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Dr. Armin Zadeh is scanning patients and assessing them on a grade scale to see if they need medication or some other treatment for heart disease. (Lloyd Fox/Baltimore Sun video)

Cardiovascular disease is the nation's top killer, but the first clue is often a major heart attack.

Many heart attack victims never have symptoms such as chest pain or shortness of breath. Even when a patient does have symptoms, doctors often don't act if the arteries aren't blocked enough to cause alarm.

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Now, a new research study suggests that people can be at risk even with lesser blockages. One of its authors, a Johns Hopkins cardiologist, has helped develop a new assessment tool designed to better flag those in danger of heart attacks.

"There is strong evidence to show these patients are at risk when their arteries are less than 50 percent blocked," said Dr. Armin Zadeh, an associate professor of medicine and member of the Heart and Vascular Institute in the Hopkins' School of Medicine. "These patients are at risk and we're not capturing them."

The 50 percent mark has long been the threshold for treatment with aspirin or statins, but when Zadeh and heart experts from New York's Mount Sinai Health System assessed death rates from patients with lesser blockages they found essentially the same risk of dying.

They came up with a new five-stage system that promotes earlier treatment.

Heart disease kills more than 600,000 men and women in the United States annually, according to the U.S. Centers of Disease Control and Prevention. There are about 735,000 heart attacks reported a year and close to three-quarters are the first one a patient has experienced.

The problem is build-up of plaque, made up of fat, cholesterol and other substances. When it hardens, it narrows the arteries and limits blood flow to the heart. When there is a full blockage or a piece of plaque breaks off and forms a clot, the heart is starved of oxygen and begins to die, and a heart attack ensues.

Zadeh can't say how many more lives could be saved by identifying heart disease earlier and he isn't advocating random screening to look for problems. But in a report in the December issue of the Journal of the American College of Cardiology, he estimated there are several million adults with concerning symptoms who don't have obstructive levels of heart disease.

Zadeh advocates for a stepped up approach to considering risk in those who do have symptoms or have a lot of risk factors such as high blood pressure and cholesterol, a family history of heart disease, and poor dietary and exercise habits.

Current practice calls for patients with symptoms or risk factors to have a "stress test," where doctors measure the heart's ability to respond to stress induced through exercise on a treadmill or chemicals. Those whose hearts perform poorly undergo a cardiac catheterization, an invasive procedure that injects dye into the arteries near the heart that shows blockages in an X-ray. Those with major blockages are treated.

To more easily capture people with less advanced blockages, Zadeh said, patients with symptoms who pass a stress test could undergo a non-invasive CT scan or MRI. Those with moderate or even mild blockages could then be treated at a doctor's discretion.

He acknowledged that such a change won't come swiftly, as doctors and insurers may balk at imaging and medicating so many more people. Stress tests cost $200 to $500. CT scans cost $400 to $600 and MRIs can cost more than $800, Zadeh said.

Some cardiologists, however, already use CT scans to get a less invasive look at patients who may be at risk and may benefit from earlier treatment. The new rankings may push more to follow suit, said Dr. John Osborne, a Dallas cardiologist and a volunteer spokesman for the American Heart Association.

He said cardiologists know stress tests aren't picking up all those at risk for heart attacks, but they don't want to subject patients to catheterization, which involves threading a catheter through an artery or vein in the groin, neck or arm leading to the heart. Doctors also may be dismissing more women with heart disease because their symptoms may be less severe or specific.

CT scans and MRIs are newer technologies than X-ray catheterizations sensitive enough to assess the level of blockages, allowing doctors to get a look at more patients' vessels. Those with 30 percent or 40 percent blockages — Osborne called it "lumpy bumpy" disease — may benefit from daily aspirin or statins, which he said were considered relatively safe for long-term use.

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"It's certainly not the first time anyone has thought of this," Osborne said of the lower thresholds for treating patients. "The advantage is this comes from respected institutions and the staging system creates a better way to describe the disease in these individuals."

While Osborne believes the benefits outweigh concerns in lowering the bar for scanning and medicating more patients, other doctors aren't sure they're ready to make changes. Among them is Dr. Michael Miller, a professor of cardiovascular medicine, epidemiology and public health at the University of Maryland School of Medicine and director of the University of Maryland Medical Center's Center for Preventive Cardiology.

He agreed that stress tests only pick up high levels of disease, but imaging a lot of people who pass that test would be expensive and perhaps not focused enough on those who are likely to develop problems.

"I'd say not so fast on doing these tests," Miller said.

He said doctors should use established methods of assessing heart disease risk factors and determine the threat of a future heart attack. That means looking at blood pressure, cholesterol levels, family history and lifestyle, and determining more narrowly who to scan or medicate.

There also is no evidence yet that medicating people with mild heart disease will prevent heart attacks or death down the road, Miller said. Medications alone may not be effective and may give patients a false sense of health, he said.

Miller said many patients would really benefit from changes to diet, exercise and stress levels. He wrote a book called "Heal Your Heart" that focuses on stress reduction.

"I wouldn't necessarily go right to CT scans or MRIs," he said. "I do a risk score and see if they are in the range I'm worried about. If a patient isn't sure they want to go on a statin and won't change their lifestyle, I'd say why don't we do the scan and let it settle the score."

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