Detecting Coronary Artery Disease: The Role of Non-Invasive Cardiac Stress Testing Webcast September 28, 2010 Preeti Kansal, M.D.

Transcription

1 Detecting Coronary Artery Disease: The Role of Non-Invasive Cardiac Stress Testing Webcast September 28, 2010 Preeti Kansal, M.D. Please remember the opinions expressed on Patient Power are not necessarily the views of Northwestern Memorial Hospital, its medical staff or Patient Power. Our discussions are not a substitute for seeking medical advice or care from your own doctor. That s how you ll get care that s most appropriate for you. Introduction What's a stress test? How do you know if you need one? And what can your physician learn from a cardiac stress test? Coming up, a cardiologist from Northwestern Memorial Hospital will answer these questions and discuss the role of non-invasive cardiac stress testing. It's all next on Patient Power. Hello and welcome to Patient Power sponsored by Northwestern Memorial Hospital. I'm Andrew Schorr. Well, we've done numerous programs on heart disease, arrhythmia, all about the heart, and, you know what, I think there's always room for more because it's such a prevalent health concern for all of us. I know just about any family, somebody has died of a heart attack or they've had a stroke, and ideally we want to prevent all that. Now, we've talked about all kinds of lifestyle changes we can make, but sometimes you just don't know what's going on in your arteries, and even someone who they think is physically fit may be candidate for heart attack. It came up, as we were recording this program, it came up just the other night. The coach of the Michigan State football team, Mark Dantonio, coached a wonderful game where they beat Notre Dame, hopefully Notre Dame is not your team, in overtime with sort of a trick play, and right after that game he had tremendous pressure in his chest, and it turned out that he was having a heart attack, and he had one of those stents put in, and he's going to be okay. But here was a basically athletic guy, so how do we know what's going on in your coronary arteries, and are you at risk? Or if you actually have been having a heart attack how do we know what the damage is? What is a Stress Test? So it all comes down to testing and imaging. We have an expert with us today who will take us through all that. That's Dr. Preeti Kansal, who is a cardiologist. She's an assistant professor at Northwestern University's Feinberg's School of Medicine and of course she's at Northwestern Memorial Hospital. Dr. Kansal, let's understand stress testing first. What does that mean? What is a stress test? A stress test is a way that we can non-invasively image the heart and assess the blood flow through the coronary arteries, which are the vessels that feed blood to the heart muscle.

2 All right, so does that mean you have to exercise? Like, I've been on a treadmill, so I believe I had one kind, so many of us as we get older and have physicals have EKGs and you're just kind of lying there and these electrodes are put on your chest and other places but you're not stressing the heart. So how is it different from when you have a stress test from just a normal EKG? A normal EKG can be done at rest, so as you pointed out you may be just lying there and not exercising, not walking but resting, and that would be a resting EKG. We can also do an EKG or a stress test while your heart rate is elevated, so either while you were walking on a treadmill we can continuously monitor your EKG with exercise or when we give you medications that might stress the heart, meaning increase the heart rate, or open arteries in the heart so that we can see how the blood flow changes through arteries. All right. Now, there are people who have had a physical, their EKG was normal, and then they have a heart attack. How does that happen, and is that why stress testing is important? A resting EKG really only tell us what the electrical activity or the conduction is through the heart at rest. However, it may change with exercise or with stress. For example, if you're running to catch a bus, if you re under a lot of emotional stress and your heart rate and your blood pressure go up, the EKG may change, and sometimes the EKG changes are subtle or we cannot see them on a regular EKG. We may need to do additional imaging of the heart, and in that case we can do an imaging-based stress test. Now, you mentioned something that I think is critical for people to understand. When we say outside of stress testing, we use this word "stress," I'm under a lot of stress, my daughter who is in high school is under a lot of stress, you know, we use that word routinely now. Certainly that coach, Coach Dantonio with an overtime victory after hours, he probably was in a pressure cooker situation. So that can be emotional stress that triggers a heart event. Yes, it could be. It could be emotional stress. It could be physical stress. Generally, it's mostly physical stress that drives up your heart rate and increases the blood pressure demands and the oxygen demands on the heart, and often when you have severely blocked vessels the heart muscle is just not able to get enough oxygen from the blood supply. So a stress test in which we increase your heart rate and increase the demands on that blood supply often is a way that we can see if you actually have flow obstructing blockages in those arteries. 2

