Abstract
Background
Prehospital electrocardiogram (PHECG) shortens door-to-balloon time in patients with ST-elevation myocardial infarction. However, it may increase the prehospital service time, thus offsetting the benefits gained. The performance of PHECG could be influenced by the proficiency of the emergency medical technicians (EMTs).
Objectives
To investigate whether there are differences in the performance of PHECG between EMT-II and EMT-paramedics (EMT-P).
Methods
This prospectively designed, retrospectively analyzed study of PHECG was conducted in Taipei from February 2019 to April 2021. Comparisons were made between EMT-II and EMT-P teams. The primary outcomes were the acceptance of PHECG suggestions and prehospital service time. The secondary outcomes were gender disparities in the primary outcomes.
Results
A total of 2,991 patients were included, of whom 2,617 received PHECG. For the primary outcomes, the acceptance of PHECG was higher in those approached by EMT-P (99.6% vs. 71.5%, p < 0.001). The scene time and scene-to-hospital time showed no significant differences. For gender disparities, the acceptance of PHECG in female patients was significantly lower in those approached by EMT-II (59.3% vs. 99.2%, p < 0.001). The scene time and scene-to-hospital time were generally longer in the female patients, especially in the younger and middle age groups. Compared to EMT-P, both were significantly longer in the female patients approached by EMT-II.
Conclusions
The acceptance of PHECG was lower in those approached by EMT-II, especially in females. Although there were generally no significant differences between EMT-II and EMT-P, the scene time and scene-to-hospital time were significantly longer in female patients, especially in those aged < 75 years approached by EMT-II.
Keywords: Electrocardiogram, Emergency medical technician, Female, Gender, Prehospital
Abbreviations
AI, Artificial intelligence
ECG, Electrocardiogram
EMS, Emergency medical services
EMT, Emergency medical technician
EMT-P, EMT-paramedics
PCI, Percutaneous coronary intervention
PHECG, Prehospital electrocardiogram
STEMI, ST-elevation myocardial infarction
INTRODUCTION
Acute ST-elevation myocardial infarction (STEMI), usually resulting from plaque rupture with total occlusion of the coronary arteries, is a cardiovascular emergency that demands early identification and treatment. In this era of reperfusion therapy, timely diagnosis and rapid transfer to an appropriate hospital for effective interventional therapy is most critical for improving the clinical outcomes.1-3 In addition to clinical signs and symptoms raising the suspicion of STEMI, electrocardiography (ECG) is key to confirm the diagnosis, based on which percutaneous coronary intervention (PCI) or thrombolytic therapy can be initiated. ECG should be performed as early as possible at the first medical contact.1-3 Although ECG is usually performed after arriving at the emergency department, prehospital ECG (PHECG) is increasingly available with advances in equipment and convenience of wireless connection to the internet. The strategic implementation of PHECG in emergency medical services (EMS) systems thus makes earlier diagnosis possible and improves the overall system of care for acute coronary syndrome.
PHECG has been reported to shorten door-to-balloon time and improve the clinical outcomes of patients with STEMI.4-10 However, the execution of PHECG inevitably prolongs the time spent on the scene, which potentially offsets the benefits gained from shortening the door-to-balloon time. Previous reports have indicated that PHECG may prolong the scene time from 2 to 11 min6 depending on factors such as patient characteristics, training of emergency medical technicians (EMTs), time of the day, etc.11,12 Proficiency of the EMTs that carry out the PHECG is another factor, and the acceptance and cooperation of the patient and their family also play roles in the overall performance of PHECG.
EMTs are often the first medical contact when acute coronary syndrome occurs in the community and EMS are called for help. Performance of PHECG by EMTs may be influenced by a variety of factors, such as the knowledge, training, and experience.13-15 In this study, we aimed to explore whether there are any differences in the activation of PHECG and acceptance by the patient or their family between EMT-II and EMT-paramedics (EMT-P). The performance of PHECG and its impact on the prehospital service time were also compared.
METHODS
This prospectively designed, retrospective analysis study used data from the Emergency Medical Services dataset of Taipei City Fire Department from February 2019 to April 2021. The study was conducted in accordance with the Declaration of Helsinki, and was approved by the institutional review board.
