Gearing Up Ways to Diagnose Bad Plaque

The appreciation of vulnerable plaque’s central role in heart disease is triggering a new medical arms race, this one to develop tests to find it early.

“We have no tools at the moment to recognize which sites are vulnerable. It’s guesswork,” says Dr. Renu Virmani of the Armed Forces Institute of Pathology in Washington, D.C.

The best method at the moment appears to be ultrasound. Using a probe threaded through an artery into the heart, doctors can scan for plaque that looks soft and suspicious.

But many in the field complain that these images lack detail and are hard to read. So the competition is on to find better ways of locating risky plaque. Among them:

* Magnetic resonance imaging. Doctors say they can already use special MRI machines to see vulnerable plaque in the carotid arteries that lead to the brain. Visualizing the heart is harder, in part because it’s moving. However, Dr. Valentin Fuster of Mt. Sinai School of Medicine in New York City says he believes this should soon be possible. One advantage: It’s all external. Unlike the other techniques, nothing is inserted into the body.

* Infrared spectroscopy. Organic compounds absorb infrared light in unique ways. So shining light on a living structure, such as an artery wall, produces a specific chemical signature, depending on what it contains. This is already used to grade the fat content of beef. Researchers at InfraReDx are developing an infrared probe that would be threaded into the coronary arteries.

* Thermography. Plaques that rupture tend to be inflamed, so they have a higher temperature. Scientists are working on probes that would check the temperature of the arteries to search for risky plaque.

* Blood tests. If accurate, this could be the most widely used method of diagnosing vulnerable plaque. One approach might be to check for proteins that result from inflammation of the arteries, which can be a sign of bad plaque.