Superior vena cava obstruction caused by ascending aortic pseudoaneurysm as assessed by multi-detector row computed tomography

Summary

We describe a case of a 64-year-old man with superior vena cava (SVC) obstruction caused by a huge pseudoaneurysm of the ascending aorta. Pseudoaneurysm of the ascending aorta is an uncommon cause of SVC obstruction. Multi-detector row computed tomography (MDCT) simultaneously clarified the SVC obstruction and coronary artery stenosis.

Introduction

Common causes of superior vena cava (SVC) obstruction include carcinoma of the bronchus, mediastinal mass, mediastinal fibrosis, and constrictive pericarditis [1]. While a pseudoaneurysm of the ascending aorta is a well-known complication after cardiovascular surgery, the cause of pseudoaneurysm in the present case was rupture of a penetrating atherosclerotic ulcer (PAU) of the ascending aorta. PAUs usually involve the descending thoracic aorta and are uncommon in the ascending aorta.

Multi-detector row computed tomography (MDCT) can provide excellent three-dimensional images, as well as visualization of the size, location, and extent of a vascular lesion. Preoperative anatomical detection is a key issue in the treatment of patients with both SVC obstruction caused by pseudoaneurysm and coronary artery stenosis. Accurate lesion-detection using MDCT contributes to a more appropriate surgical strategy.

Case report

A 64-year-old man was referred to our hospital for the treatment of paroxysmal atrial fibrillation (Paf). The patient had exhibited palpitation for several months, which had recently become aggravated. He had a history of hypertension and percutaneous coronary intervention (PCI) for inferior myocardial infarction 25 years before. The PCI had been successful, and he had been free of symptoms of coronary artery disease. At the physical examination, he only exhibited mild facial edema as a sign of SVC obstruction. We planned catheter ablation for Paf, and SVC obstruction was found when the internal juglar vein puncture was performed (Fig. 1).

Figure 1.

(A) Superior vena cavogram confirmed SVC obstruction (arrow) and collateral circulation. (B) No abnormal finding in right atrial angiography. SVC, superior vena cava.

The initial chest X-ray showed mediastinal enlargement. MDCT (Aquilion 64, Toshiba, Tokyo, Japan) scan of the chest with electrocardiogram (ECG) gating was performed, and image-construction and coronary artery evaluation were performed using a workstation (Zio Station, Zio Soft, Inc., Tokyo, Japan). Axial images showed PAUs and a pseudoaneurysm (72 mm in diameter) of the ascending aorta (Fig. 2). Three-dimensional images clearly detected the obstruction of SVC caused by the pseudoaneurysm and collateral circulation (Fig. 2), as well as significant coronary stenoses with calcification of each proximal site in three vessels (Fig. 3).

Figure 2.

Volume rendering image (A) and maximum intensity projection image (B) clearly detected SVC obstruction (arrow), saccular pseudoaneurysm (arrow head) and collateral circulation. Axial (C) and coronal multiplanar reformation (D) image showed penetrating atherosclerotic ulcer and the connection between the ascending aorta and the pseudoaneurysm with thrombus. Ao, aorta; PN, pseudoaneurysm; SVC, superior vena cava.

Figure 3.

Coronary angiogram on multi-detector row computed tomography showed significant coronary stenoses and diffuse calcifications in three vessels. LAD, left anterior descending; LCX, left circumflex; RCA, right coronary artery.

Elective aneurysmectomy, graft replacement of ascending aorta, SVC plasty with a patch, and coronary artery bypass grafting were performed. Operative findings showed a pseudoaneurysm connecting to the lateral side of the ascending aorta. Pathological findings showed that the aneurysm was filled with organized thrombus, and this was suggested to be the cause of PAU of the ascending aorta (Fig. 4). The patient's postoperative course was uneventful, and he was discharged on postoperative day 23.

Figure 4.

(A, B) Resected pseudoaneurysm. A 5.5-cm pseudoaneurysm (white arrow) observed from the adventitial side. Perforation site (white arrow head) of the pseudoaneurysm observed from the intimal side. (C) Formalin-fixed specimen. The pseudoaneurysm was filled with thrombus (black arrow). (D) EVG (elastica Van-Gieson) stain showed tearing of the intimal structure (black arrow head). a, adventitia; PN, pseudoaneurysm; m, media; i, intima.

