The utility of an electrocardiogram in high-, intermediate-, and low-risk patients presenting with chest pain to emergency department

M Sanjay; Anju Susan Kurien; Merin Hanna Abraham; Abraham Speedie

doi:10.4103/cmi.cmi_102_22

ORIGINAL ARTICLE

Year : 2023 | Volume : 21 | Issue : 1 | Page : 44-49

The utility of an electrocardiogram in high-, intermediate-, and low-risk patients presenting with chest pain to emergency department

M Sanjay¹, Anju Susan Kurien¹, Merin Hanna Abraham¹, Abraham Speedie²
¹ Department of Emergency Medicine, Christian Medical College, Vellore, Tamil Nadu, India
² Department of Cardiology, Christian Medical College, Vellore, Tamil Nadu, India

Date of Submission	13-Sep-2022
Date of Decision	08-Oct-2022
Date of Acceptance	17-Oct-2022
Date of Web Publication	17-Jan-2023

Correspondence Address:
Dr. Abraham Speedie
Department of Cardiology, Christian Medical College, Vellore - 632 004, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/cmi.cmi_102_22

Abstract

Background: In emergency department (ED), though electrocardiogram (ECG) is obtained for both typical and atypical chest pain, at certain times, it is overutilized even in patients with low-risk factors for acute coronary syndrome (ACS). This study aimed to assess the utility of an ECG in patients presenting with chest pain to the ED. Materials and Methods: This prospective study included patients presenting with chest pain to the ED during August and September 2018. Following their initial assessment at triage, patients were grouped into high-, intermediate- and low-risk categories based on their risk factors for an ACS. ECGs were acquired and categorized into ACS and non-ACS pattern and their utility in each group was assessed. Results: This study cohort contains 313 patients with a male predominance 59.1%. The mean age was 52.6 ± 15.2 years. Typical chest pain was prominent in 95 (30.4%) patients. The incidence of ischemic and structural heart diseases was 53 (16.9%) and 31 (9.9%), respectively. ACS was diagnosed in 92 (29.3%) patients; among them, ST-elevation myocardial infarction (STEMI), non-ST-elevation myocardial infarction (NSTEMI), and unstable angina were noted to be 51 (16.3%), 27 (8.6%), and 14 (4.5%), respectively. The incidence of ACS based on risk category classification was as follows: high risk 38.9% (44/113) and intermediate risk 33.8% (48/142) and no patients in low risk had ACS. Conclusions: ECG though a useful screening test to diagnose ACS, should be used judiciously in patients with low risk of ACS to optimally utilize the limited resources in ED.

Keywords: Acute coronary syndrome, electrocardiogram, emergency department, ST elevation and non-ST-elevation myocardial infarction

How to cite this article:
Sanjay M, Kurien AS, Abraham MH, Speedie A. The utility of an electrocardiogram in high-, intermediate-, and low-risk patients presenting with chest pain to emergency department. Curr Med Issues 2023;21:44-9

How to cite this URL:
Sanjay M, Kurien AS, Abraham MH, Speedie A. The utility of an electrocardiogram in high-, intermediate-, and low-risk patients presenting with chest pain to emergency department. Curr Med Issues [serial online] 2023 [cited 2023 Jun 7];21:44-9. Available from: https://www.cmijournal.org/text.asp?2023/21/1/44/367855

Introduction

Chest pain is one of the most common (5%) complaints for emergency department (ED) visits.^[1],[2] The Global Burden of Disease study estimate of age-standardized coronary vascular disease death rate of 272/100,000 population in India is higher than the global average of 235/100,000 population.^[4] Acute coronary syndrome (ACS) is a major cause of death worldwide and is also a leading cause of death in people >35 years of age.^[3],[5] Approximately one in every six deaths is caused by coronary artery disease. The standard of care for diagnosis of ACS is by an electrocardiogram (ECG) at the time of presentation, along with symptom assessment and a cardiac biomarker panel to establish diagnosis. The sensitivity of ECG in detecting ischemic changes is 68%, while the diagnosis is augmented by the use of cardiac-specific biomarkers such as Creatine kinase MB (CKMB) and cardiac troponins. ECG is an extremely useful tool in ruling out ACS, with a specificity of 97%.^[6]

ECG in ED is a primary diagnostic tool that is performed in all patients with chest pain to rule out an ACS. The role of ECG in the management of patients with chest pain is more significant in the case of cardiac origin of pain, where it may directly affect the management. However, in the case of atypical chest pain, it is primarily used to rule out cardiac causes as a differential. In resource-limited settings, the use of ECG can be prioritized based on risk stratification.^[7] The overuse of this resource can be avoided in patients who are unlikely to have a cardiac event based on their clinical profile. This study aims at analyzing the outcomes of ECG based on risk stratification of patients, to determine the utility of ECG in each risk group. ECG can also help determine any other underlying cardiac conditions and arrhythmias, and the proportion of patients having positive findings in each group has also been observed.

