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Chasing the Zebra: Diagnostic Challenges in Acute Aortic Syndrome

By Ellen Pil


 


CASE

Presentation:

  • A.S. is a 75 y.o. female with no past medical history presenting for 1 hour of sudden-onset, sharp epigastric pain radiating to her back.

Physical Exam:

  • Vital signs: BP 199/117 in right arm; 153/90 in left arm. Heart rate 79 bpm. Respiratory rate: 20 breaths/minute. SpO2: 96% on room air. Temperature: 98.3 F.

  • The patient is diaphoretic and moaning, but she is answering questions appropriately. Her cardiac and pulmonary exams are normal. Her abdomen is soft and non-distended. She has epigastric/subxiphoid tenderness and guarding, but no rebound or rigidity.


ED Course:

  • Initial diagnostics: EKG showed normal sinus rhythm without ST-T changes.

  • Initial management: A.S. was given fentanyl to facilitate imaging. A CTA of chest, abdomen, and pelvis reveals a 1.0 x 0.8 x 0.5 cm penetrating atherosclerotic ulcer of the aortic arch approximately 1 cm distal to the take-off of the left subclavian artery (images below).

  • Surgery was consulted, and the patient was admitted for aggressive blood pressure control and hemodynamic monitoring, with possible surgical intervention pending results of repeat CTA to assess for progression.


Clinical Question: What specific aspects of the patient’s history, physical examination findings, and initial diagnostic tests contribute to the accurate diagnosis of acute aortic syndrome?



SUMMARY OF EVIDENCE

Acute aortic syndrome (AAS) is a rare diagnosis with an incidence of 5.9-10.5 per 100,000 patient-years (1). It encompasses three conditions: aortic dissection (70-80%), intramural hematoma (5-25%), and penetrating atherosclerotic ulcer (2-7%) (1–3) These three diagnoses often share overlapping signs and symptoms (4). They can coexist and are investigated and managed similarly (4-6). Despite its rarity, AAS is highly morbid and requires early recognition and diagnosis (3). This blog post explores evidence for the effectiveness of various elements of patient history, physical examination, and initial diagnostic tests in the diagnosis of AAS.

Risk Factors: The risk factors for AAS vary depending on the patient’s age (7).  In patients over 70 years old, systemic hypertension, atherosclerotic disease, and iatrogenic causes (such as recent aortic manipulation or cardiac catheterization) are more prevalent. Conversely, risk factors in younger patients include connective tissue disorders, bicuspid aortic valve, and cocaine use (2,8).

History: Patients typically experience pain in the chest, back, or abdomen, although a small subset (6.3%) present without pain (9).  The International Registry of Acute Aortic Dissection (IRAD) notes that patients most frequently describe their pain as sudden, severe, and/or sharp,  whereas tearing, ripping, and migratory are less common descriptors (9). This observation is supported by a meta-analysis of pain characteristics by Ohle et al (10). Notably, both IRAD and Ohle et al. heavily rely on data from academic medical centers in Western countries, limiting the generalizability of their findings outside of this context.

Blood Pressure: Patients with AAS can be hypotensive (16.4%), normotensive (34.6%), or hypertensive (49.0%).2 While blood pressure alone is non-diagnostic, an interarm difference suggests AAS. In a 2018 retrospective case-control study of 222 patients (111 cases, 111 controls), 29.7% of patients with acute aortic dissections had a systolic blood pressure difference of >20 mmHg, compared to 13.5% of control patients (Sp 86.5%, Sn 29.7%; LR+ 2.20) (11).

Physical Exam: Ohle et al. found that the most predictive physical exam findings for acute aortic dissection were focal neurologic deficits (Sp 95%, LR+ 4.34), pulse deficits (Sp 92%, LR+ 2.48), and a new aortic insufficiency murmur (Sp 90%, LR+ 1.70) (10). However, no single physical exam finding achieved a negative likelihood ratio less than 0.5. This suggests that while the physical exam aids in diagnosis, its ability to exclude AAS is limited.

