Stress test in the Chest Pain Unit: What is essential is invisible to the eye
HUGO R. RAMOS
Instituto Modelo de Cardiología, Privado S.R.L. Universidad Nacional de Córdoba,
Facultad de Ciencias Médicas. (5021) Córdoba, Argentina. E-mail
Recibido el 06-MAYO-2019 – ACEPTADO el 17 de MAYO de 2019.
There are no conflicts of interest to disclose.
Acute chest pain is a challenge for ER physicians, because an inappropriate diagnosis of acute coronary syndrome (ACS) doubles or triples mortality in patients if they are discharged from the ER without a proper diagnosis 1].
In this issue, Salvador-Casabón et al 2], present a risk stratification proposal in patients with acute chest pain, with a score based on points arrived at by the addition of stable CAD scores, called ERGOSCORE 3]. This proposal has the advantage of being relatively simple, which could be significant because physicians have to cope with a usually high load of patients in the ER, and most physicians examining patients first are not cardiologists 4]. See the paper published. For these reasons, they are responsible for making transcendental decisions, such as requesting the proper tests in a rational manner, consulting with cardiologists or other specialists without unnecessary delays, preventing work overload in the ER, the lab or other related services, not making excessive expenses destabilizing health budgets and making them unequal; but concomitantly, not discharging patients with a severe and potentially lethal pathology 1]. This challenge could be overcome with papers as the one presented here.
However, this study deserves further consideration. First, age is not specifically mentioned as an inclusion or exclusion criterion; although the mean age was 58.23±2.48 years, this variable, by being one of the key components of the score, should have been mentioned specifically. Thus, we may assume that patients between 30 and >80 years were evaluated 3]; but this point is not specified. On the other hand, it would be important to have a full view of the number of patients with acute chest pain who visited the ER over the period of the investigation, besides those that were sent to the stress test. The CPU (Chest Pain Unit) is especially useful in patients in whom there is doubt about the diagnosis; in patients in whom the diagnosis is clear, ischemic and bleeding risk should be stratified and the diagnostic procedures and treatment should be started without delay 5]. These data are not negligible, as they would help to have a comprehensive view of the investigation. Likewise, whether there were deaths in the 15-month follow-up should have been mentioned, as this could also be a factor, that if high (>10%) could entail a significant bias when evaluating the results.
In general, the CPU should allow establishing if a patient can be discharged with a very low risk; i.e. with a clinically acceptable negative predictive value (NPV) of 99.5% during 30 days of follow-up 6].
In this study, patients were followed over a 15-month term, but how many patients returned within the first 30 or 180 days with a new acute chest pain or major adverse cardiac event?
After these general commentaries, let’s see what happened with the stress tests. The authors observed that 20/100 tests were positive and in 17/100 significant coronary lesions were found, with a sensitivity for stress test of 82%, specificity 90% and NPV 96.1%. In general, in the CPU, stress testing without imaging is useful to stratify risk in the short term rather than for an accurate diagnosis of CAD (positive predictive value usually low, with a high NPV); that is to say, the goal is to establish with the greatest possible safety (ideally 100%, but 99.5% is clinically acceptable by convention) 6,7], whether patients will not present infarction or death within the 30 days after the ER discharge. Although in this study there was a good risk stratification, there is no mention about how many patients came back or presented events within 30 days after discharge. Then, NPV is relevant at the time of making a decision 7]. Although this study was mainly based on coronary artery anatomy, having a severe obstructive lesion in the mean 15-month follow-up, does not always guarantee that such lesion was responsible for the acute chest pain when making the visit to the ER.
In favor of this study is the fact of having recorded readmissions due to chest pain; but it is not specified how many patients did it within 30 to 180 days. It can only be inferred that 17% of evaluated patients had significant coronary lesions in a mean 15-month follow-up. Moreover, we should take into account that there is myocardial ischemia, particularly in women, with no obstructive coronary artery lesions (ischemia and no obstructive coronary artery lesions - INOCA) 8]. Finally, whether readmissions within 30 days were very low, the algorithm would allow using resources rationally, avoiding unnecessary tests in patients with a low to high probability, streamlining the use of resources only in those who would benefit more with stress testing, as stated by the authors (ERGOSCORE, between 4 and 6 points).
This exploratory single-center study shows an algorithm for patients in an intermediate risk, with an NPV for discharge that could be acceptable, but is not optimal. Although there are more sophisticated imaging methods in the CPU (myocardial SPECT, stress echocardiography, coronary CT angiography, MRI), stress testing entails a relatively simple logistics, has a relative low cost, it is available in every center, even those of mean or low complexity, and it provides significant information for prognosis in the short term, as its main goal in the CPU is not establishing whether there is CAD or not with accuracy, but being a tool for risk stratification.
Brieger D, Eagle KA, Goodman SG, et al. Acute coronary syndromes without chest pain, an underdiagnosed and undertreated high-risk group: insights from the Global Registry of Acute Coronary Events. Chest 2004; 126: 461-69.
Salvador-Casabón JM, Serrano-Aísa PJ, Cantero-Lozano D, Andrés-Sánchez A. Ergoscore: propuesta de algoritmo diagnóstico de cardiopatía isquémica en la unidad de dolor torácico. Rev Fed Arg Cardiol 2019; 48 (1): __-__.
Montalescot G, Sechtem U, Achenbach S, et al. Guía de práctica clínica de la ESC 2013 sobre diagnóstico y tratamiento de la cardiopatía isquémica estable. Rev Esp Cardiol 2014; 67 (2): 135. e1-e81.
Ramos HR, Bono JO, Quiroga W, et al.Encuesta Nacional de manejo del dolor torácico. Rev Fed Arg Cardiol2006; 35: 157-63.
Than M, Herbert M, Flaws D, et al. What is an acceptable risk of major adverse cardiac event in chest pain patients soon after discharge from the Emergency Department?: a clinical survey. Int J Cardiol 2013; 166: 752e754.
Amsterdam EA, Kirk JD, Bluemke DA, et al; on behalf of the American Heart Association Exercise, Cardiac Rehabilitation, and Prevention Committee of the Council on Clinical Cardiology, Council on Cardiovascular Nursing, and Interdisciplinary Council on Quality of Care and Outcomes Research. Testing of low-risk patients presenting to the emergency department with chest pain: a scientific statement from the American Heart Association. Circulation 2010; 122: 1756-76.
Pacheco C, Quesada O, Pepine C, et al. Why names matter for women: MINOCA / INOCA (myocardial infarction / ischemia and no obstructive coronary artery disease). Clin Cardiol 2018; 41: 185e193.