Materials and Methods

Study design

This was a prospective observational study.

Study setting

This study was accomplished in the ED of one of the colossal tertiary care hospitals in Tamil Nadu, South India. Our ED accommodates 49 beds and manages all adult emergencies and traumas, including pediatric traumas.

Participants

Our study includes patients with chest pain presenting to the ED during August and September 2018.

Aim and objectives

Our study aimed to assess the utility of an ECG in high-, intermediate-, and low-risk patients presenting with chest pain to the ED. The objectives of our study were,

To determine the various patterns of ECGs in patients presenting with chest pain
To determine the percentage of patients presenting with chest pain and the abnormal ECGs suggestive of ischemia/infarction
To determine the predictive value of ECG in patients with low risk of myocardial infarction
To determine the association between the incidence of an ACS and the characteristics of chest pain (typical/atypical).

Inclusion criteria

All patients presenting with the chief complaint of chest pain to our ED were included in the study. Our study recruited a convenient sample of patients presenting to the ED between 8 am and 8 pm on all days for 2 months.

Exclusion criteria

Patients arriving at ED with chest pain between 8 pm and 8 am, traumatic chest pain and brought dead patients were excluded from our study.

Variables

Based on the demands of our study, the following variables were included in our study pro forma: patient's demographic details (age/sex), duration and the characteristics of chest pain, history of known cardiac illness (ischemic, structural, and congenital) and patient's vital signs at triage. Moreover, American Heart Association (AHA) illustrated ACS risk factors such as diabetes, hypertension, smoking, dyslipidemia, obesity, sedentary lifestyle, menopause, and family history of ACS were also elicited. Based on the patients' age and the risk factors, we classified three distinct risk categories, namely, high risk, intermediate risk, and low risk. The following were the criteria for the risk category classification:

High-risk category: (Any one criteria fulfilled):

Age >60 years or
Presence of two or more risk factors for an ACS as per AHA guidelines

Intermediate risk category:

Age group between 18 and 60 with at least one risk factor for an ACS as per AHA guidelines.

Low risk category:

Age group between 18 and 60 with no risk factors for an ACS as per AHA guidelines.

Upon initial assessment, patients were categorized based on their respective risk category and their ECG was obtained. Cardiac biomarkers were performed where indicated clinically for obtaining a definite outcome.

Outcome variable

Patients 'ECGs were interpreted and categorized into ACS and Non-ACS groups based on their ECG pattern. The final diagnosis of ACS was established predominantly by the ECG findings; however, cardiac markers were also analyzed when indicated. Considering ACS as a primary outcome, the incidence of ACS was compared against all the predetermined risk categories. The ED outcome and the hospital outcome among the high-, intermediate-, and low-risk patients were also analyzed.

Statistical analysis

This data were entered into Epidata for collection and analyzed using the Statistical Package for the Social Sciences for Windows (SPSS Inc. Released 2007, version 23.0. Armonk, New York, USA). Continuous variables were expressed as mean with standard deviation, and nominal variables as numbers and percentages.

Bias

Although patients presented throughout the day, only a convenience samples between 8 am and 8 pm were recruited in this study.

Ethical consideration

The study was approved by the Institutional Review Board and Ethics Committee (IRB approval number: 11515 dated July 08, 2018).

Results

During the 2-month study period, we recruited 313 patients with the chief complaint of chest pain to our ED [Figure 1]. Our study had a male predominance of 185/313 (59.1%) and the mean age of 52.6 years (standard deviation 15.2). About two-third of 224 (71.6%) of the patients presented to the ED within 12 h following the chest pain and more than half of them, 181 (57.8%), were triaged as priority 1 as per our ED triage protocol. Among those who had a known cardiac condition, ischemic heart disease was found to be predominant 53 (16.9%), while 33 (10.5%) patients had a structural heart disease. Majority of the patients had atypical chest pain 218 (69.6%), whereas typical chest pain was witnessed only in 95 (30.4%) patients [Table 1].

Figure 1: STROBE figure.

