Frozen Elephant Trunk Technique to Treat Extensive Thoracic Aortic Mural Thrombus

Abstract

We describe a case report of a 63-year-old man who presented with chronic left-hand weakness and the absence of a pulse in the left arm. Thoracoabdominal computed tomography (CT) revealed an extensive thoracic aortic mural thrombus. Initial anticoagulation therapy did not provide a positive result, so the patient was referred for surgery. Hybrid aortic arch surgery using the frozen elephant trunk technique was performed with excellent early outcomes. A CT performed in the early postoperative period showed that the thrombus was completely excluded from the aortic lumen by the hybrid graft. No thrombus dislodgment was detected. No thrombus recurrence was observed during 19 months of follow-up.

Thoracic aortic mural thrombus is an uncommon condition and is estimated to occur in 0.08 to 0.9% of the population, but the true incidence remains unknown and is possibly much higher than that reported in the literature. ^{1 2 3 4} Thoracic mural thrombi are usually located in the descending aorta and, less frequently, in the aortic arch, and generally develop secondarily to an atherosclerosis, malignancies, including primary tumors of the aorta, hypercoagulation disorders, polycythemia, iatrogenic conditions requiring long-term treatment with steroids, and infective and genetic disorders of the aortic wall. ^{1 2}

In its turn, aortic thrombus (AT) may cause distal arterial embolism, which significantly increases the risk of life-threatening visceral and limb ischemia. Therefore, AT requires intervention.

Case Report

A 63-year-old male patient with acute left-hand weakness associated with absence of a pulse in the radial and ulnar arteries was admitted to our cardiovascular department. Also, there were symptoms of the left lower extremity ischemia without signs of spinal cord ischemia.

According to ultrasound examination of the upper and lower extremities, thromboses of the left subclavian artery and left tibial artery were confirmed. Thoracoabdominal computed tomography (CT) showed extensive mural thrombus extending from the proximal aortic arch to the descending aorta and the celiac trunk, which developed as a result of atherosclerotic aortic lesions. The first segment of the subclavian artery was thrombosed. The innominate artery, left common carotid artery, and left vertebral artery as well as visceral aortic branches and also renal arteries were patent ( Fig. 1 ).

Fig. 1.

Preoperative three-dimensional and axial computed tomography scans of a 63-year-old male patient with a large sessile thrombus in the aortic arch and descending aorta. Three-dimensional view showing the anterior (left) and posterior planes of the aorta (center). Axial view showing aortic thrombus at the aortic arch level (upper right), the left atrium level (middle right), and the abdominal aorta (lower right).

Anticoagulation therapy using acetylsalicylic acid and low-molecular-weight heparin was first initiated for 8 weeks. During therapy, the target level of activated partial thromboplastin time was achieved, exceeding normal values by twofold (70 seconds). The blood flow in the tibial artery was restored on the therapy. However, due to the absence of significant thrombus reduction, the patient was referred for surgery. Individual verbal and written informed consent for the intervention was obtained from the patient. The patient underwent a single-stage thoracic aortic repair with the implantation of the “E-vita open plus” 24-mm hybrid stent graft (Jotec GmbH, Hechingen, Germany) into the descending aorta without oversizing.

Cardiopulmonary bypass was instituted using the innominate artery for arterial return and the right atrium cannulation for venous drainage. Myocardial protection was achieved using crystalloid cold cardioplegia (Custodiol, Koehler Chemie, Alsbach-Haenlein, Germany). At a core body temperature of 25°C, circulatory arrest was started with an antegrade cerebral perfusion via the innominate artery at a flow rate of 800 mL. No cerebrospinal fluid drainage or pressure monitoring was used.

The hybrid graft was introduced antegrade in the descending aorta under transesophageal echocardiography guidance without oversizing and was attached to the aortic arch using a 4–0 polypropylene running suture. Then, lower-body perfusion was initiated by inserting a 22F balloon-tipped arterial cannula into the graft. The innominate artery and left common carotid artery were reimplanted utilizing an island technique. The left vertebral artery was reimplanted into the left common carotid artery. Due to the prolonged arterial thrombus, revascularization of the left upper limb was performed by carotid-to-subclavian grafting. The proximal anastomosis completed the aortic repair. The operative times were as follows: CBP (cardiopulmonary bypass) time, 160 minutes; circulatory arrest with ACP (antegrade cerebral perfusion), 26 minutes; and cardiac arrest time, 97 minutes.

The postoperative period was uneventful. The patient was extubated 24 hours after the surgery. There were no signs of cerebral or spinal neurologic impairment in the early postoperative period. CT scans performed in the early postoperative period and 19 months later showed that the thrombus was completely excluded from the aortic lumen by the hybrid graft that was implanted down to level T11. No thrombus dislodgment was detected ( Fig. 2 ).

Fig. 2.

Postoperative three-dimensional and axial computed tomography scans of the aorta. Three-dimensional view showing the anterior (left) and posterior planes of the aorta (center). Axial view showing aortic thrombus at the aortic arch level (upper right), the left atrium level (middle right), and the abdominal aorta (lower right).

Discussion

Different treatment modalities have been described. Owing to the condition's rarity, no definitive consensus on aortic thrombi treatment exists.

Anticoagulation therapy may lead to complete dissolution of the thrombus in most patients, but the risk of the recurrent embolism is high, potentially reaching 25%. ² In addition, clear recommendations regarding anticoagulation regimens in these cases are missing. ³ Therefore, a careful patient selection is necessary. ⁴

Another approach is catheter aspiration and systemic or catheter-directed thrombolysis. This procedure is a minimally invasive option associated with varying success rates. However, it carries a high risk of distal embolization during the procedure itself and does not enable complete removal or exclusion of the AT. ²

Open surgical treatment (thrombectomy, total aortic replacement) is associated with high rates of perioperative complications (mainly cerebral). Postoperative mortality is reported in up to 2.6% of cases. ^{2 3}

Implantation of a stent graft to exclude mural thrombus from the blood flow has the potential to decrease the size of the thrombus and avoid distal embolization. It also has fewer perioperative complications compared with conventional surgery. However, retrograde endograft introduction and deployment increase the risk of aortic branch embolization caused by wires or devices compared with antegrade delivery. ^{2 3}

In this case, due to the extensive AT involving the arch and the descending aorta, none of the known treatment techniques were considered optimal. Therefore, we chose the frozen elephant trunk (FET) technique. The FET strategy enabled us to perform aortic arch replacement and a simultaneous antegrade endovascular procedure to exclude the AT. This technique has a reduced risk of dislodgment of the AT compared with conventional surgery or endovascular procedure alone. Utilizing this technology, we achieved satisfactory early and midterm results. There were no cases of distal arterial embolization during the 19 months of follow-up. The late cross-sectional CT scans of the thoracic aorta revealed no changes compared with the early postoperative images.

We could not find any papers that would describe thoracic AT treated with the FET technique. To our knowledge, this is the first case description of a hybrid approach to an extensive thoracic aortic mural thrombus.

To date, the number of papers devoted to thoracic AT is insufficient. Due to the absence of clear guidelines, the optimal management of these patients is still controversial and depends on the thrombus location and morphology.

Conclusion

Our report represents the possibility of a hybrid treatment in case of thoracic AT with excellent stable early and midterm results. In our opinion, the FET technique may be considered as one of the treatment strategies for such patients, especially in cases of extensive thoracic aortic mural thrombus.