Almost 500,000 people in the U.S. die each year from coronary artery disease, the most common type of heart disease. Half of those people didn’t even know they were at risk or had any symptoms of the condition, according to the American Heart Association.
This could change, however, with the adoption of more accurate ways to identify who has the disease, instead of relying on less consistent risk factors like cholesterol levels.
During the past 10 years, more than 1,000 Washington State residents have participated in the Spokane Heart Study, which might do just that—change the way coronary artery disease is identified. Every two years, study participants have given blood and urine samples, been psychologically profiled, and answered questions about diet, exercise, job stress, and family medical history. They’ve also had 10-minute electron beam computerized tomography (EBCT) scans of their hearts to see if calcium has accumulated in their arteries.
This last step measures coronary artery calcification (CAC), which Dr. Harry Mielke, study leader and former director of the Health Research and Education Center at Washington State University Spokane, predicts “will be a really important factor” in determining who is at risk for coronary artery disease, since traditional risk factors don’t necessarily correlate with actual risk.
Coronary artery disease begins when lesions form on the inside of blood vessels leading to the heart. Vessels become inflamed, and then fat, cholesterol, and calcium in the blood collect to form a plaque, a condition called atherosclerosis. This buildup narrows the vessels, preventing blood and oxygen from getting to the heart. Sometimes the plaque ruptures and causes a harmful blood clot elsewhere in the body.
When the study was started in 1994, high blood pressure, high cholesterol, smoking, obesity, and diabetes were well-known as risks to heart health. “We were going against mainstream medicine [by looking at coronary artery calcification],” Mielke says. Today, the Center for Disease Control and Prevention has joined the study, conducting some difficult analyses of blood and urine, and researchers in Switzerland are duplicating the study there.
“Traditional risk factors are pretty weak,” Mielke says, pointing out that many people know someone who died unexpectedly from a heart attack despite apparent good health. EBCT scans, which show calcium found in arterial plaques, can potentially provide quick, quantifiable measurements of heart disease risk.
According to Mielke, one unique aspect of the Spokane Heart Study is the focus on people who aren’t sick. He says preventative measures like bypass surgery and angioplasty work pretty well when people know they’re sick—the problem is identifying the people who are at risk but asymptomatic.
The study results show that almost half the subjects whose EBCT scans showed calcium deposits had no traditional risk factors but could still be at risk for developing additional heart problems.
Some participants had high cholesterol levels but showed zero artery calcification, suggesting that they aren’t at risk at all.
Besides being able to detect heart disease in “low risk” patients, heart scans using computerized tomography have serious advantages to other methods of detection. “There’s nothing to it,” says Mielke, noting that the procedure is noninvasive and fast. All patients have to do is hold their breath for about 20 seconds, while the table they’re lying on is shuttled through a donut-shaped machine. Electrodes on the surface of the skin monitor heart rate and trigger the machine to take pictures at specific, standardized points during the heart beat. The result is a series of cross-sections showing the patient’s chest. Calcium, both in bones and arteries—if it’s present—shows up white on a dark background, similar to an X-ray, and can be measured.
Compared with coronary angiography, considered the “definitive test” for heart disease according to the Mayo Clinic, EBCT scans are remarkably simple. In angiography, a catheter is routed through an artery from the arm or groin to the heart, and a dye is injected in the vessel, which shows narrow points on an X-ray.
Despite the ease of EBCT scans, Mielke emphasizes that it’s still too early to change recommendations related to heart disease detection. The research team is currently putting together data to determine who should get the $300 scan and whether people with high cholesterol and no coronary artery calcification should stop taking cholesterol-lowering drugs. They also plan to continue the study for another decade.
In the meantime, the program has set up a good research base and provided an important way to involve the community in research, Mielke says. “Spokane has always been on the cutting edge of heart research.”