Association of Symptoms and Mode of Transportation to Emergency Department In Patients with Acute Coronary Syndrome

Abstract

Background:

Patients with acute coronary syndrome (ACS) with symptoms matching their expectations of a heart attack are more likely to use emergency medical services (EMS) than not.

Objective:

To determine whether presenting symptom clusters are associated with EMS use in ACS patients and if EMS use or symptom clusters are associated with prehospital delay.

Methods:

This secondary analysis used data from the PROMOTION trial, a randomized clinical trial that enrolled 3,522 subjects with a history of or at-risk for ACS from five sites in the United States, Australia, and New Zealand. Subjects were randomized to usual care or an educational intervention to reduce prehospital delay. During the 2-year follow-up, subjects admitted for ACS were asked about symptoms, time of symptom onset, and mode of transportation to the hospital. Symptoms were grouped into Classic ACS, Pain Symptoms, and Stress Symptoms clusters.

Results:

Of 3,522 subjects enrolled, 331 sought care for ACS during follow-up; 278 had transportation mode documented; 121 (44%) arrived via EMS. Classic ACS plus pain symptoms (AOR=2.66, p = 0.011), classic ACS plus stress symptoms (AOR=2.61, p = 0.007) and classic ACS plus both pain and stress symptoms (AOR=3.90, p = 0.012) were associated with higher odds of EMS use versus classic ACS symptoms alone. EMS use resulted in a 68.5-minute shorter median delay (p = 0.002) versus non-EMS use. Symptom clusters were not predictive of delay time in the adjusted model (p = 0.952).

Discussion:

Although chest symptoms were the most prevalent symptoms for most (85%), the combination of classic ACS symptoms with other symptom clusters was associated with higher EMS use. Further research is needed to determine whether a combination of symptom clusters helps patients correctly interpret ACS symptoms to better understand how symptom clusters influence EMS use.

Introduction

Timely diagnosis and treatment of patients with acute coronary syndrome (ACS) decreases mortality and morbidity.¹ If treatment begins within one hour of symptom onset, survival increases by 50%, or by 23% if within 3 hours of symptom onset.² Because patients cannot distinguish between the types of ACS events based on symptoms alone, they are encouraged to seek care immediately for any suspected heart symptoms.³ Current guidelines advise that patients with a history of ACS with symptoms lasting > 1 minute take one dose of nitroglycerin (NTG).² If angina symptoms do not subside within 3–5 minutes, patients are advised to call Emergency Medical Services (EMS) immediately.² However, many patients do not follow guideline recommendations and delay seeking care for 2.5–3 hours.^{1,2, 4}

The largest component of treatment delay is prehospital delay (time of symptom onset to hospital arrival).^5–7 During this time interval, the patient needs to recognize symptoms, interpret the cause of symptoms, and take actions to seek medical care. Use of EMS has been associated with decreased prehospital delay for patients experiencing symptoms of ACS.^8–16 Moreover, in-hospital treatment is faster^17–19 and survival improves for patients who arrive by EMS as compared to those using other modes of transportation to the hospital,^4,20 especially for those with ST-segment-elevation myocardial infarction. Yet studies reveal that many patients with suspected ACS do not use EMS as their mode of transportation to the hospital, with utilization rates ranging from 14.7% to 66%.^{8–14, 16–19,21–30}

Aspects of the ACS symptom experience have been associated with EMS use. For example, having more persistent,²⁴ more severe,²⁸ or unbearable^10,16,21 symptoms or symptoms that start abruptly and reach maximum intensity within minutes^12,22 have all been shown to be associated with EMS use. Interpreting symptoms as cardiac in origin,^9,10,14,23 symptoms that match expectations of what a heart attack is,⁹ including symptoms that are associated with use of NTG⁹ or other anti-anginal medications,⁹ are also associated with EMS use. Specific symptoms such as nausea,^12,16,23 vomiting,^22–24,28 dizziness,^12,23,28 syncope,²⁵ sweating,^12,23 and dyspnea²⁸ have all been associated with EMS use in patients with suspected or documented ACS. However, ACS symptoms commonly occur in clusters, defined as two or more symptoms, related to one another, occurring at the same time.³¹ Yet, the association between ACS symptom clusters and EMS use as a mode of transportation to the hospital is unclear. Therefore, the purposes of our study were to determine 1) if clusters of presenting symptoms are associated with EMS transportation to the emergency department (ED) in patients with ACS and 2) evaluate if EMS transportation or symptom clusters are associated with prehospital delay time.