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Table 1: Baseline demographics (n=313)

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Among the various risk factors for an ACS, diabetes mellitus 133 (42.5%), systemic hypertension 137 (44%) and smoking 75 (24%) were documented in higher incidence; female patients in particular (n = 128) more than half of them 65 (50.8%) had attained menopause. Based on the age and risk factors, the risk stratification category of patients showed 113 (36.1%) as high risk, 142 (45.4%) as intermediate risk, and 58 (18.5%) as low risk. At presentation to the ED, their examination findings revealed tachycardia (heart rate [HR] >100 beats/min) in 109 (34.8%) patients, while bradycardia (HR ≤60 beats/min) in 32 (10.2%). 57 (18.2%) patients were hypoxic (SpO₂<94%) on arrival to ED and hemodynamic instability (SBP <100 mmHg) was elicited in 45 (14.4%) patients [Table 2].

Table 2: Vital signs and the risk factors of patients at presentation to the emergency department (n=313)

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Patient's ECG pattern revealed ST-segment elevation in 20 (17.7%) high risk, 32 (22.3%) intermediate risk and nil patients in low risk category (P = 0.013). Ischemic changes (ST segment depression and T wave inversion) was noted in 29 (25.7%) high risk patients, 33 (23.2%) intermediate-risk patients and 2 (3.4%) low risk patients (P = 0.004). Arrhythmia with ischemic changes was seen in patients with high-risk 4 (3.5%) and intermediate-risk category 2 1.4%) only. Arrhythmia without ischemic changes was noted in 23 (20.4%), 13 (9.2%), and 11 (19%) patients in high-, intermediate-, and low-risk categories, respectively. ECGs suggestive of normal sinus rhythm/other Non-ACS patterns in high-, intermediate- and low-risk patients were as follows: 37 (32.7%), 62 (43.7%), and 45 (77.6%) (P < 0.0001) [Table 3].

Table 3: Electrocardiogram pattern and the final diagnosis of patients based on risk stratification category

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A definite diagnosis of an ACS (ST-elevation myocardial infarction [STEMI], non ST-elevation myocardial infarction [NSTEMI] and unstable angina) in high-, intermediate- and low-risk categories was determined primarily by the initial ECG findings and correlation with cardiac biomarkers were achieved wherever indicated. A total of 92/313 (29.3%) patients in the study population were diagnosed to have an ACS, and all were belonged to either the high- or intermediate-risk categories, and none of the patients had ACS in low-risk category (P < 0.001). Among patients who had an ACS, STEMI (ST-elevation myocardial infarction) was diagnosed in 20 (17.7%) high-risk and 31 (22%) intermediate-risk patients; NSTEMI in 15 (13.3%) high-risk and 12 (8.5%) intermediate-risk patients and the diagnosis of unstable angina was elicited in 9 (8%) high risk and 5 (3.5%) intermediate risk patients [Table 3]. Based on the risk factors, the incidence of an ACS was predominantly higher in patients with two or more risk factors 44/113 (38.9%) when compared to patients with one risk factor 48/142 (33.8%); moreover, none of the patients with no risk factors were diagnosed to have an ACS. Hence suggests that the presence of multiple risk factors is associated with a higher prevalence of ACS in that population.

Summation of ED and hospital outcomes determined, 93/113 (82%) patients in high risk, 122/142 (86%) in intermediate risk and 54/58 (93%) in low risk were discharged stable from the hospital, while 10 (9%) in high risk, 4 (3%) in intermediate-risk and 1 (2%) in low-risk category succumbed to the illness. The overall mortality rate was found to be 4.8% [Figure 2]. One patient in the low-risk category died due to the cardiogenic shock secondary to refractory ventricular arrhythmia.

Figure 2: ED and hospital outcome based on risk stratification category.

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Discussion

This study focused on the risk stratification for an ACS as the major criteria in patients presenting to ED with complaints of chest pain before considering further investigations like ECG. As discussed earlier, acute chest pain has drastically increased the patients visit to ED in recent times. Diagnosing the cause of acute chest pain in ED remains a formidable task because of the extensive etiology that ranges from benign to potentially lethal. Hence, ECG remains a feasible and comprehensive method in diagnosing both the structural and the functional abnormalities of the heart.^[8],[9] Although ECG remains a primary diagnostic tool, sometimes they are overutilized in patients with low-risk factors for an ACS. Hence, our study focused on assessing the utility of an ECG in high-, intermediate- and low-risk patients presenting with chest pain to the ED. An US article published that the majority of the patients admitted with chest pain were not diagnosed to have an ACS, and such overtriage had enormous implications in the US health-care system, estimated at about 8 million dollar annual cost.^[8]

