Volume 3, Case 12
Andrew K. Feng, M.D.
Kapiolani Medical Center For Women And Children
University of Hawaiʻi John A. Burns School of Medicine
A 14 year-old boy is brought into the Emergency Department just after midnight after having woken from sleep approximately ten minutes ago because of severe back pain and abdominal pain radiating into his throat. The pain is also described as "pressure" pain. No history of trauma or similar attacks of pain in the past. No other concurrent illnesses or symptoms.
Exam: VS T35.8 C, P86, R32, BP 110/74, O2 saturation 100% on room air. Weight approximately 70 kg. He is obviously writhing in intense pain. Heart regular without murmurs. Lungs sounds are clear on auscultation with equal breath sounds bilaterally. Peripheral pulses are normal and equal bilaterally. Skin is warm and dry. Abdominal exam is also unremarkable with good bowel sounds, and no palpable masses or costovertebral tenderness.
What would you do next?
At this point, the father settles down enough to be able to give you more of a coherent history. He relates to you that he had another son who had died at about 12 years of age from an aortic dissection and subsequent rupture. A chest radiograph is obtained.
View CXR.
The CXR is read as being relatively normal although there may be a suggestion of some mediastinal widening. A CT of the chest and abdomen is ordered.
View CT.
The CT of the thorax shows an aortic dissection extending from the aortic root to at least the level of the renal arteries. In the upper image taken through the aortic arch, an intimal flap is visible in the aortic arch (black arrow). In the lower image taken through the abdomen, the intimal flap is more obvious in the descending aorta (black arrow). There also appears to be an infarcted area in the left kidney. An aortogram is ordered.
View aortogram.
This contrast study shows the catheter tip at the aortic root. The aortic root is irregular. Since contrast does not enter the carotid vessels, the catheter is presumed to be in the false lumen of the aortic dissection which is dilated at the aortic root. An imprint of the brachiocephalic artery (a non-contrast filled vessel impinging on the contrast filled false aortic lumen) is seen overlying the aorta. Subsequent views revealed a complex flap of the dissection in the descending aorta.
Aortic dissection is rare, but catastrophic when it occurs. Therefore, a high index of suspicion and appropriate early intervention are paramount if the patient is to survive. The majority of non-traumatic causes of aortic dissection occurs in the older population, and hypertension is the overwhelming leading risk factor. Those who develop aortic dissections under 40 years of age more commonly have an underlying connective tissue disorder, congenital heart defect, or are pregnant. For the purposes of this teaching case, most of the discussion will focus on the younger population.
Classification of aortic dissection is either by the DeBakey or the Stanford types. The former was classified first and divides the types into those involving the ascending, transverse, and/or descending aorta (Type I), those involving the ascending aorta only (Type II), and those involving the descending aorta only (Type III). The latter classification distinguishes dissections mainly by the involvement of the ascending aorta: any dissection involving the ascending limb is Type A, and those that involve just the descending aorta are Type B. Approximately 75% of the cases are of Type A, which also is more commonly associated with the younger patients and those with connective tissue and congenital heart disorders.
Pathophysiology centers mainly on the integrity of the vessel wall. Most cases show a weakening in the media including lesions involving smooth muscle, elastin and collagen. In Marfan's Syndrome, medial cysts with mucopolysaccharide deposits, disarray of muscle fibers, and fragmentation and loss of elastin fibers can be seen histologically in the face of dissection. Furthermore, the aortic root is made up of approximately 60% elastin and is the most common point of dilatation and dissection in these patients. In one study, up to 60% of infants and children under 4 years old were found to have a certain degree of aortic dilatation (Sisk). Other familial conditions without Marfanoid features but presenting with aortic dissection include anuloaortic ectasia, familial dissecting aneurysm, Ehlers-Danlos Syndrome, and osteogenesis imperfecta. In addition, history of hypertension or a specific triggering event is often absent for this population.