Methods

In this secondary analysis, we used data from the PROMOTION (Patient Response tO Myocardial Infarction fOllowing a Teaching Intervention Offered by Nurses) trial,³² a randomized clinical trial to reduce patient prehospital delay in obtaining treatment for ACS. In the PROMOTION trial, we tested an individualized face-to-face educational intervention designed to reduce patient delay in seeking treatment for ACS symptoms in 3522 patients from 5 sites in the United States, Australia, and New Zealand.³² Patients with a history of or at-risk for ischemic heart disease were enrolled, randomized to usual care or intervention, and then followed for 2 years for occurrence of ACS symptoms. Patients were instructed to call the investigators (after the acute event was over) when they sought treatment for symptoms they believed were cardiac in origin. All patients were also telephoned monthly in order to ask them about possible visits to the ED for ACS in case the patient had not contacted the investigators. Patients who sought care for symptoms of presumed ACS were interviewed using techniques the investigators developed to assist patients to closely estimate the time of symptom onset. Transportation used to arrive at the ED was categorized as ambulance, private automobile, or other (e.g., public bus, taxi, walked). For this analysis, mode of transportation was categorized as: EMS (ambulance) or non-EMS (non-ambulance) use.

During follow-up, patients who were admitted for suspected ACS symptoms were asked about eight types of symptoms: chest pain/discomfort/pressure, arm pain/discomfort, shortness of breath, sweating, upset stomach/nausea/vomiting or indigestion, sense of dread/anxiety, back/shoulder pain, and neck/throat/jaw pain. Based on work by Riegel et al.³¹ on symptom clusters, these symptoms were grouped into Classic ACS Symptoms, Pain Symptoms, and Stress Symptoms clusters. Classic ACS Symptoms included chest pain/discomfort/pressure. Pain Symptoms included arm pain/discomfort, back/shoulder pain, and neck/throat/jaw pain. The arm pain/discomfort could be in the left arm, right arm, or both arms. Stress Symptoms included shortness of breath, sweating, upset stomach/nausea/ vomiting or indigestion, and sense of dread/anxiety. A fourth symptom cluster, Diffuse Symptoms, also from Riegel et al.,³¹ was identified, but these symptoms were not common, and they overlapped with symptoms from other clusters. Since Classic ACS, Pain Symptoms, and Stress Symptoms clusters provided mutually exclusive partitions of the eight types of symptoms observed, only these three were analyzed in the current study.

Pre-hospital delay time was calculated as the number of minutes from symptom onset to ED presentation based on medical records or subject interviews if data were not available from the medical record. Delay times were categorized as < 60 minutes, 60 to 120 minutes, and > 120 minutes.

Sample

Of the 3,522 patients with a history of or at risk for ischemic heart disease enrolled in the PROMOTION study, 3,087 (88%) completed 2-year follow-up.³² A total of 565 patients had ED admissions with symptoms suggestive of ACS.³³ Of the 565, 331 (59%) were diagnosed with ACS and were included in the current analysis. Among these 331 patients, 278 (84%) had documented mode of transportation used to get to the ED. Thus, the patient sample for the analysis included these 278 ACS patients. Among the 278, pre-hospital delay time was available for 260 patients (94%); 217 (83%) had delay times collected from the medical record and 43 (17%) from interviews conducted by research staff.

Data Analysis

Patient sample characteristics were assessed using descriptive statistics, both overall and by transportation mode (EMS versus non-EMS). Bivariate analyses of mode of transportation group differences were conducted using t-tests or Wilcoxon rank sum tests for continuous variables and Chi-square or Fisher’s exact tests for categorical variables. Age at enrollment was categorized as ≤65 years, 66–79 years, and ≥80 years. Multiple logistic regression was used to estimate adjusted odds ratios (AORs) of EMS versus non-EMS transportation mode by symptom clusters, after adjusting for patient sex, age, randomized group assignment and site. Multivariable median regression modeling³⁴ was performed to assess the joint associations of symptom clusters and transportation mode with prehospital delay time after accounting for patient sex, age, randomized group assignment and site. All analyses were performed in SAS v9.3 (SAS Institute, Cary, NC). A two-sided p < 0.05 was considered statistically significant.

