Aortic dissection

Aortic dissection is an acute condition in which the innermost layer of the aorta (intima) ruptures, allowing blood to enter the middle layer (media) and form a false lumen. The condition is associated with high mortality rates and requires emergency diagnosis and treatment.

Etiology and Pathogenesis

Dissections commonly develop in patients with underlying conditions such as:

• Hypertension (70–90 % of cases): Elevated blood pressure leads to chronic damage to the vascular wall;
• Genetic disorders: Marfan syndrome (impaired fibrillin production), Ehlers — Danlos syndrome (weak connective tissue), Loeys — Dietz syndrome (TGF-β mutations);
• Atherosclerosis: Weakening of the intima due to inflammation and damage;
• Iatrogenic factors: Aortic surgery, invasive procedures (e.g., catheterization);
• Traumas of the thorax or abdominal cavity;
• Other causes: Vasculitis (e.g., Takayasu arteritis, giant cell arteritis), pregnancy (typically after week 28); infections such as syphilis or mycotic lesions.

As a result of primary damage to the intima, blood penetrates the middle layer, the media, of the vessel. Over time, a false lumen forms, which may dilate or even rupture outwardly, causing massive bleeding. Aortic dissection may have a range of consequences, including:

• Disruption of blood flow in the aortic branches, resulting in ischemic complications (affecting the brain, kidneys, intestines, limbs, etc.);
• Aortic regurgitation;
• Cardiac failure.

Classification

1. Stanford classification:

• Type A: The ascending aorta is affected (with or without involvement of the aortic arch);
• Type B: The dissection is confined to the descending aorta.

However, prior to 2019, this classification did not account for isolated aortic arch lesions or combined damage to the aortic arch and descending aorta. To address this gap, a third type — non-A-non-B dissection — was introduced.

2. DeBakey classification:

• Type I: The dissection extends from the ascending aorta to the aortic arch or beyond;
• Type II: The dissection is confined to the ascending aorta;
• Type III: The dissection affects only the descending aorta (IIIa — up to the diaphragm, IIIb — below the diaphragm).

3. By duration:

• Acute: The first 14 days from the onset;
• Subacute: 15–90 days;
• Chronic: More than 90 days.

Clinical Manifestations

Individual symptoms depend on the location of the lesion, the degree of aortic branch involvement, and the associated complications.

• Acute pain: Sharp, ripping, or stabbing pain that may migrate; its exact location corresponds to the site of dissection (type A — thorax or back; type B — lumbar region or abdomen);
• Hypotension or shock due to massive bleeding;
• Differences in heart rate and blood pressure between arms;
• Neurological disorders: Fatigue, fainting, symptoms of brain ischemia;
• Cardiovascular symptoms: Acute myocardial infarction (the coronary arteries are involved), acute aortic regurgitation;
• Renal failure: Disruption of blood supply to the kidneys;
• Intestinal ischemia: Abdominal pain, bloody diarrhea;
• Cardiac tamponade in pericardial hemorrhage;
• Acute limb ischemia due to arterial occlusion.

Diagnosis

Physical examination: Interlimb differences in blood pressure; pulse deficit; aortic regurgitation murmur.

Laboratory tests: Elevated D-dimer within the first hours after onset; biomarkers indicating myocardial damage in cases of ischemia.

Investigations:

• CT angiography (the gold standard): A rapid and precise detection of a dissection, including its length and complications.
• Transesophageal ultrasound: A highly sensitive modality, particularly for detecting type A dissections.
• MRI: Typically utilized for stable patients who do not require urgent medical intervention.

Treatment

Aortic dissection may be treated differently depending on its type and complications.

1. Medical treatment (more common for type B dissections):

Optimal antihypertensive, antianginal, and lipid-lowering therapy is administered. During the acute phase, continuous monitoring in intensive care units (ICUs) is essential.

2. Surgical treatment (more common for type A dissections):

• Open surgery (a cardiopulmonary bypass and hypothermia are typically employed).

The affected segment of the aorta is resected and replaced with a graft. If the aortic arch is involved, the brachiocephalic trunk is replanted into the graft. However, if the brachiocephalic trunk is also compromised, it should be grafted. In cases involving the aortic valve, aortic valve replacement (AVR) is performed. Sometimes, valve-sparing AVR is also feasible.

• Endovascular procedures (TEVAR):

A stent graft is placed to isolate the false lumen. This procedure is particularly suitable for stable patients with complications or type B dissections.

• If the aorta ruptures or cardiac tamponade develops, emergency surgery becomes the only viable option.