Table of Contents

 

1. Abstract
2. Case Presentation
3. Introduction
4. Critical Appraisal Of The Literature
5. Epidemiology
6. Pathophysiology And Etiology
   1. Pathophysiology
   2. Etiology
   3. Connective Tissue Disorders
   4. Intramural Hematoma
   5. Penetrating Atherosclerotic Ulcer
7. Differential Diagnosis
8. Prehospital Care
9. Emergency Department Evaluation
   1. History
   2. Physical Examination
   3. Risk Stratification
10. Diagnostic Studies
    1. Laboratory Testing
    2. Biomarkers
    3. Imaging
       1. Chest Radiograph
       2. Transthoracic Echocardiogram
       3. Transesophageal Echocardiogram
       4. Computed Tomography
       5. Magnetic Resonance Imaging
    4. Which Diagnostic Modality To Use?
11. Treatment
    1. Shock
    2. Complications
    3. Type A Dissections
    4. Type B Dissections
12. Special Circumstances
    1. Intramural Hematoma
    2. Penetrating Atherosclerotic Ulcer
    3. Chronic Dissections
13. Controversies And Cutting Edge
    1. Noninvasive Surgical Management
    2. Point-Of-Care Ultrasound
    3. Use Of D-dimer
14. Disposition
15. Summary
16. Risk Management Pitfalls For Acute Aortic Syndromes
17. Time- And Cost-Effective Strategies
18. Case Conclusions
19. Clinical Pathway For Management Of Acute Aortic Syndromes In The Emergency Department
20. Table and Figures
    1. Table 1. Chief Complaints That Include Aortic Dissection In The Differential Diagnosis
    2. Table 2. High-Risk Features For Aortic Dissection
    3. Table 3. Chest Radiograph Findings In Aortic Dissection
    4. Table 4. Imaging Modalities For Acute Aortic Syndromes
    5. Table 5. Medication Therapies For Acute Aortic Syndromes
    6. Figure 1. Classification Systems For Aortic Dissections
    7. Figure 2. Chest Radiograph In An Aortic Dissection
    8. Figure 3. Transesophageal Echocardiogram With Doppler Of The Ascending Aorta
    9. Figure 4. Contrast-Enhanced Computed Tomography With Type A Aortic Dissection
    10. Figure 5. Contrast-Enhanced Computed Tomography With Type A Intramural Hematoma
    11. Figure 6. Noncontrast Magnetic Resonance Angiogram Of Type A Aortic Dissection
    12. Figure 7. Aortogram Of Aortic Dissection
    13. Figure 8. Subxiphoid View Of Point-Of-Care Ultrasound With Pericardial Effusion
    14. Figure 9. Transabdominal Point-Of-Care Ultrasound Showing An Aortic Dissection
21. References

Abstract

Aortic dissection, intramural hematoma, and penetrating athero- sclerotic ulcer are parts of a spectrum of acute aortic syndromes that represent uncommon - but potentially deadly - diagnoses seen in the emergency department. The differential for acute aortic syndromes is large, as many conditions (including the much more common conditions of acute coronary syndromes and pulmonary embolism) present with many of the same chief complaints. This review looks at the features and classifications of acute aortic syndromes and presents evidence regarding the risk factors and chief complaints that can assist emergency clinicians in identifying the patients who require further investigation. Although no set of clinical factors has been shown to rule out aortic dissection, elements of a complete history and physical examination are critical in identifying patients who may be at risk for these diseases. In addition, the advantages and disadvantages of the various available advanced imaging strategies, the evidence regarding efficacy of laboratory testing (including D-dimer), as well as surgical and nonsurgical treatment options are reviewed.

Key words: aortic dissection, acute aortic syndromes, intramural hematoma, penetrating atherosclerotic ulcer, Marfan syndrome, connective tissue disorders, TEVAR

Case Presentation

You are working an overnight shift when EMS arrives with a 55-year-old male with severe substernal chest pain and shortness of breath for the past 2 hours. The patient has a history of hypertension and type II diabetes. His blood pressure is 200/110 mm Hg, and his heart rate is 110 beats/min. A prehospital ECG was performed, which shows ST elevation in leads II and III as well as a VF consistent with an acute myocardial infarction, and you call a STEMI alert. The cardiologist calls back from your STEMI alert and states that she is coming in from home to see the patient. To save time, she wants to meet the patient directly in the heart catheterization lab on the second floor. After you get off the phone, you quickly look at the chest radiograph and notice that the mediastinum appears widened. You wonder if it’s a good idea to start anticoagulation and send the patient to the catheterization lab right away…

