Aortic Dissection Archives - UCSD Ultrasound

December 2, 2020March 4, 2021

Case 25: Aortic Dissection

A 44 year old male with a history of heroin abuse presents to the emergency department with altered mental status. Per EMS, the patient was found on the street with decreased level of consciousness and poor respiratory effort. EMS was concerned about opioid overdose, and he was treated with 4mg Narcan, with improvement in his mental status.

Upon arrival to the ED, he was noted to be agitated and tachypneic with RR in the 40’s.

Vitals: BP 90/65 mmHg, HR 110, O2 100% on RA, glucose 158.

He is alert and oriented to person, month, and place, but appears agitated and confused. He denies any complaints other than shortness of breath, and states he felt fine before using heroin. He denies any past medical history.

Exam notable for tachycardia, diffuse rhonchi throughout all lung fields, 2+ nonpitting lower extremity edema. He is neurologically intact with 2+ pulses throughout.

A bedside echocardiogram was performed, what do you see? What are your next steps?

aortic dissection suprasternal ultrasound

Answer and Learning Points

Answer:

The first two images show a parasternal long-axis view, with a dilated aortic root measuring approximately 4.2cm. Also notice the pericardial effusion with a homogenous layer that appears fixed to the pericardium. At the time it was unclear whether this represented a clot within the pericardial sac, or was superficial to it.

Given the dilated aortic root, a suprasternal short-axis view was obtained to assess the proximal aorta, with the short axis view seen on the third image. A flap was visualized in the aortic lumen, significant for an ascending aortic dissection. The dissection was then visualized in the abdominal aorta, extending distal to the common iliac arteries, seen in the last images.

The patient was placed on esmolol drip and later required vasopressor support. CT angiography was obtained, confirming a Type A aortic dissection. He was transferred to a nearby hospital for emergent repair of his ascending and descending aortic dissection.

Per the operative report, the patient had developed a significant pericardial effusion by the time he reached the OR, and the visualized homogenous layer above most likely represented a blood clot within the pericardium.

Learning Points:

- While CTA remains the gold standard for diagnosis of aortic dissection, POCUS remains a great tool for diagnosing both ascending and descending aortic dissection, particularly in the unstable patient.
- In addition to directly visualizing the dissection flap, TTE can also be used to identify patients with high risk features, such as those with cardiac tamponade, severe aortic dilatation, severe aortic regurgitation, regional wall motion abnormalities, and decreased ejection fraction (1).
- TTE has been shown to have a sensitivity of 78-90% and specificity 87-96% for type A dissection in older studies (2,3), and in more recent studies showing improved sensitivity up to 97-99% (1,4,5) and specificity 100% (4) with improved image quality.
- The suprasternal notch views are particularly useful in evaluating the proximal ascending aorta, and allow the operator to assess for aortic dissection, coarctation, dilatation of the aortic arch, and retrograde flow from the descending aorta.

References

1. Sobczyk D, Nycz K. Feasibility and accuracy of bedside transthoracic echocardiography in diagnosis of acute proximal aortic dissection. Cardiovasc Ultrasound. 2015;13:15.

2. Evangelista A, Flachskamp FA, Erbel R, Antonini-Canterin F, Vlachopoulos C, Rocchi G, et al. Echocardiography in aortic diseases: EAE recommendations for clinical practice. Eur J Echocardiogr. 2010;11:645–58. doi: 10.1093/ejechocard/jeq056.

3. Nienaber CA, von Kodolitsch Y, Nicolas V, Siglow V, Piepho A, Jaup T, et al. The diagnosis of thoracic aortic dissection by noninvasive imaging procedures. N Engl J Med. 1993;328:1–9. doi: 10.1056/NEJM199301073280101.

4. Cecconi M, Chirillo F, Constantini C, Iacobone G, Lopez E, Zanoli R, et al. The role of transthoracic echocardiography in the diagnosis and management of acute type A aortic syndrome. Am Heart J. 2012;163(1):112–8. doi: 10.1016/j.ahj.2011.09.022.

5. Nazerian, P., Vanni, S., Castelli, M. et al.Diagnostic performance of emergency transthoracic focus cardiac ultrasound in suspected acute type A aortic dissection. Intern Emerg Med9, 665–670 (2014). https://doi.org/10.1007/s11739-014-1080-9

This post was written by Rachna Subramony MD, Alex Anshus MD, with editing from Sukhdeep Singh MD, Charles Murchison MD and Amir Aminlari MD.

August 26, 2017July 22, 2020

Feasibility and accuracy of bedside transthoracic echocardiography in diagnosis of acute proximal aortic dissection

Background

Acute aortic dissection is a life threatening condition that requires prompt diagnosis and definitive management; dissection involving the ascending aorta is undoubtably an indication for emergent surgical intervention. Previous data suggests that the mortality of type A dissection increases by 1-2% for every hour that passes which further highlights the importance of rapid diagnosis [1-2]. Currently, CT is considered the gold standard that enables the visualization of the entire aorta and can distinguish among the different types of acute aortic syndromes; however this is not always available, requires transferring patients to the CT scanner, and can ultimately generate a significant delay in treatment. Ultrasound is an easily available alternative imaging adjunct that may prove useful in rapid diagnosis of acute aortic dissection, specifically, type A dissection that require emergency surgical intervention.

