What are saccular aortic aneurysms and their different types?

From the Guidelines

Saccular aortic aneurysms are localized outpouchings or balloon-like protrusions that affect only a portion of the aortic wall circumference, and they can be classified into different types based on their location and etiology. These aneurysms typically appear as asymmetric bulges on one side of the aorta. There are several types of saccular aortic aneurysms based on their location, including:

• Thoracic saccular aneurysms, which occur in the chest portion of the aorta and can affect the ascending aorta, aortic arch, or descending thoracic aorta 1
• Abdominal saccular aneurysms, which develop in the abdominal section of the aorta, often below the renal arteries (infrarenal)
• Thoracoabdominal saccular aneurysms, which span both chest and abdominal regions Saccular aneurysms can also be classified by etiology as:
• Atherosclerotic (most common, caused by plaque buildup)
• Inflammatory (associated with conditions like giant cell arteritis)
• Infectious (mycotic aneurysms from bacterial infection)
• Traumatic (resulting from injury) According to the 2022 ACC/AHA guideline for the diagnosis and management of aortic disease, saccular aneurysms are more likely to be symptomatic at smaller sizes than fusiform aneurysms 1. The guideline also recommends elective repair of patients presenting with saccular AAA, although size guidance is lacking due to limited natural history data 1. Treatment typically involves surgical repair when they reach 5-5.5 cm in diameter or show rapid growth (>0.5 cm in 6 months), with options including open surgical repair or endovascular stent grafting depending on location and patient factors 1. The goal of treatment is to reduce the risk of adverse aortic events, such as aortic dissection, rupture, and aortic-related death, by replacing the aneurysmal aortic segment with a prosthetic graft or excluding blood flow from the aneurysmal sac using endovascular stent grafts 1.

From the Research

Definition and Types of Saccular Aortic Aneurysms

• Saccular aortic aneurysms are a type of aneurysm that has a more ominous natural history than the typical fusiform aneurysm, although this is not documented in the literature 2.
• They are characterized by their unique shape, which predisposes them to rupture.
• Saccular aneurysms can be found in various locations, including:
  • Distal arch
  • Descending thoracic aorta
  • Visceral aorta
  • Infrarenal aorta

Classification and Location

• Saccular aortic aneurysms can be classified based on their location:
  • Group A: distal arch
  • Group B: descending thoracic aorta
  • Group C: visceral aorta
  • Group D: infrarenal aorta 2
• They can also be classified as:
  • Saccular abdominal aortic aneurysms (SAAA) 3
  • Multiple saccular aneurysms of the abdominal aorta 3

Characteristics and Risk Factors

• Saccular aortic aneurysms are rare, but when present, they are most commonly found in the thoracic and suprarenal aorta 2.
• They are more likely to be symptomatic and require surgical intervention 2, 4.
• Risk factors for rupture include:
  • Size and type (saccular) of the aneurysm
  • Intraluminal thrombus
  • Multiplicity of the aneurysm
  • Adjacent positions of the aneurysms 3
• Saccular AAAs are considered to be at higher risk of rupture than fusiform AAAs, and should be treated at smaller diameters 5.

Treatment and Management

• Expeditious repair is indicated for symptomatic saccular aneurysms, and intervention is usually advocated even when they are asymptomatic 2.
• Treatment options include:
  • Patch graft repair
  • Tube graft replacement
  • Endovascular techniques 2, 4, 5
• Beta-blockers do not significantly influence aortic aneurysm growth, and further studies are required to find a suitable medical therapy to reduce growth rates 6.