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Against Stress Testing

Justin Morgenstern, MD

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EM:RAP 2019 September Written Summary 465 KB - PDF

Against Stress Testing

Justin Morgenstern MD

Take Home Points

  • The commonly cited miss rate of 2% for MI after negative ED chest pain work-up is no longer supported by the literature. The number is likely much lower.
  • Stenting does not appear to benefit patients with positive stress tests.
  • Stress testing is not accurate.
  • Why do we order stress tests? Morgenstern has not ordered a stress test in the last five years.
    • We have to know our pretest probability. Once we have done our chest pain work-up in the ED, how many of our patients go on to have an MI?
    • We need to think about what we will do with the results of the test. Who benefits from invasive testing and treatment? Which chest pain patients need PCI?
    • We need to know about the accuracy of the test itself and whether or not it actually helps.
  • How often do we miss MI? You usually hear a number of 1-2%. However, when you actually read the literature, a different number emerges.
    • The classic study that quotes a rate of 2% is Pope, et al in the NEJM.
      • Pope, JH et al. Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med. 2000 Apr 20;342(16):1163-70.
      • They concluded in the abstract that we mistakenly sent home or missed 2.1% of MI patients. If you actually read the study, it turns out that they worked up 10,689 chest pain patients in the emergency department and ended up sending home 19 who later had an MI. 19 out of 10,000. That is about 0.2% or about 2 in 1000. There were a few other patients with unstable angina which is tricky because it is subjective.
      • Even if you include these patients, the miss rate is about 4 in 1000. That 2 in 1000 number is consistent across the literature.
    • Foy et al looked at more than 420,000 emergency department chest pain patients and there were only approximately 400 who were discharged and later came back with an MI. This is 1 in 1000. Even when followed up to 6 months, there were still only 3 in 1000 that came back with an MI.
      • Foy, AJ et al. Comparative effectiveness of diagnostic testing strategies in emergency department patients with chest pain: an analysis of downstream testing, interventions, and outcomes. JAMA Intern Med. 2015 Mar;175(3):428-36.
    • Napoli looked at 3500 patients admitted to a chest pain observation unit. There were zero deaths and zero MIs in the follow-up period. 0%. And yet all of these patients were admitted to the hospital.
      • Napoli, AM. The association between pretest probability of coronary artery disease and stress test utilization and outcomes in a chest pain observation unit. Acad Emerg Med. 2014 Apr;21(4):401-7.
    • There are some studies reporting higher numbers such as the HEART score studies. Numbers between 0.5% and 3% are reported. However, these studies aren’t looking at just MI and death. They look at a composite called MACE which includes revascularization. If you just look at MI, the number of misses is about 2-3 in 1000. If the patient never had an MI, did they really need revascularization? Why did they put the stent in? Maybe it wasn’t necessary.
  • What do you do with a positive stress test? Do these patients need an angiogram or a stent? Stenting clearly saves lives in STEMI patients. What about patients with NSTEMI or unstable angina?
    • The Cochrane review for routine invasive management of NSTEMI and unstable angina showed that mortality was unchanged.
      • Fanning, JP et al. Routine invasive strategies versus selective invasive strategies for unstable angina and non-ST elevation myocardial infarction in the stent era. Cochrane Database Syst Rev. 2016 May 26;(5):CD004815.
    • Outside of STEMI, stenting does not save lives. When we send NSTEMI patients for catheterization, the benefit is a small decrease in minor or non-fatal MIs. This is important to know. If stenting does not save lives in patients with positive troponins, it is pretty unlikely that we will save lives with stress testing.
    • There are STEMI equivalents out there that don’t have ST elevation but need to go to the catheterization lab; Wellens, DeWinters, diffuse ST depression with ST elevation in aVR. But the benefit of routine invasive management in NSTEMI patients is very small.
    • These aren’t the patients we are sending for stress testing. These are patients with positive troponins.
    • What about invasive management in patients with negative troponins and negative ECGs?In Stergiopoulos et al, invasive management in these low-risk patients led to no difference in MI, mortality, unplanned revascularization, persistent angina, etc. If you send the patient for stress testing and it is positive leading to invasive management, you will not have helped the patient because these low risk patients do not benefit from invasive management.
      • Stergiopoulos, K et al. Initial coronary stent implantation with medical therapy vs medical therapy alone for stable coronary artery disease: meta-analysis of randomized controlled trials. Arch Intern Med. 2012 Feb 27;172(4):312-9.