3 All right. I had one of these, so let's talk about the way it worked out for me. And I'm a runner, so they put me in a treadmill, and they had me running for I don't know how many minutes, it wasn't a long time, but I was getting to be where I was huffing and puffing. I had the electrodes on, and then they had me lie down real quick, they had an ultrasound machine, and they immediately were doing an ultrasound of my heart. So is that a stress echo? You're getting a stress EKG and you're looking at live images of the heart? Yes. The important thing to understand about stress testing is that there are two components to a stress test. One is how do we stress your heart, and as you brought up with your own stress test it was walking on a treadmill, in which case your heart rate and your blood pressure go up with exercise and with the increased demand on the heart muscle. The other important part of a stress test is the imaging portion, and there are two major ways we can image the heart. One is by ultrasound, which, as you mentioned, is the type of stress test you had. So we do ultrasound pictures before and after the stress. The other option is nuclear imaging in which case a radioactive trace or isotope is injected into the bloodstream and we're able to visualize that by an x-ray camera. In that case pictures are taken before stress and after stress, and we compare the relative blood flow in those pictures. All right. Let's go back and talk about first how you stress the heart. So I was an athlete, kind of a weekend athlete anyway, so they felt that I could, you know, be on the treadmill and turn it up a little and see what happened. But some people, and I know our producer, Jamie, she was telling us about her dad, they didn't do that. They injected something. So when do you do which? It depends on the clinician's discretion, really. Ideally, we would like to exercise everyone who can be exercised or who can walk adequately and safely on a treadmill. The reason for that is that exercise often gives us additional information not just about the blockages or the lack of blockages in the arteries but it really tells us how fit you are. What does your heart rate do with exercise? What does your blood pressure do with exercise? How far can a person actually walk on a treadmill, and how well conditioned are they? And often that is something that can help motivate us and motivate patients to do more exercise and to increase their exercise capacity. The other option for those who cannot exercise are medications or pharmacologic stress testing. Of that we have two broad categories. One are vasodilators, an example of which is adenosine or dipyridamole, and that one opens up the arteries in the heart and changes the relative blood flow through those arteries in the heart muscle. 3

4 Another option is dobutamine, and that one mimics exercise so the heart rate is increased to achieve the same type of a target heart rate as we would aim for with exercise on a treadmill. So dobutamine increases the contractility or the squeeze of the heart and increases your heart rate and your blood pressure. As a clinician we often decide which one is best for the patient based on what their other medical problems are, based on how much can they actually exercise, if at all, and we have to make sure that they're not--that they don't have any potential reactions to either one of those medications before we order such a test. Now, what about age? Are there age limitations on who can have a stress test? Generally speaking, no. There is no age limitation. As you know, our population is generally aging, but we find that many more patients than ever before are also really functional at an older age, so there is no reason based on age alone to not order a stress test or to order a different type of stress test. It really depends on what the person's functional capacity is and what other their medical conditions are and what the reason is for the stress test, what do we actually intend to do with the results. We're going to get to that in a minute, the reason for stress testing, but I just want to complete the imaging part of it. So I understand with ultrasound. I had that, and there were real-time pictures right away and they did some before and after the stress on the heart as you described. What about nuclear imaging? What does that mean and how is that any different? Nuclear imaging really just refers to another type of imaging that we would do with stress testing, and that's where we would inject a radioactive isotope and we take pictures on what's called a gamma camera, but it's similar to x-ray technology. So a patient lays under a camera for about 15 or 20 minutes, gets a set of pictures taken, then they undergo the stress and then they have to get another set of pictures taken right after stress. So nuclear imaging just refers to a technique by which we can image the heart. Who Needs a Stress Test? Dr. Kansal, so who needs a stress test? We talked about the different ways you stress the heart and now the different ways you image, but who needs that exam in the first place? I think a lot of what determines whether or not a patient needs a stress test is what the clinician, the patient's doctor, whether it's their internist, their general doctor or 4