Results

Table 1 summarizes patient characteristics, symptom experiences, and delay time of the sample of 278 ACS patients. Mean age at enrollment was 67.1 years (SD = 11.3) and 126 (45%) were 66–79 years old, and 33 (12%) were ≥80 years old. One-hundred eighty participants were male (65%). Of the eight individual symptom types, chest pain/discomfort/pressure was by far the most prevalent (n=236, 85%) followed by arm pain/discomfort (n=66, 24%) and shortness of breath (n=71, 26%). Examination of symptoms clusters revealed that 236 (85%) patients experienced the Classic ACS Symptom cluster, 90 (32%) experienced the Pain Symptoms cluster, and 113 (41%) experienced the Stress Symptoms cluster. The overall median prehospital delay time was 125 minutes (25^th percentile = 71, 75^th percentile = 300); 41 (16%) had a prehospital delay of less than 60 minutes while 132 (51%) had a prehospital delay time greater than 120 minutes.

Table 1.

Characteristics of the ACS patient sample¹

Patient Characteristic2	Overall (n = 278)	ED by EMS (n = 121)	ED by Non-EMS (n = 157)	P-value
Age (years)	67.1 ± 11.3 [67.7]	69.2 ± 10.6 [70.8]	65.5 ± 11.5 [65.5]	0.0052
≤ 65 years old	119 (43)	39 (32)	80 (51)	0.0070
66 to 79 years old	126 (45)	64 (53)	62 (39)
≥ 80 years old	33 (12)	18 (15)	15 (10)
Sex				0.1081
Female	98 (35)	49 (40)	49 (31)
Male	180 (65)	72 (60)	108 (69)
Symptom3
Chest pain, discomfort, pressure	236 (85)	101 (83)	135 (86)	0.5614
Arm pain, discomfort	66 (24)	38 (31)	28 (18)	0.0084
Shortness of breath	71 (26)	29 (24)	42 (27)	0.5976
Sweating	33 (12)	19 (16)	14 (9)	0.0829
Upset stomach, nausea, indigestion	36 (13)	22 (18)	14 (9)	0.0225
Sense of dread/anxiety	25 (9)	13 (11)	12 (8)	0.3703
Back/shoulder pain	20 (7)	9 (7)	11 (7)	0.8902
Neck/throat/jaw pain	18 (6)	9 (7)	9 (6)	0.5667
Symptom cluster: Chest Symptoms	236 (85)	101 (83)	135 (86)	0.5614
Symptom cluster: Pain Symptoms	90 (32)	48 (40)	42 (27)	0.0225
Symptom cluster: Stress Symptoms	113 (41)	57 (47)	56 (36)	0.0542
Pre-hospital delay time (minutes)4	124.5 (71, 300)	109.0 (64, 240)	176.0 (81, 355)	0.0165
< 60 minutes	41 (16)	19 (17)	22 (15)	0.0877
60 to 120 minutes	87 (33)	46 (40)	41 (28)
> 120 minutes	132 (51)	50 (43)	82 (57)

^*Note.

^1.ACS = Acute coronary syndrome, ED = emergency department

^2.Reported as n (%) or Mean ± SD [Median]

^3.Symptoms reported from patient interview

^4.Time from symptom onset to ED presentation (n = 260; 94%)

median (25^th percentile, 75^th percentile) reported.

Of the 278 ACS patients, 121 (44%) were transported by EMS and 157 (56%) arrived at the ED via private or other non-EMS transportation. Average age was higher (t = 2.81, p = 0.005) among those who arrived at the ED by EMS (M = 69.2 years) than among those who used other transportation (M = 65.5 years). Specifically, a greater percentage of those >65 years old arrived via EMS (68% vs. 49% of ≤65, χ² = 9.94, p = 0.007).

The prevalence of specific symptoms was also higher in those transported by EMS than in the non-EMS group: arm pain/discomfort (31% vs. 18%, χ² = 6.95, p = 0.008) and upset stomach/nausea/indigestion (18% vs. 9%, χ² = 5.20, p = 0.023). Also, the prevalence of the Pain Symptoms cluster was higher in those arriving by EMS than by other modes of transportation (40% vs. 27%, χ² = 5.21, p = 0.023). The Stress Symptoms cluster showed a higher prevalence of those arriving by EMS as compared to non-EMS (47% vs. 36%), but this was not statistically significant (χ² = 3.71, p = 0.054). Finally, median prehospital delay time was longer (Wilcoxon = 13554.0, p = 0.02) for non-EMS transportation (Med = 176 min, 25^th percentile = 81, 75^th percentile = 355) to the ED than for EMS transportation (Med = 109 min, 25^th percentile = 64, 75^th percentile = 240). Figure 1 presents the percentages of patients with the symptom clusters by prehospital delay time category and transportation mode. The Classic ACS Symptom cluster in combination with the Pain Symptoms or Stress Symptoms cluster was more prevalent among those with >120 minutes prehospital delay time with either transportation mode. But, among those with >120 minutes prehospital delay time Classic ACS Symptoms alone were substantially more frequent among those choosing other transportation than among those arriving via EMS.