The next week, you are working at a free-standing ED where the patients are checking in at record volume. You are getting pressure to see and discharge patients as fast as possible when you see a 21-year-old male presenting with chest pain radiating to his back, along with some shortness of breath. The patient reports no improvement in symptoms with over-the-counter analgesics. The patient plays on the local varsity basketball team. He has no known medical history, and his social history is negative for tobacco, alcohol, or illicit drugs. He appears slightly anxious and has a blood pressure of 155/90 mm Hg and a heart rate of 95 beats/min. He is tall and thin and has reproducible chest tenderness. Your CT scanner has unexpectedly gone down and is unavailable for the rest of the night. ECG shows a normal sinus rhythm without evidence of ischemia and a plain chest radiograph appears normal. As you start to watch your department getting backed up, the nurse states that he is concerned about this patient. You assess the patient as low risk for pulmonary embolism, so you decide to get a D-dimer, which comes back negative. You wonder if this patient has something more significant and what your diagnostic options are…

Introduction

Over 250 years ago, the first description of aortic dissection was made during an autopsy of King George II after he suddenly died “while straining on the toilet.” Over 60 years later, the term “dissecting aneurysm” was coined by René Laennec, which brought both recognition and confusion to this disease, confusion that persists to the present day.1 In 1955, Dr. Michael DeBakey and his team were the first to successfully repair a dissecting aortic aneurysm; ironically, many years later, Dr. DeBakey himself suffered an acute aortic dissection.¹

While the term “dissecting aneurysm” is still used, aortic dissection and aortic aneurysm are 2 distinct disease processes. Acute aortic dissection is part of a spectrum often referred to as acute aortic syndrome. This encompasses not only aortic dissection but also its variants, including aortic intramural hematoma and penetrating atherosclerotic ulcer.¹ While aortic dissection usually presents with severe pain, its presentation can be more subtle and should be considered in anyone with chest pain and pain with either syncope or focal neurological deficits.

Aortic dissection is a potentially life-threatening diagnosis, and it requires a heightened suspicion. Unfortunately, the diagnosis of aortic dissection in the emergency department (ED) is missed 16% to 38% of the time.^2,3 Litigation surrounding missed aortic dissection has also become more common.⁴ Morbidity and mortality of aortic dissection is high, and it requires aggressive management to prevent poor outcomes. Mortality for an untreated type A dissection is thought to be approximately 1% to 2% per hour in the first 48 hours, 50% by day 3, and 80% by 2 weeks.^1,5 Type B dissection has a mortality of approximately 10% at 30 days for lower-risk patients and up to 70% in high-risk groups.^1,6 However, recent advances in surgical repair have greatly improved outcomes in these patients. This issue of Emergency Medicine Practice will discuss nontraumatic aortic dissection and its anatomic variants, intramural hematoma and penetrating atherosclerotic ulcer. A review of the pathophysiology, risk factors, and appropriate imaging for aortic dissection will be discussed. Treatment options, both surgical and nonsurgical, will also be reviewed, including new noninvasive management techniques.

Critical Appraisal Of The Literature

A literature search of Ovid MEDLINE®, PubMed, and the Cochrane Database of Systemic Reviews was performed using the search term aortic dissection. The search was limited to the English language, humans, and adults, from 1993 through July 2013. Abstracts and articles were reviewed for applicability related to the acute management and diagnosis of aortic dissection. Policy statements from the American College of Cardiology Foundation/American Heart Association (ACCF/AHA) (including 8 other societies), the European Society of Cardiology, the Japanese Circulation Society, and the American College of Radiology (ACR) were also reviewed.^7-10 Currently, the American College of Emergency Physicians (ACEP) is developing a clinical policy for aortic dissection, but it was not available at the time of writing of this article.

Because of the low incidence of aortic dissection, the majority of literature on this topic comes from registry data such as the International Registry of Acute Aortic Dissection (IRAD). IRAD was established in 1996 and now consists of 30 large referral centers in 11 different countries, and it assesses clinical features, treatment, and outcomes for patients with an acute aortic dissection from this large retrospective database.¹¹ While the IRAD database is one of the most important sources of data on aortic dissection, it is important to understand the limitations of registry data, which include the lack of controls as well as the heterogeneity in data from protocol revisions over time. Other registry data also exist, such as the German Registry for Acute Aortic Dissection Type A (GERAADA), which consists of 50 cardiac centers and includes data for new treatment strategies.¹² Very few prospective studies exist in regard to acute aortic dissection, and these studies are generally observational in design. The remaining literature consists of case reports and series.

