- Commonest aortic emergency
- Incidence is twice that of ruptured abdominal aortic aneurysm
- Rare less than 40 years of age
- Most commonly seen between 50 and 70 years
- Male: female ratio is equal
- Associated with hypertension, Marfan's syndrome, bicuspid aortic valve
Pathology
- Intimal tear results in blood splitting the aortic media
- Produces a false lumen that can progress in an antegrade or retrograde direction
- Rupture can occur back into the lumen or externally in to pericardium or mediastinum
- External rupture often results in fatal pericardial tamponade
- Commonest site of intimal tear is within 2-3 cm of aortic valve
- Also seen in descending aorta distal to left subclavian artery
- Dissection can result in occlusion of aortic branches
- Most commonly involved are renal, spinal, coronary or iliac arteries
Classification
- Two classifications in common use:
- Stanford - Type A and B depending on whether ascending or descending aorta involved
- DeBakey - Divided into Types I, II and III as above
Clinical features
- Usually presents with tearing chest pain radiating to the back
- Often associated with an episode of collapse
- Examination may show
- Reduced or absent peripheral pulsed
- Soft early diastolic murmur
- Chest x-ray usually shows a widened mediastinum
- Diagnosis can be confirmed by echocardiogram or CT scanning
Picture provided by Jon Matthews, Derriford Hospital, Plymouth
- If aortic branches occluded there may clinical evidence of
- Acute renal failure
- Paraplegia
- Acute limb ischaemia
- Cerebrovascular accident
- Inferior myocardial infarction
Management
- All patients require urgent management of associated hypertension
- Type A dissections usually require surgical intervention
- Surgery performed via a median sternotomy and on cardiopulmonary bypass
- Dissection excised and aorta replaced with graft
- Aortic valve is preserved is possible
- An evolving CVA or established renal failure are contraindications to surgery
- Type B dissections may be treated without surgery
- Requires fastidious blood pressure control
- Surgery should be considered if evidence of aortic expansion
- Surgery for Type B dissections is associated with significant risk of paraplegia
- Without operation the prognosis for Type A dissections is poor
- 40% die within 24 hours and 80% die within 2 weeks
- Operative mortality is approximately 25%
Bibliography
Aziz S, Ramsdale D R. Acute dissection of the thoracic aorta. Hosp Med 2004;
65: 136-142.
Chen K, Varon J, Wenker O C, Judge D K, Fromm R E, Sternbach G L. Acute thoracic aortic
dissection. J Emerg Med 1997; 15: 859-867.
Dmowski A T, Corey M J. Aortic dissection. Am J Emerg Med 1999; 17: 372-375.
Pretre R, Von Segesser L K. Aortic dissection. Lancet 1997; 349: 1461-1464.
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