This year, more than 8 million Americans will have a heart attack. The question is, which 8 million?

With heart disease the leading killer of Americans, predicting cardiac risk has become one of the primary goals of general medicine. Doctors measure cholesterol and blood pressure to figure out how likely someone is to have heart troubles and how aggressively they need to be treated.

It’s why coronary calcium screening has so many doctors very excited. Evidence is mounting that the simple, non-invasive imaging procedure is a much more effective tool in determining an individual’s risk of a heart attack. That could help doctors avoid treating patients who don’t need treatment and better identify those who do.

“We no longer have to judge books by their covers,” said Dr. Rick Koch, a cardiologist with Bend Memorial Clinic. “We can look inside. We get to the hard and narrow — literally — and see which individuals are at risk.”

The key is prevention

In the past, treatment decisions were based on population studies, taking into account the statistical probabilities associated with age, sex, smoking status, diabetes, hypertension, cholesterol and family history. A questionnaire along with a couple of quick and cheap tests could give doctors a fairly good idea of a patient’s risk.

Still, none of those markers actually meant that patients had coronary artery disease. There are many patients who have many of the risk factors for heart disease but have won the genetic lottery and will never have a heart attack. Before coronary calcium screening, doctors would wind up treating those patients anyway.

“What it does is take it away from a population-based approach to estimating risk for an individual,” said Bruce McLellan, a cardiologist with Heart Center Cardiology in Bend. “Because once you’ve identified calcium in someone’s arteries, you know they have plaque. There’s no other explanation.”

That’s not the same as knowing your risk of a heart attack, he said, but the two are highly related.

A calcium score of 101 to 300 conveys a seven times higher risk of a cardiac event than somebody with a score of zero. A score of more than 300, and it’s nine times higher.

“If your calcium score is zero, your risk of having a heart attack in the next year is 0.3 percent. No other blood test, no other stress test, no other imaging study that we use in clinical medicine has that kind of negative predictive value,” McLellan said. “Yes, we will miss a few, but the number will be very small.”

That number will be much smaller than without a calcium scan. Many patients aren’t diagnosed with coronary disease until they show up at the emergency room with chest pains or a full-blown heart attack.

“One number that hasn’t changed in cardiology through all this stuff, if you have a heart attack, 50 percent of people never get to have a second one,” Koch said. “So the key is to prevent the first one.”

The calcium score represents the amount of calcium in your coronary arteries. Calcium builds up in the plaques formed by cholesterol. When those plaques burst, they can clog arteries supplying blood to the heart, causing a heart attack. Doctors know that calcium makes up about 20 percent of the plaque, so the volume of calcium corresponds with the risk.

“Think of it as the tip of the iceberg,” McLellan said, “the part that’s now visible to us by a noninvasive, simple study.”

Saving lives

Because it takes 20 years or more for coronary calcium to build up, doctors recommend screening men over the age of 40 and women over the age 50 if they have a single risk factor. Doctors discourage those falling outside the guidelines to get the scans because they carry a small but not insignificant risk from the radiation involved. There’s no reason for a patient who has a high score once to ever retest, and those with zero scores shouldn’t come back for a second test for three to five years.

The test takes only a few seconds. Patients don’t need to change out of their clothes or prepare in any way for the test.

Doctors can then tell the patients exactly what their risk of a heart attack is over the next 10 years and how much their risk will drop if they do all the right things. Merely taking aspirin and cholesterol-lowering medication can cut their risk by 25 percent to 40 percent. Lifestyle changes, such as quitting smoking, eating a healthy diet and exercising, can further reduce their risk.

The utility of coronary calcium screening has been controversial, prompting many insurers to wait for further evidence and the backing of the medical establishment. The American College of Cardiology and the American Heart Association endorsed the scans in 2006 for individuals at intermediate risk.

Dr. Bruce Brundage, medical director of the Heart Institute of the Cascades in Bend, served on the panel that wrote the recommendation. He believes insurance companies and other preventive health organizations may soon follow suit.

“I think the weight of the evidence has finally tipped the scales, so that over the next several years, they’ll probably fall in line,” he said.

Critics of widespread screening say there are still important questions to be answered about the ability of calcium screening to save lives and the cost-effectiveness of widespread screening.

Screening will only save lives, they say, if it leads to medications and lifestyle changes. But no studies have examined whether a high-calcium score actually leads to treatment and better outcomes.

At BMC, Koch has recently revised the reports that patients get after their calcium scans to show them their current risk and how much that risk could drop if they do all the right things.

“We see all these people who don’t want to be on a cholesterol-lowering medication,” he said. “I’ve never had someone, after showing them one of these graphs, say ‘No, I won’t do it.’”

Cost-effectiveness

The cost-effectiveness of calcium screening also has not been established. But McLellan says that’s also true for cholesterol testing, which is the basis of coronary risk analysis today.

“We’re fooling ourselves if we think we’re doing it right now because we’re not. It’s never been proven to be cost-effective except in the highest risk group,” he said.

With tests available locally for less than $100, compared to the national average of $300 to $600, the cost-effectiveness equation could change dramatically.

And because a zero calcium score can often rule out the need for treatment, insurers could recoup the $99 cost of the scan fairly quickly. Patients on cholesterol medications, which require additional blood and liver testing, can rack up $100 in costs in a month taking a brand name drug or a year taking a generic.

“Let’s say you just magically lowered the cost of this down to the cost of a lipid panel. How much resistance would there be? People would flock to it,” McLellan said.

Some insurance companies have started covering the test, including Medicare in some regions of the country, although not in Oregon.

Colonoscopies and mammograms are universally recommended. Yet colonoscopies are much more expensive than a calcium scan and outcomes data on mammography is much weaker.

“I think it’s irresponsible for us to not be identifying people who are at risk of dying from the number one killer of men and women in this country,” Koch said. “Anything we can do as health professionals to identify these individuals early is terrific.”