The left atrial posterior wall (LAPW) plays a critical role in atrial fibrillation, but the underlying mechanism remains unclear. In the present study, we sought to characterize the histological features of the LAPW. Different atrial regions were dissected from hearts of normal Sprague-Dawley rats and humans. Haematoxylin/eosin and van Gieson staining were used to analyse atrial cardiomyocyte arrangement and collagen distribution, respectively. Intercellular junctions were evaluated by transmission electron microscopy. In contrast with other atrial regions, the LAPW exhibited more disorganized cardiomyocytes, larger intercellular spaces and variable myocardial fibre arrangement. The proportion of collagen was significantly higher in the LAPW than in other atrial regions. Interestingly, desmosomes were sparse along with intercellular gaps in the LAPW. In summary, distinct disarrangement of cardiomyocytes and an abundance of collagen exist in the LAPW. The sparsity of desmosomes in the LAPW may be related to the heterogeneous distribution and separation of atrial myocytes.
SkanesACMandapatiRBerenfeldO: Spatiotemporal periodicity during atrial fibrillation in the isolated sheep heart. Circulation1998; 98: 1236–1248.
2.
MandapatiRSkanesAChenJ: Stable microreentrant sources as a mechanism of atrial fibrillation in the isolated sheep heart. Circulation2000; 101: 194–199.
3.
ChenJMandapatiRBerenfeldO: Dynamics of wavelets and their role in atrial fibrillation in the isolated sheep heart. Cardiovasc Res2000; 48: 220–232.
4.
MansourMMandapatiRBerenfeldO: Left-to-right gradient of atrial frequencies during acute atrial fibrillation in the isolated sheep heart. Circulation2001; 103: 2631–2636.
5.
NattelS: New ideas about atrial fibrillation 50 years on. Nature2002; 415: 219–226.
6.
JalifeJBerenfeldOMansourM: Mother rotors and fibrillatory conduction: A mechanism of atrial fibrillation. Cardiovasc Res2002; 54: 204–216.
7.
LazarSDixitSMarchlinskiFE: Presence of left-to-right atrial frequency gradient in paroxysmal but not persistent atrial fibrillation in humans. Circulation2004; 110: 3181–3186.
8.
HuangJLTaiCTLinYJ: The mechanisms of an increased dominant frequency in the left atrial posterior wall during atrial fibrillation in acute atrial dilatation. J Cardiovasc Electrophysiol2006; 17: 178–188.
9.
CorradiDCallegariSBenussiS: Myocyte changes and their left atrial distribution in patients with chronic atrial fibrillation related to mitral valve disease. Hum Pathol2005; 36: 1080–1089.
10.
HaissaguerreMJaïsPShahDC: Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med1998; 339: 659–666.
11.
OralHPapponeCChughA: Circumferential pulmonary-vein ablation for chronic atrial fibrillation. N Engl J Med2006; 354: 934–941.
12.
NademaneeKMcKenzieJKosarE: A new approach for catheter ablation of atrial fibrillation: Mapping of the electrophysiologic substrate. J Am Coll Cardiol2004; 43: 2044–2053.
13.
CappatoRCalkinsHChenSA: Worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circulation2005; 111: 1100–1105.
14.
WangKHoSYGibsonDG: Architecture of atrial musculature in humans. Br Heart J1995; 73: 559–565.
15.
BergerJMRonaG: Functional and fine structural heterogeneity of atrial cardiocytes. Methods Achiev Exp Pathol1971; 5: 540–590.
16.
LegatoMJ: Ultrastructure of the atrial, ventricular, and Purkinje cell, with special reference to the genesis of arrhythmias. Circulation1973; 47: 178–189.
17.
HoSYSanchez-QuintanaDCabreraJA: Anatomy of the left atrium: Implications for radiofrequency ablation of atrial fibrillation. J Cardiovasc Electrophysiol1999; 10: 1525–1533.
18.
NathanHEliakimM: The junction between the left atrium and pulmonary veins. An anatomic study of human hearts. Circulation1966; 34: 412–422.
19.
