By Maria O’Rourke, MD, Byron Mendenhall MD & Elisa M. Aponte, MD
1. What are the significant findings in the below ultrasound images?
2. What is the pathophysiology of this particular disease process?
3. What are the potential complications of this entity? Can emergency physicians reliably use POCUS to diagnose and treat these complications early?
A 61-year-old morbidly obese male with a history of hypertension presented to the ED with acute onset of midsternal chest pain with radiation to his back and associated nausea and dizziness. On arrival, he appeared uncomfortable and was diaphoretic. His vital signs were BP 112/42, HR 63, RR 18 and oxygen saturation 95% on room air. The initial 12-lead EKG demonstrated ST wave depression in the lateral leads without ST elevation. While in the ED the patient had a second episode of back pain with associated left leg numbness. Distal pulses were equal and lower extremities were warm to touch. Point of care transthoracic echocardiogram (TTE) showed no pericardial effusion in the subxiphoid view but additional views were limited secondary to the patient’s body habitus. A clinical diagnosis of aortic dissection was suspected however a CT angiogram was unable to be performed due to the weight limitations of our facility’s CT scanner. Cardiac anesthesia was paged and the decision was made to electively intubate the patient and perform a transesophageal echocardiogram (TEE) with their assistance in the ED. After the standard 4 view limited resuscitative exam was unremarkable, suspicion for dissection was still high so upper esophageal images were obtained
Bedside TTE has been the mainstay in helping to diagnose and manage critically ill patients that present to the ED. However, TTE images can be difficult to obtain in patients in cardiac arrest due to multiple barriers including ongoing CPR, patient body habitus, and poor visualization of the heart due to increased lung pathology. Resuscitative point of care TEE is an evolving tool for emergency physicians in cardiac arrest patients who present to the ED. It can be used to prevent interruptions of CPR, aid in the diagnosis of wall motion abnormalities due to myocardial infarctions, and diagnose acute thrombosis in patients with pulmonary emboli.1 The new ACEP Guidelines for the Use of Transesophageal Echocardiography (TEE) in the ED for Cardiac Arrest published in April 2017 recommends the following four views for a limited point-of-care TEE exam: Mid-esophageal four-chamber view, Mid-esophageal long-axis view, Transgastric short axis view, and Mid-esophageal bi-caval view.2 However, if one suspects aortic dissection views of the aorta at the mid-esophageal level will need to be obtained. This view is currently not one of the recommended views but can be obtained as one withdraws the probe.
What are the significant findings in the above ultrasound images?
Upper esophageal (SAX) 2D images showing proximal descending aorta with an intimal flap and tear that creates flow between the true and false lumens. Perioperative upper esophageal 3D image show intimal tear in the aortic arch.
What is the pathophysiology of this particular disease process?
Aortic dissection is a degeneration of the aortic media and begins with an intimal tear. As blood collects, the layers of the aortic wall separate, and dissection can occur. Stanford Type A dissections involve the ascending aorta and arch and Type B dissections involve the descending aorta.
What are the potential complications of this entity? Can emergency physicians reliably use Point-of-Care Ultrasound (POCUS) to diagnose and treat these complications early?
ACS and aortic dissection can present similarly and a high degree of suspicion must be considered to avoid missing this life threatening diagnosis. Risk factors include uncontrolled hypertension, congenital disease, drug use that can increase aortic wall stress, and trauma. Patients can present with chest or back pain, syncope, and numbness, tingling or weakness of the lower extremities. Complications can include dissection into the coronary arteries, dissection proximally into the carotid arteries which can present with neurologic deficits, or distal involvement affecting the renal, spinal or iliac arteries. EKG changes in aortic dissection can often appear similar to that of patients who present with acute myocardial infarction. Treatment with thrombolytics will lead to adverse outcomes and possibly death.
Emergent consultation with your cardiothoracic surgery consultants for immediate repair is needed for a Type A dissection.
Patient was transferred to an outside facility for higher level of care. CT angiogram was later obtained and confirmed a Stanford Type A aortic dissection extending down to the left iliac artery. Cardiothoracic surgery was consulted and the patient was emergently taken to the operating room. Perioperative TEE was performed which showed Type A aortic dissection with the intimal tear originating from the aortic root and extending into the descending aorta. The ascending aorta was dilated and the aortic root measured 3.0 cm in diameter.
Aortic dissection is an increasingly missed and reported diagnosis. Point of care TEE can be useful in the acute setting in identifying either ascending or descending dissection. The initial diagnostic test of choice is CT angiogram, however if CT is unavailable TEE can be utilized.3 Current ACEP guidelines for point of care ED resuscitative TEE do not include adequate views for diagnosing ascending or descending aortic dissection.
Image 1: Upper esophageal descending aorta Short Axis (SAX) 2D image showing descending aorta with intimal tear.
Image 2a and 2b: Upper esophageal (SAX) 2D image.
2a. Demonstrating the flow from the true lumen to the false lumen via the tear in the intimal flap.
2b. Proximal descending aorta with an intimal flap and tear that creates flow between the true and false lumens. The true lumen is above the false lumen in this picture
Image 3. Upper esophageal (LAX) 2D image of the distal aortic arch demonstrating the tear in the intimal flap.
Image 4: Upper esophageal (LAX) 2D image of the distal aortic arch with color flow demonstrating true and false lumen.
Image 5: Upper esophageal 3D image of intimal tear in aortic arch.
Image 6. Upper esophageal 3D image of intimal tear in aortic arch.