Developed by the Professional Advisory Board National Marfan Foundation in cooperation with the New York State Department of Health.
What constitutes and aortic dissection?
An aortic dissection is a tear in the inner layer of the aortic wall. This allows blood to enter and separate the inner and outer layers of the vessel (Figure 1). Dissection can weaken the outer wall, resulting in rupture or formation of an aneurysm; occlusion of aortic branch vessels causing myocardial infarction, stroke, kidney failure, bowel ischemia, paraplegia, or limb ischemia; and disruption of the aortic valve, resulting in valvular insufficiency and cardiac failure.
Figure 1. Aortic dissection. In Marfan syndrome, most tears in the aortic wall occur just above the aortic valve.
What are the symptoms of aortic dissection?
The primary symptom of an aortic dissection is severe pain usually in the chest (front, back or both), but occasionally in the abdomen when the tear begins in that part of the aorta. However, dissections can also cause a variety of other symptoms: pain, pallor, pulselessness, parathesiae and paralysis (the 5 P's). If a branch of the aorta is blocked, weakness in one or both legs or arms may be evident. In rare situations, the physical symptoms of a stroke or transcient ischemic event could be a result of a dissection. There can be fever, as well, if a dissection has gone on for a while, and there is slight leakage of blood through the thinned wall of the torn section of the aorta or, occasionally, if there is a clot within the aortic wall. A number of other symptoms can occur due to a dissection, but they are not that typical. In addition, the symptoms of a dissection can be mimicked by other causes.
For a person with Marfan syndrome or another aortic disease, there are no consistent, standard symptoms of an aortic dissection. However, any type of pain in the chest, back or abdomen that is along the midline of the body—in front, back or both—that is either especially severe or sharp and has a burning or tearing quality, or is relatively severe and totally different that has ever been felt before, has the possibility of being an aortic dissection and should be evaluated promptly. If the individual's primary care physician who, it would be hoped, is familiar with Marfan syndrome, is not available, the local emergency room may be much more accessible and be able to act more quickly.
If chest or abdominal pain is experienced by a patient with Marfan syndrome who has already had aortic surgery, it may or may not be related to the portion of the aorta that has already been repaired. There is a propensity for a patient with Marfan syndrome to develop new dissections or aneurysms, either near previously repaired segments of the aorta or in other parts of the aorta.
Why is emergency diagnosis and treatment of aortic dissection an important issue?
An aortic dissection that does't stop tearing will ultimately become a fatal rupture. In fact, there is an 80-90 percent fatality rate associated with acute aortic dissection originating near the heart without urgent surgical intervention by an experienced physician. This makes it essential to evaluate symptoms that could be related to a dissection even when there is a 90-95 percent chance that the patient does not have an aortic dissection. Even a five percent risk of a missed dissection results in a substantial number of deaths.
Although aortic dissection is uncommon, it is not rare. However, when it is does occur, it is commonly catastrophic. Because it is not a reportable condition, information on the incidence of aortic dissections is scant. Based on available medical information, there are probably 5,000-10,000 dissections a year in the United States. However, the number may be underreported since dissections that do not result in death or cardiovascular surgery may be recorded under a different diagnosis, such as chest or abdominal pain. The number of dissections may be also underreported because so few autopsies are conducted, and many deaths are attributed to "heart attack" or "sudden death," when the cause is actually a dissection.
Unless someone has a known diagnosis of Marfan syndrome—a genetic disorder of connective tissue—or very obvious physical characteristics that would indicate Marfan syndrome or another predisposing condition, aortic dissection would rarely be the first diagnostic consideration for an emergency room patient with chest pain. The misdiagnosis of people with clear characteristics of Marfan syndrome further compounds this problem.
Which populations at risk for an aortic dissection are emergency physicians most likely to encounter?
People with Marfan syndrome are among those at high risk for aortic dissection. In addition, other people who have known or unknown enlargement of the aorta, bicuspid aortic valves, high blood pressure, or have family history of aortic dissections are also at substantially increased risk for aortic dissections.
Women with Turner syndrome, a chromosomal condition causing short stature and infertility, are also predisposed to ascending and descending aortic dissections. These groups merit closer attention in an emergency department.
