DR. ALPERT: I think that is so crucial, Dr. Harrington. The assessment of the treadmill exercise ECG, based on the ST segment alone, is really obsolete, and we don’t emphasize much on that. I see that in many places. The exercise ECG, all the factors that you talked about, the hemodynamic factors, arrhythmia, the heart rate, the functional capacity, and the heart rate recovery, all are extremely important.
If those factors are actually looked at in a careful way by using the Duke treadmill score or some integrated score, when you compare that score to the nuclear or exercise echo, which I also am an advocate of, and if you use all the exercise treadmill test information, then the stress imaging tests are nearly as accurate as the standard ECG exercise stress test when you look at all the exercise data alongside the ST segment. Examples include total exercise time, maximum heart rate achieved, symptoms during or after exercise, blood pressure, and heart rate response.
There was the paper by Leslee Shaw and Nanette Wenger5 that came out in late 2011, comparing myocardial perfusion stress imaging with exercise treadmill testing in low-risk women. This study showed that, in these women, there was very little or no significant difference in 2-year outcomes between the 2 tests, but the treadmill test was much less expensive. We don’t teach that, and all the factors you just mentioned are neglected factors, Dr. Harrington.
DR. HARRINGTON: Yes, but in light of full disclosure, I introduced myself from Stanford, but I spent the 22 years before that at Duke and am well familiar with Dan Mark’s work in developing the notion of the Duke treadmill score,6,7 which again I think is underutilized. It’s easy to order the imaging test. And as you say, Dr. Amsterdam, I think all 3 of us would agree there’s an important role for imaging as an adjunct to exercise testing, but I think it’s very easy to forget that you might not need it.
DR. AMSTERDAM: Absolutely, if you want to localize ischemia or estimate the extent of ischemia, those are appropriate indications. I want to note the role of stress testing in the patient who has been inactive and wants to undertake a vigorous exercise program, say, jogging or walk/jog. If such a patient has multiple risk factors, or is a male over 40 years of age or a postmenopausal woman, a stress test should be considered to provide a rational activity goal.
DR. ALPERT: Just to highlight something that you both said, because I think it’s very important: so often, people just look at the ST segment and the heart rate and say that the patient didn’t achieve a 95% heart rate, and therefore, the test doesn’t give us the answer. But, in fact, the patient had a very excellent heart rate and blood pressure product, but perhaps didn’t quite achieve 85% or 90% of the predicted maximum heart rate.
I see this all the time in the coronary care unit. A patient comes in with atypical chest pain, but only limited data can be obtained from his/her history on risk factors, etc, so you want to be a 100% certain before discharging him/her. So, we do a routine stress exercise test: an ECG test. The result shows that the patient maybe didn’t quite achieve a 90% predicted maximum heart rate, but still had a very strong peak exercise heart rate-blood pressure product and no symptoms.
For me, that’s all the information I need, because the patient came in with atypical rest pain. If the patient had unstable coronary disease, he/she would not be asymptomatic when I push the heart rate and blood pressure up to a reasonably good level, even if the patient didn’t achieve the full diagnostic level that we normally like.
So again, I think you need to look at the whole test. You may also need to check whether there were arrhythmias. I’ve had a number of patients complain of palpitations. They say, “when I go for a walk in the morning, I get palpitations.” Sometimes, I’ll put them on the treadmill to see what are these palpitations, and often, as you both have seen numerous times, it turns out to be a small number of premature ventricular contractions or atrial premature beats. Then, you reassure the patient and you say, “We saw what it is and it’s nothing for you to worry about.” So sometimes, the exercise test in that setting is actually therapeutic.
Let’s talk a little bit about something that Dr. Amsterdam mentioned: the exercise prescription and screening of a person who is going to start an exercise program. Often, these are patients who have seen their primary care doctor. The primary care doctor points out that their lipids are abnormal and they have a diabetic tendency, some glucose intolerance, and slight hypertension. The patients are given a number of medicines, and then, the primary care doctor refers them to a cardiologist.
The patient, with a reasonable number of risk factors, is going to start a vigorous exercise program; let’s say he/she has a positive family history of coronary disease developing in his/her relatives in their 50s. When you see such a patient with lots of risk factors who’s going to start exercising, does it change your attitude about a routine exercise test?