    • Cardiologists will often say that stents reduce angina symptoms. There were some older studies that suggested that stents might decrease pain but they were fundamentally flawed because both patients and doctors knew they had received a stent.Pain is extremely susceptible to placebo effect. The ORBITA study was the only double-blind study on the topic and it was conclusively negative; stents do not improve chest pain, angina, exercise tolerance or quality of life.
  • Stress tests are not incredibly accurate. The accuracy of stress testing is complicated because we use them to assess multiple things. What we care about in the emergency department is whether or not the patient will die or have an MI in the short term. We use stress testing to protect our patients (and ourselves) from these bad outcomes. There are multiple observational studies looking at stress testing after ED work-ups.
    • Meyer et al looked at 7178 ED chest pain patients and had 903 patients with negative work-ups discharged for an outpatient stress test. Nobody died. There were 3 MIs and only one MI was in the first 30 days after discharge. All 3 MIs had negative stress tests. This was sensitivity of 0%. There were 150 who had abnormal or positive stress tests. Of those, 122 had confirmatory testing of no coronary artery disease. 80% of the positive tests were false positives. It is not clear that the 20% true positives had any benefit from the tests. There were 10 stents placed but these were patients with negative troponins and normal ECGs so they probably weren’t helpful. The positive stress testing likely caused unnecessary invasive interventions.
      • Meyer, MC et al. A critical pathway for patients with acute chest pain and low risk for short-term adverse cardiac events: role of outpatient stress testing. Ann Emerg Med. 2006 May;47(5):427-35.
    • This only looks at short term death and MI. Maybe you want to find coronary artery disease to guide medical management and prevent certain long term outcomes? Can stress tests find coronary artery disease?There are a lot of numbers out there. A lot of studies are biased because not everyone gets the same gold standard. In Froelicher et al, every patient got both an exercise stress test and an angiogram. Exercise stress testing has a sensitivity of 45% and a specificity of 85% for the presence of coronary artery disease. This is bad!
      • Froelicher, VF et al. The electrocardiographic exercise test in a population with reduced workup bias: diagnostic performance, computerized interpretation, and multivariable prediction. Veterans Affairs Cooperative Study in Health Services #016 (QUEXTA) Study Group. Quantitative Exercise Testing and Angiography. Ann Intern Med. 1998 Jun 15;128(12 Pt 1):965-74.
    • There are multiple different types of stress tests. Most probably have sensitivity and specificity of 80%. This is better but still not good enough. It is not sufficient to rule in or rule out disease. If you apply these numbers to extremely low risk patients (such as patients with a negative ED work-up), it results in more false positives than true positives. This doesn’t help us.
    • There are a few RCTs evaluating stress tests available. There are two that looked at emergency department patients. Lim et al looked at 1500 emergency department patients with normal ECG and negative biomarkers. These patients were randomized to get a nuclear stress test or clinical assessment based on risk factors.
      • Lim, SH et al. Stress myocardial perfusion imaging for the evaluation and triage of chest pain in the emergency department: a randomized controlled trial. J Nucl Cardiol. 2013 Dec;20(6):1002-12.
    • Frisoli et al looked at 105 low risk ED chest pain patients with two negative troponins and a low risk HEART score. Patients were randomized to immediate discharge from the hospital or admitted for stress test.
      • Frisoli, TM et al. Henry Ford HEART score randomized trial: rapid discharge of patients evaluated for possible myocardial infarction. Circ Cardiovasc Qual Outcomes. 2017 Oct;10(10).
    • There was no difference found in either trial. The stress test did not help. The only difference was higher costs and longer admissions in the stress test group.
  • Stress testing doesn’t help our patients. What should we do? If the patient has negative troponins and normal ECGs, Morgenstern discharges almost all of these patients to follow-up with their primary care doctor. There is the rare patient with the perfect story or who is so high risk that they are admitted with a negative work-up.
  • What do these patients need after their negative ED work-up? They need risk factor modification. They should receive counseling about diet, exercise and smoking. All patients need their blood pressure, cholesterol and diabetes status evaluated. Stress testing doesn’t help with this.
  • Does the patient need antiplatelet therapy? There are patients who are so high risk that they will need aspirin no matter what the stress test says. There are patients who are so low risk that they don’t need aspirin. There may be a gray area where the stress test might help. However, the stress test is horribly inaccurate. Just decide whether or not the patient’s pain was due to angina. If yes, then treat with aspirin. If no, then don’t.