5 their cardiologist, feels is going on with the patient. A lot of times we commonly do it for example for a preoperative evaluation. Maybe somebody is going for a different surgery, like a joint replacement or a vascular surgery or something else that the surgeon or the anesthesiologist would like to get a preoperative risk assessment. So a lot of times stress testing can help us with that. The other things that are common indications for a stress test are after a bypass surgery or after an angioplasty. And probably the most common thing is when a person comes in with chest pain or palpitations or shortness of breath and we want to figure out why they might have some of these symptoms. Coronary disease is probably the most common cause of death in Americans rights now. Stress testing is one way that we can non-invasively figure out the extent of blockage that patients may have in the arteries that supply the blood to the heart. What does the Stress Test Show? Yeah, it's so important. I think most people--since it's really non-invasive is give you information so that you can know for you, the physician, and us the patient what's going on and we have a plan. So tell us what you're looking for. So I think most people understand that the coronary artery brings blood to the heart muscle, not to be pumped but to keep that muscle healthy and strong, so blockages are not a good thing. So tell us about what you're looking for when you do that stress test. What we're looking for is flow-limiting obstructions to the arteries or flow-limiting blockages. And what that means is a blockage that's generally over 70 or 80 percent that limits the amount of blood that is actually feeding the heart muscle. When we actually do the stress test or when we look at the images or look at the EKGs we're looking at changes, for example, in the pictures or in the function of the heart before and after stress. Presumably areas that do not get enough blood flow either do not squeeze as well or don't take up those radioactive nuclear isotopes that we talked about as much as areas that are getting enough blood flow. So there may be a difference in the pictures before and after stress if there are flow-limiting blockages in the arteries. All right. And when we talk about blockages is this cholesterol, calcium? Is it like the inside of a rusty pipe, I've heard that analogy? What could it look like? It is often a combination. We typically expect that it is a buildup of cholesterol which really occurs throughout our adult life and builds up as you get older, and sometimes it's intermixed with calcium buildup. And it really is a plumbing system that sometimes gets blocked up, and sometimes stents or angioplasties or even bypasses are the only ways to open those arteries. 5

6 All right. And when you do this then had somebody typically had pressure or pain or maybe an exam is done and you're looking for something but maybe somebody really didn't have acute symptoms, maybe it was even some sort of checkup and then, voila, there it is. In other words, are you always symptomatic? No, we're not always symptomatic. Classically diabetics don't have as many symptoms as other people do. For many reasons their symptoms are often more subtle than non-diabetics, and their risk for coronary disease is much higher than the average person. And, as you know, each individual is different. Some people get palpitations, some people get shortness of breath, and some people get classic chest pain. Everyone does not get classic chest pain, and that's why it's really important to have a good physician who knows what symptoms to look for and when to send you for a stress test as opposed to not sending you for an evaluation of what may otherwise be atypical symptoms. Now, if someone has previously had a heart attack would a stress test be used sometimes, you know, with some regularity in the past to just see how the heart is doing or medications are doing? Where does it come in if you've already had a heart attack? It's definitely useful, and it's one of the most common indications for a stress test is for some sort of a clinical way to monitor a person after either a heart attack or after they've had their arteries opened either by bypass surgery or an angioplasty. That's definitely one of the most important indications for a stress test is how do we monitor how the medications are doing, the way we opened your arteries, are they still open, are your bypass grafts still open or it is the stent still open. We don't necessarily want to send someone just for another angiogram for an invasive procedure to look at those things. We often use a stress test to look and see how well everything is functioning. Now, when you have one of these tests, so it's showing sort of the plumbing you described, but it also can show the rhythm under stress, how are these related? So the heart inherently has what we would call an electrical system, which is the rhythm, and that's what the EKG shows. And it has a plumbing system, which is the coronary arteries that provides the blood and the oxygen and the nutrients to the muscle and throughout the rest of the body. And often they're related to each other. At times of stress when the heart may not be getting enough blood supply or enough oxygen sometimes the rhythm becomes compromised, and you can get different rhythm disorders which show up on an EKG. 6

