Aortic Aneurysms: An Essential Guide to Surgical Management and Key Considerations

Dr Nick Ng Zhi Peng, Consultant, SingHealth Duke-NUS Vascular Centre; Department of Vascular Surgery, Singapore General Hospital
 

Small, asymptomatic aortic aneurysms can be followed up in primary care. However, for aneurysms that require intervention, treatment is tailored based on size, location and occasion (patient's fitness). The SingHealth Duke-NUS Vascular Centre shares the key considerations for both open and endovascular repair, so general practitioners can advise patients on their options and what to expect.
 

INTRODUCTION

Aortic aneurysms occur when the aorta is enlarged or dilated by more than 50% of its native size. As the aneurysm increases in diameter, the risk of rupture also increases. This can lead to massive bleeding and catastrophic circulatory collapse, with the mortality risk from a ruptured aneurysm as high as 50 to 80%.

In the previous issue of Defining Med, we shared about what GPs can look out for in primary care, when surveillance is sufficient and when active management or surgery should be considered. This article will focus on the surgical management of the condition.
 

OPEN VS. ENDOVASCULAR SURGERY FOR AORTIC ANEURYSMS

Aortic aneurysms may be repaired with open surgery, where the aneurysmal segment is replaced with a graft, or with endovascular stenting, where the inside of the aneurysm is lined and thus excluded by graft components delivered from peripheral arteries.
 

1. OPEN SURGICAL REPAIR

Open repair has been long considered the gold standard as when successful, it is often longer lasting, without need for active surveillance or reintervention. Open surgery, however, is fraught with high peri- and intraoperative morbidity and mortality.

Large incisions
It requires big incisions – dissection of the aortic segment involved from proximal to distal, and cross clamping of the aorta while the aneurysm is repaired or replaced with a graft.

Incisional hernias that arise are a long-term complication given the nature of these large incisions, and may contribute to the long-term morbidity.

Physiological stress
Cross-clamping of the aorta places huge physiological stress on the body due to the sudden increase in cardiac afterload. Prolonged clamp time also leads to increased ischaemic time to the downstream organs such as the visceral organs, bowel and lower limbs.

Significant blood loss
In addition, in difficult or complex open repairs, significant blood loss may be encountered especially when there is a need to reimplant visceral arteries. This is especially so in the open repair of thoracic aorticaneurysms (TAAs) and thoracoabdominal aneurysms (TAAAs).

The need to reimplant important arteries such as the carotid, innominate, renal or visceral and iliac add to the complexity of the repair and overall surgical time. Sometimes, patients have to be put on cardiopulmonary bypass (a heart-lung machine), especially for TAAs.

Postoperative ICU care
Postoperative ICU care is expected and inpatient stay can range from weeks to months depending on the development of perioperative complications, nosocomialinfection(s) as well as the patient’s rehabilitative potential.

These complications include:

• Cardiac events
• Cerebrovascular accidents
• Bowel and limb ischaemia
• The need for temporary or long-term dialysis

2. ENDOVASCULAR REPAIR OF AORTIC ANEURYSMS (EVAR)

EVAR is increasingly popular, and has largely surpassed open repair as the preferred mode of repair since the first one was performed in 1990.

How it works
The idea is to place a covered stent that extends from a non-aneurysmal segment to another non-aneurysmal segment across the aneurysm. This stent graft and its components are increasingly delivered purely percutaneously.¹

The key is that the covered stent(s) seals or excludes flow into the aneurysm, and reduces or stops the aneurysm sac from being perfused and expanding over time. At the same time, perfusion to vital organs is maintained.

Sealing at proximal and distal ends of the aneurysmis crucial to prevent forward and back filling of the aneurysm. The ideal seal zones are thus long, straight, non-angulated and not lined with thrombus. This is known as the aneurysm neck.

Over the last decades, sizing techniques and several adjuncts have allowed for the technology with EVAR to take off even with complicated or hostile aortic necks.

Potential complications
An aneurysm sac that continues to fill despite having been stented across is known as an endoleak, and this is the Achilles’ heel of EVAR. Depending on the nature and severity of these endoleaks, further intervention may be needed, and hence surveillance is an important part of this surgical option.

Post-EVAR surveillance is needed to check if the stent grafts have migrated, components are intact, and stentlumens have stenosed or thrombosed. The aneurysmsac must be monitored for any continued perfusion or increase in size over time.²

Slower endoleaks or continued perfusion from collaterals such as the inferior mesenteric artery or lumbar arteries can be monitored or intervened less urgently as they do not pressurise the sac as much, while proximal, distal or endoleaks due to component malfunction or misalignment require urgent re-intervention.

Other complications specific to EVAR techniques include access site complications resulting in bleeding orextremity ischaemia. The need for contrast also places patients at risk for contrast-induced nephropathy.