D-Dimer: ACEP advises that clinicians do not rely on D-dimer alone to exclude aortic dissection, and ACC/AHA guidelines recommend against using D-dimer to screen for AAS (12). False negative rates vary widely, but have been reported to be as high as 18% (13).  False negatives are more likely in patients with intramural hematomas or penetrating atherosclerotic ulcers, as well as in patients who have had symptoms for over 24 hours (9,14).

ECG: Though useful in identifying alternative etiologies (such as STEMI) for AAS symptoms, ECG has poor diagnostic value for identifying AAS. In the IRAD database, 31.3% of patients had a normal ECG, while an additional 41.4% had non-specific ST-segment or T-wave changes (2).

Chest X-Ray: Though mediastinal widening is the classic chest x-ray sign of AAS, it was absent in 21.3% of patients in the IRAD database (2). Ohle et al.’s meta-analysis reported a wide range for the specificity (24-78%) and sensitivity (76-94%) of mediastinal widening; however, study heterogeneity prevented pooling of estimates (10).

POCUS: In a recent study involving ED residents, three signs of aortic dissection were sought using both transthoracic echocardiography (TTE) and abdominal aorta POCUS: a pericardial effusion, intimal flap, or an aortic outflow tract diameter exceeding 35 mm. The protocol yielded a sensitivity of 93.2% and a specificity of 90.9%, though the results were limited by lack of masking to laboratory results or chest radiographs (15). While ACEP advises against relying on bedside TTE to definitively diagnose aortic dissection, if suspicion arises from abnormal TTE findings, immediate surgical consultation and/or escalation of care is recommended (12).


Risk Scores: A multicenter, observational, mixed prospective and retrospective cohort study in the UK found that clinical gestalt outperformed each of four tested risk scores (16). However, clinical gestalt and all risk scores had a very high negative predictive value (>99%) due to the low prevalence of AAS (0.3%), and the study was limited by missing clinical gestalt data for 26% of patients, compared to 4-7% missing data for the risk scores. One of the tested scores, the Acute Aortic Dissection Detection (ADD), is a frequently used tool that combines elements of the history and physical examination to identify patients at risk of AAS (17). Even among patients with a score of 0, categorized as “low risk”, the prevalence of AAS was 5% (18).  Moreover, in an emergency medicine population, the specificity of the ADD risk score is only 12.3%, potentially exposing patients to unnecessary testing (10).  Hence, ACEP advises against using clinical decision rules alone to identify very low risk patients (12).


IMAGES




RECOMMENDATIONS


  • Risk factors in AAS vary by age. In older patients (≥70), ask about a history of hypertension, atherosclerosis, or previous aortic manipulation or cardiac catheterization. In younger patients, ask about cocaine use, bicuspid aortic valve, and connective tissue disease.

  • Ask patients to describe the onset, intensity, and quality of their pain. Pain from AAS is most commonly described as sudden, severe, and sharp.

  • Measure the blood pressure in both arms and perform a thorough cardiovascular and neurologic exam. A pulse deficit, interarm blood pressure difference >20 mmHg, focal neurologic deficit, or new aortic insufficiency murmur are suspicious for AAS.

  • ECG is not useful in diagnosing AAS, but it can identify an alternative etiology for symptoms of AAS. A normal chest x-ray does not exclude AAS—mediastinal widening is absent in over 20% of patients.

  • POCUS should not be used as the primary modality to diagnose AAS, though it may be helpful if CTA is unavailable. TTE findings that are concerning for AAS warrant immediate surgery consultation.

  • D-dimer and risk scores should not be used independently to exclude AAS.


REFERENCES


  1. Vignaraja V, Thapar A, Dindyal S. Acute Aortic Syndrome. In: StatPearls. StatPearls Publishing; 2024. Accessed May 9, 2024. http://www.ncbi.nlm.nih.gov/books/NBK576402/

  2. 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

  3. Harris KM, Strauss CE, Eagle KA, et al. Correlates of delayed recognition and treatment of acute type A aortic dissection: the International Registry of Acute Aortic Dissection (IRAD). Circulation. 2011;124(18):1911-1918. doi:10.1161/CIRCULATIONAHA.110.006320

  4. Akin I, Kische S, Ince H, Nienaber C. Penetrating aortic ulcer, intramural hematoma, acute aortic syndrome: when to do what. J Cardiovasc Surg (Torino). 2012;53(1 Suppl 1):83-90.

