Die Like a King

A 73 year old man is brought into your Emergency department with severe abdominal pain.
His ambo sheet reads:

Ambulance Sheet
He is brought into the resuscitation area and commenced on oxygen. IV access is obtained, analgesia and fluids are started. CXR is shown below:

CXR
His Venous Blood Gas (VBG) is shown below:


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)

aortic dissection abdomen from hqmeded.com on Vimeo.

CT Angiogram was performed:

CTA Aortic Disection

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.

AORTIC DISSECTION

KEY POINTS

  • 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.

BACKGROUND

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.

PATHOPHYSIOLOGY

‘Aortic dissection is a longitudinal cleavage of the aortic media created by a dissecting column of blood.’

— Rosen’s.

There are 3 possibilities as to how the blood gets into the media:

  1. Atherosclerotic ulcer leading to intimal tear.
  2. Disruption of vasa vasorum causing intramural haematoma.
  3. 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.

CLASSIFICATION

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.

Clinical Features

Probably best summed up with some actual evidence from the International registry of Acute Aortic Dissection

IRAD clinical features aortic dissection

MANAGEMENT

  • 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
  • FUTURE DIRECTIONS:

    • 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.
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    Comments

    1. Rufus says

      A remarkably unforgiving diagnosis… the subject of a current coronial inquest in the UK.
      “The inexperienced doctor discovered a heart murmer but did not realise that his aorta blood vessel had torn…
      He told the inquest that the junior doctors who were involved in the care of Emile may never have come across a torn aorta before.”

      http://www.telegraph.co.uk/news/uknews/8022633/Cambridge-historian-dies-after-junior-doctor-misses-heart-condition.html

    2. says

      I had a Type B Dissection about 5 months ago. It was almost missed as a possibility despite a family history being pointed out. I was a bit out of it but my wife tells me that my BP was out of control for about 14 hours before a nurse decided to call the Cardiologist. I gave him a hard time because of the drugs they had me on and he didn’t deserve it -- I have no idea what his name is but he was at Joondalup Health Campus. Once diagnosed I was rushed to Sir Charles Gardiner and put into a medically induced comma for a few days -- no idea why! All fixed now and I monitor my BP 3 times a day. It’s usually pretty good, sometimes it gets up to around 150/80 HR 80 but is normally about 120/60 HR 63. Sometimes as low as 91/48 HR 55. The point is that I’m alive and rather happy about that. Aortic Dissection can be missed easily if the Doctor isn’t on the ball. I’m glad that they eventually were on the ball for me.

    3. Sally says

      Craig, glad you’re now better from your aortic dissection. Unfortunately as you say it is easily missed -- even if the doctor IS on the ball. Because most doctors don’t want to subject every patient with severe chest pain to a high-dose radiation CT scan, which is the only way currently to diagnose this condition. So I wouldn’t be too harsh on your doctors… and the ones who diagnosed it finally probably were just lucky!

      Peter, is IV labetalol not available just a Perth thing? I’m pretty sure I’ve seen it recently in my department in Melbourne. Or maybe things have changed since your post -- I realise I’m reading it a long way after you wrote it! Great picture of the kidneys, btw.

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