Figure 1:

Percentage of ACS patients in each pre-hospital delay time category by symptom cluster and mode of transportation to ED (n = 260).

Table 2 presents the multivariable associations of symptom clusters with transportation mode. The odds of arriving via EMS were 166% higher for those with the Classic ACS + Pain Symptoms clusters than for those with the Classic ACS Symptom clusters alone, adjusting for sex, age, randomization arm, and site (AOR = 2.66, Wald χ² = 6.49, p = 0.011). The odds of arriving via EMS were also higher for those with Classic ACS + Stress Symptoms (AOR = 2.61, Wald χ² = 7.16, p = 0.007) and for patients with symptoms from all three clusters (Classic ACS + Stress Symptoms + Pain Symptoms) (AOR = 3.90, Wald χ² = 6.26, p = 0.012) than for those with the Classic ACS Symptom cluster alone. The odds of arriving via EMS were higher for those with the Stress Symptoms cluster alone than for those with the Classic ACS Symptom cluster alone (AOR = 3.12, Wald χ² = 4.51, p = 0.034).

Table 2.

Predictors of Use of EMS according to symptom clusters (n = 277)

Symptoms cluster combination	AOR	95% CI for AOR	P-value
Chest symptoms onlyRC	-
Pain only	2.70	(0.73, 10.1)	0.139
Stress only	3.12	(1.09, 8.92)	0.034
Chest + Pain	2.66	(1.25, 5.66)	0.011
Chest + Stress	2.61	(1.29, 5.27)	0.007
Pain + Stress	1.78	(0.38, 8.41)	0.467
Chest + Pain + Stress	3.90	(1.34, 11.3)	0.012

^*Note. Logistic regression additionally adjusting for patient sex, age, intervention arm, and study site. RC = reference category. One person excluded who was not a member of any symptoms cluster. Overall df = 6 test p = 0.0324 for any differences between patterns. AOR = adjusted odds ratio for EMS versus non-EMS transportation mode.

Results from the multivariable median regression of prehospital delay time are presented in Table 3. There were no significant differences in median delay time among symptom clusters (df = 6, χ² = 1.59, p = 0.952) after controlling for transportation mode, patient sex, age, randomization arm and site. Median delay time was 68.5 minutes shorter for those arriving via EMS than for those coming by non-EMS in this adjusted model (b = −68.5, χ² = 8.80, p = 0.002).

Table 3.

Predictors of median pre-hospital delay time in minutes according to symptom clusters and transportation mode (n = 259)

Covariate	b	95% CI for b	P-value
Symptom cluster combination
Chest symptoms onlyRC	-
Pain only	1.10	(−254.75, 256.95)	0.993
Stress only	−20.49	(−142.89, 101.91)	0.742
Chest + Pain	28.65	(−41.16, 98.46)	0.420
Chest + Stress	13.43	(−55.19, 82.05)	0.700
Pain + Stress	−81.66	(−322.03, 158.70)	0.504
Chest + Pain + Stress	1.03	(−97.62, 99.68)	0.984
Transportation mode
EMS	−68.52	(−111.90, −25.13)	0.002
Non-EMSRC	-

^*Note. Median regression additionally adjusting for patient sex, age group, intervention arm, and study site. RC = reference category. One person excluded who was not member of any symptoms cluster. Overall df = 6 test p = 0.952 for any differences between combinations of symptom clusters.

Discussion

While chest symptoms were the most prevalent symptom type for most (85%) of our sample, we found that patients experiencing the Stress Symptoms cluster (shortness of breath, sweating, upset stomach/nausea/vomiting or indigestion, sense of dread/anxiety) had greater than three times the odds of using EMS as their mode of transportation to the ED as compared to those experiencing the Classic ACS Symptom cluster. The literature suggests several plausible reasons for why this symptom cluster may be associated with a higher odds of EMS use. For example, it is widely accepted that individuals who have more severe,²⁸ abrupt onset,^12,22 and unbearable symptoms^{7, 10,12,16,23} are more likely to use EMS, presumably based on the belief that an ambulance is needed because of the emergent nature of the condition and EMS is the fastest possible mode of transportation to the hospital. Some investigators have hypothesized that nausea/vomiting, dyspnea, and vertigo equates to unbearable symptoms^21,40 moving the individual’s level of threat beyond “annoyance” or simply being “bothersome” to a situation that needs more immediate treatment^{7, 16, 21–22} as provided by EMS.

