Aortic Dissection

Don’t Miss This Diagnosis!

Robert L. Rogers, MD, FAAEM

Program Director

Combined Emergency Medicine/Internal Medicine Residency

Department of Surgery/Division of Emergency Medicine and Department of Internal Medicine

University of MarylandSchool of Medicine

Baltimore, Maryland

EDUCATIONAL OBJECTIVES:

At the conclusion of this presentation, each participant should be able to…

1. Describe common and less well-known risk factors for aortic dissection

2. Recognize atypical and subtle presentations of aortic dissection

3. List reasons for the missed or delayed diagnosis and describe a useful approach to

decrease the chance of successful litigation

4. Describe physical examination and radiographic pitfalls in the diagnosis of

aortic dissection

5. Citenew developments and current literature pertaining to aortic dissection

Why is aortic dissection an important topic for emergency physicians to know well?

  • Thoracic aortic dissection can be extremely difficult to diagnose.
  • Mortality rates are estimated at 50% by 48 hours if undiagnosed.
  • Mortality rates increase by 1%/hour if undiagnosed.
  • Prompt detection and therapy impact on survival rates.
  • Time is aorta.

Risk Factors

The detection of thoracic aortic dissection (TAD) may be greatly enhanced by performance of a thorough risk factor profile.

Every chest pain patient should undergo a risk factor analysis of the top three deadly chest pain entities: acute coronary syndromes, pulmonary embolism, and thoracic aortic dissection.

Traditional Risk Factors for TAD:

  • Hypertension (only ~ 50% are hypertensive on presentation)
  • Male sex
  • Age (tends to occur in older patients, but don’t forget that young patients can develop TAD as well.)
  • Pregnancy (also a risk factor for coronary artery dissection)
  • Family history (not connective-tissue disease related)
  • Connective tissue disease(Marfans and Ehler-Danlos)

Less Common Risk Factors:

  • Cocaine (Type B more common)
  • Turner’s syndrome
  • Bicuspid aortic valve
  • Iatrogenic (cardiac catheterization)
  • Coarctation of the aorta
  • Trauma
  • Ecstasy (NMDA) use and weight lifters-associated TAD

Atypical Presentations

The key to making the diagnosis of this lethal aortic disease may depend on how familiar you are with well-described atypical and subtle presentations?Although textbook presentations may occasionally occur, they tend to be the exception rather than the rule. Atypicalreally is typical.

  • International Registry of Aortic Dissection (IRAD)-Study by Hagan, et al. that involved 464 patients with confirmed TAD. Mean age: 63 years, 65.3 % males, 62% type A dissections

The findings:

pulse deficit 15 %

aortic murmur 31.6 %

normal chest x-ray 12 %

absence of mediastinal widening 34 %

syncope 12 %

painless 2.2%

Conclusions from this study:

(1)Classic findings of aortic dissection are often absent

(2)Don’t rely on textbook presentations

KNOW THE FOLLOWING PRESENTATIONS WELL:

(1) TAD and Stroke-Neurologic deficits have been noted to occur in approximately 18-30% of TAD cases. In 5-10% of the cases, TIA/CVA symptoms are seen. Remember that patients who present with stroke and the inability to communicate may not be able to give a chest pain history. If you are about to infuse tPA for a suspected ischemic CVA, stop for a moment and convince yourself that the patient doesn’t have an aortic dissection.

As a rule of thumb, consider TAD in the following scenarios:

  • Chest pain and any neurologic symptoms (CVA, dysphagia, etc.)
  • Chest pain and limb paresthesia

(2) Painless TAD and Syncope-Patients with TAD do not always present with chest pain. In the IRAD study, 2.2% of TAD cases were painless. Other studies have shown that as many as 15% of TAD cases are painless. The point is this: Absence of pain does not rule out the diagnosis. Patients may also present after a syncopal episode. The underlying pathophysiology of syncope is related to proximal rupture into the pericardium with resultant tamponade. Add TAD to your differential diagnosis of unexplained syncope.

(3) TAD and Paralysis-Spinal cord involvement has been documented in 10% of TAD cases and is thought to be due to perfusion abnormalities in the greater radicular artery (artery of Adamkiewicz), a large branch from the aorta that perfuses a large portion of the thoracic and lumbar spine.

