Aortic Dissection – Causes, Diagnosis, Treatment, Ongoing care

Basics

Description

Intimal tear in the aorta resulting in hematoma formation. Accumulating blood in false lumen of arterial wall leads to propagation of dissection (1):

  • Stanford classification (most widely used):
    • Type A: Involves ascending aorta and aortic arch regardless of site of intimal tear
    • Type B: Involves descending aorta
  • DeBakey classification (based on origin site):
    • Type 1: Originates in ascending aorta, propagates at least as far as aortic arch
    • Type 2: Involves only ascending aorta
    • Type 3: Originates in descending aorta, may propagate proximately or distally
  • Svensson:
    • Class 1: Classic dissection with true and false lumen
    • Class 2: Intramural hematoma or hemorrhage
    • Class 3: Subtle dissection without hematoma
    • Class 4: Atherosclerotic plaque rupture and ulceration
    • Class 5: Iatrogenic
  • Synonym: Dissecting aneurysm

Epidemiology

  • Predominant age varies with cause
  • Type A dissection average age 60
  • Type B dissection patients generally older
  • Patients with Marfan syndrome have mean age 36
  • Approximately 2/3 of patients are male
  • Studies indicate peak time of day between 8 and 9 AM
  • Some studies also report slightly higher incidence in winter months

Incidence

About 3 cases per 100,000 people per year

Prevalence

United States:

  • Diagnosed in 1 in 10,000 patients admitted to hospital
  • Found in 1:350 patients at autopsy
  • Numbers may be slightly higher due to unexplained deaths at home or in hospital without autopsy

Risk Factors

  • Most common associated factors:
    • Hypertension (about 70% of patients)
    • Old age
    • Atherosclerosis
    • Previous cardiovascular surgery, particularly repair of aneurysm or dissection
  • Collagen abnormalities:
    • Marfan syndrome
    • Ehlers-Danlos syndrome
  • Recreational drug use:
    • Smoking
    • Cocaine
  • Inflammatory vasculitis:
    • Takayasu arteritis
    • Giant cell arteritis
  • Chest trauma
  • Turner syndrome
  • Bicuspid aortic valve
  • Uncommonly seen in infants following infection
  • Also seen in infants during balloon dilation of aortic coarctation
  • Reports of dissection in patients with untreated coarctation of the aorta

Genetics

Up to 20% of patients with thoracic aneurysm or dissection were found to have first-degree relatives with aneurysm or dissection. Studies have found the TGFBR1 and TGFBR2 genes are related to aneurysm and dissection in isolated cases and in patients with Marfan’s syndrome. Other research has found ACTA2 gene mutations to be involved in isolated and familial dissections and aneurysms.

General Prevention

  • Rigorous medical management of precipitating risk factors such as hypertension
  • Surveillance of aortic root and replacement when appropriate in patients with collagen disorders (e.g., Marfan, Ehlers-Danlos)

Pathophysiology

In most cases, dissection develops in the absence of aneurysm, but the false lumen that can be created during dissection can later expand to form an aneurysm. In patients with inherited connective tissue disease, abnormal and/or deficient proteins lead to weakening of vessel walls. Bicuspid aortic valves may also lead to an acquired dysfunction of vascular walls and smooth muscle cells. Histological investigation of postmortem and biopsy specimens reveal cystic medial necrosis, especially in those patients with known preexisting aneurysm

Etiology

Although the exact sequence of events is controversial, aortic dissection is likely the result of multiple pathological processes. Stress on the aortic wall from hypertension, intimal damage with subsequent tear, rupture or ulceration of atherosclerotic plaques, and involvement of vasa vasorum and intramural hematoma may be contributory.

Commonly Associated Conditions

See Risk Factors

Dissection of aorta, dissection of thoracic aorta , Aortic Dissection, Marfan syndrome, Aortic dissection, Electrocardiography, X-ray computed tomography, Aorta, ehlers danlos syndrome, chest trauma, descending aorta, cardiovascular surgery,

Diagnosis

History

  • High level of clinical suspicion is key to correct and prompt diagnosis
  • Typical patient is a hypertensive man aged 60–80
  • Positive family history raises index of suspicion
  • Subjective complaints (2):
    • 85% of patients report abrupt onset of pain
    • Pain was more often described as sharp, less often as tearing or ripping
    • 90% of patients stated that the pain was “severe” or “worst ever”
    • Patients with type A dissections more often report chest pain
    • Patients with type B dissections more often report back and abdominal pain
    • Symptoms overlap between type A and type B dissections

