Thoracic Aortic Dissection: 5 things to make the diagnosis

CASE

A 70 year old man, is brought to the Emergency Department by ambulance. He was drinking a coffee with friends and developed sudden severe chest pain. His past medical history is coronary artery disease and hypertension. He became hypotensive in the ambulance and was in some distress. He has had a bolus of fluid and has now stabilised with a blood pressure of 115/72. The ambulance report no clinical findings. He has been awake and alert, but as he arrives in the department he finds he cannot speak. He has an expressive aphasia. The working diagnosis at this point must be thoracic aortic dissection.

A bedside ultrasound of the heart, demonstrates a pericardial effusion. He has a ascending thoracic aorta, with carotid extension leading to a stroke.

Thoracic aortic dissection is often called the great mimic because it can look like any of:

• a subarachnoid haemorrhage,
• an inferior myocardial infarction,
• a stroke,
• a vascular event of the lower limbs,
• a testicular pain
• and more.

It has a bimodal distribution, manifesting in the young,(usually genetic) and in the older patient, (an issue of the intima), secondary to hypertension. It is far less common then cardiac ishaemia- about 1:1000. However it can have dire consequences, with an 80% chance of mortality when associated with rupture and up to 2% rate of mortality per hour, untreated.

Why do we miss it?

Because we don’t think of it.

What are the risk factors?

• age>50
• hypertension
• 3^rd trimester pregnancy
• cocaine use
• history of cardiac surgery
• congenital issues such as – bicuspid aortic valve, Turners/Marfans

Here is the key to diagnosing thoracic aortic dissection.

Think of it in these 5 circumstances:

1   Chest pain PLUS
          -Neurological symptoms and/or
          -Vascular symptoms

2   Symptoms above and below the diaphragm

3   In the patient with syncope (occurs in up to 13% of cases)

4   In the patient with inferior myocardical infarction
          -It can occur in up to 5% of those with thoracic aortic dissection.

5   Cephalgia – beware the sudden onsent of headache.

 

Symptoms:

In the landmark study, the IRAD (The International Registry of Acute Aortic Dissection) by Hogan P G et al, JAMA, 2000;283;897-903 the symptoms and clinical findings are shown.

Symptom: Chest Pain

• Chest pain (72.7%)
• Abrupt pain (84.8)
• Severe/worst (90.6)
• Sharp pain (64.4)
• Tearing/ripping(50.6)

We therefore see that 72.7% of patients presented with chest pain, not 100% In those that had chest pain, the suddenness and severity of the pain are the most important characteristics. The classic textbook description of tearing or ripping pain was only present in 50% of cases.

The position of the pain is important, as it may indicate where the dissection is occurring. Anterior chest pain is associated with dissection of the ascending aorta, whereas pain into the upper back is associated with dissection of the arch, moving down to the descending aorta. Lower back pain occurs as the dissection descends.

Position of Pain

• Anterior chest(60.9)
• Posterior chest(35.9)
• Back pain(53.2)
• Radiating(28.3)
• Migrating(16.6)

The symptoms are primarily caused by peripheral artery dissection and malperfusion syndrome.

Dissection can occur along

• The renal arteries can result in renal failure
• The artery of Adamkiewicz can results in leg weakness and paraplegia.
• The superior mesenteric artery can result in bouwel ischaemia.
• The right coronary artery can result in inferior myocardial infarction
• The carotids can present with stroke.

Examination Findings

• Hypertension SBP>150mmHg(49%)
• Shock/tamponade SBP<80mmHg(8.4%)
• Aortic Regurgitation murmur (31.6%)
• Pulse deficit(15.1%)

According to the above, we must look at the vitals, listen for a diastolic murmur and feel for a pulse deficit.

I would also add, do a quick bedside ultrasound of the heart looking for a pericardial effusion.

THE CHEST X-RAY

One of the main areas of litigation in this condition is fibrinolysis being given in an inferior infarction without a chest x-ray. The patients in question had a dissection and the use of lysis was fatal.

How good is the chest x-ray?

CHEST X-RAY FINDINGS

• Widened mediastinum( 61.6%)
• Normal mediastinum/ aortic contour(21.3%)
• Abnormal Aortic contour (49.6%)

The x-ray is very important as up to 80% of patients will have a widened mediastinum or an abnormal aortic contour.

Think of it in other causes

Think of it as a sudden severe headache. Certainly chase the more likely diagnosis of subarachnoid haemorrhage. However if nothing is found, think of carotid malperfusion. A good case study to read is Notre, B et al, Arotic Dissection mimicking subarachnoid haemorrhage, Anesth Analg 2005, July: 101 (1) 233-4.

A quick word about D-Dimer for diagnosing Dissection

There has been a lot of interest and ruling out a dissection with a normal D-Dimer.

Most studies are retrospective and some have prospective cohorts.

We need appropriate validated studies as there are major consequences of missing this condition.

This is not prime time yet. We cannot rule it out with a normal d-dimer.