European Journal of Cardiovascular Medicine

An enlarged left atrium usually occurs with chronic rheumatic mitral valve regurgitation or mixed mitral disease due to the increased pressure in the left atrium and weakened cardiac wall due to pancarditis [1,2]. This can lead to atrial fibrillation and both these factors predispose to the formation of thrombus with the left atrium which can lead to systemic thromboembolism. If the thrombus is left as such it can become dense, calcified and organized posing a technical challenge for removal due to adhesions and lack of a cleavage plane. Due to the increased risk of stroke and sudden death, once diagnosed it should be considered an indication for urgent surgery.

Transthoracic and transoesophageal echocardiography, contrast enhanced computed tomography are the modalities of choice for the diagnosis of left atrial thrombus. Urgent surgery is necessary which includes correction of the mitral valve abnormalities, careful removal of the thrombus and volume reduction of the chamber.

We present case series of 6 patients diagnosed with enlarged LA with chronic thrombus to highlight the various methods of surgical management and its outcomes.

Case 1:

68-year-old man was admitted with progressive shortness of breath with bilateral swollen feet. Physical examination revealed signs of right sided heart failure with decrease air entry along both lung bases. A mid-diastolic murmur was heard at the apex together with pansystolic murmur at left lower parasternal region. Electrocardiography showed atrial fibrillation with enlarged right ventricle. Marked cardiomegaly was seen on chest roentgenogram. Transthoracic echocardiogram revealed severe mitral stenosis with regurgitation, dilated left atrium, atrial fibrillation, and organised large thrombus in the left atrium (11 × 10 cm) with severe tricuspid regurgitation.

Surgery was performed using standard cardiopulmonary bypass (CPB) with moderate hypothermia and antegrade blood cardioplegia. The stenosed mitral valve was exposed through an inverted T-shaped biatrial incision.  A huge organized thrombus measuring 15 × 8 × 5 cm was removed using blunt dissection and creating a plane between organised thrombus and left atrium (Fig. 1).The empty left atrium was carefully and thoroughly rinsed with water and the pulmonary veins are aspirated with the sucker to remove all possible remnants of thrombotic material. Left atrial reduction plasty was performed by suture plication of posterior wall with a 5-0 Prolene suture. Mitral valve was replaced with St. Jude Medical valve 29-mm. Tricuspid valve was repaired using contour 3 D annuloplasty ring and modified Cox-maze III procedure was done. Postoperative course was uneventful and patient was discharged on 7^th day after surgery.

Case 2:

A 55-year-old female patient presented with progressive shortness of breath with surgical history of closed mitral commissurotomy. A mid-diastolic murmur was heard at the apex.  Marked cardiomegaly was seen on chest roentgenogram. Transthoracic echocardiogram revealed severe mitral restenosis with mild regurgitation, dilated left atrium, and organised large layered thrombus in the left atrium.

Surgery was performed using standard CPB with moderate hypothermia and antegrade blood cardioplegia. The stenosed mitral valve was exposed through an inverted T-shaped biatrial incision.  A huge organized thrombus was removed from left atrium using blunt dissection and creating a plane between organised thrombus and left atrium(Fig. 2). The presence of dense adhesions forced us to remove thrombus in piecemeal. The empty left atrium was carefully and thoroughly rinsed with water and the pulmonary veins were aspirated with the sucker to remove all possible remnants of thrombotic material. Left atrial reduction plasty was performed by suture plication of posterior wall with a 5-0 Prolene suture. Mitral valve was replaced with St. Jude Medical valve 27-mm and modified Cox-maze III procedure was done. Post operative course was uneventful.

Case 3:

A 57-year-old female presented with progressive shortness of breath, repeated coughing and recurrent paroxysmal nocturnal dyspnoea. Physical examination revealed a mid-diastolic murmur heard at the apex.  Chest roentgenogram revealed huge cardiomegaly and giant left atrium (Fig. 3). Echocardiogram revealed severe mitral stenosis with mild regurgitation, severely dilated left atrium, atrial fibrillation, and organised large organised thrombus in the left atrium.

