Introduction

Visceral artery aneurysms (VAAs) are rare, and their prevalence is difficult to estimate (0.1 to 2%) as autopsy studies suggest that they may be more common than it is thought^1,2. However, they are more frequently detected because of the advances in diagnostic imaging tests and constitute a challenge for physicians, as they usually occur in young asymptomatic patients. Nevertheless, up to 25% may present as rupture which is associated with high mortality (up to 70%)^1,3. Multiple VAAs have been described in 20% of patients⁴.

Traditionally, VAAs have been managed with clinical and imaging surveillance or with open surgical repair. Although the indications for treatment are not strictly defined, most authors have agreed that aneurysms should be treated when the diameter is > 2 cm, or when are rapidly growing, symptomatic or ruptured, or in women of childbearing age^1,4. In 2020, the Society for Vascular Surgery (SVS) established clear guidelines and recommendations³.

In recent years, endovascular therapy has gained ground and is even considered the first option in many cases according to the most recent recommendations^2,3,5. Nowadays, almost any anatomy can be approached with the large number of endovascular techniques available, in many cases using flow diverters (FDs) and electrolytically detachable coils (microcoils) used to treat intracranial aneurysms.

The aim of our study was to describe the experience in endovascular management of VAAs using different techniques in a single center, with short-, mid-, and long-term results.

Material and methods

We retrospectively collected all patients with VAAs undergoing endovascular treatment at a single center (Clínica La Sagrada Familia, CABA, Argentina) between May 2010 and May 2020. Only patients with true aneurysms and followed up for a minimum of 6 moths were included. Cases of ruptured aneurysms, traumatic pseudoaneurysms or those iatrogenic or due to infections were not included. In all the cases, the diagnosis was made by computed tomography angiography with 3D reconstruction or magnetic resonance angiography, and preoperative planning was performed by 3D angiography using a single plane equipment (Allura Clarity FD 20; Philips Medical Systems 2012^®) (Fig. 1)⁶.

Figure 1 Technical planning with 3D angiography 

Clinical and demographic data as age, sex, hypertension (HT), smoking habits (SH), dyslipidemia (DLP), coronary heart disease (CHD), oral anticoagulation and chronic kidney failure (CKF) were analyzed. The treatments used included FDs, microcoils, a combination of both or covered stents (CS). The decision to choose between them was based on technical and anatomic aspects, such as vessel diameter, tortuous vessels, length to cover, presence of collateral vessels, and clinical aspects, as emergency status (Fig. 2). Flow diverters were used for small diameters and when it was necessary to navigate through significantly tortuous arteries, or in case an important collateral emerged from the segment to be covered by the device. Coil embolization was restricted to cases of saccular aneurysms with very narrow necks or when definitive embolization of the vessel was planned. The combination of uncovered stent and coils was used in cases with a wide neck, as stents prevent coils from migrating into the lumen of the main vessel. Covered stents were chosen when immediate exclusion of the aneurysm was desired with preservation of the vessel.

Figure 2 A and B: Renal artery aneurysms before and after treatment with microcoils. C and D: Aneurysm of the superior mesenteric artery before and after treatment with FD. 

The patients were followed up with computed tomography angiography whenever possible, or otherwise with angiography (due to the presence of artifacts) at 6 and 12 months. Those patients who underwent stenting were treated with dual antiplatelet therapy (ASA 100 mg/day and clopidogrel 75 mg/day in most cases) for a minimum of 6 months and then with ASA alone indefinitely. The study protocol was approved by the Committee on Ethics of the institution. Primary technical success was defined as complete exclusion of the aneurysmal sac confirmed by intraoperative angiography, and secondary technical success was defined as complete exclusion of the aneurysmal sac confirmed by angiography or computed tomography angiography during follow-up, after the primary intervention, without any type of adjuvant procedure. Sac shrinkage was defined as any reduction recorded during the follow-up period compared with the preoperative diameter.