Benefits
While accepted that EVAR has lower perioperative and intraoperative morbidity, and shorter length of stay or need for ICU compared to open repair (no need for large incisions or cross-clamp, less blood loss), the overall costs and long-term need for surveillance and reintervention can be significant.²

Nevertheless, this makes EVAR an attractive method of repair for elderly and patients who are less surgically fit. In the majority of uneventful EVAR, length of stay ranges from one to five days.²

SPECIAL SURGICAL CONSIDERATIONS BASED ON ANATOMY

Surgical treatment of aortic aneurysms requires a good understanding of aortic anatomy, and assessment of the aortic neck and distal seal zones with proper evaluation of the access vessels.

1. THORACIC AORTIC ANEURYSMS (TAA)

Size-wise, TAAs are usually repaired when larger than 6cm or when they are symptomatic or eccentric in nature. The aneurysm’s relation to the innominate, left carotid and left subclavian arteries is crucial to determine the best approach.¹ The risk of embolic stroke is significant for both open and endovascular repair.

Open surgery
Open surgery for TAAs requires open thoracotomy, aortic clamping and the use of cardiac bypass. Open repair of ascending or arch aneurysms requires reimplantation of arteries to the head and neck into the graft. These repairs can be associated with high cardiac and stroke risks. This is usually performed by cardiothoracic surgeons.²

Endovascular surgery
Endovascular stenting of TAAs, while less morbid, needs to take into account the seal zones and coverage required. If the length of stent required to seal the aneurysm covers important arch branches, complex EVAR techniques are required to establish flow into these major arch vessel(s).²

Fenestrated EVAR (FEVAR) is one such well established endovascular treatment option. These devices may be ‘off-the-shelf’ or customised.

• Fenestrations are gaps in the mesh of the stent that can be small, large or semicircular/incomplete holes (scallops) that are reinforced with nitinol wires.² 
  
  
• Custom-made devices (CMD), as the name suggests, are specifically ordered, individually tailored, designed and manufactured based on measurements from a patient’s preoperative CT angiography imaging, as opposed to the use of combining standard available devices.
  
  They are most useful when the aneurysm can be treated in a less time-sensitive and more elective setting, as they take several weeks to make.²

In time-sensitive cases, CMDs are unsuitable and a hybrid approach may be necessary where thoracic EVAR (TEVAR) is performed with chimneys (chimney EVAR [ChEVAR]) or snorkels, along with debranching and open surgical cervical bypasses (i.e., carotid-carotid and carotid-subclavian bypasses) to achieve aneurysm sealing while preserving perfusion to brain, spinal cord and upper limb.⁵

•  Spinal perfusion is a consideration as the more extensive and proximal a segment of aorta that needs to be stented across, the higher the risk of spinal ischaemia with resultant temporary or permanent neurological deficits in the form of paralysis or incontinence.²
   

2. THORACOABDOMINAL AORTIC ANEURYSMS (TAAA)

TAAAs are often also known as juxtarenal or pararenal aneurysms in relation to the renal arteries.

Open surgery
Open repair of these aneurysms is often high-risk and challenging as they require operating in a very deep cavity, with a need to employ a supra-coeliac aortic clamp. Sometimes these surgeries may result in having to sacrifice or reimplant renal or visceral arteries.

Prolonged clamp time or dislodgement of clots can occur in the visceral vessels (coeliac axis, superior mesenteric artery and renal arteries) resulting in ischaemic bowel, renal infarcts and acute lower limbs.

Endovascular surgery
Like endovascular repair for TAAs, FEVAR or ChEVAR techniques can also help preserve perfusion to renal and visceral arteries.

Infrarenal abdominal aortic aneurysms (AAAs) with short, angulated or conical necks and high thrombus load at the aortic neck may also require the use of these techniques to extent proximal coverage safely. In some cases, proximal sealing of infrarenal AAAs with hostile neck can be achieved with endoanchors (Figure 4).

For TAAAs, FEVAR is increasingly well-established, safe and durable in both emergent and elective settings. They may be performed with ‘off-the-shelf’ devices or CMDs. ‘Off-the-shelf devices’ have standard multi-branches (four branches) and are anatomically suitable in 88% of patients.

They are more readily available in emergencies but limited when the need for additional branches, retrograde-direction branches, or aortic diameters outside the standard size range arises. Some studies have also shown concerns regarding long-term branch stability and higher stenosis of target vessels with higher secondary reintervention rates.²

Physician-modified endografts created by modification of conventionally available endografts have been described to overcome the limits of custom-made and ‘off the-shelf’ fenestrated devices with good results. However, they require much more experience and technical ability, and their long-term durability is still under-studied.²
 

3. MULTIPLE ANEURYSMAL SEGMENTS

Some patients have aneurysms in more than one aortic segment. At Singapore General Hospital (SGH), these cases are discussed in a multidisciplinary aortic meeting and the most life-threatening, symptomatic segment is treated first, preferably from proximal to distal.