Consider TAD in the following scenarios:

  • Chest pain and limb (particularly lower extremity) weakness or paresthesia
  • Chest pain and spinal cord syndromes: transverse myelitis, progressive myelopathy, paraplegia, quadriplegia, and anterior spinal cord syndrome.
  • Unexplained lower extremity weakness (without chest pain)

(4) TAD and Myocardial Infarction-The coexistence of TAD and myocardial infarction occurs in about 1-7% of cases of TAD. Due to greater shear forces against the right lateral aortic wall, right coronary ostial occlusion and malperfusion is more common.

(5) Isolated Abdominal Pain-Many case reports have been published over the last several years documenting the fact that TAD (proximal or distal) may present with isolated abdominal pain. Given the frequency of abdominal pain ED visits and the extensive differential diagnosis, picking up TAD-associated abdominal pain may be difficult. In general, have a very low threshold to obtain a CT scan to evaluate for TAD.

Consider TAD in the following scenarios:

  • Unexplained abdominal pain in the presence of hypertension
  • Combination of chest and abdominal pain
  • Abdominal pain and cocaine use
  • Unexplained abdominal pain and an “ill-appearing” patient

(6) TAD and “the other complaint”-Many cases of missed TAD have been shown to be related to the failure to address two or more seemingly separate complaints.

Here are a few examples of real cases from my institution:

  • A 37 year-old male presented with a complaint of chest pain and left lower leg pain and numbness. His only medical problem was hypertension. His BP on presentation was 180/100. The physician who saw this patient essentially dismissed the leg complaint and thus missed a valuable opportunity to make the diagnosis of TAD. The patient had a type- B aortic dissection and subsequently died.
  • A 49 year-old male presented with a complaint of substernal chest tightness and transient decreased vision in his left eye.The treating physician completely ignored the visual complaint and addressed the chest pain. Chest pain and blindness, or transient visual disturbance, is actually described in the literature as a presentation of TAD. Once again…chest pain in combination with “the other complaint.”
  • A 29 year-old female 8 months pregnant presented with blurry vision and shortness of breath. The patient ended up dying of a ruptured, proximal aortic dissection. Pregnancy is a risk factor for TAD, and every pregnant patient with chest, back, or chest and back pain may very well have a TAD. Authorities on this subject would argue that a diagnosis of TAD simply could not be made in a case such as this one. It is mentioned only to highlight the risk factor and mention that TAD is more common in the 3rd trimester.

Consider TAD under the following circumstance:

  • Chest pain combined with “the other complaint” (especially neurologic symptoms)

(7) Cough, Hoarseness, and SVC Syndrome-Thoracic aortic dissection may present with symptoms that are subtle, vague, or not easily attributable to aortic disease. Cough has been described and is thought to be secondary to compression of the left main-stem bronchus by the aortic hematoma/dissection. Proximal aortic dissection may also cause recurrent laryngeal compression and lead to hoarseness (Ortner’s syndrome). Lastly, proximal dissections may rarely compress the superior vena cava and lead to clinical signs/symptoms of SVC syndrome.

(8)Young patients with TAD-Most patients with TAD are between the ages of 50-70. However, emergency physicians are seeing more young patients (even without connective tissue disease) with the disease. A key mistake is to not consider the diagnosis simply because the patient is young.

  • Young patients can have acute aortic diseases such as TAD.

Consider the case of Jonathan Larson, writer of the Broadway musical Rent.

  • Jonathan Larson died at the age of 35 from a type A thoracic aortic dissection. He was seen three separate times in an emergency department in New York before he was found dead in his apartment by his roommate. Mr. Larson presented initially with a complaint of severe chest pain and was diagnosed with food poisoning, despite no symptoms of nausea, vomiting, or diarrhea. What is interesting is that his chest x-ray showed a significantly widened mediastinum. He later presented with chest and back pain. He was quoted as saying, “You’d better call 911. I think I am having a heart attack.” Mr. Larson was later diagnosed as having Marfans disease.

Why was the diagnosis of TAD not entertained? Probably the most important reason was the fact that Jonathan Larson was only 35 years old and had no known medical problems.

Why do we miss the diagnosis?

Daniel Sullivan in his work, “High-Risk Acute Care: The Failure to Diagnose…”, has outlined several reasons for the delay or missed diagnosis of TAD. Having an understanding of these reasons may help us do a better job at detecting this disease early.

