Back to Menu

NEW, SOPHISTICATED SCANNING TECHNIQUES FOR DIAGNOSING CORONARY HEART DISEASE - THE ISSUE OF ENTREPRENEURIAL OVERUSE

(July 2002)

A multicenter study of a marvelous and sophisticated technique called magnetic resonance angiography for the diagnosis of narrowing of the coronary blood vessels of the heart appears in the December 27, 2001 issue of The New England Journal of Medicine. The investigators from many centers around the world studied a total of 109 patients, most of whom were referred to cardiac units for symptoms suggesting blockage of the coronary blood vessels by arteriosclerosis; 79 percent had chest pain. In these 109, two studies were compared - a catheter was inserted into a blood vessel, threaded into the heart and dye injected to visualize the coronary blood vessels; before that, the magnetic resonance scan, a non-invasive technique that takes about one hour, was performed.

The results with the magnetic resonance scan were quite impressive, but some cases of narrowed coronary blood vessels were missed (false negative results). Additionally, in at least 30 percent of cases, positive results turned out to be incorrect (false positives), a finding virtually ignored in the discussion. The investigators were also impressed with the ability of magnetic resonance imaging to identify people who have symptoms such as chest pain, but who turn out to have normal coronary blood vessels. They argue that, in a large percentage of such patients, the invasive coronary angiography could be avoided. Their study group (109 persons) was relatively small so that claim needs more documentation. Of course, if positive results are found with the non-invasive magnetic resonance imaging or if results are indeterminate or unsatisfactory, the invasive coronary angiography procedure will be needed either to better define the extent of disease or treat it by opening up the coronary blood vessel using a balloon or stent.

So, this technique looks interesting, but requires a lot more evidence before its role will become clear. But, a big worry is that entrepreneurs will use this technique or two other coronary artery disease detection tests, computed tomography (CT) and electron beam tomography, to get the general public to undergo these expensive studies to determine if they have coronary heart disease and, if so, how much. That is a very big worry - and it will happen; indeed, it is happening now. None of these techniques is adequately documented for such purposes. The false negatives (thus, falsely assuring the individual there is no problem) and the false positive rate (probably requiring additional studies and often invasive procedures) will almost certainly be very significant. And, all that huge expense that will enrich the entrepreneurs will be useless unless they can show, in properly conducted studies, that the tests actually reduce the frequency of heart attacks or heart attack deaths.

The promoters will have to show in those with no symptoms that such tests are better than checking risk factors (especially blood pressure, blood cholesterol levels, high-density lipoprotein cholesterol [HDL-good cholesterol] levels, and smoking patterns) and making the lifestyle changes or taking medications, if necessary, to reduce risk. At present, there is no such evidence for magnetic resonance or computed tomography, and inadequate evidence for electron beam tomography. Electron beam has the most evidence of the three, and there is now a huge push by cardiologists for its use to determine the amount of calcium in coronary blood vessels of the heart. Many want to do the electron beam routinely in persons with or without symptoms saying high scores are predictive of heart attacks and justify a vigorous approach to risk factors (such as high cholesterol, high blood pressure, smoking, etc). But, the usual risk factors should be approached vigorously anyway. There is inadequate evidence that electron beam adds significantly to looking for the usual risk factors, there are too many false positives, and its routine use was NOT recommended in a recent statement of the authoritative American College of Cardiology and the American Heart Association. Electron beam to determine the amount of calcium in the coronary blood vessel needs more study before its use can be recommended as a routine diagnostic procedure.

Remember, if these sophisticated tests are used more extensively than they should be (particularly for people without symptoms or known coronary heart disease), somebody has to pay. If insurers or employers or managed care companies pay for inadequately documented tests, everybody’s health insurance costs go up.

Kim, W.Y., et al. Coronary magnetic resonance angiography for the detection of coronary stenosis. The New England Journal of Medicine. Vol 345 (December 27) Pgs 1863-1869. 2001.