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Ann Thorac Surg 2002;74:1691-1694
© 2002 The Society of Thoracic Surgeons
a Department of Cardiovascular Surgery, Hôpital Nord-CHU, Saint-Etienne, France
b Department of Echocardiography, Hôpital Cardiologique-CHU, Lille, France
Accepted for publication May 30, 2002.
* Address reprint requests to Dr Grandmougin, Service de Chirurgie Cardiovasculaire, Hôpital Nord-CHU, Pr X. Barral, 42055 Saint-Etienne, Cedex 2, France.
e-mail: daniel-grandmougin{at}wanadoo.fr
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Introduction |
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A 82-year-old woman with a medical history of chronic atrial fibrillation, was urgently referred for surgical management of an atrial myxoma. The patient was otherwise healthy, except for obesity (96 kg/160 cm). Despite chronic atrial fibrillation (at least 12 years), no oral anticoagulant therapy had been administered. The patient related a recent and unusual paroxysmal postural dyspnea, worsened by minimal exertion and significantly decreased by decubitus.
On admission, the patient was apyretic, and physical examination was normal with muffled heart sounds because of obesity and irregular pulses. A discrete systolic murmur was focused in the median axillary line in the fourth left intercostal space. The electrocardiogram assessed atrial fibrillation with no low-voltage QRS complexes. Chest roentgenogram showed a cardiomegaly (cardiothoracic ratio: 0.56) with a moderate left atrial enlargement and without any increased pulmonary vasculature. Echocardiography (transthoracic and transesophageal) disclosed a giant spherical and free-floating mass approximately 4 cm in diameter (Fig 1A), filling the left atrium, bouncing and rebounding off the mitral valve, with a partial and intermittent protrusion through the annulus (Fig 1B). No evidence of septal or wall attachment was found. The mitral valve was thin without any stenotic mechanisms, however, with a trivial leak. The left atrium was enlarged (50 mm). The mass was smooth, homogenous, without any calcifications, and well demarcated. Neither tissular invasion nor infiltration were disclosed. The aortic valve was competent without any gradient, and the left ventricle was free of thrombus.
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In our case, this echographic feature was an important step to invalidate the suspicion of isolated left atrial myxoma. The potential for complications has been established recently by Abe and colleagues [7], who correlated systemic embolism in atrial fibrillation with the shape, site, mobility, number, and maximum dimension of left atrial thrombi. Thus, independently of other criteria, mobility of the thrombus remains the most important risk factor for cerebral or arterial embolic events. Transthoracic echocardiography optimized by a transesophageal analysis appears to be the main, primary, noninvasive tool for diagnosis of this particular thrombus; it is also used to assess the potential of complications, although incidental diagnosis has been established by routine echographic examination as a prelude to surgery. However, as previously related [4], when considering macroscopic characteristics of a ball-thrombus, embolism usually is not associated with this specific subgroup of thrombi. This paradoxical specificity is probably related to an endothelial-like superficial layer, coating the surface of ball-thrombi, whose integrity may reduce the propensity to aggregate platelets. Furthermore, the spherical shape of the ball-thrombus may prevent mechanical injuries, as it rolls like a pebble in the left atrial cavity.
If low pressure in the left atrium, emphasized by decreased atrial transport due to fibrillation, induces a pejorative blood stagnation leading to thrombus formation, it may also decrease the propensity of mechanical collision between the thrombus and the atrial wall. Thus, the formation of a ball-thrombus may result from an initial free-floating or mural microthrombus, with an accretion phenomenon gradually enlarging the mass like a growing snowball. Thus, if a rolling spherical shape resulting from chronic blood stagnation appears to be partly a parameter preventing an embolism, it also should be considered as the growth factor of the ball-thrombus.
Therefore, the initial microthrombus step is dominated by the risk of embolism [3], whereas the major consequence of a single free-floating ball-thrombus is acute hemodynamic decompensation, even sudden death due to the left ventricular inflow obstruction, the so-called "hole-in-one thrombus" effect [8]. In the case of concomitant ventricular location, risk of sudden death appears to be dramatically increased by a "hole-in-two thrombi" effect, as was reported [9]. However, ball-thrombus and embolic events have been reported [4] and result from either fragmentation of the ball-thrombus as it is traumatized by the valve during the ventricular systole, or the atrium itself independently from the ball-thrombus, then depending on previous mitral surgery or chronic atrial fibrillation.
Our observation is rare as it is associated with a moderate mitral leak without any stenotic disease. Therefore, atrial fibrillation remains the prime mover of the physiopathogenic mechanism. We further speculate that postural dyspnea clearly results from an increased mobility towards the mitral valve during verticalization of the patient.
Therapeutic strategy depends on several factors mainly represented by: (1) echographic characteristics; (2) clinical state and symptoms; and (3) previous medical history (mitral valve disease, recent valve surgery, atrial fibrillation, or giant left atrium).
Single anticoagulant therapy may be an interesting and successful option [10], nevertheless requiring a regular echographic follow-up to control the outcome of the thrombus and assess its disappearance. However, considering the potential complications, surgical management remains the main option. We believe that detection of a ball-thrombus in the left cavity requires urgent surgical removal, particularly when the following pejorative echographic criteria are present: (1) surgical mitral valve disease; (2) enlarged or giant left atrium; (3) atrial fibrillation; (4) complete mobility; (5) diameter greater than 1 cm; (6) multiple ball-thrombi; and (7) left ventricular location ("hole-in-two thrombi" effect).
In addition to the thrombus removal, the surgical procedure may include complementary steps depending on the preoperative findings. Thus, left atrial reduction, mitral valve replacement or repair, atrial radiofrequency, or Cox Maze procedures have to be considered.
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This article has been cited by other articles:
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  J. H. Lee, S. K. Kang, C. W. Lee, J. K. Song, J. S. Park, and S. J. Choo Giant Left Atrial Ball Thrombus in a Patient With Chronic Nonvalvular Atrial Fibrillation Ann. Thorac. Surg., January 1, 2008; 85(1): 313 - 315. [Abstract] [Full Text] [PDF]
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 A. Matana, L. Zaputovic, O. Simic, and Z. M. Kastelan The protective effect of mitral stenosis on the embolization of a free-floating left atrial myxoma Eur J Echocardiogr, August 1, 2006; 7(4): 322 - 325. [Abstract] [Full Text] [PDF]
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