All the statistical calculations were performed using Rstudio Team (2020) software package (Rstudio: Integrated Development for R. Studio, PBC, Boston, MA). Quantitative variables were expressed as mean ± standard deviation or range, and qualitative variables as frequencies and percentage, and were compared using the Student’s t test or the chi square test, as applicable. A p value < 0.05 was considered statistically significant.

Results

During the study period, 22 patients underwent endovascular treatment of VAAs at our institution. Four patients who were followed up for less than 6 months were excluded. Therefore, we analyzed 19 procedures in 18 patients (9 men and 9 women). Mean age was 61.9 ± 8.8 years (64.4 for men and 59.4 for women), with a mean length of hospital stay of 1.94 days and a mean follow-up of 40 months. The splenic artery was the most commonly affected vessel (n = 9, 50%); and of these cases, 5 were women (55.6%). Mean preoperative aneurysm size was 30.1 ± 12.82 mm. The distribution of aneurysms, their size and the techniques used are shown in Table 1. There were no cases of mortality within the first 30 days and no aneurysm-related mortality during the follow-up period.

Table 1 Anatomic distribution and size of the aneurysms 

Two patients required reintervention (11%). The first patient was a man with a splenic artery aneurysm measuring 50 mm, who presented persistent filling of the sac and underwent surgical repair with interposition of a prosthetic graft on the following day (this reintervention was not analyzed as a procedure because it was not an endovascular intervention). The second patient was a woman with a splenic artery aneurysm of 46 mm, who initially received treatment with FDs and microcoils. Fifty-six months later she presented with persistent filling of the sac with a diameter 6.5% higher. A CS was implanted with complete exclusion of the sac documented intraoperatively and after 8 months (Fig. 3).

Figure 3 A: Patent aneurysm of the splenic artery treated with FD and microcoils (arrow). B: Reintervention using covered stent. 

Flow diversion was the strategy most used (n = 8, 42.1%). The treatments performed are shown in Table 2. Fourteen procedures were performed via the femoral access and the brachial access was used in 5 cases. Only one patient required thrombectomy of the brachial artery due to thrombosis of the puncture site, with favorable outcome (5.3%).

Table 2 Treatments performed 

Overall primary technical success was 38.4%, while secondary technical success was 47.4%, 68.4% and 94.7% at 3, 6 and 12 months, respectively. However, the primary technical success of FD was 12.5% vs. 54.4% for the other techniques (p < 0.05). Secondary technical success at 3, 6 and 12 months was 25%, 87.5% and 100%, respectively, for patients treated with FD vs. 63.6%, 63.6% and 90.9%, respectively, for the other treatments. Only one patient with aneurysm of the gastroduodenal artery presented asymptomatic stent thrombosis at 11 months, with aneurysmal sac shrinkage of 31.3%. This resulted in a patency rate of 94.4% by the end of the follow-up period. Three patients with splenic artery aneurysm were treated in the setting of non-specific abdominal pain (26, 28 and 29 mm in diameter); 2 of them were treated with CS and the remaining patient underwent sac embolization with microcoils.

The aneurysmal sac grew in only one patient and required re-intervention. After 8 months of followup, the aneurysmal sac remained stable. Thirteen patients (72.2%) presented sac shrinkage (mean shrinkage of 16.5%), including 3 complete shrinkages, while in 4 patients the sac remained stable. The mean diameter of the aneurysmal sacs at the end of the follow-up period was 23.4 mm (p = 0.02689).

Discussion

To our knowledge, so far, this is the largest series of AAV cases in a single institution in the Argentine Republic. Our case series does not differ from those of international publications^7-10. Both Sessa and Cochennec published 42 and 51 cases over 27 and 15 years, respectively^7,9.

