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Nonobstructive membrane of the left atrial appendage/ Sol atriyum apendiksinde nonobstruktif membran.

Introduction

The left atrial appendage (LAA) is a small, muscular extension of the left atrium. It is located anterolateral^ and lies in the left atrioventricular sulcus, superior to the proximal portion of the left circumflex artery (1).

The membranes of the LAA cavity are very rare. The origin of membranes involving the LAA, and their clinical significance is not clear (2). To our knowledge, only six cases of LAA membrane have been described to date. In this report, we describe a case with nonobstructive membrane within the body of LAA and discuss the transesophageal images mimicking a membrane in the body of LAA.

Case Report

A 69-year-old female presented with fatigue and worsening palpitations at rest. A 12-lead electrocardiogram showed atrial flutter with rapid ventricular rate. The patient had received a permanent DDD pacemaker in our department 2 months earlier because of nodal rhythm. Coronary angiogram was normal. Her electrocardiogram showed intermittent sinus rhythm and some pacing beats during follow up. Cardioversion was contemplated for atrial flutter which was probably recent-onset. A 2-D echocardiogram was normal except for slightly dilated left atrium. A transesophageal echocardiography (TEE), showed that LAA was free of thrombus. Imaging of the LAA in multiple planes demonstrated a thin, linear, mobile membrane traversing the body of the LAA (Fig 1). Color Doppler did not show flow acceleration across this membrane (Fig. 2). Pulsed-wave Doppler confirmed low flow velocities across the membrane (Fig 3), indicating no obstruction.

Discussion

Further developments in imaging techniques and the use of biplane and multiplane TEE have allowed visualization of the LAA, which previously was difficult to demonstrate by other imaging methods. Accuracy of LAA thrombus detection with TEE is important in the pre-cardioversion evaluation of patients with atrial fibrillation and flutter (1).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

Several studies have emphasized that vary in volume and shape, and are often composed of multiple lobes (3, 4). To our knowledge, very few cases of a membrane involving the LAA have been described (2, 5-8). In two reports (5, 6), obstructing membranes at the opening of the LAA, causing functional stenosis have been described and in four reports nonobstructive membranes located in the body of the LAA have previously been presented (2, 7). Similar to previous findings, we presented a case that has a thin mobile membrane-like structure across the LAA cavity. It does not cause an obstruction in the LAA cavity as demonstrated by normal flow velocities on pulsed-wave Doppler of the LAA and by a lack of turbulence with color flow Doppler. As emphasized by Coughlan et al. (5) the origin of membranes in LAA is not clear. The most likely explanation for the origin of these membranes would appear to be a congenital anatomic variation. Previous reports after incomplete surgical ligation or recanalization of the LAA have emphasized the potential for stagnant blood flow within the LAA and possible thrombus risk with systemic embolization (9,10).

The differential diagnosis of linear structures which appear in LAA may also include prominent pectinate muscles, side lobe artifacts and partial resorbtion of prior LAA thrombi. Most LAAs (97%) had pectinate muscles [greater than or equal to] 1mm in width. Small pectinate muscles (<1mm (3%)) were noted only in the first and last decades (1). In our case there were no imaging characteristics of prominent pectinate muscles. Correale et al. (2) presented a case of membrane-like structure which seems to be the roof of LAA cavity and the echo-free space below might be localized pericardial fluid within the pericardial sinus. They suggest that this situation should be taken into account in differential diagnosis of linear structures appearing within the LAA. In our case there was no pericardial effusion. Limitation of our case includes the lack of surgical confirmation and the lack of detailed pathologic analysis of the excised membrane. In our case, there was no thrombus in LAA, and the patient was cardioverted without any complications and she was discharged in sinus rhythm and in good condition.

Conclusion

We described, in one case, pre-cardioversion TEE findings of a thin, linear, mobile, and nonobstructive membrane within the cavity of the LAA. The clinical implications and origins of these kinds of membranes are not clear; however, they may represent an anatomic variant. The echocardiographer should pay attention to the LAA during examination.

References

(1.) Veinot JP, Harrity PJ, Gentile F, Khandheria BK, Bialey KR, Eickholt JT, et al. Anatomy of the normal left atrial appendage: A quantitative study of age-related changes in 500 autopsy hearts: implications for echocardiographic examination. Circulation 1997; 96:3212-5.

(2.) Correale M, Ieva R, Deluca G, Biase M. Membranes of left atrial appendage: Real appearance or pitfall. Echocardiography 2008; 25:334-6.

(3.) Agmon Y, Khandheria BK, Gentile R Seward JB. Echocardiographic assessment of the left atrial appendage. J Am Coll Cardiol 1999; 34:1867-77.

(4.) Ernst G, Stollberger C, Abzieher F, Veit-Dirscherl W, Bonner E, Bibus B, et al. Morphology of the left atrial appendage. Anat Rec 1995; 242:553-61.

(5.) Coughlan B, Lang RM, Spencer KT. Left atrial appendage stenosis. J Am Soc Echocardiogr 1999; 12:882-3.

(6.) Ha JW, Chung N, Hong YS, Cho BK. Left atrial appendage stenosis: Echocardiography 2001; 18: 295-7.

(7.) Bakris N, Tighe DA, Rousou JA, Hiser WL, Flack JE 3rd, Engelman RM. Nonobstructive membranes of the left atrial appendage cavity: Report of three cases. J Am Soc Echocardiogr 2002; 15:267-70.

(8.) Correale M, Ieva R, Deluca G, Di Biase M. Membranes of left atrial appendage: real appearance or "pitfall". Echocardiography 2008; 25:334-6.

(9.) Katz ES, Kronzon I. Incomplete ligation of the left atrial appendage: Diagnosis by transesophageal echocardiography. Am J Noninvas Cardiol 1992; 6: 262-3.

(10.) Fisher DC, Tunick PA, Kronzon I. Large gradient across a partially ligated left atrial appendage. J Am Soc Echocardiogr 1998; 11:1163-5.

Nursen Postaci, Murat Yesil, Asil Isci, M. Erdinc Ankan, Serdar Bayata

Department of Cardiology; Ataturk Teaching Hospital, Izmir, Turkey

Address for Correspondence/Yazisma Adresi: M. Erdinc Arikan MD, Department of Cardiology, Ataturk Teaching Hospital, Izmir, Turkey Phone: +90 232 243 43 43/2426 Fax: +90 216 428 57 77 E-mail: arikanmd@hotmail.com
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Title Annotation:Case Reports/Olgu Sunumlari
Author:Postaci, Nursen; Yesil, Murat; Isci, Asil; Arikan, M. Erdinc; Bayata, Serdar
Publication:The Anatolian Journal of Cardiology (Anadolu Kardiyoloji Dergisi)
Date:Oct 1, 2009
Words:1022
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