Discussion

Common causes of SVC obstruction include carcinoma and constrictive pericarditis [1]. A pseudoaneurysm of the ascending aorta is one of the well-known complications after cardiovascular surgery. Although rare, this entity is still potentially fatal if left untreated. However, the present patient had no history of the diseases described above or surgery. MDCT and postoperative pathological findings suggested that the cause of the pseudoaneurysm was PAU of the ascending aorta.

In SVC syndrome, the obstruction of venous drainage leads to the dilation of collateral veins in the upper part of the chest and neck, edema and plethora of the face, neck, and upper part of the torso, suffusion and edema of the conjunctiva. The present case only exhibited mild facial edema probably because of adequate collateral circulation (Fig. 2). Benign disease has been shown to account for only 10% of the common causes of SVC obstruction [2], and more than 90% of SVC obstructions are seen as a manifestation caused by malignancy. Pseudoaneurysm of the ascending aorta due to PAU rupture is a rare cause of SVC obstruction.

PAU refers to an atherosclerotic lesion with ulceration that penetrates the internal elastic lamina and allows hematoma formation within the medial layer of the aortic wall [3]. A typical CT finding is a crater that penetrates the aortic wall layers, and causes a bulge outside the internal contour of the artery. Intramural hematoma (IMH) of the aorta was reported to originate from a PAU [4], and Ganaha et al. demonstrated that the presence of PAU in acute phase was the factor that predicted progression of IMH [5]. PAU is more frequency observed in the descending aorta. There are often multiple ulcers, and they may range in size from 2 to 25 mm in diameter and 4 to 30 mm in depth [6]. The ulcer can develop into IMH, which can cause a limited intramedial dissection or a saccular pseudoaneurysm [7]. The true incidence of PAU is uncertain, but in a retrospective study ulcers could be identified in 7.6% of patients who were admitted with acute aortic dissection [8]. Evangelista et al. prospectively monitored 50 patients diagnosed with IMH for a mean of 45 months using CT, magnetic resonance imaging, or transesophageal echocardiography, and the IMH had progressed to classical dissection in 6 patients (12%), evolved to fusiform or saccular aneurysm in 15 (30%), and evolved to pseudoaneurysm in 12 (24%) [9].

PAU is typically seen in elderly patients with hypertension and atherosclerosis and usually involves the descending thoracic aorta. Our patient had a 25-year history of hypertension, and MDCT showed that the PAUs which led to pseudoaneurysm were located in the ascending aorta. PAU in the ascending aorta is very rare, and Troxler et al. reported that only 6 of 130 PAU patients showed PAU in the ascending aorta [4]. Furthermore, Coady et al. retrospectively reviewed the images of 198 patients diagnosed with aortic dissection and concluded that only 2 patients had PAU in the ascending aorta [10]. PAU, similar to IMH, usually occurs in the setting of atherosclerosis such as elderly patients with long-standing hypertension. Histological study in the operated cases revealed descending aortic IMH to be frequently associated with atherosclerotic change as compared with ascending aortic IMH which usually developed with no significant atherosclerosis [11].

MDCT is presently one of the most useful modalities for evaluating patients with acute aortic syndrome such as aortic dissection, intramural hematoma, PAU, or rupture of thoracic aorta due to aneurysm [12], [13]. MDCT provides precise information about the arterial lumen, walls and extraluminal structure in addition to coronary artery in a single examination. It is possible to obtain images synchronized with ECG, not only for the coronary artery but also for evaluation of the ascending aorta to reduce pulsatility artifacts. We performed MDCT to simultaneously evaluate SVC obstruction and the coronary artery because of prior PCI. Pseudoaneurysm of the ascending aorta and significant coronary stenosis in three vessels were found, and this contributed to successful coronary artery bypass in addition to aneurysmectomy without the need for invasive coronary angiography.

In conclusion, pseudoaneurysm caused by PAU in the ascending aorta is uncommon and is considered to be associated with a higher risk of aortic rupture. MDCT is a useful modality of choice in such cases, and accurate detection using MDCT is essential for the selection of a suitable surgical strategy.