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Hidden Heart-Attack Risks
They can make you more vulnerable, but they won’t show up on conventional tests
BY ANNE PAILLARD
Feiza Persram was 16 when her father, 56, died of a stroke. “He suddenly collapsed at work without warning,” she recalls. “My mother was devastated, left alone with eight children to raise.” Years later, Persram’s 42-year-old brother had a fatal heart attack, also with no previous signs of heart disease. And a few months after, her 52-year-old sister succumbed to a massive coronary. Since then, four more of Persram’s siblings have died prematurely of heart disease.
Now 62, Persram began her own battle with heart disease in 1999 when she felt mild chest pain while driving. “I had a full physical exam, including an ECG, and the results came out fine,” she says. The four-foot-eleven Toronto seamstress and mother of two tried to do everything right—eating well, exercising and avoiding stress. She weighed 125 pounds and—other than her family history—had no commonly known risk factors for heart disease. Her cholesterol was borderline at 5.7, just above the Heart and Stroke Foundation of Canada’s desirable level of 5.2. Obviously something is wrong with my family, thought Persram, but what?
That question led her to Dr. Vivian Rambihar, a cardiologist at Toronto’s Scarborough Hospital, who gave Persram a battery of special tests. Finally, one blood test revealed a high level of a worrisome, genetically determined fat particle called Lp(a) that may raise heart-attack risks even when the usual cholesterol readings are fine. A typical Lp(a) reading in Caucasians and Asians is under 20; Persram’s was 32. Fortunately, Rambihar was able to lower it by putting Persram on a special niacin regimen and prescribing medication to lower her cholesterol.
More and more cardiologists across the country are testing patients for hidden heart-attack risks, and a surprising number of us can’t assume we’re safe. In the Quebec Cardiovascular Study, an ongoing evaluation of over 2,000 initially healthy men aged 45 to 76, about ten percent of those with early heart disease had none of the “big four” controllable risks: high cholesterol, high blood pressure, diabetes or smoking. And according to the Heart and Stroke Foundation, about half of all heart-attack victims have normal cholesterol levels.
Testing for hidden risks is especially important for those with a family history of premature heart disease—“about 40 percent of the population,” says Rambihar. “If you have a male relative who had a heart attack by age 55 or a female relative who had one by age 65—grandparents, aunts and uncles included—you need testing.”
Others who could benefit are those who already have a risk, such as high cholesterol or diabetes, or who have been diagnosed with heart disease even though they have no known risk factors. Here are five newly recognized heart-attack risk factors and what we know about them.
Lp(a)
Until now, the substance in the blood getting most of the blame for heart attacks has been “bad” LDL cholesterol. But researchers have begun to recognize that one particular member of the LDL family, Lp(a), carries an additional heart risk.
A recent University of Oxford analysis of studies involving 5,400 people with heart disease found that those in the top third of Lp(a) levels had a 70-percent higher risk of having a heart attack than those with lower concentrations. In another study of patients with premature coronary-artery disease, done mainly at Tufts University and New England Medical Centre Hospital, there was an “excess” of Lp(a) in 19 percent of the group.
What seems to make Lp(a) so troublesome is its unique design. Ordinary LDL is a ball of cholesterol wrapped by a strand of protein. As LDL travels through an artery, this protein can latch on to plaque and deliver the cholesterol cargo. But Lp(a) has an extra protein strand that’s shaped like a natural clot buster in the blood. Scientists suspect this look-alike protein actually tricks blockages into soaking up more cholesterol instead of acting as a clot buster.
Special blood tests can identify the problem, but neither a low-fat diet nor most drugs that lower LDL will budge high levels of Lp(a). Two exceptions are physician-supervised doses of the B vitamin niacin and, for women past menopause, estrogen.
Homocysteine
This amino acid, found in everyone’s blood, is estimated to figure in ten to 15 percent of heart attacks and 30 to 40 percent of strokes. A high homocysteine level is considered to be above ten.
