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.https://www.ncbi.nlm.nih.gov/pubmed/25622287
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.https://www.ncbi.nlm.nih.gov/pubmed/24730402
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.https://www.ncbi.nlm.nih.gov/pubmed/27226069
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. https://www.ncbi.nlm.nih.gov/pubmed/22371919
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. https://www.ncbi.nlm.nih.gov/pubmed/16631982
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.https://www.ncbi.nlm.nih.gov/pubmed/9625682
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.https://www.ncbi.nlm.nih.gov/pubmed/24026478
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).https://www.ncbi.nlm.nih.gov/pubmed/289
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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