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Welcome to the European Society of Cardiology. Our mission: to reduce the burden of cardiovascular disease in Europe
 
Vol10 N°17
03 Feb 2012

A look at Atrial Septal Aneurysm  

An article from the e-journal of Cardiology Practice

Shah M 

Shah M
Topics: The Cardiac Consult
Authors: Shah MD.
Atrial septal aneurysm is a rare cardiac abnormality that is usually detected during routine echocardiography or evaluation of ischemic stroke. It may be isolated or in presence of other defects, of which most often patent foramen ovale. Atrial arrhythmias and arterial embolism are associated complications that must be treated with anticoagulants and rate control.



Case Report

A 53 year-old female presents with transient left side weakness which slowly improves over 3 days thereafter. Patient has a few years’ history of on and off palpitations. Clinical examination reveals an irregular pulse, at 102 beats per minute (bpm), pulse deficit of 6 bpm, and a 130/80mmHg blood pressure. Peripheral pulses are normal. Cardiovascular system examination confirms irregular heart. Although heart sounds are normal, a systolic click and a grade iii/iv systolic murmur in the pulmonary area is heard. Central nervous system examination reveals mild weakness in left lower limb. Patient is nevertheless able to walk unsupported. Hemogram, serum lipids, kidney function tests and liver function test results are within normal range. The echocardiogram reveals atrial fibrillation with a ventricular rate of 90/min, normal QRS and T waves. Chest X-Ray shows normal cardiac size and clear lungs. Computerised tomography of the brain is normal and shows no evidence of hemorrhage. Transthoracic echocardiography reveals normal-size chambers, valves, and a prominent moderator band in right ventricle. Intra-ventricular septum is intact. Intraatrial septum shows a large bulge in fossa ovalis area towards right atrium with limited excursions of this part of the atrial septum. No evidence of thrombus in any chamber or atrial appendage nor evidence of shunt (Figures 1, 2, 3). Carotid Doppler and ultrasound studies are normal. 


Fig. 1 Transthoracic echocardiography of heart

a) Apical 4-C view 

 

b) Apical 4-C view, annotated. 

 

c) Sub costal view, annotated. 


 

Patient has ischemic cerebrovascular embolic stroke with left side hemiparesis, atrial fibrillation with atrial septal aneurysm fossa ovalis. The ischemic cerebrovascular accident- is most likely cardioembolic stroke.
Atrial septal aneurysm is rare (ASA) and is most often an accidental finding however it could be a contributing factor to cardioembolic stroke even though no thrombus in aneurysm or left atrium can be seen in transthoracic echo. Patient was started on anticoagulants and rate control for atrial fibrillation.

Background

Although exact definitions of ASA vary according to size (2, 3, 7), and stage (mobility) of the aneurysm (17, 18) atrial septal aneurysm is a localised “saccular” deformity, generally at the level of the fossa ovalis, which protrudes to the right or the left atrium or on both sides. Albeit rare, atrial septal aneurysm is a well recognised cardiac abnormality. Previously diagnosed on autopsy only, it is now frequently being picked up on routine echocardiography or during evaluation of ischemic stroke. Studies link it with peripheral embolism and cardioembolic stroke, pulmonary embolism and atrial arrhythmias, even though clinical significance is uncertain. Further, it can be secondary to interatrial pressure difference or may be the result of a primary malformation involving the fossa ovalis region or the entire septum (1). In patients with chronically elevated atrial pressures, as in mitral stenosis, atrial septal aneurysms are also rare therefore acquired origin seems unlikely. Congenital malformation of the atrial septum probably contributes to development of ASA, as was suggested by Hanley PC and colleagues (2).

Associated cardiac abnormalities

Atrial septal aneurysm may be isolated or associated to another anomaly. Commonest association is patent foramen ovale (PFO). Silver and Dorsy found patent foramen ovale in 8 out of 16 patients (3). Other associations are atrial septal defect (2), mitral valve prolapsed (4,5) tricuspid valve prolapse, marfans syndrome, sinus of valsalva aneurysm and aortic dissection (1). Shunt across ASA is more frequently detected with transesophageal echocardiography than with transthoracic echocardiography (1). Association with mitral and tricuspid valve prolapse and other abnormalities such as Marfans syndrome, sinus of valsalva aneurysm may point to common inherent connective tissue deficiency (6). Familial clustering of ASA has also been reported (13).