In the 1960s at Boston’s Massachusetts General, doctors examined a young girl with a genetic disease that caused a buildup of homocysteine in the blood. The girl had a relative who had died at the age of eight from a similar illness 30 years earlier at the same hospital. When Dr. Kilmer McCully dug out the old records and peered through his microscope at tissue from the long-dead child, he realized that the boy had the arteries of an old man.
Several months later McCully’s antennae were alerted by news of a two-month-old boy who died of another genetic disease that caused homocysteine buildups. When he looked at the child’s tissue samples, once again he saw clogged arteries. “I began to suspect that people whose homocysteine levels were high might be at risk for heart attacks,” recalls McCully.
McCully’s theory produced controversy and led to further research. Since then, hundreds of studies on homocysteine have been published in medical journals around the world. One major study conducted at 19 centres in nine European countries looked at 1,550 men and women under the age of 60. Those with the highest homocysteine levels (more than 12) had a twofold greater risk of having an attack.
The good news about elevated homocysteine is that it’s easily corrected in most people. However, there is no definitive proof yet that lowered levels will reduce the chance of a heart attack. High homocysteine coincides with a deficiency of the B vitamin folic acid and, in some cases, vitamins B-6 and B-12. “If you eat lots—five to six servings a day—of leafy green vegetables, citrus fruits and legumes, you should get the recommended 400 micrograms of folic acid,” says Dr. Sammy Chan, a cardiologist at two teaching hospitals in Vancouver and a regional spokesman for the Heart and Stroke Foundation.
But doctors estimate that less than ten percent of the population eats that much folic-acid-rich food. “Those who don’t have a healthy diet should take supplements,” says Chan. He adds that older people have higher levels of homocysteine than younger people and therefore may need more folic acid.
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Although high fibrinogen levels are linked to heart-attack risk, science hasn’t yet demonstrated a cause-and-effect relationship. One theory is that the more fibrinogen, the bigger the clots that form after an atherosclerotic plaque breaks.
“High fibrinogen usually coexists with other factors, especially obesity and cigarette smoking,” says Dr. Robert Hegele, director of the Blackburn Cardiovascular Genetics Laboratory at Robarts Research Institute in London, Ont. A first line of defence against surplus fibrinogen is to declare war on other factors known to damage arteries.
“Although there are no drugs that can lower fibrinogen, people can still reduce levels by adopting preventive measures such as exercising, quitting smoking and controlling weight and blood pressure,” says Dr. Jeffrey Weitz, hematologist and professor of medicine at McMaster University and director of the Experimental Thrombosis and Atherosclerosis Group at the Henderson Research Centre in Hamilton.
Calcium Deposits
Calcium accumulates in arterial blockages, which are made up of cholesterol and other substances.
One day Dr. Bruce Brundage, a cardiologist at Bend Memorial Clinic in Oregon, had a brainstorm while studying a new scanner capable of taking X-rays of the heart between heartbeats. “It dawned on me that this ultrafast scanner could capture sharper images of calcium,” says Brundage. “If a scan showed a lot of calcium in a patient’s arteries, that person was at an increased risk of having dangerous obstructions.”
Used clinically in the United States for more than ten years, ultrafast scanning of coronary arteries has only recently become available in Canada. The equipment has been installed in fewer than a dozen centres in British Columbia, Alberta, Ontario, Quebec and Newfoundland. Proponents say that scanners are capable of spotting trouble long before an angiogram can. The test may also motivate people to lower their risk.
Take Doug Moseley, an emergency physician at Burnaby Hospital, who was 50 when he heard the test would be available at St. Paul’s Hospital in Vancouver in the fall of 2001. Although Moseley had high cholesterol and a family history of atherosclerosis, he ate well, got plenty of exercise and considered himself healthy. But when he began having occasional chest tightness and spells of sweating while at work in the ER, he decided to have the heart scan. “I had to lie on a table for about ten minutes and briefly hold my breath while the machine took X-rays of my heart,” says Moseley. “When I got the results back I was shocked!”
