Evaluation of the results of penetrating atherosclerotic ulcers surgical treatment

Introduction

Penetrating atherosclerotic ulcers (PAU)of the aorta are a rare disease, but in case of a rupture it may lead to haemorrhage and decease. Its clinical course is often asymptomatic, the first symptom being the rupture. Symptomatic ulceration counts among the so-called Acute Aortic Syndromes (AAS), next to aortic dissection, intramural haematoma and aortic injury. The incidence of AAS described in the literature is of 2.6-3.5 cases/100 000/per year, out of which PAU forms just 2-8% [1-4]. Unlike dissection and intramural haematoma, PAU are involved in pathologies of the internal elastic lamina — not the aortic media [5]. Penetrating atherosclerotic ulcers of the aorta were first described in 1934 by Shennan; in 1986 Stanson began investigating the pathogenesis and the natural history of PAU [6, 7].

In course of the penetrating atherosclerotic ulceration, a rupture of the degenerated internal lamina takes place which results in the lamina media being directly exposed to the effects of the arterial blood pressure. As a consequence, a haematoma appears in the lamina media, weakening it. At further stage, a visible external convexity of the artery wall appears. Penetrating atherosclerotic ulcers mainly involve the aorta (more frequently the thoracic part than the abdominal), but can be also found in other arteries: femoral artery, coronary arteries and brachiocephalic trunk have also been described [8-11]. In 1998, for the first time, Murgo described an effective PAU supply with the use of stentgraft [12].

The development of blood vessel imaging techniques and the progress of endovascular surgery have increased the number of attempts to approach the subject of penetrating atherosclerotic ulcers treatment.

Figure 1. Penetrating atheroslerotic ulcers located in the descending aorta before and after endovascular treatment
Rycina 1. Penetrujące miażdżycowe owrzodzenia aorty zstępującej przed i po leczeniu wewnątrznaczyniowym

Aim of the study

The aim of the present study is to assess endovascular PAU treatment results.

Material and methods

At the Department of General, Vascular and Transplantation Surgery, Medical University of Warsaw, between January 1st 2006 and June 30th 2011, 28 patients were treated due to penetrating atherosclerotic ulcers of the aorta and the iliac artery. The group subjected to investigation was formed by 22 men and 6 women. The average age of male patients was of 69.4 years (with a median of 68; range: 53-86, SD 8.3), and in case of female patients, of 63.5 years (median: 62.5, range: 56-77, SD 7.6). The overall average age was of 68 years (median: 67, range: 53-86, SD 8.4). Twenty six patients (92%) were diagnosed with arterial hypertension, 12 (42%) with ischemic heart disease and 9 (32%) with chronic limb ischemia. All members of the group were diagnosed with PAU via computed tomography, and in case of 7 people (25%) ulceration was preliminarily suspected based on the results of abdominal ultrasonography. In case of 6 patients (21%) PAU was localised only in the descending aorta (fig. 1), and in the infrarenal aorta as regards 21 (75%) (fig. 2). One patient (3%) had the disease diagnosed in the left iliac artery (fig. 3). In case of one patient, ulcerations of the thoracic aorta and the abdominal aorta coexisted, and two other patients had double lesions, in the infrarenal and the thoracic aorta subsequently. In one case (3%), a PAU rupture was diagnosed during a random ultrasound examination where a retroperitoneal haematoma became visible. The patient did not report any pain symptoms and his condition was stable. A subsequently executed computed tomography confirmed a slight retroperitoneal haematoma with a visible spot of contrast leak through a ruptured, ulcerated atherosclerotic plaque.

Figure 2. Penetrating atheroslerotic ulcers located in the infrarenal aorta
Rycina 2. Penetrujące miażdżycowe owrzodzenia w odcinku podnerkowym aorty

Figure 3. Penetrating atheroslerotic ulcers located in the common left iliac artery
Rycina 3. Penetrujące miażdzycowe owrzodzenia lewej tętnicy biodrowej wspólnej

In case of 12 patients (42%), the arteries in the ulcerated areas had transverse diameter dimensions which allowed the detection of aneurysm. Based on computed tomography, the PAU morphology was defined as well. The average width was 14.5 mm (median: 14, range: 6-29, SD 6) and the average depth 13.4 mm (median 12, range 5-22, SD 6).

