Myocardium Extending from the Left Atrium onto the Pulmonary Veins: A Comparison Between Subjects with and Without Atrial Fibrillation

Abstract

Rapid discharges from the myocardium extendingfrom the left atrium onto the pulmonary vein (PV) have been shown to initiate AF, and AF may be eradicated by the catheter ablation within the PV. However, if there is any difference in the distribution patterns of the myocardial sleeve onto the PV between the subjects with and without AF is to be determined. Twenty-one autopsied hearts were examined. Eleven patients previously had AF before death and another 10 patients had normal sinus rhythm as confirmed from the medical records including ECGs before death. After exposing the heart, the distance to the peripheral end of the myocardium was measured from the PV-atrial junction in each PV. Then, the PVs were sectioned and stained and the distal end of myocardium and the distribution pattern were studied. The anteroposterior diameter of the left atrium was also measured. In 74 of 84 PVs, the myocardium extended beyond the PV-atrial junction. The myocardium was localized surrounding the vascular smooth muscle layerforming a myocardial sleeve. The peripheral end of the myocardial sleeve was irregular and the maximal and minimal distances were measured in each PV. The myocardium extended most distally in the superior PVs compared to the inferior ones and the maximal distance to the peripheral end was similar between the AF and non-AF subjects (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 patients 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 patients with AF compared to those without AF. In conclusion, the myocardium extended beyond the atrium-vein junction onto the PVs. The distribution patterns 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.

New Therapeutic Strategies for Atrial Fibrillation: 3. Catheter Ablation of Atrial Fibrillation: Its Indication and Problems

“…The degree of extension of myocardium was the longest in the superior left PV and the shortest in the right inferior PV (4). The extension of myocardium onto the PVs determined by us was highly correlated with the frequency of foci within PV as reported by other workers (4,5). However, the histology of the myocardium on the PVs showed no difference between the AF and non-AF patients.…”

Electrical Excitation of the Pulmonary Venous Musculature May Contribute to the Formation of the Last Component of the High Frequency Signal of the P Wave

“…Furthermore, it has been shown that an electrical connection of the PV musculature and left atrial muscle may be more fixed in patients with AF than in those without, [7][8][9] while there is sometimes no myocardial extension into PVs in the patients without a history of AF.…”

Pulmonary Venous Flow Pattern and Atrial Fibrillation: Fact and Controversy

“…Moreover, Steiner et al (2006) reported that amyloid deposition and scarring in myocardial sleeves t e n d e d t o b e o b s e r v e d m o r e f r e q u e n t l y i n AF patients relative to control patients. Interestingly, the incidence of atrial myocardium extending beyond the PV-LA junction up to the PV periphery in all the examined PV specimens is commonly reported to be 88 to 89% (Tagawa et al, 2001;Steiner et al, 2006).…”

“…Importance of the myocardial sleeves as arrhythmogenic foci in AF is confirmed also in the human postmortem studies. Tagawa et al (2001) investigated myocardial sleeve distribution in patients with AF or without AF. They showed that the significantly longer distance of sleeves extending to the peripheral end of PV in AF patients relative to the distance in control patients was confirmed in inferior but not superior PV.…”