Left atrial ball thrombus after edge-to-edge mitral valve repair

Abstract

A thrombus can develop in the left atrium during atrial fibrillation because the loss of contractile function leads to blood flow stasis. Anticoagulation therapy is indicated for prevention of systemic embolism, usually maintaining an international normalized ratio between 2 and 3. Rarely a massive thrombosis develops in the atrium resulting in a peduncolated ball valve thrombus or in a free-floating thrombus. These two conditions are characterized by variables in the physical findings. Such masses are hazardous and upon discovery surgical treatment, often in emergency, is mandatory. We present here the case of a patient who developed an unnoticed huge left atrial ball thrombus despite warfarin therapy after previous mitral valve surgery.

<Learning objective: Risk of atrial thrombosis threatens patients suffering from atrial fibrillation. The presence of a ring and a modified valve anatomy following a surgical repair could represent an additional drive in the thrombus formation pathway. A free-floating ball thrombus in the left atrium is an unusual occurrence that may cause fatal systemic emboli or left ventricular inflow obstruction, often resulting in sudden death. In such cases, even in the absence of symptoms, prompt surgical excision is recommended.>

Introduction

As previously described by Hisatomi et al. [1] a free-floating thrombus in the left atrium without attachment to either the atrial wall or the mitral valve is uncommon, nevertheless it could have potential serious consequences. Various factors may promote thrombus formation [2], including chamber enlargement from mitral disease or mitral surgery, inadequate anticoagulation, a mitral valve stenosis curtailing the blood flow and sluggish flow resulting from atrial fibrillation.

Occasionally [3] a thrombus can grow unnoticed inside the left atrial chamber reaching considerable size, almost sealing up the entire cavity. In such cases, even in the absence of symptoms, prompt surgical excision is recommended.

Case report

A 63-year-old male was referred to our center because of the incidental finding of a giant left atrium thrombus discovered at a routine transthoracic echocardiogram.

The patient had a previous history of mitral valve repair (edge-to-edge technique plus a prosthetic ring implantation) due to severe mitral insufficiency in the setting of Barlow disease in 1998.

He suffered from an ischemic stroke in 2011 that evolved into hemorrhagic injury which required prompt neurosurgical treatment. A lateral homonymous left hemianopsia and a left facio-brachio-crural hemiparesis were left. Since this episode anticoagulation therapy with oral warfarin for persistent atrial fibrillation was begun.

Despite an acceptable coagulation profile in the two months before performing the echocardiogram with an international normalized ratio always above 2, a voluminous thrombus grew inside the left atrial chamber. Also, his coagulation profile was normal at laboratory evaluation. Notably the patient was totally asymptomatic at the time of the examination.

The transthoracic echocardiography showed a severely enlarged left atrium, a mild mitral stenosis with a mean gradient 3 mmHg, and a valvular area of 1.7 cm² associated with mild mitral regurgitation. Within the left atrium a large, spherical, free-floating mass was detected without any evident connection to the atrial wall.

In systole the mass pushed back in the left atrium by the regurgitant flow through the mitral valve, thus mimicking a pinball game. An urgent surgical excision was successfully performed and the intraoperative transesophageal echocardiography allowed to highlights the mass in detail (Fig. 1, Video S1, Video S2). The surgical operation was performed via a traditional trans-sternal approach and the left atrial thrombus was reached by a transseptal incision during a brief period of cardiopulmonary bypass. The histological examination confirmed that the floating mass was an organized thrombus, with an approximate diameter of 6 cm (Fig. 2).

Video S1

Intraoperative transesophageal echocardiogram showing the “pinball-like” movement of the ball thrombus within the left atrium.

Video S2

Multiplane intraoperative transesophageal echocardiogram.

Fig. 1.

Intraoperative transesophageal echocardiogram showing the ball thrombus approaching the mitral valve.

Fig. 2.

Intraoperative picture of the excised ball thrombus.

The postoperative course was uneventful and the patient was discharged on 6th postoperative day.

Discussion

Huge left atrial thrombus is a rare entity and generally it produces symptoms of heart failure or sudden cardiac death. Few reports in the literature describe this potentially life-threatening condition [2], [3], [4].

As reported by Yalta et al. [5] an unattached, freely moving clot within the left atrium, as in this case, is called a left atrial ball thrombus and these clots are rarely encountered and may be fatal in case of embolization or obstruction [6]. Surgical treatment for a ball thrombus is mandatory to prevent complications arising from the unstable nature of these masses. With every heartbeat the clot can fragment and embolize or be wedged in the mitral orifice. Anticoagulation therapy should be considered as a treatment for free-floating ball thrombus only in extremely high-risk cases or for patients refusing surgery.

We found this case particularly interesting because of the presence of a previous repaired mitral valve. The mitral valve plasty was performed creating a double orifice valve in accordance with the edge-to-edge technique previously described [7]. The growth of such a giant thombus related with this repair solution can represent the two sides of the same coin. On one hand the presence of an obstacle in the left ventricular inflow tract, together with persistent atrial fibrillation and atriomegaly have been a contributory cause in thrombus formation despite adequate anticoagulation therapy. On the other hand the double orifice of the repaired valve prevented the embolization of the entire thrombus or its obstruction of the mitral inlet thanks to the central stitch which acts as a gate (Video S1).

Conflict of interest

The authors declare that there is no conflict of interest.