Risk Management Pitfalls For Acute Aortic Syndromes

1. “The D-dimer was negative, so I assumed the patient did not have an aortic dissection and sent him home.” While D-dimer has shown promise in the evaluation of possible acute aortic dissection, there have been no large prospective studies to validate this strategy. Unfortunately, no biomarkers currently have been validated to rule out an aortic dissection. Intramural hematoma or aortic dissections with a thrombosed false lumen can have a false negative D-dimer. If there is sufficient clinical suspicion for an acute aortic dissection, advanced imaging is indicated.
2. “The patient didn’t have tearing chest pain, a pulse or blood pressure differential, or a widened mediastinum on chest x-ray; therefore, he couldn’t have an aortic dissection.” While studies have shown a decreased probability for an aortic dissection when none of these features are present, this strategy has not been validated to safely rule out an aortic dissection. Approximately 5% of acute aortic dissections will not have any associated pain, and 38% will not have a widened mediastinum on chest x-ray.
3. “The patient was only 28 years of age and had reproducible chest pain. I thought the patient had costochondritis, so I sent him home with NSAIDs. I didn’t know he could have had an aortic dissection!” While acute aortic dissections usually occur in those who are older, they can occur at any age. Patients with a history of (or suspected) Marfan Risk Management Pitfalls For Acute Aortic Syndromes (Continued on page 17) syndrome, another connective tissue disorder, or a history of a bicuspid aortic valve should always have aortic dissection in the differential. A thorough history and physical examination should be performed to evaluate for all possible risk factors.
4. “She was 56 years of age, with chest pain and a slightly elevated troponin. I thought it was acute coronary syndromes, and I anticoagulated her while waiting for the cardiologist to see her.” Although acute coronary syndromes are more common than acute aortic dissection, aortic dissection should always be considered in anyone who presents with chest pain, even with elevations in cardiac biomarkers. History of connective tissue disorder, bicuspid valve, or illicit drug use (such as cocaine) should increase suspicion. Studies have shown missed aortic dissections to be more likely diagnosed as acute coronary syndromes. Evaluation of the chest x-ray and a good history and physical examination can help risk stratify patients for possible aortic dissection.
5. “She was 65 years old and presented with syncope without chest pain or shortness of breath. I thought it might have been an arrhythmia, so I just admitted her to a telemetry bed.” Approximately 12% of patients with aortic dissection will have syncope. Elderly patients may not have classic symptoms associated with aortic dissection.
6. “The patient had an inferior wall STEMI on ECG and the cardiologist was unavailable to take the patient emergently to the heart catheterization lab. I gave thrombolytics because that is what I was told to do.” Two percent to 5% of patients with aortic dissections will have concurrent myocardial ischemia. Proximal aortic dissections can dissect into the right coronary artery, causing occlusion, and can present with a STEMI. If clinical suspicion for aortic dissection is present, other diagnostic modalities should be used to evaluate for proximal aortic dissection prior to anticoagulation or thrombolytics.
7. “The patient was 28 years old and had Marfan syndrome. I was concerned about an aortic dissection, but he couldn’t get a CT scan due to a contrast allergy. I got a TEE and it didn’t show an aortic dissection, so I sent him home and told him to follow up with his primary care provider.” Advanced imaging such as TEE, CT, and MRI are all very sensitive and specific; however, no modality is 100%. If there is a high clinical suspicion for an aortic dissection, a second modality should be obtained to rule out aortic dissection.
8. “The patient presented within an hour, had right hemiparesis, and was unable to speak. He was having a stroke and was within the window for thrombolytics.” Acute neurological deficits can be found in up to 30% of acute type A aortic dissections, as the Risk Management Pitfalls For Acute Aortic Syndromes (Continued from page 16) dissection extends into the internal carotids or to the spinal arteries. Thrombolytics in the setting of an acute aortic dissection can be fatal. Consider aortic dissection in patients who present with stroke symptoms, especially when patients have concurrent chest or back pain.
9. “The patient had a type B aortic dissection. These patients are only treated medically, so I didn’t consult surgery.” While uncomplicated type B aortic dissections are usually managed medically, those with a potential for rupture or organ dysfunction as a result of the aortic dissection will be considered for intervention, either with TEVAR or open surgical repair.
10. “I ordered a pulmonary embolism study for the patient, and it didn’t show a pulmonary embolism or aortic dissection. I sent the patient home and told him to follow up with his primary care provider.” CT angiography for pulmonary embolism is a different protocol than for an aortic dissection. While aortic dissections can be seen in a CT for pulmonary embolism, it might miss small dissections, as CT protocol for dissection uses smaller cuts. If clinical suspicion remains high for an aortic dissection, consider ordering a second imaging study.

Table and Figures

References

Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.

To help the reader judge the strength of each reference, pertinent information about the study will be included in bold type following the reference, where available.

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