SpachMSMillerWT3rdDolberPC: The functional role of structural complexities in the propagation of depolarization in the atrium of the dog. Cardiac conduction disturbances due to discontinuities of effective axial resistivity. Circ Res1982; 50: 175–191.
20.
SaitoTWakiKBeckerAE: Left atrial myocardial extension onto pulmonary veins in humans: Anatomic observations relevant for atrial arrhythmias. J Cardiovasc Electrophysiol2000; 11: 888–894.
21.
TagawaMHiguchiKChinushiM: Mycardium extending from the left atrium onto the pulmonary veins: A comparison between subjects with and without atrial fibrillation. Pacing Clin Electrophysiol2001; 24: 1459–1463.
ChouCCNiheiMZhouS: Intracellular calcium dynamics and anisotropic reentry in isolated canine pulmonary veins and left atrium. Circulation2005; 111: 2889–2897.
24.
KholovaIKautznerJ: Anatomic characteristics of extensions of atrial myocardium into the pulmonary vein in subjects with and without atrial fibrillation. Pace2003; 26: 1348–1355.
25.
TanAYLiHWachsmann-HogiuS: Autonomic innervation and segmental muscular disconnections at the human pulmonary vein-atrial junction. J Am Coll Cardiol2006; 48: 132–143.
26.
AllessieMABoydenPACammAJ: Pathophysiology and prevention of atrial fibrillation. Circulation2001; 103: 769–777.
27.
FusterVRydenLECannomDS: ACC/AHA/ESC 2006 guidelines for the management ofpatients with atrial fibrillation: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients with Atrial Fibrillation): Developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation2006; 114: e257–e354.
28.
VerheuleSSatoTEverettT4th: Increased vulnerability to atrial fibrillation in transgenic mice with selective atrial fibrosis caused by overexpression of TGF-β1. Circ Res2004; 94: 1458–1465.
29.
US National Institutes of Health (NIH): Guide for the Care and Use of Laboratory Animals. Publication No. 85–23, NIH: Bethesda, 1996.
30.
CorradiDCallegariSBenussiS: Myocyte changes and their left atrial distribution in patients with chronic atrial fibrillation related to mitral valve disease. Hum Pathol2005; 36: 1080–1089.
31.
World Medical Association Declaration of Helsinki: Recommendations guiding physicians in biomedical research involving human subjects. Cardiovasc Res1997; 35: 2–3.
32.
TagawaMHiguchiKChinushiM: Myocardium extending from the left atrium onto the pulmonary veins: A comparison between subjects with and without atrial fibrillation. Pacing Clin Electrophysiol2001; 24: 1459–1463.
33.
EloffBCGilatEWanX: Pharmacological modulation of cardiac gap junctions to enhance cardiac conduction: Evidence supporting a novel target for antiarrhythmic therapy. Circulation2003; 108: 3157–3163.
34.
BianWTungL: Structure-related initiation of reentry by rapid pacing in monolayers of cardiac cells. Circ Res2006; 98: e29–e38.
35.
HociniMHoSYKawaraT: Electrical conduction in canine pulmonary veins: Electrophysiological and anatomic correlation. Circulation2002; 105: 2442–2448.
36.
GoldsmithECHoffmanAMoralesMO: Organization of fibroblasts in the heart. Dev Dyn2004; 230: 787–794.
37.
YehHILaiYJLeeSH: Heterogeneity of myocardial sleeve morphology and gap junctions in canine superior vena cava. Circulation2001; 104: 3152–3157.
38.
HoSYCabreraJATranVH: Architecture of the pulmonary veins: Relevance to radiofrequency ablation. Heart2001; 86: 265–270.
39.
ShimazakiKOhshimaKHaraokaS: Accessory cell tumour: A clinicopathological study of 16 aggressive tumours containing EBV-positive Hodgkin and Reed-Sternberg-like giant cells. Histopathology2002; 40: 12–21.
40.
DenkHMollRWeyboraW: Intermediate filaments and desmosomal plaque proteins in testicular seminomas and non-seminomatous germ cell tumours as revealed by immunohistochemistry. Virchows Arch A Pathol Anat Histopathol1987; 410: 295–307.
