Aortic Aneurysm
1. Dr. Samatbek Turdaliev
2. Khan Shakira
Khan Frazia
(1. Teacher, International Medical Faculty, Osh state university, Kyrgyzstan.
2. Students, International Medical Faculty, Osh State University, Kyrgyzstan)
Abstract
Aortic aneurysm is a localized abnormal dilatation of the aorta that tends to progressively enlarge and may eventually rupture. It is generally defined as an increase in aortic diameter of at least fifty percent compared to the expected normal diameter for a given age and sex. Aneurysms are classified based on their location, size, shape, and underlying cause. The condition most commonly involves the abdominal aorta, but it may also affect the thoracic or thoracoabdominal regions.
Introduction
Aortic aneurysm refers to pathologic dilatation of aortic segment that has the tendency to expand and rupture. The extent of dilatation is debatable but one criterion is an increase in the diameter of at least 50% greater than that expected for the same aortic segment in unaffected individuals of same age and sex. Aortic aneurysms are described in terms of their size, location, morphology, and cause.
Epidemiology
The incidence of abdominal aortic aneurysms (AAA) has increased over the past two decades due to population aging, higher smoking rates, improved screening, and better diagnostic methods. AAA is more common in men, with a prevalence of 1.3–8.9% in men compared to 1.0–2.2% in women. Thoracic aortic aneurysms (TAA) occur at an incidence of about 5–10 per 100,000 person-years. Most TAAs involve the ascending aorta (about 60%), followed by the descending aorta (35%) and aortic arch (<10%). Thoracoabdominal aneurysms extend from the descending thoracic aorta into the abdominal aorta.
Key risk factors for AAA include older age, male sex, and smoking. A family history, especially in first-degree male relatives, increases risk about fourfold. Other associated conditions include atherosclerosis, hypertension, hypercholesterolemia, coronary and cerebrovascular disease, and other vascular aneurysms, though some associations are inconsistent. Genetic factors, including variants on chromosome 9p21 (such as rs7025486[A] in the DAB21P gene), also contribute to risk. Black and Asian populations and individuals with diabetes have a lower risk of AAA. TAAs may additionally result from genetic, inflammatory, and infectious causes.
Pathophysiology
· Aortic aneurysmal disease is a degenerative condition affecting all layers of the vessel wall. Its pathophysiology involves four key processes: inflammatory infiltration by lymphocytes and macrophages, breakdown of elastin and collagen by proteolytic enzymes such as matrix metalloproteinases, loss of smooth muscle cells leading to medial thinning, and neovascularization.
· Thoracic aortic aneurysms (TAAs) are strongly influenced by genetic factors, which may present as syndromic conditions or isolated aortic disease. These disorders involve abnormalities in the aortic media, vascular smooth muscle cells, or contractile proteins, often leading to dysregulated signaling pathways. Important associated conditions include Marfan syndrome, Loeys–Dietz syndrome, vascular Ehlers–Danlos syndrome, familial thoracic aortic aneurysm and dissection, bicuspid aortic valve disease, Turner syndrome, and aortopathies linked to congenital heart disease.
Natural History of Aortic Aneurysms
The growth rate of abdominal aortic aneurysms (AAA) measuring 30–55 mm is typically 0.2–0.3 cm per year, with faster expansion seen in larger aneurysms. Thoracic aortic aneurysms (TAA) generally grow more slowly, about 0.1–0.2 cm per year, though this varies individually. Descending aortic aneurysms enlarge faster (≈0.19 cm/year) than ascending ones (≈0.07 cm/year). In the ascending aorta, bicuspid aortic valve (BAV) aneurysms grow faster (≈0.19 cm/year) than those with a tricuspid valve (≈0.13 cm/year).
Rupture risk increases significantly with aneurysm size. For AAAs, rupture risk over 12 months is approximately 0% for 30–39 mm, 1% for 40–49 mm, 1–11% for 50–59 mm, 10–22% for 60–69 mm, and 30–33% for >70 mm. Additional risk factors include female sex, smoking, hypertension, rapid aneurysm expansion, and increased wall stress. Other reported risks include thrombus growth, increased wall stiffness, low FEV1, and post-transplant status.
For TAAs, annual risk of rupture or dissection is about 2% for aneurysms <5 cm, 3% for 5.0–5.9 cm, and 7% for ≥6 cm. Body size and sex also influence risk. The aortic size index (ASI) helps stratify risk: <2.75 cm/m² carries ~4% event rate, 2.75–4.25 cm/m² about 8%, and >4.25 cm/m² up to 20–25% risk.
