Point of care ultrasound for Aortic Dissection James sacca pgy-1 12/12/16

overview Aortic dissection (AD) is a life-threatening event with 1-2% increase in mortality per hour for the first 24-48 hrs Uncommonly seen in ED but often considered in differentials Classically tearing chest pain that radiates to the back Nonspecific findings of pulse discrepancies, new diastolic murmur, stroke, STEMI, widened mediastinum on CXR CTA is gold standard for diagnosis if stable Point of care ultrasound (POCUS) is becoming increasingly popular in the ED and may be useful to help rule in or out AD Emergent surgical if unstable and believed to involve the aortic root/arch sensitivity and specificity of TTE for the diagnosis of acute aortic dissection has been shown to be as high as 92% to 100% and 88% to 96%, respectively, in select studies

AD Classifications

5E’s approach EXIT Diameter >4cm Presence of flap PSL marker on l Aortic root great than 4 cm. we are taught in PSL that RA, AOT, and LA should be roughly the same size. Also look for a flap in the root of the aorta or the descending aorta in this view PSL marker on l PSL marker on R

5e’s approach cont.’d effusion Pericardial effusion is a sensitive but nonspecific sign of AD. If present with AD, suggests higher mortality rate, especially if tamponade physiology present Due to the high mortality of AD involving the aortic root with a significant pericardial effusion/tamponade, the emergency physician must act quickly to get the patient stabilized and sent quickly to the operating room under the care of a cardiothoracic surgeon. Therefore, EUS evaluation of the heart for pericardial effusion/tamponade or wall motion abnormalities due to dissection into the pericardial sac or the coronary arteries may be helpful when patients are found to have AD. SX marker on l

Mercedes benz sign Normal in parasternal short Abnormal in subxiphoid Seeing a prominent aortic valve in an unusual orientation. Blaivas & Sierzenski believe the anatomic reason for this change in the appearance of the aortic valve is most likely owing to the change in acoustic windows within the heart. The ultrasound beam emanating from the transducer is little more than a millimeter thick and a subtle change in transducer position, or in this case cardiac anatomy, can produce significant changes in the image. Because the typical aortic root diameter is less than 3.8 cm and dilated root from a dissection can frequently be over 5.0 cm it actually changes the anatomic relationships in a small area of the heart, thus, altering the window provided for ultrasound beam transmission and the view obtained. Further, dissection to the aortic valve itself may change the perceived orientation of the aortic valve leaflets, allowing the ultrasound beam to deliver images from an angle that was not previously possible.

Mercedes benz sign cont.’d Blaivas & Sierzenski attribute this finding to changes in the acoustic windows within the heart. Subtle changes in transducer position, or in this case cardiac anatomy, can produce significant changes in images seen. Dilated aortic root from a dissection can change the anatomic relationships in a small area of the heart. Also, dissection to the aortic valve itself may change the perceived orientation of the aortic valve leaflets.

suprasternal Click for videos

Carotid arteries Patients with syncope or other neurological symptoms could be due to cardiogenic shock, hemorrhagic shock, or interruption of flow through the carotid arteries

Coronary arteries Can’t POCUS these directly but pay attention for signs of MI such as wall motion abnormalities or EKG changes as disruption of flow can occur with AD

Abdominal aorta Although abdominal aortic ultrasounding to diagnose AAA is most common, it can be used effectively to diagnose AD

Abdominal aorta cont.’d Transverse longitudinal Click for videos

In conclusion There are many signs of AD that can be seen on US including dilated aorta, presence of a flap, pericardial effusions, mercedes benz sign on SX view Use doppler on the aorta to assess for true & false lumens Point of care cardiac and aortic ultrasounds are important to rapidly diagnose AD if highly suspected Even if low suspicion for AD, POCUS can quickly provide lots of additional information in your chest pain and abdominal pain patients

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