Cardiology Internal Medicine

Aortic Dissection

Aortic Dissection

Introduction – Aortic Dissection

Acute dissection of the aorta is seen in 3-4/100,000 individuals per year and is more common than ruptured aortic aneurysms. Aortic dissection is more common among men than women.

Aortic dissections are caused by an injury to the aorta’s innermost layer, the intima, which leads to the appearance of a double lumen in the aorta with flow in both the true and the newly emerged false lumen. The dissections are subdivided according to whether the primary injury occurred proximally (type A) or distally (type B) to the left subclavian artery branch. The management of type A and type B dissections differs significantly. Correct diagnosis is therefore of great importance.

Dissections are further divided into:

  • Acute ( <14 days of symptoms)
  • Chronic ( >14 days of symptoms)

Current research suggests that a further subdivision into acute (> 14 days), subacute (14 – 90 days) and chronic (> 90 days) aortic dissection may be relevant with respect to the time of invasive treatment. Type B dissections are also divided into uncomplicated and complicated variants. The latter is defined by dissection-caused perfusion disorder in organs (viscera, extremities or cerebral) or dissections complicated by rupture. Since dissections can affect all branches from the aorta, the symptoms can be highly variable.


Causes – Aortic Dissection

The most common risk factors for aortic dissection are:

  • Hypertension
  • Smoking
  • Peripheral vascular disease

In addition, aortic dissection occurs to a greater extent in certain genetic connective tissue conditions such as Marfan syndrome, Ehler-Danlos syndrome (vascular type) and Loeys-Dietz syndrome.


Symptoms

Acute dissections

  • Sharp chest pain, often with radiation towards the upper back with a tearing sensation.
  • General effect on the patient.
  • Signs of focal ischemia (eg, extremity ischemia, abdominal pain, stroke symptoms, paraplegia).

Chronic dissections

  • Usually no symptoms.
  • The most common complication is the development of aneurysm in the thoracic aorta, but these are usually asymptomatic.
  • Malperfusion with ischemic symptoms in the gastrointestinal tract or extremities can happen, but is uncommon.
  • In type A dissections with aneurysm development, signs of valvulopathies with heart failure characteristics may develop. Aneurysms in the ascending aorta or the arcus (aortic arch) can also cause local nervous system symptoms such as hoarseness due to local compression.

Clinical Findings

Severe chest pain as a single finding or in combination with any of the following signs:

  • Hypertension and pre-shock/shock
  • Absence of ischemic signs on ECG
  • Loss of pulses in extremities
  • Blood pressure difference between the arms
  • Visceral malperfusion such as acute renal insufficiency or intestinal ischemia

In type A dissection except the above:

  • New heart murmur
  • Signs of cardiac tamponade (tachycardia, weak heart sounds, jugular vein stasis)
  • Pulseless electrical activity (previously referred to as electromechanical dissociation, ie electrical activity on the ECG without pulses being detectable)

Differential Diagnoses

  • Acute myocardial infarction
  • Pulmonary embolism
  • Acute pancreatitis
  • Acute abdomen
  • Acute extremity ischemia
  • Pneumonia
  • Pleuritis

Examination and Lab Tests

  • ECG
  • Troponin, CK-MB (myocardial infarction)
  • Hb, WBC, CRP, Creatinine (bleeding, infection, renal insufficiency)
  • AST, ALT, ALP, amylase (cholecystitis, pancreatitis)

Also in A-dissection

  • CT with intravenous contrast (so-called CT angiography, CTA)
  • Echocardiography

Also in B-dissection

  • CT with intravenous contrast (CT angiography, CTA)

Treatment – Aortic Dissection

First steps (acute dissections)

  1. Put in 2 coarse peripheral lines
  2. ECG and telemetry monitoring
  3. Take lab tests as above
  4. Oxygen
  5. Ensure adequate pain relief is given (opioids)
  6. Arterial blood sampling
  7. Acute CTA
  8. Contact thoracic surgeon (in type A) or vascular surgeon (in type B)

In the case of acute blood pressure >200 mmHg: start treatment with beta-blocker intravenously. Labetalol (Trandate) 50 mg (10 ml) is given slowly by injection or infusion. The dose can be repeated after 5 minutes.

Fastest possible transfer to intensive care unit (ICU) for optimal blood pressure reduction to counteract dissection progress.

The first-hand choice is one of the following:

  • Propranolol (Inderal)
  • Metoprolol (Seloken)
  • Esmolol (Brevibloc)
  • Labetalol (Trandate)

Systolic target blood pressure is 120 mmHg if the patient tolerates this and the organ perfusion is adequate.

Pain treatment with opiates (5-10 mg morphine iv if needed).

In case of signs of rupture or organ malperfusion, the vascular surgeon should be consulted immediately!


Follow-up and Further Treatment – Aortic Dissection

Patients with established acute type A dissection should be assessed by a thoracic surgeon as soon as possible for surgery. Mortality in acute type A dissection increases by 1% per hour for the first 24 hours. The operative treatment may consist of a replacement of the ascending aorta, with or without simultaneous aortic valve replacement, or reconstruction of the ascending aorta including the aortic arch. Surgery is done through a median sternotomy with the assistance of a heart-lung machine.

In type B dissection, 90% of cases can be treated conservatively in the acute phase. The mortality rate in an acute type B dissection is around 10%. Note new onset of, or increasing chest pain or the appearance of signs of peripheral organ ischemia (including impairment of renal function). These may be signs of dissection progression and additional diagnostics (new CTA) or treatment may be indicated. The threshold for consultation with a vascular surgeon and an internal medicine specialist should be low. A complicated Type B dissection is usually treated with insertion of a stent graft into the aorta to close communication between the true and the false lumen and is sometimes supplemented with local measures to restore flow in organs with malperfusion (e.g. stenting of renal arteries or bypass surgery of the pelvic arteries). Strong evidence of stent graft treatment in uncomplicated type B dissections is not present. However, some new studies suggest that there may be a benefit with early stent graft treatment even in uncomplicated type B dissections to reduce long-term mortality. In cases where endovascular treatment of uncomplicated B dissections may be relevant, current knowledge indicates that this should be performed in the subacute phase (14 – 90 days after the onset of symptoms).

In most cases, conservatively treated patients should be followed-up via specialist clinics with imaging to check for possible aneurysm development. In conservatively treated patients, up to 30% of dissection-related aneurysms develop after 5 years.


Further Reading