A 73 year old man is brought into your Emergency department with severe abdominal pain.
His ambo sheet reads:
The differential seemed to leaning towards ischaemic bowel, however an USS was performed to exclude AAA or free fluid in his belly which showed a suspicion of an intimal flap similar to the video shown on hqmeded.com (click link below)
CT Angiogram was performed:
As you can see, there’s an intimal flap in the aorta and the left kidney is profoundly hypoperfused. The patient was taken to theatre as the dissection extended from his aortic root to beyond the bifurcation. Unfortunately repair was impossible to to the friability of the patients tissues and he died on the table.
- Often enters differential in chest pain patients — ? to the detriment of the vast majority?
- STEMI occurs in 3% of dissections. 0.1% of STEMI’s are caused by Aortic Dissection.
- Let it be diagnosed in the cath lab unless there’s a very high suspicion.
- 1% mortality per hour for first 48 hours.
- Stanford classification most widely used.
- Abrupt onset of severe or worst ever pain in 90% of proven dissections.
- Mediastinum not widened on CXR in 40%.
- CT angiogram is the investigation of choice.
- Echocardiography in the ED should be considered in the unstable patient.
The incidence of this much feared disease is about 3 per 100,000. For a city the size of Perth (1.6 million) that equates to about 1 a week. 20% die without ever making it to hospital.
King George II of Great Britain and, unfortunately, Ireland died of an aortic dissection on 25th October 1760 while on the toilet. Other famous people to have suffered this disease include the former Liverpool manager Gerard Houllier, renowned cardiac surgeon Michael DeBakey, the writer of ‘Rent‘ – Jonathan Larson – who tragically died the night before its Broadway premiere and John Ritter (star of sitcom — ‘8 simple rules’). Both of the latter 2 examples had presentations that were initially misinterpreted as being something else — adding to the heightened sense of anxiety most Emergency Physicians feel about this disease.
‘Aortic dissection is a longitudinal cleavage of the aortic media created by a dissecting column of blood.’
There are 3 possibilities as to how the blood gets into the media:
- Atherosclerotic ulcer leading to intimal tear.
- Disruption of vasa vasorum causing intramural haematoma.
- De novo intimal tear.
Once the blood starts to cleave the vessel media it can propagate forwards or backwards, as well as extending back into the true lumen or rupturing externally. Most that rupture externally won’t make it to hospital, therefore aortic dissection in the ED is manifest predominantly with obstructive symptoms caused by the false lumen occluding the true lumen, particularly at branching points leading to neurology, pulse differentials, ischaemic gut etc.. depending on which vessel is occluded.
80% of dissections occur in non-aneurysmal vessels, so the term ‘dissecting aortic aneurysm’ is probably best avoided.
Use the Stanford system. It’s the simplest, the most widely used and often directly correlates with the best treatment for the patient.
- Type A — Involves ascending aorta. Can extend distally ad infinitum. Surgery usually indicated
- Type B — Involves aorta beyond left subclavian artery only. Often managed medically with BP control.
Probably best summed up with some actual evidence from the International registry of Acute Aortic Dissection
- MEDICAL MANAGEMENT
- EMERGENT BLOOD PRESSURE AND HEART RATE CONTROL
- The aim is to reduce shearing forces on the Aorta and thereby prevent disease extension.
- Shearing forces depend on the blood pressure and the rate of rise of the arterial pulse (δP / δt) – often referred to as the ‘double product’.
- This is one of the exceptionally few times you should aim to aggressively lower the patients blood pressure in the Emergency Department, but always in conjunction with rate control.
- Target BP is the lowest possible that still maintains end-organ perfusion (mentation, urinary output).
- If you want numbers, aim for SBP < 120 and HR = 60.
- Labetalol is often quoted as the agent of choice as it has both α and β effects.
- Labetalol is not available IV in Australia – other possibilities include a combination of Esmolol + GTN.
INDICATIONS FOR SURGERY
Persistent pain Type A Branch Occlusion Leak Continued extension despite optimal medical management
- Endovascular repair options — especially for type B dissections.
- in some centres the future is now.
- D-Dimer — Not safe to use in the ED.
- 95% negative predictive value quoted by some.
- From a study where the patient population has a story ‘so suggestive’ of aortic dissection they were getting angiograms.
- NOT reflective of the ED population and has not been prospectively validated in any meaningful way.