Aortic dissection is the primary cause of death in individuals with Marfan syndrome. Through education of the medical and lay communities, it is hoped that individuals with enlarged aortas will have medical and surgical intervention initiated before the aorta tears or ruptures.
Physicians in the emergency room should be aware of the classic features of Marfan syndrome:
- Disproportionately long arms, legs, fingers and toes
- Pectus carinatum
- Pectus excavatum
- A very marked curvature of the spine.
- Presence of lens dislocation may also be a telltale sign of Marfan syndrome.
When should an aortic dissection be considered as a diagnosis?
It is important to recognize signs of aortic dissection. It is the leading cause of mortality in people with Marfan syndrome; and it is relatively rare in younger individuals without severe hypertension.
If someone doesn't have a diagnosis of Marfan syndrome or any other predisposing condition for aortic disease, the symptom of severe unprecedented pain in the midline of the chest or abdomen should at least raise the possibility of a dissection in the mind of the emergency room physician. The location of the pain indicates the portion of the aorta involved in the dissection (Figure 2). Pain that penetrates from front to back (midscapular) at the outset, and changes location over time, may also indicate an ascending dissection. The changing location of the pain is an indication that the dissection is progressing.
Someone with chest pain who has a murmur of aortic regurgitation—a diastolic murmur indicating a leaking aortic valve—would also be at risk of having an aortic dissection, although it is possible to have aortic regurgitation due to an enlarged aortic root (Figure 3) and an unrelated case of chest pain. In addition, someone with high blood pressure who is having pain in the middle of the body may have a dissection, although the physicians would probably not consider it as the first diagnosis. An asymmetry of blood pressure, detected when the measurement is taken in both arms, is also a sign of a possible dissection. This is the way a substantially larger number of people can have aortic dissection correctly diagnosed in an emergency department setting.
Figure 2. The entire aorta and its major branches. The aorta is roughly divisible into four segments: ascending (including the root); arch; descending thoracic; and abdominal.
Figure 3. Enlargement of the aortic root. In the main figure, the heart is in diastole and the aortic valve is closed, preventing blood that has just been pumped into the aorta from leaking backwards into the left ventricle. The aorta is moderately dialated. The large arrow shows normal diastolic flow of blood from the atrium into the ventricle. In the inset, the aortic root is considerably dialated and the aortic valve can no longer prevent backward leakage of blood (aortic regurgitation).
Rather than think that every chest or abdominal pain is a dissection, the key is to remember certain characteristics that make dissection a more likely possibility, and ensure that aortic dissection is considered as a possible diagnosis. Then, if the diagnostic evaluation and therapeutic approach for the more common problems aren't giving a clear answer, the physician could cast a wider net to include tests that would evaluate for a dissection.
What information should the emergency department staff obtain from the patient with chest pain?
Upon arrival in the emergency room, the patient should be asked to clearly describe the pain—its location and severity, and the extent to which it is different from previous pain. While gathering the medical history, the patient should be asked about any known diagnosis of Marfan syndrome or other form of aortic disease, as well as any knowledge about the status of his or her aorta from previous tests. Many people with Marfan syndrome are knowledgeable about their medical status. However, emergency department physicians should be able to evaluate individuals with suspected aortic dissection, independent of Marfan syndrome. The clinical features of aortic dissection are not unique to people with Marfan syndrome, except that the incidence of dissection in individuals under the age of 45 is markedly increased in people with Marfan syndrome and other forms of aortic disease.
What part of the physical exam raises the possibility of an aortic dissection?
During the physical examination, it is important to check the blood pressure in both arms and the pulses in both wrists, both legs and both sides of the neck over the carotid arteries. If an aortic dissection is present, a difference in blood pressure can sometimes be found between the arms and the differences in the pulse can be detected.
High blood pressure could indicate a number of factors:
- A predisposing factor to aortic dissection.
- Pain from the dissection
- A partially or completely blocked artery to one or both kidneys.
- An abnormally large difference between the top (systolic) blood pressure and the bottom (diastolic) blood pressure, could be due to a leakage of blood back into the heart (aortic regurgitation).