The ulceration symptoms were observed in case of 7 diseased (25%) and were related with pains inside the chest, abdomen and in the lumbar area, depending on the PAU location. All the patients, irrespective of the size of the ulceration and the symptoms, were qualified for surgical treatment. The patients were subjected to endovascular surgeries, if they complied with the standard requirements regarding such treatment. In one case, due to iliac arteries coarctation which ruled out the possibility of stentgraft introduction, the patient was treated using the method of open repair with aortic replacement and conventional tube graft positioning. In case of a diseased woman diagnosed with two ulcerations inside the thoracic and the abdominal aorta, thoracic stentgraft implantation aortobifemoral bypass was carried out. Stentgraft implantation in this case was abandoned due to hostile aneurismal neck anatomy.

Twenty one endovascular surgeries were carried out using regional anaesthesia (epidural or spinal), and the other 7 — using general anaesthesia. The surgical approach involved the femoral arteries (bidirectional in case of abdominal stentgrafts and one-sided during the thoracic stent grafts implantation). The prostheses were introduced under digital subtraction angiography (DSA) guidance, having executed an aortography at the beginning of the surgery in order to precisely identify the position of the ulceration and the aortic branches. Intraoperatively, heparin was served in doses of 0.5 mg per kg body weight. Overall 28 stentgrafts were implanted: 14 Zenith®, 7 Excluder®, 3 Relay®, 2 TAG®, 1 Valiant® and 1 Endurant®. One patient had two stentgrafts implanted inside the thoracic aorta (TAG® and Excluder®). In case of two patients who were subjected to open surgery, aortobifemoral bypass (InterGard®) solutions were installed. After the stentgraft implantation, still on the operating table, aortography would be performed in order to confirm the cut-off of blood flow inside the lumen of the ulceration and the stent graft patency. During the post-surgery period, low molecular weight heparins were served in prophylactic doses in combination with acetylsalicylic acid, 75 mg per day. After the discharge, meanwhile, acetylsalicylic acid alone would be used. Before leaving the hospital, the patients were examined using computed tomography in order to assess the effectiveness of the treatment. Further follow-ups of the patients involved computed tomography check-ups, after 3, 6 and 12 months and later: repeated annually. The average follow-up period was 27 months (median: 24, range: 6-72, SD 17).

Figure 4. Cumulative rate of freedom from reintervention evaluated according to Kaplan-Meier method
Rycina 4. Skumulowany wskaźnik czasu wolnego od reinterwencji (metoda Kaplana-Meiera)

Results

In none of the cases was it necessary to perform additional procedures intraoperatively. Cumulative rate of freedom from reintervention is presented in figure 4. In one case, on the third day after the stentgraft implantation right limb thrombosis appeared due to kinking which in consequence led to acute limb ischemia.

Thrombectomy was performed and an additional Visi-Pro 9 × 37 stent was implanted to eliminate the kinking. In case of one patient, a computed tomography carried out after three months detected an endoleak around a limb of the bifurcated stentgraft (IB type leak) resulting in the ulceration being filled with blood. The patient was qualified for treatment, in the course of which an additional stentgraft was implanted which effectively eliminated the leak. In case of another patient, during a computed tomography performed 6 months after the surgery a type II endoleak became visible. An effective leak elimination was achieved through performing embolisation by endovascular trombin injection.

Discussion

Surgical treatment of aorta pathologies remains a significant clinical problem. It refers especially to asymptomatic diseases, such as the abdominal aortic aneurysm (AAA) or the penetrating atherosclerotic ulcers. In case of AAA, surgery is recommended based on the maximum transverse diameter of the aorta (55 mm for men, 52 mm for women). These guidelines were established based upon decades of prospective investigation involving large groups of patients. It was possible because of the relatively high AAA incidence, estimated at 5-7% of the population of people over 60 [11]. The penetrating atherosclerotic ulcers are a much rarer disease. The incidence here is estimated at just 2-8% of diseased people suffering from acute aortic syndromes [12, 13]. The incidence of asymptomatic PAU in the society, meanwhile, has not yet been defined at all. A significant question here is the diagnostic imaging of ulcerations. Lesions within the thoracic aorta remain out of reach for the classic USG examination, while minor ulcerations of the abdominal aorta can be easily overlooked by the examining person. Within the group described in the present paper, 25% of the patients had been diagnosed with PAU. The development of imaging modalities brings an increase of ulceration detections. The commonly accepted methods of imaging that disease are: computer tomography, magnetic resonance imaging, transesophageal echocardiography and intravascular ultrasound [1, 2, 14, 15]. Computed tomography and magnetic resonance enable performing accurate measurements and assessing the ulceration morphology. In the investigated group, the average PAU width was 14.5 mm, and the average depth of 13.4 mm. According to Eggebrecht, the risk of rupture and other complications is higher in case of dimensions exceeding 20 mm of width and 10 mm of depth [16].

