Heart disease is not only the most widespread, deadliest malady of modern civilization, it is also one of the most difficult to diagnose in its early stages. By the time you feel chest pains, the disease is already far advanced. Thus, groups such as the American Heart Association direct their exhortations to avoid heart disease-exercise regularly, watch your diet, don`t smoke-to everyone, the healthy and the unsuspecting sick alike.
It`s good advice, of course, to eat your vegetables and lay off fatty foods. But it can be especially difficult to order a salad for lunch instead of the burger and fries you really want when your own coronary arteries may be clean as a whistle for all you know.
If there were some way a healthy person could know his personal cardiac health, physicians agree, it would be wonderful for individualizing prescriptions to avoid heart attacks.
Even better, suppose your doctor could show you a picture of what your arteries look like today and then show you again in a year so you could actually see how clean living had brightened your prospects.
In fact, some cardiologists are already doing just that in a limited way, and they predict that within five years it will be common for healthy people to get detailed pictures of the state of their cardiac health. And probably at a price that will make such routine tests relatively attractive.
New technology could bring a virtual revolution in the value and scope of physical examinations for the healthy.
For years the gold standard to diagnose heart health has been angiography, an expensive procedure that can be both painful and risky for the patient. It requires that a small tube, called a catheter, be inserted into a blood vessel, usually in the groin, and then snaked through the circulatory system into the major vessels of the heart itself.
Once the catheter is placed within a coronary artery, it can deliver bursts of contrast fluid that show up on X-ray images, providing a picture of how blood flows through the artery. By looking at these images, called arteriograms, doctors can determine if blood is flowing freely or if walls of the vessel have become so thickened and scarred that the passageway for blood is dangerously narrowed.
It can cost $4,000 or more for angiography, which requires a hospital stay, so physicians order it only when they are fairly certain a person has serious heart disease. Often, arteriograms are made in preparation for open-heart surgery.
Angiography is not a procedure any physician would recommend for a person free of symptoms who is only curious about his cardiac health.
But there is a broad array of alternative cardiac-imaging technology waiting in the wings that poses little or no risk to the patient, doesn`t require hospitalization and is much cheaper than angiography.
As with angiography, some of the newest imaging techniques rely on X-rays to put together pictures of the heart, its arteries and the flow of blood through them, but others use powerful magnetic fields and radio waves or ultrasound, an updated version of the sonar pioneered in World War II to locate enemy submarines.
Virtually all of the newest imaging devices rely on high-technology electronics that collect raw data and convert it to digitized signals that are assembled by sophisticated computers into fascinating images of the heart.
These computer-enhanced images may appear in color, they may move and they may even be seen in three dimensions.
They tell a cardiologist much more about the heart than merely whether the coronary arteries are blocked, although that it is a major purpose for the new technology.
”All of these techniques provide anatomic information, but some are also giving us biochemical information and functional information,” says Dr. James V. Talano, director of cardiology graphic services at Northwestern University Medical School and editor of the American Journal of Cardiac Imaging.
The new imagers provide physicians with pictures of the beating heart following a heart attack that can show whether a section of heart muscle is dead or alive. They can assist doctors in deciding whether it would be useful to open up or replace arteries leading to that part of the heart damaged by an attack.
This information is unavailable from arteriograms, Talano says. The new imaging technology gives physicians much more help in deciding when a patient needs aggressive therapy such as surgery and when medications and risk modification are sufficient.
One form of ultrasound technology called TEE, for transesophageal echocardiography, provides a glimpse of cardiology`s future. TEE uses a small probe that is placed down the patient`s throat into the esophagus, where it sounds out pulses of very high-frequency sound waves.
Sitting right next to the heart, the TEE probe sends back signals converted into images of the coronary arteries in real time. As the physician moves the probe around, he watches images of the coronary arteries on a television screen.
Dr. David McPherson, director of the cardiovascular image-processing lab at Northwestern, is using TEE in one study to determine the effects of cholesterol reduction in a series of patients whose genetic makeup causes them to have exceptionally high cholesterol levels in their blood.
Diet and even medications don`t lower the cholesterol significantly for these people, so doctors are using a radical approach: processing their blood to extract cholesterol from it. By using TEE, McPherson is monitoring the condition of major coronary arteries in these patients.
The goal is to see over time if lowering their cholesterol can check or even reverse the thickening of artery walls that otherwise will lead to heart attacks.
Scientists in Finland recently used ultrasound to measure plaque buildup in sets of identical twins to contrast the effects of smoking cigarettes. In this study, the Finns found that the artery walls of twins who smoked thickened at rates noticeably greater than in their nonsmoking siblings.
Although ultrasound monitoring of arteries is largely limited to research projects at the moment, as doctors improve their ability to monitor changes in artery health in this group, it provides experience for following the coronary status of healthy patients.
In McPherson`s lab, researchers are working on ultrasound technology that makes three-dimensional pictures of the heart. They are doing work with animals to learn how a heart attack looks in 3-D in its earliest stages.
The goal here is one day to have a machine available in hospital emergency rooms where 3-D heart images could be made within a few minutes after a person with chest pains arrived. Such equipment could help doctors quickly diagnose people suffering heart attacks. It could also let physicians observe the heart in motion as anticlotting medication is given to stop the attack.
Ultrasound equipment is favored by many cardiologists as the most versatile cardiac-imaging tool because it is relatively inexpensive, portable and easy to use.
A development pioneered by Dr. Steve Feinstein at the University of Chicago may also make ultrasound even more useful in years to come. Feinstein has developed microbubbles that are tinier than blood cells themselves.
These microbubbles, which can be inserted into the body intravenously through the arm, provide an excellent target for the soundwaves to bounce off of as they flow in the bloodstream through the coronary arteries. Microbubbles can greatly enhance the ability of ultrasound devices to measure the rate of blood flow, for example, and is another indication of how this technology is improving on several fronts simultaneously.
Most cardiologists who work with new imaging technology agree that within five years any healthy person who wonders if he has coronary artery disease and, if so, how bad it is, ought to be able to find out.
For some patients, the future is now. At the University of Illinois, Dr. Bruce Brundage is using state-of-the-art X-ray technology called ultrafast computerized tomography (CT) to spot calcium deposits in coronary arteries.
Follow-up exercise tests with ultrafast CT can determine the functional significance of this disease, and the images provide patients with a graphic picture of their coronary status.
One patient of Dr. Brundage`s has high cholesterol and has sometimes been reluctant to take medication to control it, Brundage says.
”I gave him a picture of his arterial calcium to put on his desk to remind himself every day to take his cholesterol medication,” Brundage says. ”It`s a great motivator.”
Some researchers say that this noninvasive cardiac imaging may soon provide new insights into therapies for fighting high blood pressure.
Although the cause of most high blood pressure is still a mystery to physicians, it is known that very high blood pressure is associated with increased risk for heart attacks and strokes and that using drugs to lower blood pressure reduces those risks.
But some blood-pressure drugs work by reducing the amount of fluid in the body and others by relaxing the walls of blood vessels. If new imaging technology can tell a physician whether a patient`s high blood pressure is due to excess fluid or to narrowed arteries, the doctor can then tailor his medication choice to fit the patient`s need, researchers predict. Such technology is currently being tested.
Physicians who have used new cardiac-imaging machines are virtually unanimous in saying they expect that this equipment more and more will be used to help keep healthy people healthy as well as to treat the ill after they suffer heart attacks.