These procedures often need to be staged and the risk of spinal ischaemia can be significant.
 

4. CONCOMITANT ILIAC ANEURYSMS OR SHORT ILIACS

Many patients with aortic aneurysms also have concomitantiliac aneurysms. These may be bilateral or unilateral and may involve only the internal iliac or common iliac artery, or both.³

Endovascular surgery
Standard EVAR for such patients would be inadequate and techniques available include the use of iliac branch devices (Figure 5), or embolisation of the internal iliac artery with stent extension into the external iliac artery.

Iliac branch devices allow coverage from the common iliac artery into both the external and internal iliac arteries to preserve flow. Sufficient length and diameterof the iliac branches are important considerations.

Embolisation of the internal iliac artery may result in buttock claudication, sexual dysfunction as well as rectal ischaemia, especially if done bilaterally and simultaneously.

These techniques may also be employed for cases with short common iliac arteries to get adequate seal zones.

5. MYCOTIC ANEURYSMS OR INFECTED STENT GRAFT

Mycotic aneurysms are some of the most formidable surgical diseases.^4,5

Open surgery
Open surgery involves ligating or excising/explanting the infected segment of the aorta or previous stents. The walls of these aortas may be highly friable and not hold sutures well. A period of antibiotic treatment pre-surgery may be required. These patients are also often immunocompromised.

Post-excision of the aortic segment, an extra anatomical bypass such as an axillo-bifemoral oraxillo femoral-femoral bypass is required (Figure 6). 

Alternatively, the use of patient’s lower limb veins or xenograft to reconstruct the aorta in situ as a neoaortoiliac system (NAIS) procedure may be performed. This is a challenging procedure, but ultimately may avoid the use of prosthetic graft material in a septic patient.⁵

Management of these cases is performed together with the help of an infectious disease physician.

Endovascular surgery
Increasingly, endovascular stenting is performed for mycotic aneurysms to prevent immediate catastrophic rupture.

However, these patients then require lifelong antibiotics and run the risk of persistent stent graft infection where the entire infected segment along with the stent graft has to be removed eventually. Persistent infection or inflammation may also lead to the formation of aortoenteric/aortobronchial fistulas, where the prognosis can be grim.^4,5
 

CASE VIGNETTES

At SGH, the Department of Vascular Surgery, along with the Departments of Vascular and Interventional Radiology and Cardiothoracic Surgery (National Heart Centre Singapore), perform approximately 60-70 surgeries a year for a plethora of aortic aneurysm-related pathology, both complex and standard in nature.

This represents one of the highest volumes in Singapore. About a fifth of these surgeries are performed open while the rest are done with either endovascular or hybrid techniques.

We share some cases performed by the team below. Early referrals of all aortic aneurysms or pathologies to our vascular surgeons are always welcomed.

CASE A
A 75-year-old male smoker with triple vessel disease presented with sudden back pain from a leaking AAA. Aneurysm neck was short rendering standard EVAR unsuitable.

Fortunately, repair was successfully performed with EVAR and single chimney of lower renal artery. The patient recovered well with normal renal function atfollow-up over two years post-procedure and perfusion to kidneys are maintained. Figure 7A shows leaking AAA; 7B shows infrarenalstent deployment; 7C shows main body stent andrenal stents deployed; and 7D represents surveillance duplex showing no endoleak and renal stents well perfused.

CASE B
A 65-year-old male smoker of 70 pack-years, having declined coronary artery bypass graft (CABG) for triple vessel disease a year ago, presented with increasing back pain.

Known infrarenal aortic aneurysm had increased from 3.8cm to 4.9cm in 8 months. Successful EVAR was performed along with coiling of the left internal iliac artery in view of his short left common iliac artery.

Figure 8A is an angiogram of the aneurysm, while 8B shows the completion of stent deployment.

Figure 8C shows the successful exclusion of flow in the aneurysm by stent grafts while maintaining perfusion to the coeliac axis, superior mesenteric artery, bilateral renal arteries and lower limbs.

TAAAs > 6cm, EVAR and OPEN

CASE C
Below are images from CMD cases.

Figure 9A shows preoperative planning based off CT angiography – inner branch technology seen with planning diagram.

Figures 9B and 9C show TAAAs and post-stenting– multiple stent grafts come off the main body stent to maintain reno-visceral perfusion while excluding aneurysm.

Figures 9D and 9E show successful cannulation of renal and visceral arteries followed by stent deployment, which is increasing performed with the use of a steerable sheath (especially in patients with thoracic interventions) to allow complete repair from a retrograde approach, avoiding upper limb access totally in some cases.