Screening
Ultrasonography is the main screening tool for abdominal aortic aneurysm (AAA) due to its high sensitivity (about 95%) and specificity (100%). Computed tomography (CT) and magnetic resonance imaging (MRI) are not used for routine screening because of higher cost and risks such as radiation exposure (CT) and contrast-related complications; they are mainly reserved for preoperative planning.
The development of a new AAA after a normal ultrasound at age 65 is rare and usually not clinically significant. Screening is therefore targeted toward high-risk groups. The U.S. Preventive Services Task Force recommends a one-time ultrasound in men aged 65–75 years who have a history of smoking. The Society for Vascular Surgery advises one-time screening for all men over 65, or starting at 55 years in both men and women with a family history of AAA.
Clinical Presentation
1. Unruptured aneurysms
· Usually asymptomatic and found incidentally on examination or imaging
· May be detected during screening programs
· Possible complications:
o Distal embolization (rare)
o Acute thrombosis (rare)
· Non-specific symptoms:
o Chronic vague abdominal or back pain (due to pressure or organ distension)
o Sudden severe back/lumbar pain may suggest impending rupture
· Abdominal aortic aneurysm (AAA) may cause:
o Ureterohydronephrosis (especially inflammatory or iliac involvement)
· Thoracic aortic aneurysm (TAA):
o Often asymptomatic and incidental finding (X-ray, CT, MRI, echo)
o May present with:
· Aortic regurgitation
· Heart failure (aortic root dilation)
· Embolic events (mural thrombus/atheroma)
· Mass effect symptoms
2. Ruptured abdominal aortic aneurysm (AAA)
· Classic triad:
o Sudden abdominal/flank pain (may radiate to groin/scrotum)
o Hypotension/shock
o Pulsatile abdominal mass
· Severity of shock varies with rupture site and size
· Types of rupture:
o Anterolateral rupture → intraperitoneal → often fatal
o Posterolateral rupture → retroperitoneal → may be temporarily contained
· Retroperitoneal rupture:
o Can stabilize briefly (“biphasic course”)
o Rapid deterioration within hours
· Rare complications:
o Contained chronic hematoma
o Rupture into duodenum
o Aortocaval fistula:
· Leg edema
· High-output heart failure
· Abdominal bruit
3. Ruptured thoracic aortic aneurysm (TAA)
· Sudden severe chest or back pain
· Possible outcomes depending on site:
o Pleural rupture → hemothorax, hypotension
o Mediastinal rupture → mediastinal bleeding
o Esophageal rupture → hematemesis (aortoesophageal fistula)
o Tracheobronchial rupture → hemoptysis
· Infected TAAs more likely to form fistulas
· Thoracic aortic dissection is more common than rupture
Treatment / Management
Risk factor modification
· Smoking cessation slows aneurysm growth
· Control of hypertension and hypercholesterolemia may reduce risk (evidence limited)
· Regular moderate exercise is safe in small aneurysms and may slow growth
Medical therapy
· No drug has proven to reliably stop aneurysm progression
· Studied drugs:
o Beta-blockers
o ACE inhibitors / ARBs
o Statins
o Antiplatelets
o Antibiotics and anti-inflammatory agents
· Doxycycline (MMP inhibitor) showed no significant benefit in trials
· Overall: medical therapy is supportive, not curative
Indications for aneurysm repair (AAA)
Decision based on balance between rupture risk and surgical risk
Small aneurysms (3.0–3.9 cm):
Very low rupture risk
No surgery required
Regular ultrasound follow-up
Moderate aneurysms (4.0–5.5 cm):
Consider repair if:
Growth >1 cm/year
Symptoms develop
Size thresholds for repair:
≥5.5 cm in males
≥5.2 cm in females (higher rupture risk at smaller size)
Thoracic aortic aneurysm (TAA) repair thresholds
Ascending aorta: surgery at ≥5.5 cm
Bicuspid aortic valve, Marfan syndrome, familial TAA: ≥5.0 cm
Loeys–Dietz syndrome:
o ~4.2–4.6 cm (or even >4.0 cm in some recommendations)
Turner syndrome:
o ≥3.5 cm or ≥2.5 cm/m²
Additional factors influencing surgery
Family history of dissection/rupture
Rate of aneurysm growth
Patient sex and body size
Presence of valve disease or need for cardiac surgery
Overall comorbid conditions
Patient and physician preference
Interventions for Aneurysm Repair (EVAR)
Endovascular Aneurysm Repair (EVAR)
Minimally invasive treatment for abdominal aortic aneurysm (AAA)
Involves insertion of a stent graft via femoral artery access
Excludes aneurysm sac from circulation
