SEARCHING FOR HIDDEN HEART RISKS

Here's an increasingly common scenario that highlights both the promise and the pitfalls of our ability to detect and treat heart disease. Enticed by ads pitching "a quick, painless heart scan that could save your life," a man books one, just to be on the safe side. Much to his surprise, the electron-beam CT scan shows heavy calcium deposits in his coronary arteries. He takes the picture to his cardiologist. Further tests show a narrowed coronary artery, and she suggests balloon angioplasty to open it, followed by placement of a metal-mesh stent to hold the artery open. Aghast at the idea of walking around with a blocked coronary artery, the man agrees. The angioplasty goes without a hitch and he goes home, feeling as if he's been saved from a heart attack and is in the clear.

Unfortunately, he hasn't and he's not. Recent breakthroughs in imaging technology have given doctors unprecedented access to the insides of our hearts. The latest CT and MRI scanners can spot bulges in our coronary arteries long before they become blockages. But the benefits aren't nearly as clear-cut as the "close call" anecdotes imply. A patient like the one we just described would gain nothing from these tests and procedures--no protection against a future heart attack, no increase in life expectancy, not even a reduction in pain or discomfort. And the procedure itself could harm him. That's not to say that early detection isn't important. The sooner you know you're headed for heart trouble, the better your chances of doing something about it. But the critical warning signs are more likely to show up on a state-of-the-art blood test than on a dazzling 3-D image.

How can it be that angioplasty for a narrowed coronary artery that isn't causing any symptoms offers little or no protection from a future heart attack and doesn't help you live longer? In all likelihood, the one blockage that was opened represents just the tip of the atherosclerosis iceberg. For every plaque that bulges into the lumen (the channel through which blood flows), many others protrude outward, nestling deep into the artery wall. These plaques don't block blood flow, don't cause symptoms and evade detection on stress tests, angiograms and current heart scans. Yet they are just as likely as the protruding plaques that get "fixed" with angioplasty to break open and produce a blood clot that totally blocks the artery, causing a heart attack, stroke or even sudden death.

Make no mistake. Bypass surgery and angioplasty effectively relieve chest pain and other symptoms brought on by plaque that juts into a coronary artery enough to restrict blood flow. These procedures are also terrific for halting a heart attack in progress. But they don't ease the long-term threat posed by the numerous low-profile plaques. And because atherosclerosis is a systemic problem, plaque in one coronary artery almost inevitably means plaque in the others, as well as in the arteries supplying the brain, kidneys and legs. This presents a serious challenge for both finding plaque and treating it.

Since the advent of angiography in the 1960s, doctors have been able to peer into coronary arteries and see the most obvious plaques. Today angiograms are the gold standard for finding bumps, bulges and blockages in an artery's lumen. That said, there are a few downsides to these special X-rays. An angiogram is an invasive procedure--a doctor inserts a thin, flexible tube called a catheter into a blood vessel in the groin and gently maneuvers it into a coronary artery--with a small but very real risk of serious side effects such as a torn artery, heart attack or death. Furthermore, it is a bit like trying to understand a doughnut by looking at the hole, since an angiogram shows only the lumen of the blood vessel and can't highlight the myriad vulnerable plaques bulging away from the channel. Researchers hope to overcome this by attaching various probes to the catheter. Some emit sound waves or light, which bounce off the squishy, fat-filled center of soft plaque in different ways than they bounce off healthy artery walls. Others measure temperature; vulnerable plaques tend to be hot spots of inflammation. None of these tests is quite ready for prime time.

Meanwhile, breakthroughs in scanner and computer technology are yielding detailed, three-dimensional images of the heart that rival and may even surpass angiograms. The newest CT scanners collect so much information at once that they nearly freeze the beating heart and may reveal "hidden plaque." An image from the top-of-the-line, 64-slice CT machines costs under $1,000 and the procedure takes a few minutes, compared with $4,000 and up to an hour for an angiogram. An important early use of these machines will be in emergency rooms, where they can speed the time it takes to determine whether someone with chest pain is having a heart attack.

The constant cycle of inflammation-related damage and repair that leads to atherosclerosis shrouds artery walls with crusty calcium deposits. Another kind of CT scan, the electron-beam CT, can precisely measure the amount of this calcium. As a general rule, the more extensive the calcium deposits, the more extensive the atherosclerosis. A low score is reassuring, but it doesn't mean you're completely off the hook--dangerous hidden plaques that can nonetheless cause blood clots tend to have less calcium than those that chronically clog arteries.

While these new scans may help people with chest pain or other heart-disease symptoms, people who don't have symptoms but are concerned about their heart health should stick to the basics. Before doctors had tools to see inside the heart and blood vessels, they used clues such as blood-pressure and cholesterol levels to gauge heart-disease risk. These tests are still the bedrock of early detection, and they're getting more sophisticated. The numbers you really need to know are your blood pressure, cholesterol (LDL and HDL), body-mass index and 10-year risk for heart disease (which you can calculate at health.harvard.edu/NEWSWEEK). If you have heart disease, getting your numbers into the healthy range is critical.

Set to join these tests is a blood test for C-reactive protein (CRP). The level of this protein in the bloodstream mirrors the amount of subtle, chronic inflammation that drives atherosclerosis. The higher your CRP level, the greater your chances of developing heart disease. (The American Heart Association classifies CRP of below 1mg/L as low risk and above 3mg/L as high risk.) Research by Harvard cardiologist Paul Ridker, M.D., and others shows that testing for CRP as well as cholesterol levels helps identify people at high risk for heart disease. Trials are underway to determine if treating people with medications based on their CRP levels saves lives.

What should you do if you're lucky enough to be free of any signs of heart disease and your numbers are in the healthy range? Put a moratorium on further testing and continue doing what you are doing. You would be better off spending the money you'd plunk down for a heart scan to join a health club instead.