7 Normally, in an otherwise healthy person with exercises--you would know just going for a jog as someone who exercises your heart rate should go up with exercise. That's a normal response. Sometimes when the blood supply to the heart muscle is compromised we may know this on an EKG because maybe the heart rate doesn't go up as it should. It may not go up appropriately, or it may not come down appropriately with rest after exercise. So they're all related in a multitude of different ways, but often the blood supply to--an obstruction in the blood supply to the heart may cause a rhythm disturbance that we would see on an EKG, which is why we monitor the EKG during the entire stress test, not just check one at rest and check one after stress. Now, I understand you look at the wall of the heart as well, like the thickness of the wall. So where does that come in when you start to get these images of maybe looking at something that's been going on long term? So one type of stress test, which is a stress echo, which is an ultrasound done before and after, the ultrasound images look at the structure of the heart. They can look at the valve function and they look at the thickness and the squeeze or the motion of the heart at rest and with stress. When the heart is not getting enough blood supply the walls of the heart may not squeeze adequately when they're under high stress. When the blood pressure is elevated, when the heart rate is elevated and the demands of the heart muscle are increased, if there are blockages in the arteries and the heart muscle is not able to get enough blood supply to the muscle oftentimes one of the first things we find on an ultrasound would be that it doesn't squeeze as well or that the walls of the heart muscle don't come in adequately as they should. So that's something that we can see with a stress echo. And when somebody has that condition is that what you typically refer to as heart failure? No. That is different than heart failure. That just means that they have a positive stress test. Heart failure means that even at rest the heart muscle is weakened and it doesn't squeeze as well as it should, and often the person has shortness of breath or swelling in their legs, has other systems that we term heart failure. But obviously so the warning signs are people could later get to that point but the question is when they're under some sort of stress is there something going on, when their demands on their body. And let's say if you didn't do these exams could it then become the thing where they can have trouble going up the stairs or just even walking any time? In other words, would they progress to that sort of heart failure situation? 7

8 They can. Not necessarily. I think the concept of heart failure is at a different end of the spectrum than the stress testing. The stress testing is usually how we diagnose coronary disease or we do follow up, like we talked about, after bypass surgery or after an angioplasty or a stent placement. And heart failure is something that usually occurs when people have had a lot of untreated coronary disease, untreated high blood pressure, untreated rhythm problems, but that really can also come from a multitude of other sources. I see. Actually from the standpoint, I mean, that probably is a different concept and much more complicated than our topic for today. I should say, though, to our audience that we have done programs on heart failure with Northwestern specialists and be sure to take a look for those because it is complicated but important too. Back to stress testing then. You know, we worry about this even in kids, and there was, just recently there was a high school athlete who died, and it's still not completely known what was going on, but you worry about that, undiscovered heart problems in athletes. So in younger people when would it be indicated? Let's say if somebody was going to be doing races or even, you know, if somebody wants to run a marathon, they hadn't exercised in a long time, and you have to sign all these releases, when do you want to get worked up in that way? I think that whenever a person has got a lot of risk factors such as a family history, they've been a smoker, they've got high cholesterol or they're diabetic, it's in the very least worthwhile to have an evaluation by their internist or a cardiologist and let that physician or clinician put all of the pieces together and figure out what test if any is the right one in order to prepare a person for what may be a strenuous exercise or a regular exercise program. For younger people such as adolescents or young athletes, often those who have a bad outcome that is related to their exercise, it's rarely due to coronary disease. It's often due to arrhythmia or a rhythm problem or some other sort of structural heart disease, but again screening for those things is very important, and it's often a good idea to have that stuff done before starting a strenuous exercise program, until we see a cardiologist in the office because there may be other tests that are indicated for the evaluation of structural heart disease that may put a person at a risk for a rhythm disorder or for sudden death related to exercise. 8

