Discussion
Acute aortic dissection is an emergent, life-threatening condition with a high morbidity and mortality rate and a wide range of clinical manifestations and atypical presentations—all of which benefit from rapid identification. The combination of these factors makes diagnosis difficult, but all the more essential, especially considering the time-sensitivity of initiating treatment with intravenous antihypertensive agents and operative intervention.1
Bedside ultrasound provides a rapid and reliable method of making the diagnosis at the point of care, thus positively affecting patient care and outcome. Although existing research is limited, available data indicate that the EP can accurately diagnose acute aortic dissection and its complications using this modality.
Rapid diagnosis of aortic catastrophes at the bedside is not a novel concept. Shuman et al2 studied bedside transabdominal ultrasound on initial presentation of patients with severe abdominal or back pain, suspicious for abdominal aortic aneurysm (AAA). In this study of 60 patients, 31 of 32 AAAs were identified; these diagnoses were made prior to a surgeon’s evaluation.
More recently, Kuhn et al3 completed a similar study of EP use of beside ultrasound in the ED. Although their study lacked strength secondary to small sample size, it did indicate the ability to accurately determine the presence of an AAA with minimal training and experience.
Bedside Ultrasound Versus Other Imaging Modalities
There are multiple imaging modalities to consider when evaluating a patient with a possible aortic dissection, the decision of which should also take into account the ability to determine alternative diagnoses.
Bedside Ultrasound. This modality provides the EP with a quick, easy tool to evaluate multiple, potential life-threatening emergencies immediately at the bedside in a patient with suspected aortic dissection.4 Numerous studies have documented a sensitivity of 78% to 87% and a specificity of 99% to 100% for the diagnosis of aortic dissection by transthoracic and transabdominal ultrasound when an undulating intimal flap is visualized.5
Computed Tomography Angiography. In comparison to beside ultrasound, computed tomography angiography (CTA) has a sensitivity of 96% to 100% and a specificity of 96% to 100%.6,7 However, since CTA requires the use of iodinated contrast material, it is relatively contraindicated in the setting of acute kidney injury, a condition not uncommon in patients with acute aortic dissection.
Magnetic Resonance Imaging. Currently the gold standard for the identification of aortic dissection, magnetic resonance imaging has both a sensitivity and specificity of 98%.7,8 The major disadvantages of this test are the lack of availability and the length of the study itself.
Chest X-ray. A chest X-ray is commonly used as a screening test for aortic dissection, despite 12% to 20% of patients with aortic dissection having a “normal” X-ray.6
Transesophageal echocardiography. Another good modality for diagnosing aortic dissection is transesophageal echocardiography (TEE), which has a sensitivity of up to 98% and a specificity of up to 97%.8 This test, however, requires an experienced operator at the bedside, typically a cardiologist, and is an invasive study that requires the use of sedation and occasionally general anesthesia. A TEE is limited by its inability to visualize the descending aorta below the stomach.6-8
Conclusion
There are several benefits to using bedside ultrasound at the point of care to diagnose aortic dissection. This modality provides not only a rapid, noninvasive, and painless study requiring no radiocontrast media, but also has a high specificity for detection of aortic dissection. Moreover, it also allows the provider to evaluate for other potential life-threatening emergencies such as concomitant abdominal aortic aneurysm, intraperitoneal hemorrhage, pericardial effusion, and cardiac tamponade.9,10
Dr Venezia is a resident in the department of emergency medicine, Eastern Virginia Medical School, Norfolk. Dr Sawyer is a clinical instructor in the department of emergency medicine, Eastern Virginia Medical School, Norfolk. Dr Byars is an associate professor in the department of emergency medicine, Eastern Virginia Medical School, Norfolk.
For a video clip showing a transverse view of the abdominal aorta with the dissection flap clearly visible mid-lumen of the proximal aorta, visit https://vimeo.com/111462170.
For a video clip showing a longitudinal view of the abdominal aorta with the dissection flap clearly visible in the mid-lumen of the aorta, visit https://vimeo.com/111462168.
For a video clip of a cardiac view demonstrating large pericardial effusion in the patient with aortic dissection, visit https://vimeo.com/111462169.
For a video clip demonstrating ultrasound of the parasternal long axis view with a phased array probe, visit https://vimeo.com/111462167.