Physical Exam

  • Hypotension and shock are more common with type A dissection.
  • Hypertension is more common with type B dissection.
  • Syncope or cerebrovascular accident symptoms
  • Any pulse deficit
  • Auscultation of aortic regurgitation
  • Signs of congestive heart failure
  • Limb ischemia
  • Acute myocardial infarction/angina
  • Spinal cord syndromes/deficits (3)
  • Features of tamponade

Diagnostic Tests & Interpretation

  • Important to use easily available testing to assist in prompt diagnosis
  • Blood testing, EKG, chest x-ray, CT scans, and echocardiograms can all assist in diagnosis.
  • A normal EKG and chest x-ray cannot be used to rule out the diagnosis if clinical suspicion is high.
  • EKG may show (2):
    • Normal findings in up to 1/3 of patients
    • Nonspecific ST-T changes (about 40%)
    • Left ventricular hypertrophy (about 25%)
    • Ischemic changes (about 15%)
    • Acute MI (about 3%)
    • Old MI with Q waves (about 7%)

Lab

Possible novel markers for aortic dissection include a combination of D-dimer, elastin fragments, and smooth-muscle myosin heavy-chain protein. Presently, none of these tests are used routinely as diagnostic tools, and several authors debate the use of D-dimer alone, with research being inconclusive as to its sensitivity and specificity.

Imaging

  • Chest X-ray may show:
    • Normal findings in about 15% of patients
    • Widening of the mediastinum (about 60%)
    • Abnormal aortic outline (about 50%)
    • Abnormal cardiac silhouette (about 25%)
    • Calcified or displaced aorta (about 15%)
    • Pleural effusion (about 19%)
  • Studies suggest that CT scan with IV contrast, transesophageal echocardiography, and MRI imaging all provide around 95% sensitivity and specificity for diagnosis:
    • MRI may be better for patients where clinical suspicion and pretest probability for aortic dissection are already high.
    • CT scan may be better to rule out dissection in those patients where clinical suspicion and pretest probability are both low.
    • Transesophageal echocardiography can be done at the bedside of an unstable patient in 15–20 minutes, and can offer additional information about heart function (4).
    • In reality, the ready availability and speed with which CT scans can be performed in many hospitals may outweigh the above considerations.
  • Both MRI and CT scans can be used by clinicians to assess the extent, size, and location of the dissection, as well as involvement of the branches off the aorta, although some sources suggest MRI as the preferred modality for precise anatomic definition.

Diagnostic Procedures/Surgery

Contrast angiography can be used specifically as a diagnostic tool, especially when visceral perfusion defects are suspected. Angiography may also be used as entry point into endovascular treatment of dissection.

Pathological Findings

  • ∼60% of intimal tears occur in the proximal ascending aorta. Remainder are between origin of left subclavian artery and ligamentum arteriosum, descending aorta (20%), aortic arch (10%), and abdominal aorta.
  • Although medial necrosis is found in aging aortas, it is more extensive in patients who develop aortic dissection.
  • Cystic medial necrosis is seen in patients with defects in elastin and connective tissue organization (e.g., Marfan, Ehlers-Danlos).
  • Death usually is due to rupture and tamponade.

Differential Diagnosis

Myocardial infarction, pericarditis, pericardial tamponade not from aortic dissection, angina or atherosclerotic embolism, pulmonary embolism, pneumonia, pleurisy, acute pancreatitis or cholecystitis, penetrating duodenal ulcer, Mallory-Weiss tear or esophageal rupture, mediastinal pathology, musculoskeletal pain

Treatment

Due to the acute nature of aortic dissection, there are no randomized controlled trials related to treatment and management.

Medication

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For uncomplicated dissection of descending aorta (Stanford B), medical therapy is indicated.

First Line

The cornerstone of medical management is blood pressure control using beta blockers, including propranolol, metoprolol, labetalol, and esmolol

Second Line

  • For patients with severe asthma, calcium-channel blockers may be used
  • If hypertension is refractory to initial therapies, nitroprusside can be considered, but the patient should be evaluated for possible surgical intervention at that time

Additional Treatment

General Measures

  • Patients should be monitored in intensive care units
  • Arterial BP monitoring is preferred, particularly in less stable patients
  • Pain control should involve the use of morphine
  • If surgical repair of aneurysm is indicated, do not delay repair to evaluate for CAD and valvular dysfunction
  • Prompt correction of hypotension, along with identification of the cause, are essential
  • Hemodynamically unstable patients will likely require intubation and mechanical ventilation

