Presenting Features of AAD

Features of pain

These are the typical features of the pain in AAD:

• Abruptness in onset – usually patients can state exactly what they were doing at the onset of pain
• Often maximal at the time of onset
• Commonly sharp in nature although a ‘tearing pain’ is often described
• Occurs in the anterior chest in 70-80% of patients with Type A dissection
• Upper back pain is experienced in about 50% of patients and more commonly in patients with a Type B dissection.

These are the less common presenting features of the pain of AAD:

• Sudden abdominal pain occurs in a minority of patients although this is much more likely to be due to ruptured abdominal aortic aneurysm (AAA), perforated hollow viscus or ischaemic bowel
• Sudden radiation of pain to the neck, throat or jaw
• ‘Migratory pain’ which typically starts where the aortic tear is and progresses to a branch vessel e.g. chest pain to arm pain (subclavian involvement); back pain to leg pain (common or external iliac involvement). This is often unilateral and occurs in approximately 20% of patients
• Short duration of pain. This may occur if the dissection process has stopped or if there has been a re-entry tear into the true lumen with relief of intra-luminal pressure

Presenting without pain

AAD may present without pain (5-15%) and occurs in the following circumstances:

• Syncope: this may be the presentation of acute dissection and the patient may remain confused or in coma
• Stroke: the neurological deficit in these patients occurs almost simultaneously with the primary aortic tear so no pain is experienced at all, or the pain may not be expressed (e.g. if dysphasic)
• Acute cardiac failure: this is usually due to sudden aortic annular dilatation with immediate severe aortic regurgitation or coronary artery dissection with complete vessel occlusion and consequent cardiogenic shock
• Paraplegia: occurs when the dissection occludes the origin(s) of the spinal arteries. This is typically painless
• The elderly: in the very old, pain perception is sufficiently reduced that the dissection process does not cause a noxious stimulus.

Pitfalls

• Dismissing AAD from the differential diagnosis because the pain is in the anterior chest
• Excluding AAD because the patient has pain for only a short period or has no pain at all
• Not appreciating that migratory pain is highly specific for AAD