Surgery was performed using standard CPB with moderate hypothermia and antegrade blood cardioplegia. The stenosed mitral valve and organised left atrial thrombus was exposed through an inverted T-shaped biatrial incision.  A huge organized thrombus measuring 14 × 8 × 5 cm was removed using blunt dissection and creating a plane between organised thrombus and left atrium. The surgical volume reduction of the giant LA and maze procedure was performed. Mitral valve was replaced with St. Jude Medical valve 27-mm. Post operative course was uneventful.

Case 4:

A 62-year-old female presented with progressive shortness of breath with atrial fibrillation. Physical examination revealed a mid-diastolic murmur was heard at the apex and ejection systolic murmur at aortic area. Cardiomegaly was evident on chest roentgenogram. Transthoracic Echocardiogram revealed severe mitral stenosis with mild regurgitation, sever aortic valve stenosis, dilated left atrium, and organised large thrombus in the left atrium.

Surgery was performed using standard CPB with moderate hypothermia and antegrade blood cardioplegia. The stenosed mitral valve was exposed through an inverted T-shaped biatrial incision.  A huge organized thrombus measuring 8 × 6× 5cm was removed using blunt dissection and creating a plane between organised thrombus and left atrium. The empty left atrium was carefully and thoroughly rinsed with water and the pulmonary veins were aspirated with the sucker to remove all possible remnants of thrombotic material. Left atrial reduction plasty was performed by suture plication of posterior wall with a 5-0 Prolene suture. Mitral valve was replaced with St. Jude Medical valve 27-mm and aortic valve with St. Jude Medical Regent 19mm valve. Post operative course was uneventful.

Case 5:

A 54-year-old female with history of balloon mitral valvuloplasty presented with progressive shortness of breath, palpitation, repeated coughing and recurrent paroxysmal nocturnal dyspnoea and bilateral pedal oedema. There was a history of repeated pleural and ascitic fluid paracentesis due to congestive cardiac failure.  Physical examination revealed a mid-diastolic murmur heard at the apex. Cardiomegaly on chest roentgenogram. Echocardiogram revealed severe mitral stenosis with mild regurgitation, dilated left atrium, severe pulmonary hypertension, low ejection fraction and organised large thrombus in the left atrium with severe tricuspid regurgitation. 

Surgery was performed using standard CPB with moderate hypothermia and antegrade blood cardioplegia. The stenosed mitral valve was exposed through an inverted T-shaped biatrial incision.  A huge organized thrombus was removed, there was no cleavage plane which led to leaving a raw area on left atrium, which was covered with autologous pericardium to decrease risk of future thrombus formation. Mitral valve was replaced with St. Jude Medical valve 25-mm and tricuspid valve repaired with the ring annuloplasty.  Post operatively patient died on post operative day five due congestive cardiac failure.

Case 6:

A 60-year-old female presented with progressive shortness of breath. History of closed mitral commissurotomy and ballon mitral valvotomy. Physical examination revealed a mid-diastolic murmur heard at the apex.  Cardiomegaly was seen on chest roentgenogram. Echocardiogram revealed severe mitral restenosis with mild regurgitation, dilated left atrium, and organised large thrombus in the left atrium.

Surgery was performed using standard CPB with moderate hypothermia and antegrade blood cardioplegia. The stenosed mitral valve was exposed through an inverted T-shaped biatrial incision. The organized thrombus measuring 7 × 9× 5 cm was removed by making a cleavage between organised clot and left atrial wall. The empty left atrium was carefully and thoroughly rinsed with water and the pulmonary veins were aspirated with the sucker to remove all possible remnants of thrombotic material. Left atrial reduction plasty was performed by suture plication of posterior wall with a 5-0 Prolene suture. Mitral valve was replaced with St. Jude Medical valve 27-mm. After uneventful postoperative hospital course, patient was discharged on 7^thpostoperative day.

