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For other articles and previous issues click here. July 26, 2004 Aortic
Dissection: Problems at the Pump The good news is that aortic dissection, the condition that killed actor John Ritter last September—one week shy of his 55th birthday—is rare. According to the American Heart Association, aortic dissection strikes between 2,000 and 10,000 people annually in the United States. Unfortunately, however, only a lucky few survive. “While it is an uncommon condition, if it occurs at a specific location in the aorta, the ascending aorta, it’s almost always catastrophic if not treated immediately,” says Deepika Gopal, MD, a clinical cardiologist and cardiac imaging specialist who is the medical director of cardiovascular MRI at the Medical City Hospital in Dallas. The aorta has three layers. The condition occurs when blood seeps between them and creates a new channel. The pericardium, the section in which the heart sits, is a tight structure. “There isn’t much room for the blood that is collecting. When the root of the aorta tears, so much blood collects in that area that it completely compresses the heart, and the heart is unable to pump blood,” Gopal says. Not only is the condition often fatal, but it also strikes without warning. Typically, patients come to the emergency department (ED) complaining of excruciating pain. “They complain of a boring chest pain that goes from front to back,” says Michael P. Federle, MD, chief of abdominal imaging and professor of radiology at the University of Pittsburgh Medical Center. Typically, the pain that penetrates from front to back at the outset changes location over time, indicating that the dissection is progressing. The one good thing is that the pain is so excruciating that the patient can’t stay at home and goes to the ED for treatment, which is critical for his or her survival, says Christopher L. Hansen, MD, FACC, director of nuclear cardiology at the Jefferson Heart Institute of Thomas Jefferson University Hospital in Philadelphia. Patients might believe they are having a heart attack because some of the symptoms, such as chest pain, are similar. However, the treatments for heart attack, such as blood thinners and clot-busting drugs, increase bleeding and would be dangerous for a patient with an aortic dissection. The tear can also trigger a stroke or heart attack, among other cardiac events, depending on which arteries are affected. Blood tests that indicate a heart attack are generally negative in a patient whose aorta has torn. Another tip-off is that the blood pressure in the patient’s two arms may differ or the patient may lack a pulse in one arm. Imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI), and transesophageal echocardiogram (TEE) are also useful in diagnosing an aortic dissection. “The diagnosis is usually made after a suspicious chest x-ray—showing mediastinal widening—and a high index of suspicion,” Hansen says. Gopal says a study published in the New England Journal of Medicine in 1993 showed each of the three modalities to have a sensitivity of approximately 98%. Thanks to advances in technology, she says, she would guess the sensitivity with MRI and TEE to be close to 100% today—10 years later. However, Gopal says TEE is the best test in an emergency situation because the echo machine is portable, can be taken to the patient’s bedside, “and yields all the pertinent information before surgery, especially when performed by experienced operators.” Hansen says the accuracy of a diagnosis with a TEE depends on the operator’s skill. “You need someone who is certified because it’s something that, if you’re not careful, could be easy to miss,” he says. A TEE allows the cardiologist to view the internal structures of the heart and the heart’s major vessels by inserting a probe down the throat. The tip of the probe emits ultrasound waves that echo within the chest wall cavity. The echoes are picked up, and they create an image of the heart that is displayed on the video monitor. TEE is often the safest modality in the ED when the patient is unable to travel to the CT or MRI suite, Gopal says. Most ED physicians would probably use a CT scan with contrast over an MRI because it’s easier to get a CT scan on a patient who is in excruciating pain in the middle of the night, Hansen says. The CT scan is most sensitive when radiographic contrast is given. Also, he says, the patient must be closely monitored, and “that’s hard to do on a magnet. It’s difficult to get an electrocardiogram on someone in a magnet. These patients are critically ill and they are frequently on a ventilator and multiple intravenous medications.” Testing is important, Hansen says, because while “most savvy emergency room physicians have a high index of suspicion for aortic dissection, it can be overlooked because it’s not a common problem.” Indeed, the American Heart Association says the disease may be underreported because it is difficult to determine whether death was caused by an aortic dissection, a heart attack, or sudden cardiac death without an autopsy. Aortic dissection is not a reportable disease. Early recognition of the condition is crucial because an untreated ascending aortic dissection is fatal to 33% of patients within 24 hours, 50% within 48 hours, and 75% within two weeks of onset, Gopal says. Precise diagnostic imaging is important because treatment depends on whether the condition involves a tear in the ascending aorta (known as Type A) or descending thoracic aorta (known as Type B). Type A is twice as common as Type B, Federle says. Type A generally requires surgery, whereas Type B dissections may be medically managed depending on their extent of involvement of the aorta and its branches, Gopal says. If Type B is noted, the physician may prescribe medications aimed at reducing blood pressure with intensive care unit monitoring. This approach is intended to stabilize the torn section, preventing further damage. Medications include antihypertensives, which lower blood pressure and thus