Moseley’s calcium reading was 700—severe plaque is 400 or greater. An angiogram revealed a 70-percent narrowing of the left coronary artery and a 30-percent obstruction in the right one. Instead of undergoing angioplasty, Moseley opted for a strict low-fat diet and an intense fitness/exercise regime. His cholesterol has dropped significantly, he has lost over 20 pounds and now feels great.
Leg Blockages
Doctors can get information about a patient’s arteries just by adding an extra step to a routine blood-pressure test: taking a blood-pressure reading around the ankle. The ankle reading is divided by the arm reading. An ankle-brachial index equal to or below 0.9 is a danger sign.
The aim is to detect blockages in leg arteries, a sign that trouble may be brewing in the coronary arteries. Some people with leg-vessel obstructions have pain when they walk and get relief at rest. “However, those with only mild blockages may have no pain at all,” says Dr. Yvan Douville, a vascular surgeon at St. François d’Assise Hospital in Quebec City and past president of The Canadian Society for Vascular Surgery.
In June 2002, 72-year-old Robert Hambrook, of Burlington, Ont., went to the Preventive Heart Disease Clinic for a full physical exam. Although the five-foot-eight 170-pound retired steel salesman could walk five kilometres a day with no difficulty and had normal cholesterol and blood-pressure levels, an ankle-brachial index test revealed a mild obstruction in the arteries of the left leg. Hambrook now follows a fat-free diet, takes vitamin supplements and maintains a strict exercise program.
The test seems to be a powerful predictor of life span. A University of California study of 565 people age 66 or older found that over a ten-year period those with an ankle-brachial index of 0.8 or less were five times likelier to die of cardiovascular disease than people with a higher index. Such patients can be given the appropriate treatment, including cholesterol-lowering drugs, antihypertensives or surgery.
On the horizon, researchers are looking into a blood test to screen patients for C-reactive protein, a substance produced by the liver when there is inflammation in the body. The test derives from the new theory that inflammation—possibly as a result of chronic microbial infections such as gum disease or arthritis—contributes to the clogging of arteries. If this is true, it raises the prospect of treating heart disease with antibiotics and vaccines.
Another promising approach to heart-attack prevention is gene testing. Many risk factors can lead to coronary-artery disease, some of which can be a single gene, a group of genes or a combination of environmental factors—such as diet or smoking—and genes, says Dr. Carl Breckenridge, professor of biochemistry and vice-president of research at Dalhousie University in Halifax. “Once scientists identify these genes in people with a family history of heart disease and understand their roles, we’ll be able to intervene therapeutically and treat more people who are most at risk.”
Should you be tested for any of these hidden heart-attack risks? Today, while tests are available to most people, they may be expensive. Patients with one or two important risk factors for heart disease should ask their doctors about specialized testing, advises Dr. Brett Heilbron, clinical assistant professor at the University of British Columbia and a cardiologist at St. Paul’s Hospital.
“While awaiting the results of more studies, the potential for benefit may be very high and the side effects of treatments are little or nil,” concludes Dr. Rambihar.
For more information, have your doctor contact a university medical centre with a high-risk or preventive cardiology section. Or visit the Heart and Stroke Foundation’s Web site at www.heartandstroke.ca.
ADAPTED FROM AN ARTICLE BY ABBY AVIN BELSON
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What's Your Risk? What puts you most at risk for a heart attack? Here are 12 factors to use to examine your lifetsyle and current state of health:
(Sources: the American Heart Association; the faculties of medicine at the University of California, Davis and the University of Maryland, and the Heart and Stroke Foundation of Canada) For more information and to assess your risk, try the tools available on this web site: |
ILLUSTRATION: JAMES TURNER
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