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Tim V. -

This is really well done. Thanks, Justin.

Steve D. -

I completely agree with all that and would probably not want a stress test myself. That said, it is standard of care in the US so very hard to not do.

Justin M., M.D. -

I agree entirely. Stress testing is used routinely, and you don't want to be the sole doctor who chooses not to use it, especially when we know that there will be occasional misses. I would be careful about the term standard of care. From my conversations, I believe there are a few physician groups in the US that don't routinely use stress testing, so there are definitely groups of similar prudent physicians who would consider not ordering a stress test acceptable care, but I am not a legal expert. Rather than trying to change individual practice, I think it is much better to present the data to your entire group, and make a formal protocol on what to do, which then essentially sets the standard of care for your group. Although I think you could eliminate stress testing all together, it probably makes sense to start with the low hanging fruit - such as patients with low HEART scores. I never order stress tests, but things are definitely different in Canada and New Zealand where I work. I have never worked in the United States. But I think we are all very similar, in that we just want to provide the very best care for our patients, and I think stress testing is probably hurting a lot of patients, so it is worth the effort to (slowly) make this change.

donald b. -

Thanks for the great segment - really helpful. It wasn't clear to me if Dr. Morgenstern was referring to only low-risk patients (assuming using heart score to do initial risk stratification) that should not have stress tests?
Would intermediate-risk patients also fall into the group that doesn't need stress testing? Currently, we are ruling out our intermediate-risk patients in an obs unit with a longer rule out (up to 12 hours) and then arranging for cards follow up (and usually stress testing). Do the referenced studies include these non-low risk patients?
We are in a rural, semi-austere environment where follow up is a challenge so this would be a major change to our practice and a great benefit to our patients if we didn't actually need to schedule stress tests - any additional information on this would be super-helpful.
Thank you very much
Don Bader
Fort Defiance, AZ

Justin M., M.D. -

Hi Don. Thanks for the question.
Unfortunately, the answer is a little complex, because there isn't a single definitive study you can point to for "the answer". However, when I am making this argument, I am talking about stress testing in ALL patients. I have not sent a single patient for a stress test in probably 7 years.
Many of the observational studies looking at stress testing were limited to lower risk patients. However, there is pretty good evidence that even the patients we don't consider low risk won't benefit from stress testing. For example, a study by Napoli in 2014 looked at chest pain patients admitted to an observation unit, and out of 3500 patients, not a single one had and MI during the follow up.
I will also note - the 2/1000 miss rate that I quote is for all comers, so that does include the intermediate risk group you are talking about (but they may be washed out by lower risk patients).
Even without specific evidence in the moderate risk group, the rest of the logic still holds. What are you going to do with the results? If the patient had negative troponins, we have clear evidence that they don't benefit from stenting / invasive management. And the stress test still has horrible sensitivity and specificity for coronary artery disease. So it is an inaccurate test that doesn't lead to any change in management. So your pretest doesn't really matter - the test can't possibly help.
I couldn't cover all the evidence in a short EM:RAP piece. If you are interested in digging a little deeper into the evidence, I have a lot of references in my blog posts on the topic (there are 6 parts):

All the best

Ian L., Dr -

In the Pope JH study NEJM 2000
894 patients had MI diagnosed after work up
972 had unstable angina after work up .
11 patients refused admission despite medical advice .
The missed rate of MI was 19/889 .
For unstable angina the miss rate was 22/966 .
After adjusting for age sex risk factors and Comorbidities the ratio of deaths in those discharged to those admitted was 1.9 :1.0
It was May 1993 - Plus 7 months when CK -MB was the biomarker.

Mortality in those hospitalised for MI was 9.7% for those discharged 10.5 % (2)
With Unstable Angina Mortality in the discharged was 5.0 % ( 1) those admitted to hospital 2.1 %
So in this study misses with adjustment for various factors resulted in greater deaths than finds - ratio 1.9 : 1.0 as at 1993 but in a small sample .
Re -"never doing a stress test" .
A 60 year old diabetic male with a blood pressure of 160 systolic non smoking and total cholesterol of 7 wants to get fitter and undergo an exercise programme at a gym .
His 10 year risk of a cardiovascular event in 10 years is 25-29% by the Australian and New Zealand Cardiovascular Risk Calculatons .
He ought to have a stress test and calcium score plus or minus a CCTA in my view .

Justin M., M.D. -

Thanks for the comment
1) With regards to the Pope study, I think you have to be very careful when considering the denominator. Although it is true that they missed 2% of MI patients, that only represents 0.2% of all chest pain patients. Seeing as we don't know which patients are which, for the patient in front of you - who is an undifferentiated chest pain patient - the risk of a missed MI is 0.2%.
In terms of the mortality risk, it's hard to take the adjustments too seriously. The actual, unadjusted mortality was identical between the group of patients that went home with missed MIs and the patients diagnosed on their first visit. There was no difference. Which is an important point I didn't bring up in the podcast: we didn't hurt these patients at all by missing them. Their outcomes were exactly the same.