Chronic mitral valve disease can lead to enlargement of the left atrium. This enlargement is due to the increase in the volume and pressure within the cavity. This acts as an adaptation mechanism which helps to reduce pulmonary congestion and consequently pulmonary hypertension and pulmonary edema [3]. However, this mechanism is not fool proof and as the left atrial pressure continues to increase, there is gradual increase in the pulmonary venous pressure [2]. A left atrium of size greater than 65 mm can be termed as Giant Left Atrium (GLA) [4]. GLA has also been defined as one that touches the right lateral side of the chest wall on Chest X Ray [1] or a ccardiothoracic ratio on CXR of >0.7 combined with a left atrial anterior-posterior diameter of>8 cm on transthoracic echocardiography [5]. This condition is usually related to rheumatic mitral valve regurgitation or mixed mitral valve disease [4] but can also be associated with mitral valve prolapse, heart failure and chronic atrial fibrillation [2,3,5]. An enlarged left atrium can predispose to the development of atrial fibrillation which in turn can lead to further increase in the size of the left atrium [6]. Both these conditions have been theorised to lead to stasis of blood and as a result thrombus formation [7]. However, not all GLA’s lead to the development of thrombus [8,9] and the size of the thrombus varies depending on individual left atrial factors [10]. Another reason for the development of thrombus may be due to injury to the endocardium of the left atrium which increases the risk of atrial fibrillation and thrombus formation [11]. Furthermore, an increase in fibrinopeptide A, thrombin-antithrombin III complex and Von Willebrand factor antigen was noted in patients with GLA which is another reason theorised for thrombus formation [12]. These thrombi are prone to infection, systemic embolization and sudden cardiac related death. Hence the early detection and management of this condition is essential.

In the era when echocardiography was not available, thrombosed giant left atrium were routinely misdiagnosed as mediastinal tumours [13]. The diagnostic modalities nowadays include a chest computed tomography or a  transoesophageal or 3d transthoracic echocardiogram. The 3D transthoracic echocardiogram, however is better at differentiating between a thrombus and a left atrial myxoma [14,15]. These can also be differentiated clinically by the fact that left atrium thrombi have relatively high incidence of embolic events [16]and that they grow more rapidly in size than myxomas [17]. Cardiac MRI, though useful in identifying atrial thrombi, especially in the left atrial appendage, is not commonly used owing to high cost and long time required [18].

Surgery is indicated when a thrombus and a myxoma cannot be differentiated despite the use of echocardiography and chest computed tomography as histopathologic examination can provide a definitive diagnosis. This is especially important as there have been few reported cases of development of myxomas in the presence of pre-existing mitral stenosis [19]. Surgery should also be considered in the event of infection of thrombus. Surgery is also the treatment of choice in case of organized thrombus as use of anticoagulants can lead to fragmentation of the thrombus resulting in systemic embolization [20].

The goal of surgery in patients with valvular hear diseases with dilated left atrium with organised left atrial thrombus is to repair or replace the valve, to alleviate compressive symptoms produced by the dilated left atrium, surgical thrombectomy to prevent embolization, revert atrial fibrillation and volume reduction of the left atrium. Volume reduction can be attempted by plication of the left atrium. However, this is not required in most cases owing to complications like circumflex coronary artery injury, obstruction of the pulmonary vein  and stricture of the oesophagus. The left atrial appendage should be ligated  in all cases as this is the most common area of thrombus formation. If the thrombus is chronic, dense, fibrotic, calcified or adherent to the atrial wall, it’s excision then becomes technically difficult. This difficulty was overcome in our centre by performing an inverted T-shaped biatrial incision which allowed for good exposure and identification of a line of cleavage between organised thrombus and left atrial wall which aidin excising the thrombus in toto by blunt dissection. In a challenging case where it is difficult to remove all thrombotic area without leaving the residual material, the raw area of left atrium can be covered with autologous pericardium to prevent further thrombus formation [21].

Post operative anticoagulation management is equally important to prevent a recurrence of the condition and also to aid in the working of the new mitral prosthesis. As recommended in certain studies, we prefer to add heparin after surgery along with oral anticoagulants and Aspirin to tide over the time period required for the oral anticoagulants onset of action to develop [22,23]^.

The surgical thrombectomy should be offered to all patients with organised left atrial thrombus. Approach through the inverted T-shaped biatrial incision and careful blunt dissection in order to separate organised thrombus from left atrial wall is a very effective strategy of ‘en bloc’ thrombectomy.  This surgical technique of ‘en bloc’ thrombectomy is safe and effective. In a challenging case where it is difficult to remove all thrombotic area without leaving the residual material, the raw area of left atrium should be covered with autologous pericardium to prevent further thrombus formation. 

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