Classification by form
Depending on the configuration of the vessel wall deformation, the following forms of aneurysma are distinguished:
- Saccular: localized protrusion of the wall.
- Fusiform: uniform dilation of an arterial segment.
- Cylindrical: elongated dilation of a vessel.
Also distinguished are false aneurysms (organized hematomas communicating with the lumen) and arteriovenous aneurysms (pathological shunts between an artery and a vein).
Atherosclerotic aneurysms
The most common type, occurring in individuals aged 65–70, predominantly men. The pathogenesis is associated with the destruction of the musculoelastic framework of the media due to the progression of an atherosclerotic plaque.
- Localization: most frequently the lower abdominal aorta.
- Morphology: size 6–15 cm, shape is usually fusiform.
- Features: the lumen is often filled with layered thrombotic masses, creating a risk of thromboembolism.
Syphilitic involvement
Develops as a complication of tertiary syphilis in the form of syphilitic mesaortitis. Specific infiltrate destroys elastic fibers, replacing them with fibrous tissue. Localization in the thoracic aorta and large dimensions (15–20 cm) are characteristic. It is dangerous due to erosion — atrophy of the bone tissue of the vertebrae and ribs caused by the constant pressure of the pulsating aneurysm.
Dissecting aneurysm
A critical condition in which blood penetrates into the thickness of the wall through intimal tears. The main predisposed factor is arterial hypertension and idiopathic cystic medial necrosis of the aorta. The primary intimal tear is usually localized 1–2 cm above the aortic valve. Dissection can extend to the aortic bifurcation, causing obstruction of branching arteries.
Briefly: answers to topical questions
What are the main causes of arterial aneurysms?
The main causes of arterial aneurysms are congenital and acquired factors.
Acquired causes include:
- Atherosclerosis — causes the destruction of the musculoelastic framework of the tunica media during the progression of an atherosclerotic plaque.
- Syphilis — leads to specific inflammatory involvement of the aortic wall.
- Acute bacterial infections.
- Trauma — mechanical damage to the vessel wall.
For dissecting aneurysms, the cause is unknown, and arterial hypertension is indicated as a contributing factor.
Congenital aneurysms include protrusions of the vessel wall caused by structural defects and hemodynamic load; sources also indicate a congenital absence of the smooth muscle tunica media of arteries.
What does the aortic intima look like macroscopically in syphilitic mesaortitis?
Macroscopically, the aortic intima in syphilitic mesaortitis acquires a specific "shagreen skin" appearance. The inner lining of the vessel becomes uneven, wrinkled, and bumpy. These characteristic changes occur as a result of the formation of multiple scar retractions in the tunica media. Scarring occurs after necrosis and destruction of the elastic framework of the wall by a specific inflammatory infiltrate, which ultimately leads to uneven sclerosis.
What microscopic changes occur in the aortic wall in syphilitic mesaortitis?
Microscopically, diffuse gummatous infiltration without capsule formation is observed in the aortic wall in syphilitic mesaortitis. The following changes occur:
- Inflammation — spreads from the adventitia and small vessels (vasa vasorum), which exhibit signs of vasculitis.
- Destruction — specific infiltrate and necrosis cause the destruction of elastic fibers of the tunica media (tunica media).
- Sclerosis — proliferation of granulation tissue occurs with its subsequent maturation into coarse connective tissue and replacement by fibrous tissue.
What specific complications does a dissecting aortic aneurysm cause?
Specific complications of a dissecting aortic aneurysm are associated with impaired blood flow and rupture of the vessel wall. The main complications include:
- Arterial obstruction — blocking the ostia of branching vessels, which leads to impaired blood circulation in the corresponding organs.
- Aneurysm rupture — external rupture with blood spilling into the surrounding tissues.
- Cardiac hemotamponade — hemorrhage into the pericardial cavity, which leads to sudden death of the patient.
Atherosclerosis — abdominal aorta (lower), Syphilis — thoracic aorta (upper), Dissection — hypertension (inside the wall).
Class and exam questions
What is erosion in syphilitic aneurysm?
This is the process of bone tissue atrophy (of ribs or vertebrae) under the influence of constant pressure from a pulsating aneurysm.
Where is an atherosclerotic aneurysm most commonly localized?
In the lower part of the abdominal aorta, in the interval between the renal artery ostia and the bifurcation.
What is the difference between a false and a true aneurysm?
A false aneurysm is an organized hematoma that maintains communication with the vessel lumen, whereas a true aneurysm is a dilation of the vessel wall itself.
What else to study on this topic
- Mechanisms of development of aortic medial necrosis.
- Differential diagnosis of clinical manifestations in compression of the esophagus and recurrent nerve.
- Hemodynamic consequences of arteriovenous fistulas.
- Microscopic changes in mucoid degeneration of the media.
- Comparative characteristics of complications in various types of aneurysms.
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