 0.05) and 5.7 +/- 2.4 vs 1.7 +/- 1. 9 mm for the right inferior PV (P < 0.001) in the subjects with and without AF, respectively. The diameter of left atrium was slightly dilated in AF p atients but insignificantly (4.1 +/- 0.1 vs 3.6 +/- 0.1 cm, P > 0.07). The myocytes on the PV were less uniform and surrounded by more fibrosis in pat ients with AF compared to those without AF. In conclusion, the myocardium e xtended beyond the atrium-vein junction onto the PVs. The distribution patt erns of the myocardium was almost similar between subjects with and without AF, but the histology suggested variable myocytes in size and fibrosis in patients with AF.