By Shirley Wu, MD and Meghan K. Herbst, MD, FACEP
Chief Complaint: Unresponsive
Clip 1 - Watch on YouTube
Clip 2 - Watch on YouTube
1. What anatomy and pathology are shown in the clips above?
2. What are some additional sonographic findings that may be seen in patients with this condition?
3. How can ultrasound findings help emergency physicians make clinical decisions pertaining to this disease?
An 84-year-old female with history of hypertension and dementia presented from home to the emergency department unresponsive. Her granddaughter found her in the bathroom after one episode of vomiting complaining she didn’t feel well for the past 2-3 hours. EMS found the patient with a pulse of 30 bpm and systolic blood pressure of 60 mmHg. On arrival, her heart rate improved to 70 bpm, with a systolic blood pressure of 80 mmHg after a small fluid bolus. She followed simple commands and was answering questions with 1-2 words. Her mucous membranes were dry, heart sounds were regular, and lungs were clear bilaterally. With palpation of the abdomen the patient moaned and tried to push the examiner’s hand away, and examination of the lower extremities revealed trace edema bilaterally. A point of care ultrasound (PoC US) was immediately performed, which showed evidence of an aortic dissection. The cardiothoracic surgery team was promptly called and evaluated the patient while she was in the CT scanner. Chest, abdomen and pelvic CT Angiogram confirmed a type A dissection extending from the aortic root to the bilateral common femoral arteries.
Role of Aorta Ultrasound in the Emergency Department
PoC US of the aorta is most frequently used to detect or rule out an abdominal aortic aneurysm (AAA). As one of the core ultrasound applications listed by the American College of Emergency Physicians, PoC US of the aorta performed by emergency physicians is close to 100% sensitive and specific for AAA.1,2 However, there are also several specific signs of aortic dissection that can be appreciated on PoC US and should not be missed given the high morbidity and mortality associated with this disease.
In our case, identification of this patient’s aortic dissection led to prompt consultation with the hospital’s cardiothoracic and vascular surgery teams and expedited CT imaging.
Answers to questions
1) Clip 1 shows a transverse view of a normal caliber abdominal aorta with a hyperechoic intimal dissection flap that moves independently with the patient’s heart beat. The primary landmark for the aorta is the hyperechoic spine with acoustic shadowing just posteriorly. The left renal artery can be seen emerging from the aorta on the right of the screen. To the anatomic right of the aorta (left of the screen) is the IVC. Anterior to the aorta and IVC are non-dilated loops of bowel. Clip 2 shows a parasternal long axis view of the patient’s heart. The left ventricle squeeze appears overall good, and the aortic outflow tract does not appear to be dilated. No pericardial effusion or dissection flap is visualized.
2) While hypertension is present in approximately 75% of individuals with an aortic dissection, hypotension in the setting of an aortic dissection may indicate retrograde dissection to the pericardium potentially leading to pericardial effusion and tamponade.3 A parasternal long axis cardiac view may reveal an intimal flap within the aortic outflow tract, aortic valve insufficiency, pericardial effusion, or tamponade physiology, and this view should be included when suspecting a type A dissection given the high morbidity and mortality associated with this disease. Additionally, type A dissections have been associated with aortic dilatation.3,4 When suspecting a type A dissection, evaluating the heart for dilatation of the aortic outflow tract to greater than 4 cm on a parasternal long axis view may support a proximal dissection, especially if a dilated root is accompanied by a pericardial effusion and/or a dissection flap.
3) PoC US findings of a dynamic intimal flap and/or a dilated aortic outflow tract with a pericardial effusion in the setting of a suspected aortic dissection can rule in an aortic dissection. These findings not only aid in the diagnosis but can also expedite care, as with this case. It is important to note, however, that while these findings are specific, they are not sensitive for dissection.5-7 In other words, patients with true aortic dissections may not have detectable aortic dissection flaps, pericardial effusions, or dilated ascending aortic roots.
With this individual, there was neither pericardial effusion nor aortic outflow tract dilatation (and the hypotension was likely secondary to excessive vagal tone) but the visualization of a dissection flap alone prompted diagnosis and appropriate consultation within minutes of her arrival to the emergency department.
1. American College of Emergency Physicians. ACEP emergency ultrasound guidelines—2008. Ann Emerg Med. 2009;53:550-70.
2. Rubano E, Mehta N, Caputo W, et al. Systematic Review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. Acad Emerg Med. 2013;20:128-138.
3. Meredith EL, Masani ND. Echocardiography in the emergency assessment of acute aortic syndromes. Eur J Echocardiogr. 2009;10(1):i31-9.
4. Cozijnsen L, Braam RL, Waalewijn RA, et al. What is new in dilatation of the ascending aorta? Review of current literature and practical advice for the cardiologist. Circulation. 2011;123(8):924-8.
5. Khandheira BK, Tajik AJ, Taylor CL, et al. Aortic dissection: review of value and limitations of 2-D echocardiography in a six-year experience. J Am Soc Echocardiogr. 1989;2:17-24.
6. Roudaut RP, Billes MA, Gosse P, et al. Accuracy of M-mode 2-D echocardiography in the diagnosis of aortic dissection: an experience with 128 cases. Clin Cardiol. 1988;11:553-62.
7. Victor MF, Mintz GS, Kolter MN, et al. 2-D echocardiographic diagnosis of aortic dissection. Am J Cardiol. 1981;48:1155-9.