Patients may present with a wide range of signs and symptoms. One of the most common (90%) as well as the most impressive complaints is excruciating pain. This is often described as being "cutting," "ripping," or "tearing," and originating in the anterior chest, although less commonly in the interscapular, epigastric, and lumbar areas. Back pain also tends to correlate more with distal dissections. Flank pain may suggest involvement of the renal arteries. In addition, the pain will usually begin suddenly and will persist unremittingly, often inciting the fear of death in the patient.
Cardiac involvement depends on the site of dissection and the location of the external rupture. One of the distinguishing features of aortic dissection is an elevated blood pressure, which may seem contradictory to what one would expect. This is, in part, due to renal ischemia and severe stress. Hypotension, on the other hand, occurs in approximately 20% of ascending dissections and is an ominous sign as it suggests a significant external rupture. In fact, rupture into the pericardial sac is, unfortunately, relatively common and can result in pericardial tamponade. Syncope may be a presenting symptom or sign and almost always reflects leaking into the pericardium. Because of this, syncope is usually an ominous sign and, therefore, warrants prompt surgical intervention. Aortic dissection also often leads to heart failure secondary to aortic incompetence. This may be exhibited by aortic regurgitation and can be appreciated as a new diastolic murmur.
Peripheral pulses may also be affected, depending on the extent of the dissection. Pulses in one or more extremities may be diminished or even absent. It is important, therefore, to evaluate the quality of pulses (and, possibly, the blood pressure) in all four extremities.
Neurologic changes are actually very common occurring approximately 40% of the time. Dissections involving the carotid arteries may result in encephalopathy or even stroke. Dissections extending through branches supplying the spinal cord may also lead to paraplegia. Aortic dilatation or hematoma within a dissection may also compress the recurrent laryngeal nerve resulting in Horner's Syndrome and/or hoarseness.
The most critical preliminary diagnostic test for suspected aortic dissection is a chest radiograph. Aortic shadows are seen in approximately 80-90% of the time. Other initial tests may include a hemoglobin and hematocrit, with a low value suggesting an external rupture; a urinalysis, with hematuria reflecting renal ischemia; and an electrocardiogram to detect myocardial ischemia.
Once a dissection is suspected, it may be confirmed by one of the following tests. Transesophageal echocardiography is gaining popularity as a quick and sensitive test that can be performed at the patient's bedside. One study shows a sensitivity of 99% and a specificity of 98% with results of the test provided within 20 minutes (2). An echocardiogram will also provide information on myocardial function, valvular insufficiency, and any pericardial effusion.
Computerized tomography is also gaining favor as it is highly sensitive and specific and readily accessible in most centers. The main disadvantage concerns the time necessary to perform these tests. However, ultrafast CT has improved the time factor as well as heightened the accuracy. However, the traditional gold standard, has been retrograde aortography, which involves the use of contrast to determine the full extent of the dissection as well as involvement in arterial branches. Magnetic resonance imaging also is an option, but the length of time necessary to perform the test and the accessibility are the main limiting factors.
The mainstay of medical treatment revolves around controlling blood pressure (systolic and pulse pressure). Antihypertensives should be instituted immediately if the blood pressure is high, or as soon as possible once the pressure is stable and the diagnosis is confirmed. The combination of sodium nitroprusside and propranolol is most commonly used. Labetolol can also be used as monotherapy or in place of propranolol.
Surgical intervention should be started emergently in aortic dissection if pericardial tamponade is suspected, if there are any signs of shock, or if the dissection is progressing.
Outcome remains relatively poor, but is improving with a current mortality rate of 5-30%. Death is mostly due to hemorrhage and heart failure with one study finding 93% of deaths secondary to cardiovascular complications (5). For patients with Marfan's Syndrome and other connective tissue disorders and congenital heart diseases, prevention with routine cardiac evaluations as well as elective, prophylactic surgical intervention (when indicated) are currently the best means of minimizing poor outcome.
In summary, aortic dissection and rupture is very rare, but must be considered in patients presenting with acute, intense chest pain. A good history and physical exam should lead the examiner to suspect this diagnosis, and successful outcome will be determined by timely intervention.
References