Although the mechanism behind nausea and vomiting in ACS patients is not well described, Anderson and colleagues³⁵ hypothesized that patients with ACS who experience nausea/vomiting may feel helpless or feel a loss of control such that they “need” EMS. These feelings may be compounded if there is uncertain symptom attribution, especially if symptoms arise abruptly, signaling a threat to personal safety.³⁵ Another plausible explanation for why this symptom cluster is associated with EMS use is that these particular symptoms limit transportation options, suggesting a pragmatic aspect of decision making related to mode of transportation to the hospital.^23,28 This explanation is supported by qualitative findings from Indonesia where patients were more likely to use EMS if certain ACS symptoms prevented them physically from driving themselves or riding in another person’s private vehicle, especially if they were unable to sit up.³⁶ It is also plausible that experiencing signs (vomiting) and symptoms (sweating and shortness of breath) that are visible to others may draw bystanders into the experience, potentially influencing care-seeking decisions related to transportation mode. Past research has shown that having bystanders, especially strangers, involved in decisions related to care-seeking is associated with decreased prehospital delay.^5,11 How bystanders influence the decision to use EMS is not as clear.

The fact that the Classic ACS Symptom cluster in combination with other symptom clusters was associated with a higher adjusted odds of using EMS supports the hypothesis that it takes more than “just angina” to cross the threshold to be “serious enough” to get patients with a history of ACS to seek care as compared to those without pre-existing angina.^37–39 These findings suggest that it takes more than correct symptom attribution of having symptoms with a cardiac etiology to necessitate EMS use. Although correct symptom interpretation in patients experiencing their first ACS event has been shown to be associated with higher odds of using EMS,⁵ this is not always the case for patients with recurrent events. For example, research has shown that those with pre-infarct angina^10,25 or angina that is precipitated or aggravated by exercise²⁴ are less likely to use EMS. It is thus plausible that patients in our sample, with a history of ACS or ischemic heart disease, may have grown accustomed to angina as a “familiar event”,²⁶ something that is bothersome, yet not unbearable. Investigators from prior studies have hypothesized that some patients with a history of ACS “wait and see” to avoid “going too quickly” labeling symptoms as their “typical angina” with the expectations that symptoms will resolve with rest or NTG.^24,26,38 Even if symptoms do not resolve in a timely manner, they may still select another mode of transportation to the hospital, based on appraising the situation as a lower level of illness threat²⁸ due to event familiarity.^12,24 Alternatively, other patients with a history of angina may promptly recognize and interpret symptoms accurately, yet falsely believe private transportation gets them to the hospital faster.^{12,21,23,24,27,40} These collective explanations highlight the variation in how individuals respond to an illness threat that is not always explained by accuracy of symptom interpretation.

The results of the current study align with previous observational data suggesting that EMS use is associated with decreased prehospital delay.^8–16 Specifically, EMS use resulted in, on average, 68.5 minutes less prehospital delay based on the adjusted model. However, from a clinical perspective, prehospital delay remains a problem globally because the median delay time for both groups was well over an hour (109 versus 176 minutes for EMS and non-EMS users, respectively). Furthermore, only 44% of our sample used EMS indicating that lack of EMS use is a persistent problem underscoring the need to better understand how the symptom experience informs decisions to use EMS or not. Potential causes of not selecting EMS as the mode of transport include knowledge-related factors (inaccurate symptom interpretation, low perceived self-threat), anticipated outcome-related factors (inaccurate perceptions of speed or benefits associated with EMS), environmental-related factors (affordability or geographic factors), social-related factors (social acceptability, influence of bystanders, fear of misuse), and emotional-related factors (fear, denial).⁴⁰ However, the current study did not collect these data, which may be needed to better understand the decision-making process that the patients (and/or bystanders) used to determine their mode of transportation, including decision(s) related to the timing of going to the ED.