Here are the reasons cited by Sullivan for a delay or missed diagnosis:

  • The “legal fiction”-This refers to cases of TAD that simply cannot be made. Like other diagnoses in medicine, not all cases of TAD can be diagnosed.
  • Failure to evaluate risk factors for TAD.
  • Failure to integrate patient complaints-For emergency physicians, this may very well be one of the most important. All of us are familiar with patients who present with seemingly unrelated complaints, such as chest pain and leg pain. A review of missed TAD literature highlights the fact that many cases have been missed because the treating physician failed to address all of the patient’s complaints. Also, the EP may assign a diagnosis that simply doesn’t make sense.
  • The “obvious miss” and inadequate knowledge base.
  • Inadequate knowledge of atypical and subtle presentations-Examples include unexplained syncope, chest pain and lower extremity weakness, painless TAD, chest pain and stroke-like symptoms.

How can you decrease your chances of missing the diagnosis?

In reality, there simply is no way that every case of aortic dissection can be diagnosed in the emergency department. There are, however, steps that can be taken to decrease the chance of missing this lethal aortic disease.

  • Know the subtle and atypical presentations well. Think beyond classic textbook descriptions and think of TAD more often.
  • Perform a detailed risk factor profile for TAD on every chest pain patient. Detection of one risk factor may be all you need to pick up the diagnosis.
  • Decrease your own threshold to obtain CT scans in chest pain patients. Increasingly, isolated anterior chest pain has been associated with TAD. If a patient isn’t responding to ACS therapy or something doesn’t seem right with the patient, obtain a CT scan.
  • Approach every chest pain patient as if they could have a TAD and convince yourself the patient doesn’t have it.
  • Realize that young patients without connective tissue disease can have TAD.

What should we be documenting on chest pain patients?

In order to decrease the chance of successful litigation for a missed or delayed diagnosis, emergency physicians should consider documenting certain key features of the history and physical examination. In essence, a chest pain chart should look like the search for lethal chest pain entities, acute coronary syndromes, pulmonary embolism, and thoracic aortic dissection.

Consider documenting the following in all chest pain patients:

  • Risk factor profile for TAD (HTN, cocaine, family history, etc)
  • Blood pressure in both arms (equal)
  • Pulses (symmetric)
  • Absence of aortic murmur
  • Absence of marfanoid body habitus

Limitations of the physical examination and imaging studies

Physical examination and imaging studies are important in any patient with chest pain but both have significant limitations.

What about the physical examination?

  • Bilateral blood pressure measurement-Traditionally, physicians have relied on differences in bilateral arm blood pressure to help detect TAD. Recent data over the last few years, however, has shown that as many as 19% of the population may have arm differences greater than 20 mm Hg. One high quality prospective, observational study by Von Kodolitsch et al. did show that a blood pressure differential > 20 mm Hg was an independent predictor of TAD. Measurement of bilateral blood pressures may very well be an important risk management strategy but normal or abnormal values do not rule in or out the diagnosis. The other important thing to mention is that only about 50% of patients who present with TAD are hypertensive. The other half are either normotensive or hypotensive.
  • Aortic murmur-The presence or absence of a diastolic murmur is not particularly helpful. Approximately 1/3 of patients with TAD will have this finding.
  • Pulse deficit-Noted to be present in only about 15% of cases of TAD.

What about the chest x-ray?

  • According to data from the IRAD study, up to 12 % of patients with TAD had a normal chest x-ray (completely normal). Approximately 37 % had no evidence of mediastinal widening.
  • Numerous other studies have found that the chest x-ray may be normal.
  • A normal chest x-ray might help lower your suspicion for TAD, however.

What’s new in the literature?

A number of interesting developments have occurred over the past few years.

  • D-dimer-Small studies have suggested that all cases of TAD were found to have an elevated D-dimer result. Could D-dimer in combination with another study, such as a chest x-ray, be used to rule out TAD? This clearly isn’t ready for prime time, but there are researchers looking into this as a potential strategy.
  • Soluble elastin fragments-These fragments are released into the circulation in TAD and have been shown in small studies to be helpful in diagnosing TAD. Again, we are not ready to begin testing for this quite yet, but be on the look out for this in the future.
  • Blood pressure-Recent studies have shown that normal patients without aortic dissection may have significant differences in bilateral blood pressure values. On the other hand, many patients with TAD have differences < 20 mm Hg. Use caution when using these values to make clinical decisions.

References

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