Very low blood pressure can also occur. Many people with Marfan syndrome are treated with medications to keep their blood pressure at the very bottom of the normal range. It is important to ask patients with a known diagnosis of Marfan syndrome their normal blood pressure so that, if the emergency providers detect a blood pressure of, for example, 100/60, they are aware that it is the patient's usual blood pressure and not the result of an acute event. This is essential so that doctors do not try to raise the blood pressure, which would be a potential disaster in the setting of a dissection.
What tests are necessary to confirm a diagnosis of an aortic dissection?
Once the possibility of a dissection has been raised, an imaging study of the aorta is needed. A pain that starts at the front of the chest would suggest that the aorta near the heart is involved. In this situation, a standard echocardiogram may be useful. If the pain arises in the back of the chest or in the abdomen, a computed tomographic scan (which is most sensitive when radiographic x-ray contrast is given), transesophogeal echocardiogram, or magnetic resonance imaging study is necessary.
An x-ray is NOT sufficient to rule out aortic dissection.
The particular test would depend on which of these tests is most readily available, and most expertly done and interpreted.
If a patient is having severe anterior chest pain, the emergency room physician may first consider a myocardial infarction or an inflammation of the lining around the heart. However, if the electrocardiogram doesn't show an obvious heart attack, and pericardial inflammation is being considered, a test such as an echocardiogram could document that possibility. In that situation, if the aorta is dissected close to the heart, the dissection may appear on the echocardiogram and the correct diagnosis would be achieved without having had to consider it as a first diagnosis.
What are other possible causes of chest pain?
There are many other causes for the type of chest pain associated with an aortic dissection. These include a heart attack (myocardial infarction) and inflammation of the lining around the heart (pericarditis). Problems with the esophagus and the spine also could cause pain in the same general area, although they tend to have different symptoms.
Can an aortic dissection be stabilized?
Dissections that begin away from the heart (Type B or distal dissection) often can be stabilized and may not require immediate surgery. However, a dissection that starts near the heart (Type A or proximal)—in the part of the aorta leading up to the neck—does not tend to stabilize. A dissection in this area is exposed to the full force with which the heart pumps blood on each beat, which extends the tear. Proximal dissections require immediate surgical intervention.
Information gathered from the imaging technology can indicate the likelihood of stabilization. In addition, it is important to see if the aorta in any segment is 5-6 cm or more in diameter, which would indicate elective, if not immediate, surgery. An aorta of 5-6 cm means the aortic wall has been thinned and stretched, and is at a great risk for further enlargement and, potentially, rupture.
How can a dissection be stabilized?
Upon diagnosis of a dissection, it is important to lower the blood pressure to the bottom end of the normal range, or even a little lower, with medication. In addition, either a beta blocker or verapamil is used to slow the pulse and make the heart beat with less force. These medications can be given intravenously in order to be effective in minutes.
In a dissection that starts away from the heart, if the blood pressure stabilizes, the pain stops, and there's no compromise of blood flow to the kidneys and other vital organs, then the approach is usually based on aggressive use of medications to lower blood pressure to as low as 90-100 mm Hg and to slow the pulse, and careful monitoring to ensure that the aorta doesn't enlarge further.
Surgery would be considered if the tear in the descending aorta seems to stabilize, but then grows progressively, or if there is a rapid rate of change in an aorta size not yet considered to be at risk for rupture. Regardless of the cause of an aortic aneurysm, surgery should be considered once the aortic diameter reaches twice normal. On average, this corresponds to 5-6 cm for the thoracic aorta. A lower threshold is recommended for people with Marfan syndrome with severe aortic regurgitation, family history of aortic dissection or the need for other major surgery.
A patient who is extremely anxious may be aided by some sedation, which may help potentiate the effects of medicine and control blood pressure. However, it is important for patients in this situation to be awake and alert enough to be able to describe the pain and symptoms. If someone has a large dissection that begins near the heart, or the tear is very extensive and they continue to have pain even after the blood pressure has been brought down to a low level, proceeding with surgery as soon as the surgical team is assembled is essential. In the brief time before surgery, medication to control pain can be used without loss of needed diagnostic information.
When is surgery necessary?