Feasibility and Accuracy of Bedside Transthoracic Echocardiography in Diagnosis of Acute Proximal Aortic Dissection

Clinical Question

What is the accuracy of transthoracic echocardiography (TTE) in the diagnosis of acute type A aortic dissection in comparison to CT (with reference to the intra-operative diagnosis)?

Methods & Study Design

Design
- Retrospective chart review
Population
- This was a single center study involving patients transferred due to suspected acute type A aortic dissection
- Cardiac surgery for type A dissection was conducted in 172/178 patients (1 patient refused the operation and died, 5 patients underwent cardiac arrest and died prior to transfer to the operating room)
  - Because intra-operative findings were considered the gold standard reference for the presence of aortic dissection, the 6 patients who died without cardiac surgery were excluded from the final analysis
- Inclusion criteria:
  - Referral for an urgent surgery due to proximal aortic dissection (Stanford classification Type A)
  - Available results of both CT and bedside TTE
- Excluded
  - Patients who died prior to cardiac surgery
  - 1 patient who refused surgery
  - Patients who underwent surgical repair of acute type A aortic dissection based on TTE without confirmatory CT
Intervention
- TTE was performed in the emergency department by an “experienced echocardiographer" to evaluate for: maximum ascending aorta diameter, presence of a dissection flap in the ascending aorta, left ventricular ejection fraction, pericardial effusion (and cardiac tamponade), aortic valve morphology and severity of aortic regurgitation
  - Echocardiographic findings were compared to CT findings and intra-operative findings were used as a gold standard
Outcomes
- Identification of type A aortic dissection by TTE
- Correlation of TTE measurements of maximum ascending aortic diameter with CT and intra-operative findings

Results

- Statistical analysis with chi square test did not show any statistically significant differences between CT and TTE in the detection of proximal aortic dissection.
- Additionally, echo revealed concomitant abnormalities (i.e. bicuspid aortic valve, AV calcifications, moderate/severe aortic incompetence, cardiac tamponade), which were all confirmed intra-operatively and influenced the treatment strategy (graft vs. valve-sparing surgery).
- In patients with any aortic valve abnormalities (bicuspid aortic valve, AV calcifications, significant aortic regurgitation) procedure of choice was replacement by a composite graft (77.59% vs. 49.12%), whereas patients with normal aortic valves were significantly more likely to have the valve sparing surgery (50.88% vs. 22.41%)
- There was a strong positive correlation between maximum diameter of the ascending aorta measured by TTE and CT (correlation coefficient 0.869)

Strengths & Limitations

Strengths
- This was a feasibility study, and they used a population with known acute type A aortic dissection to determine if TTE could be used to provide both a rapid and reliable diagnosis in proximal aortic dissection
- Gold standard was intra-operative findings
Limitations
- Retrospective analysis, meaning that the diagnosis of aortic dissection has either already been made or was strongly suspected prior to initiating scanning; some may argue this may falsely increase the noted sensitivity/specificity of TTE
- All patients who underwent cardiac surgery for acute proximal dissection based on TTE without CT verification (~30% patients at their institution) were excluded from the analysis
- The TTE was performed by personnel trained in advanced echocardiography which may lower the sensitivity/specificity of these findings in the hands of less experienced operators

Author's Conclusions

"Our data confirm that TTE is a reliable method for diagnosis of proximal aortic dissection. TTE provides a reliable value of maximum diameter of the ascending aorta in comparison to both CT and direct intra-operative measurement. Moreover, TTE gives the additional information that influences the operative technique of choice and identifies the high-risk patients (cardiac tamponade, severe aortic dilatation, severe aortic regurgitation). Our retrospective analysis confirms the pivotal role of TTE in the evaluation of the patients with suspected proximal aortic dissection in emergency room setting."

Our Conclusions

Our conclusions are very similar to author findings on this paper. From the emergency department standpoint, we need the ability to distinguish sick patients from not sick patients and TTE in suspected acute aortic dissection does just that. Looking at this data, TTE measurements of maximum ascending aorta diameter correlate very well with intra-operative measurements. Furthermore, TTE is very accurate at identifying complications of type A aortic dissection such as decompensated heart failure (due to acute aortic regurgitation) and cardiac tamponade, both of which will alter surgical management.

What this means is that if you suspect aortic dissection, a bedside echo should be performed immediately looking for ascending aorta enlargement, dissection flap, and/or complications of dissection. If found, cardiac surgery can confidently be consulted and the patient can either be pushed to the operating room if unstable or pushed directly to the CT scanner by the emergency medicine provider. What this does not mean is that your work up stops here if no findings of dissection are found. If you are truly concerned about aortic dissection then the next step is to proceed with CT for definitive rule out. For more information on evaluation of acute aortic dissection, please read our recent case here.