In ED, the element of typical chest pain itself is considered one of the salient clinical features that aid in the diagnosis of an ACS in patients presenting with chest pain. Studies suggest that patients presenting with typical chest pain have a potentially higher likelihood chance to have an ACS.^[8] Certain chest pain characteristics, such as stabbing, pleuritic, and positional, decrease the likelihood of ACS (likelihood ratios [LRs] 0.2–0.3). Conversely, chest pain that radiates to the shoulder or arms or is precipitated by exertion is associated with an increased likelihood of ACS [LRs (2.3–4.7)].^[8],[10] In our study, only one-third of the patients had typical chest pain, while the majority had atypical chest pain. Patients with features of typical chest pain were more likely to have needed further investigation with an ECG, whereas patients with atypical chest pain required risk stratification to consider the need of an ECG in this group. Among those who had typical chest pain, almost half of the population had an ACS; of them, the prevalence of STEMI was higher when compared to NSTEMI and unstable angina. Despite patients being presented with atypical chest pain almost 20% of them were diagnosed to have an ACS. Thus, our study also enhances the fact that the characteristics of chest pain alone may not be a reliable predictive tool to rule out an ACS and it has to be discreetly used in conjunction with various other factors to determine the diagnosis.^[11],[12]

In high- and intermediate-risk categories, more than one-third of the patients had a typical chest pain, while only a few had in low-risk category. This suggests that the prevalence of having typical chest pain is witnessed in larger proportion in high- and intermediate-risk categories when compared to low risk. Similar to various other studies, diabetes mellitus, hypertension and smoking were the most common risk factors determined in our study.^[13] It is clearly understood from multiple studies that how these risk factors can lead to the presentation of chest pain and make them high–intermediate risk for an ACS. It is also well observed that more the number of risk factors greater will be the association with cardiac events.^[14],[15] The study has also shown that postmenopausal status in women per SE places women at risk of ACS and hence ECG cannot be neglected in this population. Among diabetic and hypertensive patients, the incidence of STEMI and NSTEMI/unstable angina were similar in number, whereas, among smokers, there were two-fold rise in STEMI when compared to NSTEMI.^[15],[16] Similarly, Ralapanawa et al. reported that smoking and alcohol abuse are significantly associated with STEMI, while patients with NSTEMI or unstable angina had higher rates of hypertension.^[13] In our study, none of the patients in the low-risk category (no risk factors) were diagnosed to have an ACS, thus highlighting that the occurrence of an ACS in patients with no risk factors was potentially low.

The following ECG patterns were observed in patients with chest pain; ST-segment elevation, ST segment depression or T wave inversion, arrhythmia with ischemic changes, arrhythmia without ischemia, and normal sinus rhythm/others. Among those who had initial ECG findings of ST-segment elevation, all were diagnosed to have STEMI except for one patient who had pericarditis-induced ST-segment elevation. More than half of the patients whose ECGs were suggestive of ischemic changes had a diagnosis of NSTEMI/Unstable angina. The final diagnosis of STEMI, NSTEMI and unstable angina among high-, intermediate- and low-risk categories were as follows; more than one-third of the population in high and intermediate risk had a diagnosis of an ACS, whereas none of the patients presented with chest pain in low-risk category had a diagnosis of an ACS.

The ED outcome showed almost half of the patients in high and intermediate risk required hospital admission, while the majority of patients in low-risk category were discharged stable from the ED. This signifies that risk stratification per se can exclude or include the patients on the need for admission.^{[17],[18],[19]} Thus, although low-risk patients did not require admission yet, they were risk-stratified and subsequently discharged. More than half of our study population with chest pain were found to have no findings suggestive of an ACS and were eventually discharged, thus this result highlights that risk stratification can help us identify the population at risk and hence focus our resources on the evaluation of this specific population. In a bustling ED, this strategy can increase the availability of bed for patients in actual need for admission, thus improving the overall mortality rates.

From the results of our study, we conclude that ECG should not be neglected in patients presenting with atypical chest pain, even if it is in low-risk patients. Having said that, in an arduous situation like resource-limited setting, efforts and endeavors should be taken to avoid the overuse of an ECG and utilize the available resources to its maximum potential by percipiently using it for patients based on the clinical presentation and the risk factors for an ACS.

Conclusions

One-third of the patients presented with chest pain belonged to the high-risk category.

One-third of the patients with chest pain were diagnosed to have an ACS. The overall in-hospital mortality rate of patients presenting with chest pain was 4.8%. Although ECG is the first line investigation in patients with chest pain to rule out ACS, their risk stratification can help us prioritizing its use. In resource-limited settings, ECG use can be optimized in low-risk patients based on clinician's judgment.

Research quality and ethics statement

The authors of this manuscript declare that this scientific work complies with reporting quality, formatting, and reproducibility guidelines set forth by the EQUATOR Network. The authors also attest that this clinical investigation was determined to require Institutional Review Board/Ethics Committee review, and the corresponding protocol/approval number is dated IRB Min. No. 11515 dated 08/07/2018. We also certify that we have not plagiarized the contents in this submission and have done a Plagiarism Check.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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