strain on the heart; analgesics to alleviate pain; beta blockers to slow the heart’s resting rate and reduce the force of the accompanying heart muscle contraction, lessening the heart’s workload; and antibiotics to protect the heart valves, which are prone to infection. Medications can be given orally, or intravenously, if they need to be fast-acting. “The medication is usually Nipride, an intravenous medication that must be given with a pump in a coronary care unit with constant monitoring,” Hansen says. “The beta blockers are given to reduce the rate of ejection of the blood from the heart, which reduces the shear stress on the damaged aortic wall.” Cases that don’t respond with medication will likely require surgery. Surgery should be considered once the aortic diameter reaches twice the normal size, Hansen says. On average, this corresponds to 5 to 6 centimeters for the thoracic aorta. An aorta of 5 to 6 centimeters means the aortic wall has been thinned and stretched and is at high risk for further enlargement and potential rupture. If possible, surgeons will repair the tear. If not, they must replace the aorta or valves with prosthetics. “If there is major destruction of the aorta, it can be replaced with synthetic grafts,” Gopal says. Surgical patients need to be followed every few weeks at first, then every few months, and then annually, Gopal says. “They will need permanent follow-up.” Because aortic dissection surgery is a difficult procedure and often performed on an emergency basis, the mortality rate is high—7% to 36%, even at an experienced center, Gopal says. Aortic dissection most commonly occurs in people aged 40 to 70; the peak years are 50 to 65. Men are three times more likely to experience an aortic dissection than women. “That’s probably because there is more uncontrolled hypertension in men than women,” Federle says. A variety of medical conditions can cause the artery wall to deteriorate and separate or dissect, with high blood pressure being the most common, Federle says. Eighty percent of patients with aortic dissection have high blood pressure. Pregnancy can also increase the risk of aortic dissection because it places additional strain on a woman’s heart. Women with Turner syndrome, a chromosomal condition causing short stature and infertility, “are also predisposed to a condition called coarctation, which predisposes to aortic dissections,” Gopal says. Aortic dissection is also associated with genetic diseases such as Marfan syndrome, lupus, and giant cell arthritis, all of which are diseases of the connective tissue. Aortic dissection is the primary cause of death in individuals with Marfan syndrome, according to the National Marfan Foundation. Approximately 200,000 Americans have Marfan syndrome or a related connective tissue disorder. The classic features of Marfan syndrome are disproportionately long arms, legs, fingers, and toes; pigeon breasts, in which the breast bone protrudes forward; funnel chest, in which the breast bone is prominently caved inward; and a very marked curvature of the spine. The disorder can affect the eyes, skeleton, blood vessels, and heart. People with Marfan syndrome are particularly tall and lanky, and some are athletes in sports where their height is an advantage, such as basketball and volleyball, Federle says. In 1986, Flo Hyman, the star of the 1984 U.S. silver medal-winning women’s volleyball team, died of a torn aorta. Hyman, who had Marfan syndrome, was 31. A number of professional and college basketball players with Marfan syndrome have also died of aortic dissection. Aortic dissection has also been observed in people on cocaine binges and among weightlifters lifting very heavy loads. Because genetic disorders can cause an aortic dissection, Gopal says, “it is important to take a detailed family history from patients presenting with this condition.” Gopal says she’s always careful to question her patients about whether or not anyone in their family died suddenly from a heart condition. John Ritter’s father, Tex, a singing cowboy and film star, died of a heart condition in 1974. While an x-ray or other diagnostic images would reveal an enlarged aorta, which can lead to a rupture, doctors still don’t believe it’s necessary to routinely screen patients for the disease. “I don’t think you’re going to save the world by sending everyone for an echocardiogram to look for an enlarged aorta. All you would do is raise the national debt a couple of points,” Hansen says. However, he says, “if someone has Marfan syndrome, he or she should be monitored.” Patients with degenerative changes of the aortic wall, such as those with Marfan syndrome, are frequently followed by transthoracic echo. “It is simply not cost-effective to screen the entire population,” Hansen says. Federle says when a multimillion-dollar athlete with Marfan syndrome dies from an aortic dissection, calls for more screening reverberate around the country. However, Federle agrees that it’s not practical or reasonable to routinely screen everyone. “Only if someone is unusually tall or has other risk factors, such as high blood pressure, could you make the case for a screening and possibly prophylactic surgery,” he says. Also, screening isn’t always useful because in many cases the problem is not there until the tear starts, and once the tear starts it’s almost over. In some cases, trauma—an impact to the chest, such as in an automobile accident—can cause an aortic dissection, Gopal says. While not preventable, it’s still best to control the risk factors for aortic dissection as much as possible, the physicians agree. Prevention is similar to that of many heart problems: Stop smoking; exercise at least 30 minutes per day, three to five times per week; control weight and shed extra pounds if necessary; eat fish, fruit, whole grains, and foods rich in beta-carotenes; cut stress; and avoid drug use. Controlling diabetes is also important. — Beth W. Orenstein is a freelance health writer based in Phoenixville, Pa. |
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