Aortic Dissection in a 63-year-old Woman

A 63-year-old woman with a history of GERD is sent to the ED by her primary care physician for new onset of atrial fibrillation. She has also had 9 days of intermittent right-sided subcostal pain and had gallstones diagnosed by ultrasound 4 days ago done at another ED. The patient states that the pain lasts for hours, is sharp, and radiates to the right scapula and mid-chest. It seems to be worse after meals or with activity. She also vomits when the pain gets more severe. She denies palpitations, trouble breathing, syncope, or near syncope.

On exam she is afebrile with an irregular pulse of ~120 beats/min, a blood pressure of 162/98 mm Hg, a normal pulse oximetry reading and normal respiratory rate. She appears in no acute distress and rates her current pain as 4/10. Head and neck exam findings are normal without icterus. She has clear lungs and an irregular heart beat with a soft murmur. Her abdomen is nontender without mass. Extremities are warm with good pulses and without edema.

Laboratory data show normal liver function, troponin, and chemistry but a WBC count of 17 and a very low TSH. An ECG shows atrial fibrillation at a rate of 124 beats/min with no ischemic changes. Her portable chest x-ray is shown in Figure 1 and is read by the radiologist as normal.

She is started on diltiazem for rate control and is seen by the hospitalist for admission orders, a general surgeon for her gallbladder, an endocrinologist for her hyperthyroidism, and a cardiologist for the atrial fibrillation. They all recommend starting heparin and admitting the patient to telemetry and agree they will consider cholecystectomy once her heart and endocrine conditions are stabilized.

Do you follow their recommendations?

Answer:  

Not until you get bilateral blood pressures and a CT of the chest as she has a slightly wide mediastinum. This suggests the possibility of aortic dissection.

Obtaining historical information from this patient was very challenging as was responding to her many questions in the ED. Though it was tempting to start the heparin and let her doctors finish their work-ups after she was admitted, her LFTs and troponin were normal and there was still no solid explanation for her pain despite a bladder full of gallstones. Aortic dissection was considered unlikely but with abdominal, chest, and back pain, it had to be ruled out, especially before starting heparin. To make matters more challenging the patient was allergic to IV contrast. A transesophageal echocardiogram (TEE) was requested but the cardiologist who had seen her refused and requested an MRI instead. This was deemed reasonable as she had been in pain for well over a week. Her MRI (Figure 2) and MRA (Figure 3), demonstrate a type B aortic dissection starting at the left subclavian artery.

Figure 2. MRI shows type B aortic dissection starting at left subclavian artery.Discussion
Aortic dissection is a rare, frequently fatal condition, which is often diagnosed late, as the presentation can mimic a number of more common diseases. Typically there is some type of chest and/or upper back pain, but pain may occur anywhere in the body and is even absent in about 10% of cases. Pain may be exertional or start at rest, but is usually constant, unlike in the case presented here. Other symptoms may include ischemic manifestations that may be transient and affect the brain, spinal cord, or limbs. Unusual symptoms caused by mass affect may include SVC syndrome, dysphagia, and even hoarseness from stretch on the recurrent laryngeal nerve. Physical exam is most commonly normal, but abnormal blood pressure, the soft murmur of aortic insufficiency, or pulse deficits may occur (see summary Table below for frequencies of these findings). Risk factors for dissection may or not be present and are also listed below.

Figure 3. MRA demonstrates type B aortic dissection.Complications of aortic dissection include stroke or TIA, CHF from aortic regurgitation, limb or cord ischemia, bowel ischemia, and ischemic renal failure. More immediately life threatening complications include cardiac tamponade, myocardial infarction, and massive hemothorax. Mortality is estimated at 2% per hour, making rapid diagnosis and treatment critical. However, not infrequently patients survive the initial episode only to present days to weeks later--often in the office setting, as in this case.

Initial diagnostic imaging should be with chest films, but this is only about 65% sensitive and has unknown specificity. CT angiogram will be the diagnostic test of choice in most scenarios: sensitivity and specificity are both in the mid to high 90s. If there is a contraindication to CT then TEE or MRI are both very sensitive, but unfortunately both have the downside of limited availability and longer delays to obtain results.

Initial treatment should be started before diagnostic imaging if suspicion is high and includes lowering the pulse rate with beta-blockers or other agents followed by lowering the blood pressure. It is critical to use the limb with the highest blood pressure when titrating vasoactive agents as this limb will be the most accurate measurement of the true central blood pressure. Further treatment may be medical and/or surgical depending on the location of the dissection and any complications discovered (details in Table).
 
 

↓BP, 33%; ↑BP, 35%; aortic insufficiency murmur, 30% 
Pulse deficit: 20% (20% of normal patients have BP difference >20 between arms).
Compression/stretch: SVC syndrome, stridor, dysphagia, hoarseness.