Aortic DissectionEdit

Aortic dissection is a life-threatening condition characterized by a tear in the inner lining of the aorta, the large blood vessel that carries blood from the heart to the rest of the body. The tear allows blood to enter the wall of the aorta and split its layers, creating a false channel that can propagate rapidly. Without prompt recognition and treatment, dissection can lead to massive bleeding, organ malperfusion, or rupture. It is a medical emergency that demands rapid assessment, imaging, and decisive management.

Dissections arise from a combination of structural weakness in the aortic wall and sudden hemodynamic stress. The condition encompasses a spectrum from localized tears to extensive involvement of the aorta. The management and prognosis depend on where the dissection originates, how far it extends, and which organs are affected. Advances in imaging, surgical technique, and endovascular therapy have markedly improved survival, though the condition remains associated with substantial mortality if not promptly addressed.

Classification

Aortic dissections are categorized by location and by the pattern of involvement.

  • Stanford classification

    • Type A: the dissection involves the ascending aorta, with or without origin in the arch or descending aorta. This form is typically a surgical emergency.
    • Type B: the dissection originates after the left subclavian artery and involves the descending aorta, sometimes extending into the abdominal aorta or beyond.
  • DeBakey classification

    • Type I: a tear originates in the ascending aorta and propagates downstream to the aorta beyond the left subclavian artery.
    • Type II: confined to the ascending aorta.
    • Type III: originates in the descending aorta and may extend distally (IIIa) or both distally and proximally (IIIb).

These schemes reflect differences in prognosis and treatment strategies. For example, Type A dissections (Stanford) are generally managed with urgent surgical repair, while many uncomplicated Type B dissections are treated with medical therapy and close monitoring, reserving intervention for complicated cases.

Pathophysiology

  • Initiating event: a tear in the intima allows high-pressure blood to enter the media, creating a cavity (the false lumen) that can propagate along the aorta.
  • Propagation and consequences: as the false lumen enlarges, it can compromise branch vessels, causing malperfusion to the heart, brain, kidneys, and other organs. It can also cause aortic valve leakage or cardiac tamponade if the dissection disrupts surrounding structures.
  • Underlying predispositions: conditions that weaken the aortic wall—such as cystic medial degeneration, connective tissue disorders, and congenital anomalies—increase risk. Genetic factors and familial forms of thoracic aortic disease contribute to susceptibility in relatively younger patients. Common associations include Marfan syndrome, Ehlers-Danlos syndrome, and certain mutations involving the aortic media and extracellular matrix.
  • Hemodynamics: abrupt elevations in blood pressure or heart rate amplify shear stress on the aortic wall, promoting initiation or propagation of the tear.

Risk factors

  • Hypertension (the most important modifiable risk factor)
  • Age and male sex, with higher baseline risk in older adults
  • Bicuspid aortic valve and other congenital aortic abnormalities
  • Family history of aortic dissection or thoracic aortic disease
  • Genetic or syndromic disorders such as Marfan syndrome, Loeys-Dietz syndrome, and other familial thoracic aortic diseases
  • Aneurysmal dilation of the thoracic aorta
  • Smoking and other vascular risk factors that promote arterial stiffness

Clinical presentation

  • Sudden onset, severe chest and/or back pain described as tearing or ripping by many patients
  • Pain may migrate as the dissection propagates along the aorta
  • Discrepancy in limb blood pressures or pulse deficits, syncope, or neurologic symptoms if the brain or spinal cord is affected
  • Signs of organ malperfusion: reduced urine output, abdominal pain, limb ischemia, stroke, or mesenteric ischemia
  • In Type A dissections, there is a higher likelihood of involvement of the aortic valve or pericardium, potentially causing acute aortic regurgitation or tamponade

Diagnosis

  • Initial assessment: a rapid clinical evaluation combined with blood pressure and heart rate control measures as appropriate; ECG is often obtained to exclude myocardial infarction in the acute setting.
  • Imaging
    • CT angiography of the chest is a widely used, fast, and accurate diagnostic modality in the acute setting.
    • Transesophageal echocardiography (TEE) can be used when immediate bedside imaging is needed or when CT is not available or contraindicated.
    • Magnetic resonance imaging (MRI) provides detailed information and is useful in stable patients or for follow-up, but is less practical in emergencies.
    • Chest X-ray may show mediastinal widening but is not diagnostic on its own.
  • Laboratory studies: there is no single lab test to confirm dissection, but biomarkers such as D-dimer may be elevated and help stratify pretest probability in combination with clinical assessment.

Management

  • Initial stabilization and risk reduction
    • Place the patient on continuous monitoring in an emergency setting.
    • Control heart rate and blood pressure aggressively to reduce shear stress on the aortic wall. Typical targets include a heart rate around 60 beats per minute and a systolic blood pressure near 100–120 mmHg, achieved with intravenous beta-blockers (e.g., esmolol, labetalol) and vasodilators as needed.
    • Analgesia to reduce sympathetic drive and pain-related hypertension.
  • Surgical and endovascular treatment
    • Type A dissections: urgent surgical repair is standard to prevent fatal complications such as rupture, cardiac tamponade, or coronary involvement.
    • Type B dissections: initial management is often medical (blood pressure and heart rate control) unless there are complications such as organ malperfusion, persistent pain, rupture, or rapid expansion. In complicated cases, endovascular therapy with a thoracic endovascular aortic repair (TEVAR) or, less commonly, open surgical repair may be indicated.
  • Long-term care and surveillance
    • Lifelong blood pressure control, risk factor modification, and regular imaging to monitor the remaining aorta and the false lumen.
    • Genetic counseling and family screening when there is a familial or syndromic pattern.
    • Ongoing management of associated cardiovascular risks, including lipid control and management of other vascular diseases where appropriate.

Prognosis

  • Mortality without treatment is high, particularly for Type A dissections. Early surgical intervention for Type A dissections has significantly improved survival.
  • Even with treatment, there is a substantial risk of recurrent dissection or progression of disease in other segments of the aorta, necessitating lifelong surveillance.
  • The prognosis depends on factors such as dissection type, extent, presence of complications (e.g., malperfusion, tamponade), and time to definitive management.

Prevention and long-term care

  • Blood pressure management is central to prevention of progression or recurrence.
  • Lifestyle modifications, including smoking cessation and avoidance of illicit stimulant use, can reduce vascular stress.
  • For those with known aortic dilation or heritable aortic disease, regular surveillance with imaging and appropriate medical or surgical planning is essential.
  • Genetic testing and counseling are considered in patients with a positive family history or syndromic features to guide management for patients and relatives.

See also