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The Killer Aorta: Diagnosing Thoracic Aortic Dissection

Blog_TheKillerAortaTAD_ChestPainManBlackHoldWall_260x200px.jpgThoracic aortic dissection (TAD) is one of the most dramatic and life-threatening conditions encountered in all of medicine. Every year in the United States, there are an estimated 6,000 to 10,000 cases of TAD. Since it is an uncommon condition compared to the 5 million ED chest pain visits and more than 1 million acute myocardial infarctions, most physicians have diagnosed and treated only a few patients with TAD during their careers.When combined with a condition like TAD that has such a highly variable presentation, this limited clinical exposure contributes to the potential for delayed or missed diagnosis.

Ten medical organizations collaborated to publish a comprehensive report in 2010 entitled “Guidelines for the Diagnosis and Management of Patients with Thoracic Aortic Disease.” This report provides evidence-based guidelines regarding imaging modalities, risk factors, clinical presentations, evaluation and treatment of existing or suspected disease of the thoracic aorta.

These guidelines acknowledge the difficulty of making the diagnosis of TAD, particularly when the patient presents with atypical symptoms and findings. The report focuses squarely on the risk and safety issues related to TAD:

"This issue [of TAD] has come under greater medical-legal scrutiny, and specific cases have been widely discussed in the public domain. Widespread awareness of the varied and complex nature of thoracic aortic disease presentations has been lacking, especially for acute aortic dissection."

Common Reasons for Missed or Delayed Diagnosis

tom-syzekThe alleged failure to diagnose TAD can lead to a medical malpractice claim. Although the circumstances surrounding each case are unique, there are recurrent reasons that the diagnosis is missed or the management is delayed:

  • Failure to obtain an adequate history
  • Failure to recognize the classic presentation
  • Failure to perform a risk factor analysis specifically for TAD
  • Failure to recognize physical findings consistent with TAD
  • Failure to include TAD in the differential diagnosis, particularly in younger patients
  • Failure to integrate the symptoms and signs of multiple organ involvement of TAD
  • Failure to order appropriate diagnostic studies
  • Inadvertent treatment of other conditions that mimic TAD

Risk Factors

Risk factors associated with an increased risk of TAD include:

  • High-Risk Conditions: Marfan syndrome, connective tissue disease, family history of aortic disease, aortic valve disease, recent aortic manipulation, known thoracic aortic aneurysm
  • High-Risk Pain Features: Chest, back or abdominal pain that is abrupt or severe AND described as ripping, tearing, sharp or stabbing
  • High-Risk Exam Features: Pulse deficit, systolic BP differential, focal neurologic deficit in conjunction with pain, new murmur of aortic insufficiency, hypotension or shock state

 Signs & Symptoms of TAD

Patients may present with any combination of the following; think of TAD when a patient presents with signs and symptoms of compromised perfusion to one or more organ systems:

  • Cardiovascular: Pain in the chest, back or abdomen; dyspnea
  • Cerebrovascular: Syncope, stroke, altered mental status
  • Limb: Pain, paresthesias, pulse deficits
  • Mesenteric: Abdominal pain, GI hemorrhage, diarrhea
  • Renal: Hematuria, oliguria, anuria
  • Spinal: Paraplegia

 Differential Diagnosis – Mimics of TAD

Compared with the following conditions that can mimic TAD, aortic dissection may have the highest mortality rate: between 1% and 2% per hour for the first 24 to 48 hours.

  • Acute coronary syndrome
  • Pulmonary embolism
  • Tension pneumothorax
  • Pericarditis with tamponade
  • Pneumonia

Imaging and ECG in TAD

The chest X-ray and ECG are abnormal in the majority of TAD cases. The abnormal findings are not diagnostic but should arouse suspicion for TAD. Conversely, a normal chest X-ray or ECG does not rule out TAD. The diagnosis of TAD is made by CT, transesophageal echo or MRI.

Risk Pearls for TAD

  1. Document the presence or absence of high-risk conditions, pain features and exam features.
  2. TAD may present with any combination of pain in the chest, back or abdomen.
  3. Pain that migrates over time from the chest to the neck or back and then to the abdomen should arouse suspicion for TAD.
  4. Continuing chest pain in the face of a normal ECG and cardiac enzymes should arouse suspicion for TAD.
  5. TAD may present with neurologic, cardiac, GI, renal and peripheral vascular symptoms.
  6. Normal blood tests, ECG and chest X-ray do NOT rule out TAD.
  7. Mortality increases with every passing hour.
  8. Sometimes the presentation of TAD is so unusual that no reasonable practitioner would suspect the diagnosis.

References & Resources

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Categories: Diagnostic Error, Emergency Medicine, Patient Safety, Urgent Care

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