Plaque detector  

By Nikhil Hutheesing, Forbes Magazine

You're entering middle age with worries about heart disease but no evidence of it. What kind of tests should you get?

MY LAST BLOOD TEST ended in a statement that stunned me: "This patient score is associated with the highest coronary disease risk." My low-density lipoprotein - the bad cholesterol that clogs arteries was high in relation to my high-density lipoprotein- the good cholesterol that clears clogs away. The ratio should fall between 2.5 and 4.0; mine came to 7.9.

I am only 36, but I already have another risk factor: family history. My father survived a heart attack at 59; his mother died of one at 60. My cardiologist told me to take baby aspirin thrice weekly (to avoid blood clots) and a cholesterol-lowering pill every day. Then, to see whether more steps were warranted, he ordered a thallium stress test - a four-hour ordeal.

A radiologist injected me with radioactive thallium to light up the blood flowing through my arteries. In 12 minutes a gamma camera took 64 snapshots for a one-second movie. Next, to make a comparable movie of my heart under stress the radiologist stuck EKG electrodes to my chest and injected a technetium agent into my arm as I ran a treadmill. Then he gamma-graphed me again.

Cost: $1,700. Result: no evidence of heart disease. Degree of reassurance: negligible. A negative result doesn’t guarantee that you won’t have a heart attack while walking out the hospital door.

"There is a high incidence of these tests ordered by doctors," sighs Dr Thomas Behrenbeck of the Mayo Clinic. "Unfortunately they don't help in prevention."

The reason? Stress tests look not at the buildup of cholesterol-laden plaque but at the slowing of blood flow such buildup causes. Slowdowns show up only when arteries have narrowing 50% to 70% - way past the danger point.

"A 35-year-old who sits on his butt all day, eats corned beef sandwiches and has high cholesterol could have a completely normal stress test," says John Rumberger, a cardiologist at Diagnostic Cardiovascular Consultants in Columbus, Ohio. But he could still have severe plaque in his arteries waiting for his 42nd birthday, when one will rupture and kill him."

What, then, could possibly justify a young, asymptomatic person taking a stress test. Only this: It screen for the 5% or so with risk factors like mine who have full-blown heart disease and might need surgery. Such patients would then become candidates for an angiogram, a $4,000 test in which a catheter is snaked through the coronary arteries and used to inject X-ray dye to outline the blockages clearly. Doctors wouldn't give just anybody an angiogram because it has a 1-in-200 chance of dislodging plaque and inducing a heart attack.

Now comes a much safer technology that requires no injections and poses no risks. Called electron-beam computed tomography, it searches for the calcium crust that forms on plaque. It uses electron beams to take 40 pictures of a number of cross-sections of the heart and feeds the data into a computer where images of the heart pop up almost instantly.

The machine, called the Ultrafast CT (for computed tomography), is made by South San Francisco Bay-based Imatron and costs $1.75 million - about four times as much as a gamma camera, which explains why only 50 of them are in operation in the US so far.

The test, taken at Cardiac Imaging in New York City, was simple A radiologist told me to hold my breath 30 seconds, and images came up on computer monitor almost instantly. Verdict: no plaque.

There is one significant limitation. Unless you are like me and have obvious risk factor, the test will do little good for men under 40 or women under 45. Reason: Even if you have some fatty deposits at an earlier age, calcium isn’t likely to show up on them.

It's cheap to operate, so a test costs the patient only about $500 (About 80% of health insurance and HMO plans will cover the procedure if referred by a physician.) You could be seeing more of these machines soon. General Electric is starting to market Imatron's machine.

Electron scanning should make stress testing a rare adjunct to diagnosis rather than its main weapon. Doctors should miss far fewer at-risk patients. Just as important, its low cost and high accuracy should enable cardiologists to fine-tune treatment by furnishing them with frequent progress report. A quarter of the U.S. adult population suffers from coronary artery disease. The first and only symptom for 150,000 of them every year is death. This improvement in early detection should reduce that number.