Q4 Urgent Caring- Case Study 1-Aortic Dissections

Pete Baker, PA-C

A 32-year-old female presents with six months of atypical chest pain. She describes the discomfort as a mild, random sensation radiating left to right across her mid-sternal region. This occurs with and without exertion and lasts several minutes with days between episodes. The patient admitted no other neurovascular or cardiopulmonary symptoms, and she denies pertinent medical history. Her reasoning for waiting six months for care was a fear of doctor’s offices during the COVID-19 pandemic. Her thought was that she may have strained a muscle in her chest running after her two lively children.

A healthy young mother, who has taken care of herself, was an alert female who was a good historian of her concern.  Her past medical history included two healthy pregnancies resulting in two live births.  She has no first-degree family history of early cardiac disease, and she takes no medications. No outward signs of illness could be gleaned from her appearance. 

She was alert and awake, normotensive, normothermic, non-tachycardic, and non-diaphoretic. Her skin was without cyanosis or pallor. She denied active chest pain at the time of the exam. The physical exam revealed a faint systolic murmur heard over the aortic region. She reports no knowledge of a murmur. The remainder of the exam was normal.

Her chest X-ray showed a minimally tortuous aorta with a normal cardiac silhouette and no lung infiltration. Her electrocardiogram showed sinus rhythm without ectopy or ST-segment deviation. She remained complaint-free through the entire visit.

An echocardiogram was recommended to investigate the newly found heart murmur, as well as a follow-up with her family doctor and a referral to cardiology. Detailed emergency room precautions were given. The patient was discharged and directed to the hospital’s imaging center where a same day echocardiogram had been arranged.

The same day, the trans-thoracic echocardiogram indicated an ascending aortic dissection which was verified by the radiologist. The patient was then emergently sent to the ED. Cardiothoracic surgery was performed, repairing the aortic defect. The patient did well post-operatively and had no complications.

Discussion
Aortic dissection (AD) is the separation of the layers within the aorta as the artery exits the myocardium. Microtears in the intima of the artery begin this cascade. These tears are formed from sheering forces created by high pulsatile pressures of oxygenated blood pummeling through the aortic valve. This constant pounding, called the water-hammer effect, causes mechanical trauma, and allows a false lumen to form between the layers of the aorta. The intima and media begin to separate creating this false lumen. The buildup of blood and pressure slowly, or in some cases rapidly, expands this false lumen. Acute AD occurring within two weeks is exceptionally lethal. Chronic AD lasting over two weeks has a better, if yet still guarded prognosis. The damaged area and false lumen will eventually result in life-threatening disease. 

Sudden onset of severe chest pain with a ripping tearing sensation extending to the mid-scapular region is a hallmark symptom.¹ However, some cases provide no such red flag, and a high index of suspicion is needed. 38% of AD cases are misdiagnosed.¹ Approximately 75% of AD cases are discovered in patients aged 40 to 70, with peak incidence in ages 50 through 65.¹ 

AD may be acquired, genetic, hereditary, or traumatic. Acquired causes can be linked to coronary artery disease, hypertension, and hyperlipidemia.² Genetic conditions include Ehlers-Danlos, Marfan and Turner syndromes.² Hereditary factors include a first-degree relative with a history of thoracic dissection of their aorta.² Traumatic deceleration forces, such as high-speed automobile crashes also contribute to AD.² 

Demographics
Thankfully, AD is an uncommon condition with only 21 cases per one million persons in the Unites States (2019). However, it comes with a high mortality rate of 40%, making this a cannot miss diagnosis.^2,1 In acute AD this mortality rate increases 1% per hour, making a rapid time to diagnosis and treatment imperitive.¹  

AD strikes men more than women, however women are usually diagnosed at a later age leading to a greater mortality rate.¹ The elderly and those of non-Hispanic African heritage are at greatest risk of succumbing to this condition.² 

Patients with connective tissue disorders such as Ehlers-Danlos or Marfan syndrome are especially vulnerable to AD. The endothelial cells making up the intima are far more easily damaged in connective tissue diseases. Structural instability of the aortic wall combined with increased intima wall tension can lead to AD.¹ Hypertensive patients also are at higher risk for developing AD.¹ The increased systolic pressure of oxygenated blood being jettison from the left ventricle eventually takes its toll on the delicate lining of the aorta increasing risk for a tear. 

