This single parasternal long axis clip should make you very concerned for an aortic dissection. The first and most glaring thing you might notice is the violation of the “rule of thirds”. In the PLAX view, typically the RVOT, aortic root, and the LA are all about equal in diameter. In this clip the aortic root appears dilated. The second clue is a mobile, linear, and hyperechoic structure that appears in the descending thoracic aorta (in the far field). It appears consistent with a dissection flap but must be confirmed on additional views to ensure it’s not an artifact. Although the presence of a flap is consistent with an aortic dissection, importantly with POCUS its absence does not rule out the possibility of aortic dissection. In this case it would also be useful to assess for aortic valve regurgitation and presence of pericardial effusion, both complications of Type A aortic dissections.
The suprasternal view is a useful view when looking for Type A aortic dissections as it shows the ascending aorta and it’s arch. Typically it’s first three branches (brachiocephalic artery, left common carotid artery and left subclavian artery) are seen in the near field of the screen. Watch this video by Jacob Avila of 5minsono.com and The Ultrasound Podcast for a quick review of POCUS for aortic dissection.
In 2017 Gibbons et al, described a protocol for detecting aortic dissection. The presence of one of: pericardial effusion, aortic intimal flap, or outflow tract diameter at end-diastole >3.5cm showed a sensitivity of 100% for Type A aortic dissections and 96.4% for all dissections. POCUS can be helpful in expediting the diagnosis of aortic dissection as was shown in this case. Pare et al (2016), found that POCUS reduced time to diagnosis by over 2 hours. Delays in diagnosis of aortic dissection are associated with increased mortality rates.
Gibbons R, Smith D, Mulflur M, et al. Bedside point of care ultrasound for the detection of aortic dissections in the emergency department [abstract] Ann Emerg Med. 2017;70(4):S143.
Pare JR, Liu R, Moore CL, et al. Emergency physician focused cardiac ultrasound improves diagnosis of ascending aortic dissection. Am J Emerg Med. 2016;34:486–92.