DR. HARRINGTON: Yes, I actually send a lot of those patients for a stress test, in particular. As Dr. Amsterdam has already pointed out, for a man who is middle-aged or older or a woman who is postmenopausal, I do use the exercise test, but I spend a fair amount of time thinking about how active or inactive they really are and ask a lot of questions about what they do in their daily life while trying to gauge whether they are going to be pushing exercise more than I think they’ve been doing.
Most of these people who are thinking about embarking upon an exercise program are quite sedentary, and I find that the exercise test is helpful in many ways. It’s obviously a screening tool for ischemia, but I do believe in its use for exercise prescription, because it helps set realistic goals.
When you’ve exerted many metabolic equivalent tasks, you can use that to start a conversation with the patient about what the goals for the exercise are going to be. Don’t get discouraged starting out slow and building up, because the hardest thing with an exercise program is getting people to maintain it. So, I think the exercise test can be a good way of setting the baseline and allowing the patient to have some realistic expectations that are both safe and helpful from a psychological point of view.
DR. AMSTERDAM: I like that. I would add, Dr. Alpert, that we've been discussing patients who are sedentary and have multiple risk factors. The guidelines have discouraged, in most cases, exercise testing in the asymptomatic population, but they give a fair endorsement, a class IIa (“is reasonable”) in the diabetic patient.
But again, what is to be done with the information? An ischemic response would urge intensive risk factor modification, but diabetes is a coronary risk equivalent, and so we should already be engaging in intensive risk factor modification.
So, in general, in all patients, a positive stress test in an asymptomatic patient doesn't mean you go to the catheterization laboratory, but it does help convince the patient and the doctor to pursue more intensive risk factor modification if that's not already being done.
DR. ALPERT: It’s interesting, Dr. Amsterdam, that you mention coronary calcification, because I was just going to say that I don’t order a lot of coronary calcification CTs for somebody with a lot of risk factors, particularly someone who’s diabetic, is young, has a family history of coronary artery disease, or has been quite sedentary, except in the setting we’re just talking about. In some patients, I get the sense that they’re not taking the whole issue seriously enough or it’s the opposite: they’re extremely nervous that they’re going to have a heart attack at any minute.
I think the coronary CT is helpful in these settings. Now, if it’s very positive, then I will often do a stress test on top of it—in other words, to try and determine the burden of ischemia. That’s not a large number of patients, but it’s a group with a large number of risk factors. In this group, you just have this sixth sense that there’s a lot going on because of their long list of risk factors.
DR. AMSTERDAM: So, Dr. Alpert, will you do a coronary calcium CT without CT coronary angiography?
DR. ALPERT: Well, that’s an evolution. We’re part of the Prospective Multicenter Imaging Study for Evaluation of Chest Pain (PROMISE) trial8 right now that’s making all those comparisons, so I will just recommend that the patient have a coronary calcium CT done first. Then, if there are a lot of risk factors for atherosclerosis, we talk about whether we’re going to do a CT angiography or a stress test, and part of that will be answered in the PROMISE trial sometime in the next 18 months, when we’ll see which test was the most useful.
My prejudice is that all these tests are going to give you equivalent information in terms of the diagnosis, and maybe, even just the Framingham Risk Score will give you almost as much information. But, that’s why I don’t do many coronary calcium CTs, maybe just 1 or 2 a year, except in a particular case where I feel like they’re extremely anxious or they’re not anxious enough and not taking it seriously. Otherwise, as you’ve talked about, I usually do exercise testing to help with exercise prescription.
DR. AMSTERDAM: We usually do CT coronary angiography with coronary artery calcium scoring.
DR. ALPERT: This may change depending upon the results of the trials that are coming.
I think we’re almost out of time. This has really been a delight. It’s always a pleasure talking with both of you because you’re so knowledgeable and have so many excellent practical points. Maybe I could just summarize it by saying that the answer is that in asymptomatic patients, there are some subsets of “asymptomatic” where exercise testing is a good idea, but for the vast majority of patients, you don’t need to do exercise testing, and certainly, routine yearly exercise testing ought to be prescribed.
Do each of you have any further comments?
DR. HARRINGTON: I think you’ve summarized it well, Dr. Alpert. It’s not routine to test people who are asymptomatic, but there are things that can be learned through exercise testing, which can be applied to some patients who are asymptomatic and fall into special categories. So, a class III recommendation generally is a wise one, but there are some areas where equipoise still exists and the information may be helpful.
DR. ALPERT: Thank you very much, gentlemen.