Classification
There are two classification systems for AD. In the DeBakey system, the origin of the damaged intima is differentiated. DeBakey type I involves the ascending aorta with progression towards the aortic arch.¹ DeBakey type II involves only the descending aorta moving distally towards the thoracic aorta.¹ This system is a method to determine the precise location of the intima damage, thus allowing a cardiothoracic surgeon to make an informed decision pertaining to the repair of the AD.

In the Stanford system, type A is the ascending aorta and type B the descending aorta.¹ Stanford also delineates non-A and non-B (involving the aortic arch).¹ Type A can be further classified by entry and malperfusion (TEM) perimeters. Type A, B, non-A/B is noted, then 0 for non-visible entry in the lumen, 1 for ascending aorta, 2 for aortic arch, 3 for descending aorta.³ Malperfusion is 0 for none, 1 for coronary, 2 for supra-aortic vessels, 3 for visceral/renal/lower extremities.³ In addition, a + if malperfusion is clinically evident or a – if only a radiological finding.

Complications of DeBakey I (Stanford A) can include a retrograde progression of the AD, leading to prolapse of the aortic valve with aortic regurgitation, coronary artery obstruction and pericardial effusion.³ This type of AD is more severe and life threatening, often requiring immediate intervention. DeBakey type II (Stanford B) complications consist of malperfusion of the spinal cord, gastrointestinal tract, kidneys and lower extremities.³ Due to their chronic nature a more conservative non-surgical approach is indicated.   

Diagnosis
The most common symptom in AD is acute chest pain that radiates to the abdomen or back.¹ A ripping/tearing sensation in the thoracic/abdominal region is a pertinent descriptor from patients when describing their pain.¹ Chest pain is noted as less likely in DeBakey II (Stanford B), where pain would be more diffuse over the back and abdomen.¹ Conversely, 15% of DeBakey I (Stanford A) present with syncope.¹ Regardless of presenting symptoms, a high index of suspicion is needed when approaching the atypical chest pain patient with a possible AD. 

A computerized tomography (CT) scan of the chest is the gold standard imaging for AD.¹ Magnetic resonance angiography (MRA) is more sensitive and specific, however, may take longer and is limited by patient allergies and renal function.¹  Trans-thoracic echocardiogram (TTE) should be reserved for stable out-patient investigation of atypical chest pain or used in the emergency setting only while awaiting a CT scan of the chest.¹ Blood work such as CRP and D-dimer are used prognostically (normal results equal a good outcome; abnormal results a poor outcome).¹

Treatment
In DeBakey I (Stanford A), due to the close proximity to the myocardium, emergent surgery is indicted.¹ This is due to the anatomical change as AD progresses retrograde into the heart, affecting the aortic valve.¹ Surgical goals are to obliterate the false lumen created by the dissection and placement of synthetic graft material to strengthen the intima.¹ DeBakey II (Stanford B) treatment aims are completely different. Goals are centered around reducing blood pressure, lowering pulse and controlling pain.¹ Beta blockers and calcium channel blockers are the mainstay pharmacological treatment for these patients.¹   

Conclusion
Fortunately, aortic dissection is an uncommon event in the United States. However, due to the high rate of mortality, early detection is key in preventing death in these patients. All patients presenting with chest pain should have AD in the differential diagnosis. With 2,000 new cases every year, aortic dissection is one condition that cannot be missed.

References
¹ Sayed A, Munir M, Bahbah M. Aortic dissection: a review of the pathophysiology, management and prospective advances. Current Cardiology reviews 2011 Jul 20; 17(4). doi:10.2174/1573403X16666201014142930. https://www.ncbi.nlm.nih.gov/pmc/articles/pmc8762162.

² Nazir S, Ariss R, Minhas A, et al. Demographic and regional trends of mortality in patients with aortic dissection in the United States 1999 to 2019. JAMA 2022 Apr 5:11(7):e024533. doi 10.1161/JAHA.121.024533.

https://www.ahajournals.org/doi/10.1161/JAMA.121.024533.

³ Bach D. Review on aortic dissection: key points. American College of Cardiology Jan 2023. https://www.acc.org/Latest-in-cardiology/ten-points-to-remember/2023/01/03/20/08/acute-aortic-dissection.