Requires suitable aortic and iliac anatomy for fixation and sealing
Advantages of EVAR
Shorter operative time
Can be done without general anesthesia
Less surgical trauma and postoperative pain
Shorter hospital stay and reduced ICU need
Lower blood loss
Reduced early postoperative mortality
Disadvantages / complications
Risk of incomplete sealing of aneurysm sac
Endoleaks:
o Type I: leakage at graft ends
o Type II: backflow from branch vessels
o Type III: graft component separation or defect
Morphological requirements (key points)
Adequate proximal aortic neck:
o Diameter 17–32 mm
o Length >10 mm
o Limited thrombus (<50%) and calcification (<50%)
o Mild angulation (<60°–90° depending on segment)
Suitable iliac arteries:
o Diameter >7 mm
o Limited calcification
o Adequate length (>15 mm)
Aortic bifurcation >20 mm for bifurcated graft
Graft selection
Based on individual anatomy
Graft is usually oversized by 15–20% compared to aortic neck diameter
Oversizing ensures proper sealing and fixation
Management of iliac aneurysms
Present in up to 40% of EVAR patients
Internal iliac (hypogastric) artery often embolized with coils
Endograft extended into external iliac artery
Done to reduce risk of Type II endoleak
Prefer proximal coil placement to preserve collateral flow
Possible complications of hypogastric occlusion:
Buttock claudication (~80% of symptomatic cases)
Erectile dysfunction (~10%)
Colonic ischemia (6–9%)
Outcomes
30-day mortality ~1%
Hospital stay ~3 days
Recovery within days to weeks
Complications of Endovascular Aneurysm Repair (TEVAR/EVAR)
1. Vascular complications
Mainly due to large delivery sheath size
Risk increased in:
o Small iliac arteries
o Tortuous vessels
o Calcified arteries
o Can lead to access site injury or bleeding
Use of arterial conduits may:
o Bypass difficult anatomy
o Improve access
o Reduce complication rates
2. Neurological complications
Caused by embolization or impaired blood flow
Possible outcomes:
o Stroke (cerebral embolization)
o Spinal cord ischemia
Higher risk when:
Hypogastric artery is covered
Left subclavian artery is involved
Extensive thoracic aortic coverage is performed
Presence of:
Renal insufficiency
Intraoperative hypotension (SBP < 80 mmHg)
Prevention:
Careful device manipulation
Proper anatomical planning
Optimal graft positioning
3. Endoleaks
Common complication of TEVAR/EVAR
Defined as persistent blood flow into aneurysm sac after repair
Reported incidence varies widely:
o ~26% in some trials
o ~3–4% in others
Risk decreasing with newer generation devices
Conclusion
Aortic aneurysmal disease is a progressive and potentially life-threatening condition resulting from complex degenerative and inflammatory changes in the aortic wall, influenced by both genetic and acquired risk factors. Abdominal aortic aneurysms are more common and strongly associated with aging, male sex, and smoking, while thoracic aneurysms are more often linked to genetic syndromes and connective tissue disorders.
Most aneurysms remain clinically silent until detected incidentally or through screening; however, their natural history is characterized by gradual expansion with an increasing risk of rupture as size increases. Once rupture occurs, mortality is extremely high, particularly in abdominal aneurysms, making early detection and timely intervention critical.
Management is based on careful surveillance, risk factor modification, and selective surgical repair. While medical therapies have not shown clear effectiveness in halting aneurysm progression, lifestyle changes such as smoking cessation and blood pressure control remain important. The decision for intervention depends primarily on aneurysm size, growth rate, symptoms, and patient-specific risk factors.
Endovascular techniques such as EVAR and TEVAR have revolutionized treatment by offering less invasive alternatives to open surgery, significantly reducing perioperative morbidity and mortality. However, they require lifelong surveillance due to complications such as endoleaks, vascular injury, and neurologic events.
Overall, successful management of aortic aneurysms relies on early detection, individualized risk assessment, and a multidisciplinary approach combining surveillance, medical optimization, and timely surgical or endovascular intervention.
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