Symptomatic ascending aortic dissections or aneurysms, whether acute or chronic, require emergency surgical treatment. Acute descending aortic dissections require admission to intensive care for monitoring and blood pressure control. Those with pain that does not resolve with blood pressure control will need urgent surgery. Those with evidence of organ ischemia (kidneys, bowel, spinal cord) will also require urgent surgery. In patients with chronic descending aortic dissections, pain may indicate impending rupture and, therefore, warrant urgent surgery.
In general, the decision for immediate surgery is based on indicators of especially high risk, such as the presence of a proximal dissection, or continued pain despite blood pressure control.
Other indicators for urgent surgery are:
- Evidence of fluid in the pericardial sac around the heart with a dissection that comes back to the heart, which suggests that the tear is going into the pericardial space.
- Evidence of marked enlargement of the dissected aorta (aneurysm formation).
- Evidence of blood leakage into tissue by contrast CT scan or transesophogeal echocardiogram.
- Evidence that blood flow to one or more vital organs is being compromised.
- Evidence of an intramural hematoma, a localized collection of blood within the aortic wall that can accumulate before the dissection progresses along the length of the aorta. Intramural hematomas indicate an impending dissection, and should be treated in an identical manner.
How successful is aortic surgery?
Patients with Marfan syndrome who have leaky heart valves require appropriate prophylactic antibiotic coverage to prevent endocarditis before any invasive procedures—such as bladder catheterization, endotracheal intubation, incision and drainage—that may be conducted in the emergency room. In addition, parenteral antibiotics are required in patients with the combination of a prosthetic aortic valve and an ascending aortic graft before any invasive procedure. For this patient group, health care providers should be aware of the "Guidelines for Endocarditis Prophylaxis for People with Marfan syndrome Who Have Had Cardiac Surgery (NMF Professional Advisory Board, June 1991).
The statistics regarding the success rate of aortic surgery are not clear. However, in institutions with experienced cardiac and cardiac surgical teams, the survival rate in patients who reach the operating room without hypotension or cardiac arrest, may be 80-90 percent or more. This includes urgent surgery for dissections that start near the heart, as well as later surgery for dissections that start away from the heart. The survival rate for elective surgery for ascending aortic aneurysms is greater than 95 percent.
How is a dissection monitored?
After a patient has had a dissection surgically repaired, or has had a dissection away from the heart stabilized medically, it is important to conduct several imaging tests of the aorta in the days or weeks prior to discharge. These tests often will be repeated when the patient returns to normal activity. The CT scan, MRI or appropriate echocardiogram also may be repeated within a month or two, and again in three or six months. The methods for monitoring, and how frequently they should be performed in the long term, may depend on how completely the aorta has been repaired.
Surgery may be delayed if the aorta has not reached critical size, which many surgeons believe is 5-6 cm diameter in any region—although some may operate at an even smaller size. It is essential that the physician in charge of long-term care never loses track of the size of the aorta. The larger any segment of the aorta is, the greater the likelihood that it will continue to enlarge—because it is already stretched and thinned—and the greater the potential risk of further tearing or rupture.
Are there any other special considerations for patients with Marfan syndrome in the emergency department?
ENDOVASCULAR STENT-GRAFTING OF THE AORTA
Data on stent-grafts in patients with MFS or other related connective tissue diseases (RCTDs) is very limited. Therefore, there is insufficient information available to guide decisions regarding its safety and efficacy in these conditions. MFS and RCTDs remain a contraindication for stent-graft repair in all investigational device exemption protocols. Click here for the NMF Professional Advisory Board Statement on Endovascular Repair in Marfan Syndrome Patients
Selected References for the Diagnosis and Initial Medical Management of Aortic Dissection
Fuster V, Ip JH. Medical aspects of acute aortic dissection.
Semin Thorac Cardiovasc Surg 1991; 3: 219-24.
Rizzo RJ, Aranki SF, Couper GS, Adams DH, Collins JJ Jr.,
Kinchia NM, Allred EN, Cohn LH. Rapid noninvasive
diagnosis and surgical repair of acute ascending aortic dissection.
J Thorac Cardiovasc Surgery 1994: 108: 567-75.