Aortic Dissection – almost missed diagnosis!

Ultrasound images and text Genevieve Carbonatto

You get a handover from the overnight registrar who has had an extremely busy shift. After you get handed over several patients he describes  a 56 year old lady who woke up in the morning to go the toilet. While she was sitting , she suddely felt some paraesthesia in both her thighs associated with severe back pain and abdominal pain. She noticed that her left leg was somewhat weak.  She presented a month ago with similar back pain. Last time she presented with back pain, lumbosacral Xrays were taken and were normal and she was discharged. She has been investigated for a month for abdominal pain which she described as similar to what she was experiencing at that moment.  She is due to see her gastroenterologist next week for a gastrosopy and a colonoscopy. The neurology registrar has been contacted and is seeing the patient  and an MRI is being organised to look for  spinal cord compression.

The nurse comes to see you to tell you that this patient’s BP is 210/106 and that it is not coming down with pain relief. She also says that the patient  has just passed a small amount of red jelly like stool with her urine. She had no sensation of passing the stool.

You go and see the patient: She is still in pain despite significant amounts of morphine, but her pain is 3/10. She is not keen to retell her story, she just wants to know what is wrong with her. You ask her about the back pain. She says it is at the level of the epigastrium and that she also has abdominal pain in this area which is similar to what she has had in the past. How bad was her back pain in the middle of the night you ask. The husband answers, so bad that she screamed – get an ambulance! You examine her legs. They are warm and pink. You can’t feel a dorsalis pedis pulse or a posterior tibial pulse. You ask her to move her left leg – she can just flex her knee without gravity. She is not moving her foot. She has an  absent knee and ankle reflex on that side. She has sensation changes at the proximal area of her left leg. Her right leg is normal – normal reflexes, power and sensation. You feel for her popliteal pulses and her femoral pulses and you are finding it difficult to get a pulse. She has no radial – radial delay. Because her femoral pulses are not palpable it is not possible for you to assess for radial – femoral delay.

You are confused about the diagnosis in view of the recent past history, but you are concerned about an aortic dissection. You discuss this with the radiology consultant and the MRI is cancelled. A CT aortogram is ordered instead

This is the CT aortogram.

She has a Standford type A aortic dissection with left renal infarcts from dissection involving the left renal artery. There is an occlusion of the distal abdominal aorta to the bifurcation  extending to the proximal left common iliac artery. There was recanalisation of the left common iliac artery distally and flow was demonstated in the lower limb arteries explaining the warm legs.

This is her focused point of care ultrasound

PLAX more dedicated aortic root view.

PLAX view with colour showing aortic regurgitation. Note there is no pericardial effusion.

Size of aortic root 4.99 cm

Proximal abdominal aorta in transverse shows dissection flap.

The proximal aorta in the longitudinal plane also shows the dissection flap.

 

Discussion

Aortic dissection is often missed in the Emergency Department (1,2,3) on initial presentation, figures range from 15 – 43%.  The location of pain is the most predictive factor  for diagnosing aortic dissection , back and chest pain being the most predictive for accurate diagnosis, abdominal pain the least predictive for accurate diagnosis. Aortic dissection is 3 X more common than AAA rupture. (4) It is however uncommon, 1 in 10,000 ED patients will have aortic dissection. Only 1/4 present with classic features (2) of sudden onset of severe pain, BP differential and widened mediastinum on chest Xray. 1 in 25 patients have none of the classic features of dissection. Untreated, the mortality of an aortic dissection is 40% on presentation and 1% rate of death per hour

Clinical presentation

  • Pain 90% of cases – severe and rapid onset. May be migratory.
  • Sites of pain : chest, thoracic or lumbar back pain, abdominal pain
  • Focal neurological signs  17 % – limb paraesthesia or weakness
  • Syncope 9%
  • SOB, haemoptysis (extremely rare presentation)
  • Pulse deficits
  • Hypertension –  (aortic dissection  is one of the cardinal hypertensive emergencies)
  • Hypotension associated with cardiac tamponade or free rupture

Diagnosis

  • Chest Xray – mediastinal widening , not present in 10 -20% of cases
  • ECG – signs of longstanding hypertension , myocardial ischaemia or infarction if the dissection is extending into the coronary arteries
  • CT aortogram confirms extent of dissection and may help with the differential diagnosis if dissection is excluded
  • MRI if patient stable or if patient has a known severe iv contrast allergy
  • Ultrasound – Limited by patient, operator and machine. Remember that 80% of aortic dissections are in non aneurysmal vessels.

Treatment

The aim is to limit the progression of the dissection. This is achieved by reducing the kinetic energy of the blood flow by reducing blood velocity and decreasing the pressure differentials throughout the aorta. Therefore the aims are to

  • Reduce BP to 100- 120mmHg
  • Reduce HR to 60 -80/min
  • Control bleeding
  • Fluid resuscitate

Practically, call cardiothoracics and

  • insert iv line
  • Xmatch 6 units of blood
  • Activate massive transfusion protocols if present in your institution
  • Correct coagulopathy
  • Give iv opiates
  • Control BP and HR by B blockade. Titrate  Metoprolol 2.5 mg – 5mg iv or Propranolol 1 – 3mg iv to  BP of 120mmHg

Teaching point: The diagnosis of aortic dissection can be difficult. It is one of the  great “mimickers” along with AAA. If you think about it ultrasound can be helpful however be aware that the aorta will most likely not be aneurysmal and it may be difficult to see a flap.

References

  1. J Cardiol .2011 Nov;58(3):287-93.Sep 3.Factors leading to failure to diagnose acute aortic dissection in the emergency room.Kurabayashi M1, Miwa N, Ueshima D, Sugiyama K, Yoshimura K, Shimura T, Aoyagi H, Azegami K, Okishige K, Isobe M.
  2. Curr Cardiol Rev. 2012 May; 8(2): 152–157. Screening, Evaluation, and Early Management of Acute Aortic Dissection in the ED Reuben J Strayer,* Peter L Shearer, and Luke K Hermann
  3. Am J Cardiol. 2007 ;99(6):852–856. Frequency of and inappropriate treatment of misdiagnosis of acute aortic dissection. Hansen MS1, Nogareda GJ, Hutchison SJ.
  4. LIFL Acute aortic dissection
  5. Am J Emerg Med.2000 Jan;18(1):46-50. Diagnosis of acute thoracic aortic dissection in the emergency department. Sullivan PR1, Wolfson AB, Leckey RD, Burke JL.
  6. JAMA 2002 May 1;287(17):2262-72.Does this patient have an acute thoracic aortic dissection? Klompas M1.
  7. Ann of Emerg Med: 2015 Jan;65(1):32-42.e12. Clinical policy: critical issues in the evaluation and management of adult patients with suspected acute nontraumatic thoracic aortic dissection. American College of Emergency Physicians Clinical Policies Subcommittee (Writing Committee) on Thoracic Aortic Dissection, Diercks DB, Promes SB, Schuur JD, Shah K, Valente JH, Cantrill SV.
  8. Emerg Med Clin North Am: Acute aortic dissection in the emergency department: diagnostic challenges and evidence-based management.Upadhye S1, Schiff K.
  9. Lung Ind. 2008 Jan-Mar; 25(1): 20–21. HAEMOPTYSIS – A RARE PRESENTATION OF AORTIC ANE URYSM
    Girija Nair, MD, Professor,1 Savita Jindal, MD, Registrar,2 Abehishek Chandra, MBBS, Resident,3 Shivani Swami, Resident,3 and Pankaj Garg, MBBS, Resident3

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