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What are the Various Diagnostic Imaging Tests?

Posted Aug 24 2008 1:49pm
ANNOUNCER: For anyone with questions about the health of their heart, there are a variety of diagnostic tests available to physicians that can help provide some answers.

RICHARD P. LEWIS, MD: Cardiovascular medicine has more imaging tests than anybody else, by a long ways. Actually, the first diagnostic imaging test was a chest x-ray invented around the turn of the 20th century, so it's over 100 years old. It's still helpful.

JACQUELINE NOONAN, MD: You know, in the olden days, people used to use their stethoscope. And with the stethoscope, if you had trained well, you could diagnose rheumatic heart disease, what kind of valve was involved, by listening. And this could be helped by looking at an electrocardiogram, which would tell you which side of the heart was thicker than normal, whether the atrium was enlarged and use certainly the chest x-ray.

Then cardiac catheterization came into vogue where one could put a catheter into the heart and measure pressures, put dye in and show defects, show whether there was rheumatic heart disease, congenital heart disease or whether the heart, which is not functioning well. You could look at the coronary arteries with coronary angiography.

RICHARD P. LEWIS, MD: The rest of the cardiac testing has mostly been developed in the last 50 years, and they fall into two basic categories: invasive and non-invasive. And invasive means puncturing the surface of the body. Non-invasive means not having to do that.

The non-invasive tests consist of electrocardiogram and chest x-ray; echocardiography, which is a widely used test today; nuclear studies, where you inject a radioisotope into the blood, and then look at where it goes in the heart to see if there's areas that aren't getting enough blood, that's a perfusion scan. Or you can actually watch the heart contract with the isotope that's inside the heart's blood pool and watch the blood pool pass through the heart, and you can define how well the heart's working. That's a widely used test.

The echo is an extremely versatile test, because it'll show you all of the heart valves and how they work, the heart muscle, what kind of condition it's in, whether there's fluid in the sac around the heart, and a lot of other things that you could do. And echo's an easy test to do, and you can do it on really sick people in the intensive care unit, emergency rooms.

Now, the invasive studies, diagnostic studies, are mostly cardiac catheterization, which involves putting a catheter in blood vessels, usually the leg blood vessels, and advancing them into the heart. And there we measure pressures inside the heart, which is critical when you have abnormal heart valves, and we can also inject contrast material, that you can take an x-ray movie and see the outline of the heart chambers and see how well the heart's working, or you can see, most importantly, the heart arteries and see how they're doing.

JACQUELINE NOONAN, MD: There are CAT scans, and now there are improvements in the CAT scans, and then there's the magnetic resonant imaging, MRIs. So there are many different diagnostic tests that can be used. There are also tests that can be used to look for how good the oxygen in your heart is, which reflects the coronary blood flow. Nuclear scans, where one can do nuclear scans, both when you're resting and when you're exercising, will help us to understand whether your coronary arteries are supplying the heart sufficient blood. So there are many, many different kinds of diagnostic tests available today.

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