Mural thrombi in the non-aneurysmal and non-atherosclerotic AA are extremely rare. Although some of those have been reported without significant signs of aortic atherosclerosis on preoperative imaging, they have been found attached at atherosclerotic lesions after aortotomy, which were still caused by atherosclerosis essentially. In our case, no atherosclerotic plaque has been observed on the excised aortic wall even at the implant site. The cause of a large mural thrombus forming in high-speed blood flow environment such as AA arouses our great interest. To our best knowledge, the common risk factors include smoking, steroid use such as taking oral contraceptives, and hypercoagulable states like pregnancy and collagen disease, among which smoking can even be a sole risk of aortic thrombus. The mechanism of thrombosis in the normal AA remains unclear, but different from those based on atherosclerotic plaque disruption, the thrombus in the normal AA of relatively young(aged༜60 years) patients may form on the exfoliated endothelium[2, 4].
As for diagnostic tools, contrast-enhanced CT should be considered as the first choice because it can clearly show whether the aorta has dissection, hematoma or atherosclerosis, and whether the mass displays enhancement. Moreover, the size and location of the mass can be visually seen on reconstructive images. In our case, since the asymptomatic patient was incidentally detected a sessile mass in his non-aneurysmal and non-atherosclerotic AA, the possibility of ascending aortic tumor(e.g. sarcoma) should be taken into account. Thus, we applied PET to exclude the malignancy and evaluate the necessity of surgery. Besides, although transesophageal echocardiography is effective for evaluating the ascending aortic thrombus, this invasive procedure is very uncomfortable for patients and related to possible complications such as gastrointestinal perforation and aspiration pneumonia, which is more suitable for detecting the location of thrombus and evaluating its mobility intraoperatively. Magnetic resonance imaging can clearly show the level of the aorta but it takes a long time and seems more suitable for stable patients.
At present, there is no corresponding guidelines or consensus on the treatment of the ascending aortic thrombus. There are two main treatment approaches: surgery and conservative therapy with anticoagulant. Endovascular treatment and thrombus aspiration have been also applied in recent years. Anticoagulant should be regarded as the therapeutic cornerstone whether surgery or not, especially appropriate for the patients with high risks of surgical intervention. Some researchers have reported good outcomes of anticoagulant therapy alone. However, it may result in fatal embolism when the thrombus is larger than 1cm. As far as we concerned, surgery is supposed to be a preferred choice when the thrombus is large and floating, or occurrence of systemic embolism due to conservative treatment failure. The types of surgery mainly include simple thrombus resection and aorta replacement. Simple resection is often used when a pedunculated thrombus attached at aortic wall with a narrow stalk while a large sessile thrombus is apt to be dealt with the involved segment of aorta replacement to avoid recurrence. Considering his previous thrombotic events, we thought he may have high risk of distal embolism during conservative treatment. And we could not exclude the possibility of tumor completely so we performed surgical resection plus replacement. Of note, circulatory arrest should be achieved to avoid cross clamping the AA if the location of the thrombus is superior. Heparin and aspirin were given postoperatively, which changed to rivaroxaban after discharge. Endovascular treatment and thrombus aspiration may be considered as an alternative to patients unable to tolerate surgery. However, the efficacy and safety of these new techniques need more clinical experience to be evaluated since any endovascular manipulation has risk of injuring aortic wall or unstable thrombus shedding further causing distal embolism.