  5. Erbel R, Aboyans V, Boileau C, et al. 2014 ESC Guidelines on the diagnosis and treatment of aortic diseases: Document covering acute and chronic aortic diseases of the thoracic and abdominal aorta of the adult. The Task Force for the Diagnosis and Treatment of Aortic Diseases of the European Society of Cardiology (ESC). Eur Heart J. 2014;35(41):2873-2926. doi:10.1093/eurheartj/ehu281

  6. Evangelista A, Czerny M, Nienaber C, et al. Interdisciplinary expert consensus on management of type B intramural haematoma and penetrating aortic ulcer. Eur J Cardio-Thorac Surg Off J Eur Assoc Cardio-Thorac Surg. 2015;47(2):209-217. doi:10.1093/ejcts/ezu386

  7. Mehta RH, O’Gara PT, Bossone E, et al. Acute type A aortic dissection in the elderly: clinical characteristics, management, and outcomes in the current era. J Am Coll Cardiol. 2002;40(4):685-692. doi:10.1016/s0735-1097(02)02005-3

  8. Bossone E, Eagle KA. Epidemiology and management of aortic disease: aortic aneurysms and acute aortic syndromes. Nat Rev Cardiol. 2021;18(5):331-348. doi:10.1038/s41569-020-00472-6

  9. Evangelista A, Isselbacher EM, Bossone E, et al. Insights From the International Registry of Acute Aortic Dissection: A 20-Year Experience of Collaborative Clinical Research. Circulation. 2018;137(17):1846-1860. doi:10.1161/CIRCULATIONAHA.117.031264

  10. Ohle R, Kareemi HK, Wells G, Perry JJ. Clinical Examination for Acute Aortic Dissection: A Systematic Review and Meta-analysis. Acad Emerg Med. 2018;25(4):397-412. doi:10.1111/acem.13360

  11. Um SW, Ohle R, Perry JJ. Bilateral blood pressure differential as a clinical marker for acute aortic dissection in the emergency department. Emerg Med J. 2018;35(9):556-558. doi:10.1136/emermed-2018-207499

  12. Cantrill SV, Brown MD, Burton JH, et al. Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients With Suspected Acute Nontraumatic Thoracic Aortic Dissection. Ann Emerg Med. 2015;65(1):32-42.e12. doi:10.1016/j.annemergmed.2014.11.002

  13. Schaefer T. D-Dimer in Aortic Dissection Workup. emDOCs.net - Emergency Medicine Education. Published March 26, 2014. Accessed May 6, 2024. https://www.emdocs.net/d-dimer-in-aortic-dissection-workup/

  14. Braverman AC. Acute Aortic Dissection. Circulation. 2010;122(2):184-188. doi:10.1161/CIRCULATIONAHA.110.958975

  15. Gibbons RC, Smith D, Feig R, Mulflur M, Costantino TG. The sonographic protocol for the emergent evaluation of aortic dissections (SPEED protocol): A multicenter, prospective, observational study. Acad Emerg Med. 2024;31(2):112-118. doi:10.1111/acem.14839

  16. McLatchie R, Reed MJ, Freeman N, et al. Diagnosis of Acute Aortic Syndrome in the Emergency Department (DAShED) study: an observational cohort study of people attending the emergency department with symptoms consistent with acute aortic syndrome. Emerg Med J EMJ. 2024;41(3):136-144. doi:10.1136/emermed-2023-213266

  17. Hiratzka LF, Bakris GL, Beckman JA, et al. 2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with thoracic aortic disease. Circulation. 2010;121(13):e266-e369. doi:10.1161/CIR.0b013e3181d4739e

  18. Nazerian P, Giachino F, Vanni S, et al. Diagnostic performance of the aortic dissection detection risk score in patients with suspected acute aortic dissection. Eur Heart J Acute Cardiovasc Care. 2014;3(4):373-381. doi:10.1177/2048872614527010

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