CASE D
An ASA 2 patient underwent open surgery and reimplantation of the left renal artery for TAAA (seen on angiogram). The left renal artery was reimplanted as the origin was involved in the aneurysm as seen on CT.

Figure 10 shows a reimplanted left renal artery into prosthetic graft as it comes off aneurysm.

Mycotic aneurysms (infrarenal and thoracic)

CASE E
A 78-year-old male immunocompromised patient in the midst of chemotherapy for resected colon cancer presented with infrarenal mycotic saccularaneurysm from nontuberculous mycobacterium (FDG avid on CT PET).

He was treated with excision of the infected aortic aneurysm and in-situ reconstruction with lower limb femoral vein to create a neo-aorta.

Figure 11A is a PET scan showing FDG avid mycotic aortic aneurysm; 11B and 11C show duplex of lower limb deep veins and harvest; and 11D and 11E show the aneurysm excised and replaced with harvested vein.

CASE F
An 84-year-old male presented with chest pain radiating to the upper back as well as fever, chills and rigor from Salmonella typhi. septicaemia after consumption of raw eggs abroad.

A CT scan shows saccular arch aneurysm in Figure 12.

The schematic drawings in Figure 13 show stenting of the aortic arch with an innominate arterychimney, along with carotid-carotid and carotid-leftsubclavian bypasses and embolisation of the left subclavian artery (proximal with AVP plug) as seen on the final angiogram (Figure 14).

CONCLUSION

Aortic aneurysm disease requires very specialised and costly care. It is best treated at high-volume centres, especially when the presentations are heterogenous, and disease prevalence is relatively low but disease and treatment can be fatal.

GPs play an essential role in the initial diagnosis of and surveillance for aortic aneurysms. To read more about what to look out for in primary care, and how to assess if the risk of rupture warrants active management or consideration of surgery, please refer to the July 2025 issue of Defining Med.

REFERENCES

1. Nick Ng ZP, Tay KH, Chong TT. Total Percutaneous Access for Deployment of a Custom Made Fenestrated Stent Graft in a 90 Year Old with a Large Symptomatic Thoracic Aortic Aneurysm. EJVES Vasc Forum. 2021;51:30-33. doi: 10.1016/j.ejvsvf.2021.05.002. eCollection 2021. PubMed PMID: 34223440; PubMed Central PMCID: PMC8242995.

2. Ng, N.Z.P.; Pang, J.H.Q.; Yap, C.J.Q.; Chao, V.T.T.; Tay, K.H.; Chong, T.T. Custom-Made Device (CMD) for the Repair of Thoraco-Abdominal Aneurysm (TAA): Mid-Long Term Outcomes from a Single Southeast Asian Centre Experience in Singapore. J. Clin. Med. 2024, 13, 6145. https://doi.org/ 10.3390/jcm13206145

3. Chan WK, Yong E, Hong Q, Zhang L, Lingam P, Tan GWL, Chandrasekar S, Lo ZJ. Systematic review and meta-analysis of the prevalence of abdominal aortic aneurysm in Asian populations. J Vasc Surg. 2021 Mar;73(3):1069-1074.e1. doi: 10.1016/j.jvs.2020.08.140. Epub 2020 Sep 26. PMID: 32987145.

4. Dayna SPY, Peng NNZ, Shaun LQ. Off-the-Shelf, Hybrid, Innominate Chimney Thoracic Endovascular Aneurysm Repair for Treatment of Mycotic Thoracic Aortic Aneurysm: A Case Report. Vasc Specialist Int. 2024 Apr 24;40:11. doi: 10.5758/vsi.230126. PubMed PMID: 38679430; PubMed Central PMCID: PMC11056280.

5. Cheok S, Gan LSC, Chung SJ, Ch’ng JK. Aortic endograft infection secondary to Burkholderia pseudomallei: A case report and review of the literature. J Vasc Surg Cases Innov Tech. 2021 May 21;7(3):421-424. doi: 10.1016/j.jvscit.2021.04.023. PMID: 34278075; PMCID: PMC8263529.
 

Dr Nick Ng Zhi Peng is a Vascular and Endovascular Surgical Consultant at the Department of Vascular Surgery, Singapore General Hospital. He graduated from the Yong Loo Lin School of Medicine, National University of Singapore in 2011 and completed his surgical training with the SingHealth General Surgery Residency Programme in 2018. He obtained his Masters of Medicine (Surgery) in 2017 and FRCS (Edinburgh) in March 2019.

Dr Nick performs both open and endovascular surgery, and his areas of interest include aortic, carotid, limb salvage for chronic limb-threatening ischaemia and renovascular diseases. His aim is to manage these challenging diseases as best as possible to give patients the best quality of care and life.

GPs can call the SingHealth Duke-NUS Vascular Centre for appointments at the following hotlines: