Scientists closing in on affordable screening test for heart disease

If you’re a runner, especially an older one, you may remember James Fixx, the author of “The Complete Book of Running.” A guru of the benefits of running for cardiovascular fitness, he told how, at age 35, he quit smoking, started running, and lost 50 pounds. And yet is probably more famous for having dropped dead of a heart attack, at age 52, while out for his daily run on a tree-lined street in Vermont.

The take-home message from this cautionary tale is not to become a couch potato for fear of dropping dead while exercising. It does, however, underscore a scary fact: nearly half the heart attacks in this country come without warning.

Fixx had a dad who died at age 43 from heart disease. His family’s genetics burdened him with the hardening of the arteries that is the genesis of most heart disease. But he did all the right things: quit smoking, lost weight and began exercising. No doubt, he was pretty sure he had beaten the odds.

Nearly 40 percent of Americans are at moderate risk for heart disease. How can we do a better job of screening so we can prevent those heart attacks? Maybe if Fixx were alive today he’d be a candidate for statin therapy, further adding to his very powerful risk-reduction strategy.

A good screening test is cheap, easy, non-invasive and helps us identify those who would benefit from further testing and/or therapy. Researchers at the Mayo Clinic think they may have found the test. It’s called the aortic pulse wave velocity, or aPWV. During the test, a pencil-like device called a tonometer is placed over arteries in the neck and upper thigh.

Every time the heart beats, it sends a wave down the aorta, the major artery exiting the heart. Think of the waves that emanate from a rock thrown into a pond. The speed that wave travels in the aorta and connecting arteries depends on how elastic the aorta is. The more elastic and healthier the artery is, the slower the wave travels. If the artery is stiff because of atherosclerosis, the wave travels a lot faster. Previous studies showed that the aPWV predicted heart disease in older adults (average age 73).

Another study looked at a particular kind of CT scan called electron beam computed tomography or EBCT. The EBCT measures the amount of calcium in the coronary arteries. The amount of calcium correlates with the amount of atherosclerosis, or plaque. Since EBCT is pretty expensive, the study’s authors wondered whether the aPWV could tell us who had significant calcium deposits in the coronary arteries even though they didn’t have any symptoms of heart disease.

The study participants all had the fancy CT scan to measure just how much calcium was in their coronary arteries. Then, a few months later, they had the aPWV test. This test is easy—it takes only 10 to 15 minutes and can be done in a doctor’s office.

The researchers found that, indeed, the aPWV was positively associated with the amount of coronary artery calcium—the faster the pulse wave, the more calcium and thus more coronary artery disease. More than 60 percent of the study participants had detectable levels of coronary artery calcium. Another interesting finding: the association of aPWV and coronary artery calcium was stronger in smokers than non-smokers. Are we surprised?

This research is a first step to finding an inexpensive, non-invasive test for coronary artery disease in people who are at only moderate risk because of, say, high blood pressure or family history. As always, more studies are needed. We need, for example, to establish age- and gender-based norms. And this study was done on non-Hispanic whites, so we need to know if the results hold for other people of other races.

Still, any time we can find a test that will identify people at risk for a disease, lead to treatment to lower that risk, and do it cheaply, we’ve found a good thing. I’ll be looking forward to more research on the usefulness of the aPWV.