The Bottom Line

The use of TTE in suspected proximal aortic dissection facilitates a rapid and reliable diagnosis, and shortens the delay to definitive treatment in a subset of high-risk patients.

Authors

This post was written by Ryan Shine, MS-4 at UCSD. It was edited by Michael Macias, MD.

References

1. HIRST AE Jr, e. (2017). Dissecting aneurysm of the aorta: a review of 505 cases. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 26 August 2017, from https://www.ncbi.nlm.nih.gov/pubmed/13577293
2. Hagan PG, e. (2017). The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 26 August 2017, from https://www.ncbi.nlm.nih.gov/pubmed/10685714
3. Sobczyk, D., & Nycz, K. (2015). Feasibility and accuracy of bedside transthoracic echocardiography in diagnosis of acute proximal aortic dissection. Cardiovascular Ultrasound, 13(1). doi:10.1186/s12947-015-0008-5

July 22, 2017July 22, 2020

Case # 2: A Needle In the Haystack

A 40 year old male presented with 3 days of progressive dyspnea on exertion. He notes he was in a normal state of health prior to this and played basketball daily without issue but now he can no longer walk across the room without becoming winded. He has no chest pain, a normal chest x-ray and an ECG demonstrating sinus tachycardia

Vitals: HR 109 BP 110/72 RR 22 O2 96

Answer and Learning Point

Answer

There is evidence of severe aortic regurgitation and aortic root dilation (~6 cm) on this parasternal long axis view. In a patient without any previous cardiac history with new aortic regurgitation this is concerning for acute aortic dissection. Cardiac surgery was consulted immediately and the patient was taken straight to CT scan for confirmation of type A aortic dissection. The patient was in the OR within 1 hour and had an excellent outcome.

Learning Point

Aortic dissection is quite uncommon (~5-30 per 1 million people per year) and is often seen in patients with chronic uncontrolled hypertension or other diseases such as bicuspid aortic valve, Marfan Syndrome or Ehlers-Danlos Syndrome. Unfortunately all the "classic" indicators of dissection are actually not that common [1]. Traditionally we are taught that patients with acute aortic dissection will arrive hypertensive, while in actuality up to 1 in 4 patients with Stanford Type A dissection will have a presenting systolic blood pressure below 100 mmHg. Additionally, it is taught that a dissection presents as a “ripping or tearing” pain going to the back. Looking at the data, while over 90% of patients felt that it was the worst pain they had ever experienced, only 50% of subjects described their pain as ripping or tearing (62% described pain as sharp), only 35% had any posterior chest pain, and only 85.4% of patients described the onset of their pain as ‘acute.’ [1]

The varied presentation of this disease makes aortic dissection difficult to diagnose, and the clinician should have a high index of suspicion for this life-threatening disease process. This is where ultrasound comes in. Anyone who has a concerning chest pain story, pain above and below the diaphragm, chest pain + a neurological symptom, or signs and symptoms of acute heart failure without any previous cardiac history, should have a bedside ultrasound performed. While ultrasound cannot rule out aortic dissection, it can rapidly identify complications of dissection and expedite care in these patients whom time is of the essence.

The Approach

Perform standard abdominal aorta ultrasound evaluating for aneurysm or intimal flap. Be sure to evaluate from proximal aorta, in the epigastric region, distally to the iliac vessels. A normal aorta caliber is < 3 cm.

Obtain a parasternal long axis view:

Measure aortic root, this should be less than 4 cm. There are varying opinions on where the best place to take this measurement is, I suggest measuring the largest area you see as it is better to be on the conservative side.
Apply color doppler to evaluate for aortic regurgitation.
Assess global cardiac function. This is useful to see if a patient is compensated or decompensated as well as assist with fluid/pressor management if needed.
Evaluate for pericardial effusion. If there is evidence of effusion and concern for Type A aortic dissection, this suggests that there is communication with pericardial sac.
Evaluate descending thoracic aorta for intimal flap

References

Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): New Insights Into an Old Disease. JAMA. 2000;283(7):897-903. doi:10.1001/jama.283.7.897.
Taylor RA, e. (2017). Point-of-care focused cardiac ultrasound for the assessment of thoracic aortic dimensions, dilation, and aneurysmal disease. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 22 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/?term=22288871
C, K. (2017). Emergency department diagnosis of aortic dissection by bedside transabdominal ultrasound. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 22 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/19549013
Lang R, Bierig M, Devereux R, et al. Recommendations for Chamber Quantification: A Report from the American Society of Echocardiography’s Guidelines and Standards Committee and the Chamber Quantification Writing Group, Developed in Conjunction with the European Association of Echocardiography, a Branch of the European Society of Cardiology. J Am Soc Echocardiogr 2005; 18: 1440-63.
Rubano E, e. (2017). Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 22 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/?term=23406071