Nuclear and Non-invasive Tests – Invasive and Non-invasive Tests (Diagnostics)

by Joseph Alpert, MD

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    00:00 Now, going back to the stress test, we can do the stress test with a transthoracic echo, as I told you, and the electrocardiogram.

    00:10 But one can also inject some radioactive material that’s taken up by the heart cells in direct proportion to the blood flow. So, you do a baseline study, you exercise the patient, you give them the radionuclide again and you see if there are areas of the heart muscle that don’t get blood flow. That would be a positive test.

    00:31 Now, if the patient’s had a previous heart attack, there won’t be any radionuclide in that area where the heart attack was, but guess what? During exercise, it won’t get any bigger. It will just stay the same, showing you that there is a permanent scar there, but not lack of blood flow during exercise. Now, we can do very much more detailed imaging as I said before, using the CT scan or the MRI.

    01:00 The MRI gives us the most detailed picture of the heart. It’s also the most expensive test. Patients have to go into a little chamber to have this done. And some people are claustrophobic and cannot tolerate this test. But, it’s a very, very detailed test.

    01:18 I wanted to show you some examples here. First, the nuclear stress test and then the MRI test.

    01:26 This shows you three nuclear studies. The top one is normal and you can see nice, uniform distribution of the different views of the radionuclide. The middle one shows you, in comparison by the way, to the normal above, some small deficits. So, this is a moderately positive test. And the lowest one shows you a lot of deficit. There’s very severe atherosclerotic heart disease here. The heart is really hurting during exercise. It’s not getting enough blood flow. Now, it turns out that how much of the heart doesn’t get blood flow during the nuclear stress test is a very important piece of information because the more severe the deficit; and you saw the severe deficit versus a mild deficit, the worst is the long term prognosis. And you can see from this study, as you get from left to right, more increasing deficits on a nuclear scan, the long term outlook for death and for heart attack is much greater, the worst the scan is. So, the scan also tells us a little bit about the possible future for this patient.

    02:40 The CT scan is particularly good in a very sort of low-grade CT scan for looking for calcium in the coronary arteries. If we see calcium in the coronary arteries, that tells us that atherosclerosis is present. It doesn’t tell us how bad it is, but it tells us that there is atherosclerosis. We can do something by injecting dye. We can do a CT angiogram where we actually see the inside of the blood vessels. Not quite as good as the invasive images of the blood vessels, but pretty good. The CT angio is particularly good if the patient has a normal study. Then we can say, “Your chest pain or your shortness of breath is not due to narrowing in the blood vessels of the heart.” And here we see a CT angiogram. You saw this slide before in the Anatomy Lecture as an example of how nicely we can see the coronary arteries. Above is a colorized version done by the computer. Below are the actual images. But you can see that we get really good pictures of the insides of the blood vessels, and we could see if there were narrowings there.

    03:46 This is a very popular test. Of course, it requires that the patient receive some radiation. And we always worry a little bit about that. We don't like to give too much radiation to the patient long term. We worry of course, about an increased risk for cancer. The MRI uses magnetic resonance imaging. There is no radiation involved, but it’s, as I said before, more expensive and the patient has to be willing to sit in this little chamber, which some claustrophobic individuals are not capable of doing. Here we see an MRI in a child that actually demonstrates a ventricular septal defect. You can see the chest X-ray on the left and the MRI on the right. And you can see exquisite detail of the anatomy, all the chambers are labeled and you can actually see the VSD, that there is a connection between the two ventricles, the septum is incomplete. And MRI is used quite often in diagnosing congenital heart disease. It shows us complex anatomy very, very well.

    04:52 Now, the simple chest X-ray is a very good initial screening test. It’s not very good for just diagnosing whether a patient has coronary disease or not, but it tells us - is the heart enlarged? Is the lungs normal? Is there pneumonia? Is there severe lung disease? We get a whole lot more information baseline, just like in the baseline electrocardiogram.

    05:14 Often these two tests are done as baseline, particularly if we are considering taking the patient to catheterization or of course, to surgery.

    05:24 So, let me just show you something about the chest X-ray with a few examples to show you the kinds of things we get from the chest X-ray.

    05:32 Here’s a normal chest X-ray. And we have labeled all of the various components. You can see the heart in the center, you can see the lungs, the ribs. Down below, the diaphragm with the stomach on the left and the… and the liver on the right. By the way, when I say the stomach’s on the left, remember, this person is looking towards me. So, it’s our right, but it’s the patient’s left. And the convention is you use the patient’s left and right, not your left and right. So, the stomach is on the left side of the body and the liver is on the right side of the body. And this is a totally normal chest X-ray - nice clear lungs, nice normal heart size. Now here, what’s wrong with this patient? Clearly, the heart is enlarged, right? What could be doing that? Well, it could be a patient who'd had multiple heart attacks or it could be an individual who has a heart muscle disease that results in dilatation of the heart and heart failure. And we are going to talk about the various diseases that can cause this enlargement of the heart and the symptoms and the treatment as we go along in this series. Here we see a very enlarged heart, but in this case, the enlarged heart is because of fluid in the pericardium. The pericardial space is swollen with fluid and that fluid can put pressure on the heart and actually decrease the pumping efficiency of the heart. So, this is consistent with a large pericardial effusion. It could be a very large heart, but the uniform roundness makes it more likely that it’s a large pericardial effusion. Here is an example of a patient with pneumonia.

    07:14 The heart is not enlarged, but look on the right side of the diagram. You can see that part of the lung is filled in with white material. That’s a pneumonia. So, this is a patient, perhaps with a normal heart, but who has pneumonia. So, their symptoms of shortness of breath might not be from heart disease, but from lung disease. So, you can see the kinds of things that the chest X-ray can help us with.

    About the Lecture

    The lecture Nuclear and Non-invasive Tests – Invasive and Non-invasive Tests (Diagnostics) by Joseph Alpert, MD is from the course Introduction to the Cardiac System.

    Included Quiz Questions

    1. Sestamibi
    2. Iodine
    3. Strontium
    4. Galium
    5. Thorotrast
    1. The severity of coronary artery stenosis
    2. Valvular insufficiency
    3. Valvular malformation
    4. Coronary artery malformation
    5. Coronary artery atherosclerosis
    1. MRI images are not as detailed as CT images.
    2. Patients can feel claustrophobic in an MRI scanner.
    3. Stress and exercise tests are cumbersome to perform with MRI imaging.
    4. MRI cannot be performed on patients with pacemakers.
    5. MRI is more expensive than echocardiograms.
    1. Cardiomegaly
    2. Myocardial ischemia
    3. Valvular vegetations
    4. Ventricular septal defect
    5. Arrhythmia

    Author of lecture Nuclear and Non-invasive Tests – Invasive and Non-invasive Tests (Diagnostics)

     Joseph Alpert, MD

    Joseph Alpert, MD

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