Our diagnostic and therapeutic approach was in line with current international recommendations, even considering that they were published in 2020. Therefore, only one patient underwent subsequent surgical intervention, while the remaining patients were treated before the publication of the guidelines³. Seven patients were treated without considering the size recommended by the SVS. This represents a significant proportion of 42.1%; however, 3 of them presented with non-specific abdominal pain hardly attributable to any other cause (indication for treatment), which solved completely in all cases. Two other cases corresponded to female patients who wanted to become pregnant and had splenic artery aneurysms (which was the driving force to indicate treatment). Thus, only 2 patients were treated without considering the recommendations (10.5%).

As we have already mentioned, we did not include pseudo aneurysms. We made this decision because the rupture rate in cases of pseudoaneurysms is not only significantly higher but also affects a different population since it is essentially a different condition^5,11,12. Our reintervention rate was similar to the one reported by other series^5,7. It is worth mentioning that the only case requiring conversion to open surgery was the first in the series which could have influenced the decision-making process. We believe that, if the same situation occurs with the experience and technology we currently have, both decision and outcome will be different.

The use of FDs in this type of aneurysm is an interesting and, in our opinion, novel approach, as it is different from most publications on the subject. The differences that we observed in terms of primary technical success between FDs and other techniques can be perfectly explained by the mechanism of action of this type of device. Flow diversion is basically a fluid mechanics-based strategy which aims to decrease or eliminate aneurysmal blood flow and restore normal arterial blood flow¹³. This technique is mainly used for intracranial aneurysms, and many renowned publications suggest the use of flow diversion as a first alternative especially in small and uncomplicated aneurysms, precisely because of the risk of posttreatment rupture associated with giant aneurysms^4,15. It is true that the percentage of primary technical success achieved when FD was not used was also low (54.4%). However, most of these patients were treated with uncovered stents and microcoils, which in many cases also fail to achieve intraoperative sac exclusion. It is also important to mention that we do not advocate embolization of the main vessel as we prefer to preserve it whenever possible. However, if embolization is necessary depending on the vessel to occlude, there is often no clinical impact. This is why we prefer other techniques, as Lagana has suggested, including CS or coil embolization for cases of symptomatic or ruptured VAAs or pseudoaneurysms (although these were not included in the study), or even large aneurysms, since immediate exclusion of the sac is achieved, and leave other techniques for elective cases. However, some patients are not candidates for FDs due to anatomic and technical limitations related with the device profile and navigation⁵. The use of covered stents in VAAs was first described at the beginning of the present century^16,17. The major advantage of FDs is due to their adaptability to the anatomy of the vessels (small diameters, short lengths, tortuous anatomy and low profile), resulting in a very attractive option, and even sometimes as the only feasible option. Only one patient required reintervention due to delayed thrombosis of the sac; therefore, the clinical consequences were minimal. In addition to this, the implementation of other techniques used for the treatment of intracranial aneurysms, as 3D angiography, microguide wires, microcatheters and electrolytically detachable coils, has been extremely useful in the treatment of VAAs.

Some publications have reported late reperfusion rates of the aneurysmal sac of up to 5%, but there were no cases in our series⁷. Although we assume that our case of late reintervention involved a sac that was never primarily excluded because there were no CT scans to document it, we cannot rule out reperfusion as the reintervention was performed almost 5 years after the initial procedure, and the previous images only covered up to the first year. Other authors report stent thrombosis rates similar to ours without any clinical impact¹².

The retrospective design is a limitation of this study and, although we had an adequate follow-up which allowed an appropriate analysis of the aneurysmal sacs (40 months), we lacked mid-term images in some patients (only preoperative and long-term images). Thus, we could not perform a more detailed analysis of sac reperfusion cases. Nevertheless, despite the lack of annual follow-up, the low reoperation rate and absence of associated mortality is a promising finding, especially considering that many of these patients are young and radiation may pose a problem in the long term. Secondly, we believe that it would be interesting to analyze the different strategies in different clinical scenarios, such as elective versus emergency interventions and to evaluate the results when we count with a greater number of cases.

Endovascular treatment of VAAs is a safe and efficient strategy but requires adequate technology for preoperative planning and treatment. The technique chosen should be adapted to the anatomy and the clinical setting.