Implications for Practice and Future Research

In addition to teaching patients about classic and non-classic ACS symptoms, patients need to know that recurrent ACS may differ from the index event.^39,41 Patients with a history of ischemic heart disease should also be taught that angina may progress from their “usual” stable pattern to progressive angina (increased frequency, duration, and/or severity of symptoms) indicating that an ACS event may be imminent. Thus, nurses in critical care and acute care settings can be instrumental in teaching patients who have been admitted for ACS the difference between “stable” angina symptoms (symptoms occur with activity and resolve with rest and up to one NTG), “unstable” symptoms (symptoms that occur with less activity or at rest, last longer and occur more often, and take more than one NTG to resolve), and symptoms of a recurrent ACS event (symptoms that do not resolve with NTG).

Because correct symptom interpretation does not always result in patients using EMS as a mode of transport to the ED, nurses can also be instrumental in teaching patients and family members the many advantages of EMS use. First, most of the research to date has shown that EMS use is associated with less prehospital delay as compared to non-EMS transport – challenging one of the top reasons (“I can get to the hospital faster than an ambulance”) cited by patients about why they self-transport as opposed to EMS. Thus, discharge teaching for patients who are at risk for a future ACS event should include the fact that EMS use, on average, results in a shorter pre-hospital delay. Secondly, EMS is safer as ambulances are equipped with defibrillators and most have the capability to deliver advanced cardiac life support treatment should the patient require it. Many patients and family members do not consider the potential safety aspect of EMS use; this should be noted in discharge teaching. Thirdly, nurses working in critical care and acute care settings can help patients reframe how they view EMS, beyond a “means” to get to the hospital. EMS should be viewed as an extension of hospital care such that most patients with suspected ACS will receive a 12-lead electrocardiogram before arriving to the hospital. Pre-hospital electrocardiograms can help EMS clinicians discern if the patient is experiencing an ST-segment-elevation myocardial infarction, potentially requiring transport to a center that has cardiac catheterization laboratory capability 24 hours/day to deliver urgent reperfusion therapy (not necessarily the closest facility where patients who use self-transport drive to). Lastly, as suggested by the current ACS treatment guidelines,³ after telling someone else about symptoms, resting, and taking one NTG, calling EMS for continued anginal symptoms should be “automatic” for patients with a history of heart disease - akin to what the community norm is for someone who has a serious car accident.^12,24 Thus, discharge teaching by nurses for survivors of ACS can include role playing with the patient and their family members to “rehearse” what they would do if they develop recurrent angina symptoms post-hospitalization. Most importantly, if rest and NTG do not result in symptom resolution, role playing calling EMS is an essential component of the personalized action plan.

More research is needed with a larger more diverse population to explore how certain ACS symptom clusters are associated with increased EMS use. Including a qualitative component to provide insight into how particular symptom clusters influence decisions to use EMS may ultimately inform targets for intervention.

Limitations and Strengths of the Study

A limitation of this study was that the type of symptoms experienced and the time of symptom onset were based on the subject’s report provided retrospectively after the ACS symptoms had occurred. Thus, no direct observations were conducted to determine the exact symptoms and reasons why they selected a particular mode of transportation. Another limitation was that we did not collect other symptom characteristics such as duration, frequency, or severity of potential ACS symptoms.

However, a strength of this multi-center international study is that we reported symptom cluster data, as opposed to individual symptoms, when examining the association with EMS use which adds to the body of literature on the topic. In addition, patients were interviewed by trained research staff to gain information about presenting symptoms of their ACS event as opposed to relying on documentation in the medical record.

Conclusion

In summary, although chest symptoms were the most common presenting symptom for our sample of ACS patients, only 44 % (121 of the 278 patients) used EMS, indicating that EMS is still markedly underutilized. However, we found that the Stress Symptoms cluster or the combination of Classic ACS + Stress Symptoms + Pain Symptoms clusters were associated with higher EMS use as opposed to Classic ACS (chest) Symptoms alone, indicating that it takes more than “just” chest symptoms to motivate someone to use EMS. The results of the current study provide novel information about how patients with classic ACS symptoms may not use EMS as compared to patients experiencing other symptoms, which can help researchers and clinicians target this group of patients that may benefit from additional counseling about the benefits of EMS use as a mode of transportation to the ED. Patients with a history of ACS or ischemic heart disease should follow their personalized action plan included calling EMS for classic or non-classic symptoms that are not relieved by rest and NTG to decrease prehospital delay and ultimately improve morbidity and mortality.