Clinical Manifestations

Manifestations attributed to ASA are 1) atrial arrhythmias and 2) arterial embolism.
Interatrial septal aneurysm can act as an arrhythmic focus, generating focal atrial tachycardias. Hanley et al (2) noted atrial arrhythmias in 20 out of 80 patients (25%). Mugge A et al., in a multicenter study of 195 patients found atrial tachyarrhythmia in 47 patients (24%) and 28 patients (>14%) had atrial fibrillation (1). Schneider B et al. reported prevalence of atrial tachyarrhythmia in 26% of cases of ASA (8). Mechanism of increased prevalence of atrial tachyarrhythmia in ASA is not clear though redundancy of atrial septum could be responsible for pathogenesis of arrhythmia.
Arterial embolism is another complication associated with ASA. Presence of ASA tends to aggravate stasis of left arterial (LA) blood flow and predispose to minute LA clots and systemic thrombo embolism. 
With cardiac embolism reported in 20-52% cases of ASA, various studies have found significant association between ASA and arterial embolism  (7,9,10). Most patients (70%) had left to right shunt (7) and a higher prevalence of ASA was reported in cerebrovascular accident patients compared to the general population (7.9% vs. 2.2%) (11). A retrospective study by Mugge A et al. reported that patients with ASA, and especially those with shunts showed increased frequency of clinical events in their past compatible with cardiogenic embolism. Atrial septal aneurysm was often the only source of embolism as judged by transesophageal echocardiography (1). Salmasi AM reported higher prevalence of ASA and patent foramen ovale in Afro-Caribbean population compared to Indo-Asians, suggesting ASA as a possible cause for increased incidence of stroke in Afro-Caribbeans (12). Mechanism of cardioembolic stroke could be right to left shunting as is detected in most cases of ASA or in the thrombogenic properties of aneurysm itself. A non ejection click may occasionally be heard possibly as the IAS aneurysm bulges and tenses within LA/RA cavity thus suggesting ASA as one of the causes of systolic click (20).

Diagnosis and treatment

Echocardiography is used to diagnose ASA, either during routine echocardiography or in cases of cardioembolic cerebrovascular stroke and peripheral embolism. Compared to transthoracic echo, transesophageal echo is more sensitive in picking up ASA (1, 7). Cardiac computed tomography and magnetic resonance imaging are also useful for diagnosis of ASA (14, 15).
  • Uncomplicated and isolated ASA requires no specific treatment other than follow up. Patients should be evaluated for presence of thrombus in aneurysm. 
  • Therapeutic options for prevention of recurrent stroke in patients with atrial septal aneurysm as well as atrial septal abnormality - including patent foramen ovale (PFO), ostium secundum atrial septal defect (ASD) - are medical therapy with antiplatelet agents or anticoagulants and surgical or percutaneous closure of the defect  
  • To prevent recurrent paradoxical embolism, in presence of shunt, it is preferable to close the shunt and transcatheter procedure is now safe and effective and commonly used for this purpose (16) even though superiority of closure over best medical therapy has not been established (21). 
  • In case of atrial arrhythmia, specific treatment is given. In case of embolic episode patient needs antiplatelet drugs and preferably oral anticoagulation for secondary prevention of cardioembolic episode. 
  • The efficacy of aspirin therapy is suggested by the French PFO-atrial septal aneurysm (ASA) study, in 216 patients with cryptogenic stroke and PFO alone, recurrent stroke on aspirin was 2.3% after four years, comparable to 4.2% in patients with neither a PFO nor an ASA (19).
Conclusion
The case reports on the chance finding of atrial septal aneurysm in the case of cerebral embolism. Although atrial fibrillation is well known cause of stroke, presence of atrial septal aneurysm needs some attention as it could be contributory. There is a possibility that atrial septal aneurysm could be a culprit for strokes.


Notes to editor
Meraj-ud Din Shah. MD., DM. (Cardiology), FICC
Srinagar Kashmir
Author's disclosures: None declared.

Reader's remark:

The direction of septal motion denotes which artium has elevated pressure, i.e. mean bulging of IAS to the right denoting high left atrial pressure & vise versa.
Would you like to comment? 

Author Response:

I agree with my friend Dr Elsheikh. Indeed, direction of IAS bulge depends on pressure differencec between atria. We see IAS bulged to the right in severe mitral stenosis and similarly, IAS is bulged to the left in severe pulmonary hypertension with tricuspid regurgitation. But it should be clear that bulge of IAS as such is not ASA. There should be at least 15mm (some consider 10mm) protrusion of IAS or part of it from atrial septal plane to diagnose ASA.
We do see oscillation of ASA with respiratory and cardiac cycle. A hypothesis based on interatrial pressure gradients is proposed to explain the different motions and configurational characteristics of Atrial Septal Aneurysms. In parallel however, we should be aware that ASA is rare in situations with chronically elevated atrial pressure - as in mitral stenosis. Possible inherent congenital malformation of IAS contributes to development of ASA.  
References Main text

1. Mugge A et al: Atrial septal aneurysm in adult patients: A multicenter study using transthoracic and transesophageal echocardiography. Circulation 91: 2785, 1995.
2. Hanley PC, Tajik AJ, Hynes JK, Edwards WD, Reeder GS, Hagler DJ, Seward JB. Diagnosis and classification of atrial septal aneurysm by two-dimensional echocardiography: report of 80 consecutive cases. J Am Coll Cardiol. 1985;6:1370-1382
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Author's response

1. Mugge A et al: Atrial septal aneurysm in adult patients: A multicenter study using transthoracic and transesophageal echocardiography. Circulation 91: 2785, 1995.
2.  Hanley PC, Tajik AJ, Hynes JK, Edwards WD, Reeder GS, Hagler DJ, Seward JB. Diagnosis and classification of atrial septal aneurysm by two-dimensional echocardiography: report of 80 consecutive cases. J Am Coll Cardiol. 1985;6:1370-1382

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.