So, You Had a Heart Attack When?

Many of us started an observation unit under the directive of “let’s have a place where we can rule out MIs.”

In our practice at Emory and nationally, the proportion of observation unit patients who we place in the observation unit for stress testing has decreased over the last eight years.¹ Moreover, low risk criteria like the ECACS or HEART Pathway have better defined who would not benefit from further provocative imaging when we care for patients in the acute care part of their ED stay.^2–4 Observation of chest pain and subsequent non-invasive testing is so pervasive now that the real question is not “who needs a stress test,” but rather “who needs ANOTHER stress test.”⁵

Today, providers must operate in the “data-free” zone when it comes to stress testing warranty. In this scenario, patients who had a negative stress test return to the ED with additional pain, and the question of “do they need another stress test” presents itself. Very few studies have tried to tackle this issue in a pragmatic fashion, but the Hachamovitch paper from 2003 probably has the best risk modeling available to answer this question.⁶ As such, the warranty would be far longer than most providers would consider and dependent on a number of risk factors.

The next group of patients to consider would be people who had a stress test with a true positive outcome. Here, a patient would have known coronary artery disease (CAD). To be considered for further observation, most providers would first address whether the patient was currently having myocardial ischemia. With contemporary troponin and rapid ECG pathways, this question is simple to answer. If the patient does not have an MI, then we must address if the patient needs FURTHER imaging to determine if there needs to be an intervention on his/her coronary vessels.

While it is true that the cardiology literature still suggests that non-invasive imaging is the mainstay of following disease progression, the actual cardiology data would suggest otherwise.^7,8  In studies where patients with known coronary artery disease are randomized to medical management or repeat interventions with stents (as could be the outcome of a positive stress test), there has not been a significant difference in the outcomes across endpoints.⁹ This has been addressed multiple times over the past 15 years.

For reasons that are numerous, none of these studies addressing this phenomenon include patients with left main disease. Most of the discussion sections in these studies say that they were excluded, as the approach for left main disease is generally revascularization based. This is a reasonable exclusion; however, it creates a small caveat to the supposition that searching for more disease will not improve a patient’s outcome, because any patient with left main disease would clearly need to be revascularized.

While the “data-free” practice zone exists when in terms of warranties for stress testing, the cohort of patients with known CAD who were, at first testing, not left main disease and then progressed to NEW left main disease is planted in the “logic-free” zone. There are a handful of studies addressing progression of diffuse CAD to a new left main stenosis and hence, the numbers are exceedingly small.   The PARADIGM study from  2018 found a progression rate of 47% after two years, but two Russian studies found rates closer to 10% when evaluated at time of CABG with symptoms.^10–12 These studies showing prognosis of this aggressive variant do not use the modality of stress testing to follow the progression of disease. It would be a leap in logic to assume that a test that is anywhere from 60 to 90% sensitive to detecting ANY DISEASE at all would suddenly be sufficient to monitor an aggressive variant of the disease.¹³ If a patient presents to the ED with known CAD, an unprotected left main lesion, chest pain, and no evidence of infarct, a typical provider would probably not accept a negative stress test as a reason to discharge the patient. Moreover, no provider would place that patient in the observation unit and convince someone to put that patient on a treadmill for provocative testing.

At the end of a chest pain work up in the observation unit in a patient who has never had any testing, it’s true that a stent may not singularly improve their mortality. However, connecting that patient with follow-up care because of a new diagnosis of coronary artery disease most certainly will. Conversely, stress testing a patient with known disease, who may be on some medication and already seeing a provider for management, would not likely benefit from the subsequent intervention from a positive stress test. To be sure, there exists a small unstudied segment of individuals with the worst CAD imaginable where this pathway may not be appropriate. But, why would anyone put a patient with the worst CAD imaginable in the observation unit in the first place? 

References

1. Terry N, Ross M, Odell T, et al. The declining role of chest pain in the emergency department observation unit. Acad Emerg Med. 2018;25(Supplement):S564. doi:10.1111
2. Than M, Flaws D, Sanders S, et al. Development and validation of the Emergency Department Assessment of Chest Pain Score and 2 h accelerated diagnostic protocol. Emerg Med Australas. 2014 Feb;26(1):34-44. doi:10.1111/1742-6723.12164
3. Mark DG, Huang J, Chettipally U, et al. Performance of coronary risk scores among patients with chest pain in the emergency department. J Am Coll Cardiol. 2018 Feb 13;71(6):606-16. doi:10.1016/j.jacc.2017.11.064
4. 4Mahler SA, Hiestand BC, Goff DC Jr, et al. Can the HEART score safely reduce stress testing and cardiac imaging in patients at low risk for major adverse cardiac events? Crit Pathw Cardiol. 2011 Sep;10(3):128-33. doi:10.1097/HPC.0b013e3182315a85
5. Osborne A, Weston J, Wheatley M, et al. Characteristics of hospital observation services: a society of cardiovascular patient care survey. Crit Pathw Cardiol. 2013 Jun;12(2):45-8. doi:10.1097/HPC.0b013e318285c2b9
6. Hachamovitch R, Hayes S, Friedman JD, et al. Determinants of risk and its temporal variation in patients with normal stress myocardial perfusion scans: what is the warranty period of a normal scan? J Am Coll Cardiol. 2003 Apr 16;41(8):1329-40.
7. Klocke FJ, Baird MG, Lorell BH, et al. ACC/AHA/ASNC guidelines for the clinical use of cardiac radionuclide imaging--executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASNC Committee to Revise the 1995 Guidelines for the Clinical Use of Cardiac Radionuclide Imaging). J Am Coll Cardiol. 2003 Oct 1;42(7):1318-33.
8. Gibbons RJ, Balady GJ, Beasley JW, et al. ACC/AHA guidelines for exercise testing: executive summary: a report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines (Committee on Exercise Testing). Circulation. 1997 Jul 1;96(1):345-54. doi:10.1161/01.CIR.96.1.345
9. Stergiopoulos K, Boden WE, Hartigan P, et al. Percutaneous coronary intervention outcomes in patients with stable obstructive coronary artery disease and myocardial ischemia: a collaborative meta-analysis of contemporary randomized clinical trials. JAMA Intern Med. 2014 Feb 1;174(2):232-40. doi:10.1001/jamainternmed.2013.12855
10. Weir-McCall JR, Blanke P, Sellers SL, et al. Impact of non-obstructive left main disease on the progression of coronary artery disease: A PARADIGM substudy. J Cardiovasc Comput Tomogr. 2018 May-Jun;12(3):231-7. doi:10.1016/j.jcct.2018.05.011
11. Zalewska-Adamiec M, Bachórzewska-Gajewska H, Kralisz P, et al. Prognosis in patients with left main coronary artery disease managed surgically, percutaneously or medically: a long-term follow-up. Kardiol Pol. 2013;71(8):787-95. doi:10.5603/KP.2013.0189
12. Akchurin RS, Shiriaev AA, Rudenko BA, et al. Left main coronary artery stenosis and progression of coronary artery atherosclerosis after angioplasty and stenting in patients directed to coronary artery bypass surgery. Kardiologiia. 2012;52(1):58-64.
13. Skelly AC, Hashimoto R, Buckley DI, et al. Noninvasive Testing for Coronary Artery Disease. Rockville (MD): Agency for Healthcare Research and Quality (US); 2016. http://www.ncbi.nlm.nih.gov/books/NBK361148/. Accessed July 23, 2018.

Anwar Osborne, MD, MPM, FACEP