By: Dr. Zaid Altawil

Case Discussion

A 40-year-old male with no past medical history presented to the ED 12 hours after a minor motor vehicle collision. The patient’s car was rear-ended by another vehicle. He complains of minor back and knee pain, but is otherwise well appearing.

On physical exam, patient was found to have a grade 3/6 harsh systolic murmur. Bedside ultrasound was performed, and the patient was found to have an aorta root diameter of 6.0 cm.

As the patient was asymptomatic, he was advised to follow up with his PCP. He was then referred to TTE, and found to have a 5.8 cm thoracic aortic aneurysm with a possible dissecting flap. Patient was advised at TTE to present to the ED urgently, however he declined despite repeated explanations of the gravity of the situation, and was lost to subsequent follow up.

FIgure1.pngFigure 1. Diameter of the aortic root measuring 6.23 cm. Image obtained from Zaid Altawil MD.

Thoracic Aortic Aneurysm

  • Thoracic aortic aneurysms are more likely (up to 95%) to be asymptomatic than abdominal aortic aneurysms. Sixty percent of TAA occur in the root or ascending aorta”1
  • A diastolic murmur secondary to aortic regurgitation may be audible with advanced dis- ease, but only if the aneurysm involves the ascending aorta.1
  • As a result, most aneurysms are detected incidentally through imaging for an unrelated condition (CT for a lung nodule, or Echo for a murmur)
  • Severe chest pain or sudden death are often the first signs of a TAA1
  • Dissection is the life threatening complication. Once that occurs, long term outcomes diminish rapidly
  • Probability of rupture or dissection greatly increases once aortic diameter size increases to greater than 6.0 cm2,3,4
  • If symptomatic, surgical management is indicated regardless of size
  • Elective repair for asymptomatic TAA is reserved for aneurysms greater than 5.5cm in the ascending aorta and greater than 6.5cm in the descending aorta5
  • 5-year survival of TAAs left untreated is 54%
  • The good news is that Emergency physicians are able to visualize TAA on a focused cardiac ultrasound. Measurements obtained by Eps have been shown to be consistent with those measured on TTE for maximal diameter. 6,7,8

 

POCUS techniques

  • The parasternal long view and the suprasternal view can be used to assess portions of the thoracic aorta.
  • For the parasternal long axis, place the probe in the 3rd or 4th intercostal space, at the left sternal border. The marker should point to the patient’s right shoulder, or the 10’oclock position.

(a) Figure3a
(b) Figure 3b

(c)Figure 3c

Figure 3.(a) Ultrasound probe position for parasternal long axis view. (b) Ultrasound window from the parasternal long axis. (c) Leading edge technique for measuring aortic diameter. Images obtained from Zaid Altawil, MD.

  • The aorta can be measured with a leading edge technique. Diameters>4.0cm in the thoracic aorta are abnormal.9 
  • To obtain the aortic arch from a suprasternal view, place the probe on the suprasternal notch with the marker pointed towards 12oclock. Angle the probe inferior and to the left of the patient until the aortic arch is visualized.
    • To obtain a better view, make small changes in position in a clockwise fashion and the outline of the arch is sharpest.10

 (a) Figure 4a

(b) Figure 4b

Figure 4.(a) Ultrasound probe position for suprasternal view. (b) Ultrasound window from the suprasternal notch. Images obtained from Zaid Altawil, MD.

 

 

Take Home Points

  • Thoracic aortic aneurysms are a silent process until they are deadly
  • Parasternal long view, leading edge technique, >4cm
  • Symptomatic->admission for urgent repair
  • Asymptomatic->elective repair if >5.5cm for ascending or >6.5 for descending aorta

 

References:

  1. Kuzmik, Gregory A., Adam X. Sang, and John A. Elefteriades. “Natural history of thoracic aortic aneurysms.” Journal of vascular surgery 56.2 (2012): 565-571. http://dx.doi.org/10.1016/j.jvs.2012.04.053
  2. Davies, Ryan R., et al. “Yearly rupture or dissection rates for thoracic aortic aneurysms: simple prediction based on size.” The Annals of thoracic surgery73.1 (2002): 17-28. http://dx.doi.org/10.1016/S0003-4975(01)03236-2
  1. Elefteriades, John A. “Indications for aortic replacement.” The Journal of thoracic and cardiovascular surgery 140.6 (2010): S5-S9. http://dx.doi.org/10.1016/j.jtcvs.2010.10.001
  1. Coady, Michael A., et al. “What is the appropriate size criterion for resection of thoracic aortic aneurysms?.” The Journal of thoracic and cardiovascular surgery 113.3 (1997): 476-491. http://dx.doi.org/10.1016/S0022-5223(97)70360-X
  1. Elefteriades, John A. “Natural history of thoracic aortic aneurysms: indications for surgery, and surgical versus nonsurgical risks.” The Annals of thoracic surgery 74.5 (2002): S1877-S1880. http://dx.doi.org/10.1016/S0003-4975(02)04147-4
  1. Andrew Taylor, R., et al. “Point‐of‐care Focused Cardiac Ultrasound for the Assessment of Thoracic Aortic Dimensions, Dilation, and Aneurysmal Disease.” Academic Emergency Medicine 19.2 (2012): 244-247. http://dx.doi.org/10.1111/j.1553-2712.2011.01279.x
  1. Labovitz, Arthur J., et al. “Focused cardiac ultrasound in the emergent setting: a consensus statement of the American Society of Echocardiography and American College of Emergency Physicians.” Journal of the American Society of Echocardiography 23.12 (2010): 1225-1230. http://dx.doi.org/10.1016/j.echo.2010.10.005
  1. Daignault, Michael C., Turandot Saul, and Resa E. Lewiss. “Focused cardiac ultrasound diagnosis of thoracic aortic aneurysm: two cases.” The Journal of emergency medicine 46.3 (2014): 373-377. http://dx.doi.org/10.1016/j.jemermed.2013.04.031
  1. Kennedy Hall, M., et al. “The “5Es” of emergency physician–performed focused cardiac ultrasound: a protocol for rapid identification of effusion, ejection, equality, exit, and entrance.” Academic Emergency Medicine 22.5 (2015): 583-593. http://dx.doi.org/10.1111/acem.12652
  1. “Gulf Coast Ultrasound Hot tips- Finding the aortic arch with ultrasound”https://youtu.be/U2Ger1eqdic

 

Resident Author: Dr. Zaid Altawil
Faculty Review: Dr. Meera Muruganandan