2) With regards to your example - I still don't see any role for stress testing.
First of all, what are you going to do with the result? This patient clearly needs risk factor modification. We don't need a stress test to tell us that. The patient should definitely be encourage to exercise, although he probably needs to be counselled about how to do that safely if he hasn't exercised in years. There is no data, as far as I know, that suggests a stress test can predict who is safe to start an exercise program. This patient (with negative troponins and a normal ECG) also clearly doesn't need an angiogram or revascularization. So how is the stress test going to change your management?
Even if you thought getting a formal diagnosis of CAD was really important, the best data we have says that an exercise stress test has a sensitivity less than 50%. If you really think the information is important, are you willing to use such an inaccurate test?
With regards to CCTA - there have been a few requests for a follow up already. I'm just starting my full literature review, so I'll get back to you. (However, asking the same question - how is this going to change management - hints that CCTA is also going to have very limited utility.)
All the best

Dallas Holladay, DO -

Nice piece, I tend to agree. We can get stress tests from the ED. I rarely do it but I get a number of patients signed out to me waiting for stress test results. I've not seen cards take any positice stress tests for cath. They typically get a CT coronary study and discharge with ASA, cholesterol and possibly BP meds.

Justin M., M.D. -

Thanks for the comment.
I think you make a really important point - one of the best signs that we are using a poor test is the frequency with which we ignore the results. We know the white blood cell count is useless for abdominal pain or cough, because whenever if disagrees with our initial impression (which is the majority of the time I think), we just ignore it. Stress testing is the same in some settings. That being said, I get a lot more worried in places where the stress test results are never ignored, because the result is a lot of necessary invasive procedures.

James P. -

In my place we have no support for chest pain and it's a binary discharge home or ED obs for stress test in AM. Moderate or high risk end up getting a stress because we have nothing else to offer.

I just did this 3 days ago and the patient's stress (cardiac PET perfusion) was positive and he just got a CABG. He realistically could have been called "low risk" because he was 70 without risk factors. I called him "moderate risk" because his chest pain was concerning enough to make him a HEART score of 4 which convinced me to stress him. Should we send these home? Is this CABG potentially not beneficial based on the evidence?

Sorry I originally posted this on the main EMRAP page. I am glad you are here answering questions. Very interesting piece and I believe that in general stress testing doesn't help but it takes some of the burden off of us sending moderate to high risk patients home even if it doesn't actually provide survival benefit.

Justin M., M.D. -

Thanks for the comment
It obviously impossible to know whether CABG helped the specific patient you saw. In general, it is a little hard to discuss the benefits of CABG, because all the studies of CABG vs medical management took place in the 1970s. And there was a clear mortality benefit of CABG over medical management. However, even thought most of these patients were called "angina", the diagnosis what completely different back then. These were very high risk patients with classic stories for ACS. My guess is that the vast majority of these patients would have had positive troponins. You can get a sense of how high risk these patients are by looking at the meta-analysis (Yusuf 1994) - the medical management group had a 5 year mortality of 15%! Compare that to the modern trials I presented, in which people with negative ED workups had essentially a 0% risk of MI and death at 1 year, and I think you can tell we are talking about completely different populations.
Since the 70s, all the studies have basically compared CABG to PCI. There is a little controversy in the cardiology world, but in general it is thought that PCI is noninferior to CABG. Therefore, if we know that PCI doesn't help patients with negative troponins, I think it is safe to say that is mostly true for CABG as well. (Although there may be occasional patients with classic angina, uncontrolled by medical management, with sigificant LAD or triple vessel disease that won't have positive trops but might benefit from CABG - we don't really have the evidence to say.)
So where does that get us? I think it means that the vast majority of patients with negative troponins and normal ECGs should be sent home with no further testing. There will be an occasional patient with an absolutely classic story who you might decide to send for further investigation. However, I am also hesitant to use a stress test in the high risk patients, because it will miss too many people. (Exercise stress tests have a sensitivity of less than 50% and even nuclear studies only have sensitivities close to 80%. If you really think the patient is high risk, are you comfortable using a test that will miss 1 in 2 to 1 in 5 patients?) I think the best approach is to identify the really high risk patients clinically, and get cardiology to assess them, knowing that for the vast majority of people with negative troponins, there is no role for interventional management, so your only option is good medical management.
Unfortunately, getting rid of the stress test takes away our safety net - the problem is, I think when you look closely at that net, it is full of massive holes. We feel better that it is there, but it isn't actually helping our patients at all. In fact, overall, I think it probably hurts them, because of the massive numbers of both false positives and false negatives.
All the best

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