9 Taking Action All right. Let's talk about what to do with the information. So someone has a stress test, certain things are observed. We know there are a variety of approaches. You mentioned some, bypass, stents, balloon, angioplasty and medication, so what usually follows? What happens in the cardiologist's mind and in the discussion with the patient to individualize that care? It largely depends on what the clinical situation is with the patient. There are some people for example who they've had a bypass and they probably will always have some degree of coronary disease and some degree of an abnormal stress test, but it's the ability to tell if it's significantly different or does it match with their symptoms, and what's the clinical reason that we did the stress test and what do we do with that information. In a person who doesn't have coronary disease but we may find an abnormal stress test, then the question is how abnormal is it and does it warrant a coronary angiogram. Usually when we're looking at arteries and blockages in arteries the decision tree is really when do we proceed with an angiogram to directly look at arteries and directly see how extensive the blockages are, and from there we would decide whether or not a person would need an angioplasty or a stent placed or just more medications. Just so people understand what an angiogram is, that's where you pass a catheter up from the groin typically right up into the arteries you're looking at. Right. And that's the most direct way of looking at the blockages or the anatomy of the heart arteries. The stress tests are generally an indirect way, and it's as we talked about before, they're the way that we can non-invasively look at blood flow. But for somebody being monitored, for instance somebody that's previously had a heart attack, you can be pretty confident that's a good way to keep up with them? Yes, I think that along with regular doctor visits. The most important thing of all of this is not to skip seeing your doctor or to feel that now I've had all these things done, I don't need to see anyone again. But it's definitely one of the best ways as a cardiologist that we have to monitor how well the medical therapy is working and how well some of the mechanical therapies such as the angioplasties and stents are working. 9

10 Good point. Now, what about the need for this? I would guess it's increasing. You mentioned about diabetes. We have an epidemic of diabetes. We have an epidemic of obesity, which can't be good for the heart. So it would seem like more people need this and maybe need it more often. I think definitely, as you point out, our population is getting older and fatter. It's definitely not good for the heart, it's not good for the joints and not good for probably any other part of the body, but we definitely have an increasing number of people in the population who do have indications for a stress test and who would benefit from an evaluation of their arteries. Doctor, so you meet a lot of people with heart problems, and we talked about the sort of national problem of obesity and diabetes, what do you tell your patients or even your friends and family so they can avoid even getting to this point? What do we need to do in our lifestyle? What do you preach when you get on your soapbox, if you will? Well, on my soapbox I have to say that prevention is by far the best thing that anyone can do. It's best to be the 80-year-old person who's never really had to see the doctor very often or definitely not had to have a lot of procedures or medications done. And I find that you can learn the most from your patients, and the people who have aged successfully, I would say it's the people who have been the most active and who have exercised the most throughout their life. And I think that keeping our weight down and exercising regularly, that should be as important a part of your day as brushing your teeth or bathing should be. I think that those are the people who can avoid the cardiologist and the stress test and any of the other procedure that go along with it for the longest period of time. Right. And a sensible diet for sure. Yes. Definitely lifestyle modification, healthy eating and lots of exercise. And I would just say that of course if you have some symptoms, though, do not pass go, you know, go to the hospital, call the doctor, call the ambulance, because speed matters too. And fortunately that football coach that we mentioned, Mark Dantonio, was right there I'm sure around a lot of medical people and when he felt pressure on his chest he got care quickly, which was evaluated, right away and now he's doing well. So speed is important, too, if you have symptoms, right, Doctor? 10

11 Yes, absolutely. Particularly when it comes to the heart or to the brain every minute of time is a blood cell or a piece of heart muscle that is potentially at jeopardy, so it definitely makes a difference. The faster you get to the emergency room, which is the best place to go if you do have any symptoms, the better it is and the safer it is. Okay. And remember, chest pressure, tightness or pain, back pain, jaw pain, neck pain, and it can be different in women, so it's really important to--if you have any concern at all you want to get it checked right away. I want to leave all of us with just one image the doctor was just talking about, prevention. I was at the gym the other day. There was an elderly couple, I think they were in their 80s and they were just out for their Sunday walk on the treadmill at a pretty good clip, and I'm sure they've gotten clearance from their doctors, and I just want to be like them. They were great. So, hopefully we all can be, but if you need a workup with a stress test, it's non-invasive and can give your doctors and you a lot of information, and if you've had a heart attack you can see how everything is going. Dr. Preeti Kansal, thank you so much for being with us and explaining all this to us. Thank you. It was a pleasure. I'm Andrew Schorr. Remember, knowledge can be the best medicine of all. Thanks for joining us. For more information or to schedule an appointment with a Northwestern Memorial physician, please contact our Physician Referral Service at or visit us online at Please remember the opinions expressed on Patient Power are not necessarily the views of Northwestern Memorial Hospital, its medical staff or Patient Power. Our discussions are not a substitute for seeking medical advice or care from your own doctor. That s how you ll get care that s most appropriate for you. 11