An Unusual Cause of Recurrent Syncope - A Large Free-Floating Left Atrial Thrombus.

Rheumatic heart disease is the most common valvular heart disease in developing countries. Recurrent syncope due to a large, free-floating left atrial thrombus is a rare presentation of rheumatic mitral stenosis. We report this uncommon finding on echocardiogram in an elderly woman presenting to the emergency department with giddiness for the past few months. Copyright:

INTRODUCTION

The prevalence of rheumatic heart disease (RHD) remains high in developing countries, although there is a downward trend. Rheumatic mitral stenosis (MS) is one of the most common valvular heart diseases encountered in clinical practice. Left atrial (LA) thrombus is frequently found in the presence of atrial fibrillation and LA dilatation; however, a large free-floating thrombus in the LA is rare and infrequently seen. Wood first reported a large LA thrombus in 1814 in a 15-year-old girl who presented with rheumatic MS and recurrent syncope.[1]

CASE REPORT

A 70-year-old female presented to our emergency department with a symptom of giddiness for the past 3 months. It occurred transiently irrespective of posture. Clinical examination revealed an irregular pulse at a rate of 82 beats per min and blood pressure of 120/80 mmHg. On cardiovascular examination, the apex beat was located in the left 5th intercostal space and was tapping in nature. On auscultation, a loud first heart sound and a loud P2 were heard. An opening snap and a rumbling middiastolic murmur were heard at the apex and lower midparasternal area. There was also a moderate-intensity systolic murmur in the tricuspid region. Based on the history and examination, a clinical possibility of MS of rheumatic origin along with transient ischemic attack was suspected. Electrocardiography showed atrial fibrillation (AF). Chest radiography revealed a normal cardiothoracic ratio and straightening of the left heart border. Echocardiography showed thickening and doming of both mitral leaflets, with a mitral valve area of 0.6 cm2. The mean gradient across the mitral valve was 14 mmHg. Moderate tricuspid regurgitation with a right ventricular systolic pressure of 64 mmHg was observed. There was a large, freely floating “ping-pong” ball-like thrombus in the left atrium measuring 36 mm in diameter [Figure 1]. The findings were confirmed on transesophageal echocardiography, and a small LA appendage thrombus was also visualized along with spontaneous echo contrast [Figure 2]. Computed tomography scan of the head was normal. The patient underwent mitral valve replacement with a 26-mm St. Jude Medical mechanical heart valve and was prescribed oral anticoagulants with regular monitoring of the international normalized ratio.

Figure 1

Transthoracic echocardiogram in parasternal long-axis view thickened mitral leaflets with doming and large thrombus in the left atrium. LA = Left atrium, LV = Left ventricle, MV = Mitral valve

Figure 2

(a) Four-chamber view on TEE showing “ping pong” ball-like thrombus (b) Short axis view on TEE showing a large thrombus in the left atrium. LA = Left atrium, TEE = Transesophageal echocardiography, LV = Left ventricle, RA = Right atrium, RV = Right ventricle

DISCUSSION

The estimated prevalence of RHD in India is 1–5.4 per 1000.[2] It is the most common cause of valvular heart disease in India. Clot formation in MS usually occurs in the LA appendage. The propensity for thrombus formation increases in the presence of an enlarged LA and AF. Two hypotheses have been proposed regarding the formation of a free-floating thrombus. First, a small mural thrombus in the LA wall gradually grows and projects into the LA cavity. The stalk gets thinned and detached over time, leading to a free-floating thrombus. The surfaces get polished and become smooth with the impingement of the structures in the LA.[34] Second, a ball-shaped thrombus forms by itself rather than any prior attachment to the LA wall. This was suggested based on the finding of laminations in the thrombus, similar to the appearance of onion skin, and the presence of central cavitation.[5] The varied clinical presentations of LA thrombus are syncope, peripheral embolism, and, rarely, sudden death.[6] The varying intensity of the murmur during the change of posture should alert the physician to a large LA thrombus. When there is a large ball-like thrombus, systemic embolization is less likely because there is a superficial endothelial layer that prevents platelet aggregation. However, owing to mechanical trauma to the ball-like thrombus during ventricular systole and the impact on the walls of the atrium, the surface of the thrombus is damaged, leading to embolization.[7] The most common complication of such a thrombus is sudden death due to mechanical mitral inflow obstruction, known as the “hole-in-one” thrombus effect.[8] The mechanism of syncope in our case was probably embolization of showers of small thrombi due to mechanical impingement of the large LA thrombus on the adjacent structures, as clearly demonstrated in Videos 1 and 2. Another pathophysiologic mechanism of syncope is transitory occlusion of the mitral valve orifice by the free-floating thrombus. Therefore, careful attention needs to be paid to the management of patients with severe MS and AF for the early identification and management of this life-threatening complication.

CONCLUSIONS

LA thrombus is common in patients with rheumatic MS and AF. Early recognition of this clinical entity of recurrent syncope with a large free-floating LA thrombus is of utmost importance. First, it may lead to the catastrophic complication of sudden death, and second, surgery is the treatment of choice.

Declaration of patient consent

The authors certify that we have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images, videos, and other clinical information to be submitted in the journal. The patient understands that her name and initials will not be published, and all efforts will be made to conceal their identity to ensure anonymity.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.