The major potential risks connected to PAU are ruptures which may even lead to decease. In the literature, the incidence of ulceration rupture is estimated at even 40% [16]. Furthermore, among other complications there are the apparitions of aortoesophageal or aortobronchial fistulas which are also a direct life threat [17, 18]. Among the described patients, only in one case (3%) a PAU rupture was detected, its only symptom being a slight retroperitoneal haematoma found by chance during an USG of the abdominal cavity. So far, the procedure for PAU patients has not been defined. Some authors recommend performing surgeries on patients with clinical symptoms, maintaining that in cases of high-risk asymptomatic patients conservative treatment is acceptable [19]. It has to be taken into consideration that patients suffering from penetrating atherosclerotic ulcers are mostly elderly people, the majority of whom are significantly burdened with coexisting diseases which means that a typical surgery, involving a replacement of the artery segment which experienced pathological lesions, would implicate an increased morbidity rate. The introduction of aneurysm endovascular treatment with the use of stentgrafts opened a new chapter in the development of aortic surgery. This method is also applied in aortic dissections and injuries treatment, as well as in cases of intramural haematomas and penetrating ulcers. In the presented material, stentgraft implantation was the method of choice for PAU patients treatment. In two cases, open repairs were performed involving aortic replacement with bifurcated vascular prostheses implantation into the abdominal aorta, given that the patients had coexisting aneurysm and contra-indications for endovascular method application. Endovascular treatment seems to be an efficient way of eliminating the impact of arterial pressure on the ulceration. The overall analysis of publications regarding 209 patients from different centres, presented in 2009 by Eggebrecht, enabled the assessment of the effectiveness of endovascular PAU treatment [16]. Technical success, consisting of cutting off the ulcerated area from blood flow, was recorded in case of 96% patients. The average re-intervention figure was 5%, but in some cases reached 25% [12]. The mortality figure during hospitalisation time reached 7%, and the overall mortality figure related to PAU over the follow-up period was of 2% [16]. In comparison with the above mentioned data, the treatment results from the Department of General, Vascular and Transplantation Surgery, Medical University of Warsaw confirm the effectiveness of the endovascular method as regards elimination of penetrating ulcers of the aorta. The re-intervention figure connected to the stentgraft implantations was of 10%, in two cases being due to endoleak, and in one case to stentgraft limb thrombosis. One should notice that all of the re-interventions were carried out within 7 months of the date of surgery. Also, all of them were related to stentgrafts inside the infrarenal aorta. Meanwhile, no complications connected to spinal cord ischemia were observed, the incidence of which was of 4% according to Eggebrecht’s publication [16].

The natural history of PAU has not yet been well researched. The limitation for the present publication is its retrospective character which did not enable an assessment of the ulceration changes over a period of time, since all of the patients, irrespective of the presence and the dimensions of the symptoms, were qualified for surgical treatment. According to presently existing information, the dynamics of the ulceration growth is not constant, but is characterised by significant alternations. In 2001, Quint published a paper describing how he had investigated, using 33 cases as examples, the chronologic evolution of ulcerations over the average follow-up period of 18 months. It turned out that in 21 cases the ulcerations did not evolve, in 10 cases grew and in two cases diminished [20]. Determining the factors directly influencing the ulceration evolution would be much helpful as regards conservative PAU treatment. Undoubtedly, one of such factors is arterial hypertension, with which 92% of the members of the investigated group were diagnosed.

Penetrating atheroslerotic ulcers locations are vary, but the ones most frequently described are inside the descending aorta. A manifest phenomenon among the investigated patients was the quantitative advantage of PAU inside the abdominal aorta. Furthermore, in the investigated material, in one case the ulceration was detected in the common iliac artery. Such PAU location has never been published before.

Conclusions

Endovascular treatment of penetrating atherosclerotic ulcers of the aorta seems to be an effective method of rupture prevention, involving low complication and re-intervention figures, but it is required that guidelines regarding clinical procedure are defined. The complications only appeared after surgeries of PAU located inside the infrarenal aorta.

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