Surgery/Other Procedures

  • Stanford A type dissection:
    • Surgery is the treatment of choice for dissections of the ascending aorta (80% treated surgically) to prevent aortic rupture and cardiac tamponade, while relieving any aortic regurgitation that may be present (2).
    • Patients who are inappropriate surgical candidates (comorbid medical conditions, patient choice, very advanced age) have an in-hospital mortality of 50% after 30 days.
    • Surgical correction aims to resect ascending aorta and arch, and replace them with a graft.
    • Other procedures, including repair/replacement of aortic valves and coronary arteries, may be indicated depending on the extent of the dissection.
    • Many different surgical options exist and depend on the extent of dissection.
  • Stanford B type dissection:
    • Surgical resection of aorta for type B generally associated with worse outcomes than medical management.
    • Surgical indications for Stanford B include (2):
      • Continued aortic expansion
      • Impending aortic rupture
      • Occlusion of major aortic branch to renal, mesenteric, or iliac arteries
      • Persistent and recurrent chest pain
      • Periaortic or mediastinal hematoma
  • Poor prognostic factors for surgical success:
    • Age >70 years
    • Abrupt-onset chest pain
    • Hypotension, shock, or tamponade at presentation
    • Renal failure
    • Pulse deficit
    • Abnormal ECG, ST segment elevation
    • History of aortic valve replacement
    • Renal and/or visceral ischemia
  • Stenting of complicated type B dissections seems to be a reasonable and safe alternative to surgical management, although further follow-up is needed

In-Patient Considerations

Initial Stabilization

  • Admit to ICU
  • Intubate hemodynamically unstable patients
  • Control BP:
    • Systolic 100–120 mm Hg
    • IV beta blocker to achieve HR 60
    • Determine etiology of hypotension:
      • Blood loss
      • Tamponade
      • Heart failure
  • Pain control

Admission Criteria

Low threshold for admission in presence of thoracic or abdominal pain, radiographic corroboration, or pulse deficit.

Ongoing Care

Follow-Up Recommendations

Patient Monitoring

  • Maintain systolic BP at 120 mm Hg (16 kPa) or below, as tolerated
  • Routine chest films and/or chest CT may be helpful for patient treated medically long term.
  • During follow-up, pay careful attention to signs and symptoms of aortic insufficiency, chest or back pain, and development of saccular aneurysms as displayed on chest films.

Diet

NPO until surgical evaluation is complete and patient classified as medical therapy only.

Patient Education

Depending on etiology, emphasis must be placed on risk factors and prevention of recurrence:

  • Smoking cessation
  • Blood pressure control with beta blockers
  • Diabetic control

Prognosis

  • Hospital survival estimate, treated medically and surgically: 70% (2)
  • Data for Type A dissections treated surgically show a 90% survival rate at 3 years (5).
  • Survival at 10 years similar for medically and surgically treated patients.
  • Redissection risk:
    • 5 years: 13%
    • 10 years: 23%

Complications

Redissection, localized saccular aneurysm, cardiac tamponade, aortic valvular insufficiency, progressive aortic enlargement. Stent placement risks include paraplegia, stroke, embolization, side-branch occlusion, infection

References

1. Golledge J, Eagle KA. Acute aortic dissection. Lancet. 2008;372:55–66.

2. Hagan PG, Nienaber CA, Isselbacher EM et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA. 2000;283:897–903.

3. Gaul C, Dietrich W, Friedrich I et al. Neurological symptoms in type A aortic dissections. Stroke. 2007;38:292–7.

4. Nair HC, et al. Transesophageal echocardiography evaluation of thoracic aorta. Ann Card Anaesth. 2010;13:186.

5. Tsai TT, Evangelista A, Nienaber CA, Trimarchi S, Sechtem U, Fattori R, Myrmel T, Pape L, Cooper JV, Smith DE, Fang J, Isselbacher E, Eagle KA, International Registry of Acute Aortic Dissection (IRAD) et al. Long-term survival in patients presenting with type A acute aortic dissection: insights from the International Registry of Acute Aortic Dissection (IRAD). Circulation. 2006;114:I350–6.

Additional Reading

See Also (Topic, Algorithm, Electronic Media Element)

Hypertension; Ehlers-Danlos Syndrome; Marfan Syndrome

Codes

ICD9

  • 441.00 Dissection of aorta, unspecified site
  • 441.01 Dissection of aorta, thoracic

Snomed

  • 308546005 Dissection of aorta (disorder)
  • 233994002 dissection of thoracic aorta (disorder)

Clinical Pearls

  • 90% of patients with aortic dissection report acute pain, more often sharp than tearing, and located in the chest, abdomen, or back
  • Maintain a high level of suspicion and act quickly if the diagnosis of aortic dissection is suspected.
  • Survival at 10 years similar for medically and surgically treated patients.

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