Prehospital ECG provided by the Taipei EMS System
The EMS of Taipei City is provided by EMTs at two levels, i.e. EMT-II and EMT-P. There are a total of 45 EMS teams in Taipei, including 41 EMT-II teams and 4 EMT-P teams. Each team is comprised exclusively of either EMT-II or EMT-P, with no mixing of the two levels of EMTs within a single team. Each team is responsible for the general emergency calls in a specific region of responsibility. If the call is a predefined critical condition such as out-of-hospital cardiac arrest or major trauma, the nearest EMT-P team will be activated as the second tier for advanced care if the primary responsible team is EMT-II only. For patients with chest pain requiring help, the nearest EMT-II or EMT-P team will be activated according to the location of the patient. The EMT will then evaluate the patient and give prehospital management as needed at the scene. During the study period, four EMT-P teams and 10 of the 41 EMT-II teams were equipped with ECG machines. PHECG was performed in these teams if the condition met the inclusion criteria described below.
Study design
The goal of the study was to compare the efficacy of the activation and performance of PHECG between EMT-II and EMT-P teams in patients calling EMS due to chest pain or signs or symptoms suggesting acute coronary syndrome. The inclusion criteria were patients with chest pain or angina-equivalent signs and symptoms indicating the need for PHECG by the 14 EMT teams equipped with ECG machines. The indications for PHECG were adults (≥ 20 years old) with non-traumatic chest pain, or those who met at least two of the following four criteria: breathless, cold sweating, nausea or vomiting, and a history of heart diseases (including coronary artery disease, valvular heart disease, cardiomyopathy, congestive heart failure, cardiac arrhythmia, etc.). The exclusion criteria were: age less than 20 years, trauma, pregnancy, refusing to be transferred to the hospital, and those in whom PHECG was performed but not completed due to any cause.
The primary endpoints of the study were: (1) the acceptance of PHECG as suggested by the EMTs, and (2) the prehospital service time, including scene time, transportation time, and scene-to-hospital time. The scene time was defined as the duration from the arrival of the EMTs at the scene to departure for the hospital. The scene-to-hospital time was defined as the time from the arrival of the EMTs at the scene to arrival at the hospital (Figure 1). Considering that the transportation time could be influenced by the distance from the scene to the hospital, the transportation speed (calculated as the distance between the scene and hospital divided by transportation time) was also compared. The secondary endpoints focused on gender disparities in the primary endpoints and included: (1) the acceptance rates of PHECG suggestion, and (2) the prehospital time (including scene time, transportation time, and scene-to-hospital time).
Figure 1.
The process of prehospital care for chest pain patients in the emergency medical services system. EMT, emergency medical technician; PHECG, prehospital electrocardiogram.
Collection of data
The following data were recorded for analysis. Patient information including age, sex, underlying diseases (such as hypertension, diabetes mellitus, heart diseases, stroke, etc.), and acceptance of PHECG or not. EMS data included the level of EMTs providing prehospital care, the level of service (basic life support or advanced life support), and prehospital service time (including scene time, transportation time, and scene-to-hospital time). Clinical information included computer interpretation of PHECG (suspected STEMI or not), and final diagnosis at the hospital (confirmed STEMI or not).
Statistical analysis
SPSS version 24 was used for statistical analysis (IBM Inc., Armonk, NY). Descriptive statistics were presented as numbers, percentages or averages (± standard deviation). For continuous variables, the independent sample t test or Mann-Whitney U test was used for analysis. For categorical variables, the chi-squared test or Fisher’s exact test was used. If avariable had a p value < 0.05 in univariate analysis, it was included in linear regression analysis. In simple linear regression analysis, a p value < 0.05 was considered statistically significant.
RESULTS
A total of 2,991 patients were collected during the study period. Excluding 62 patients in whom PHECG was not completed, 2,929 patients were included for analysis. Of these patients, 1,068 were approached by EMT-II and 1,861 by EMT-P (Figure 2). Of the 1,068 patients approached by EMT-II, 764 (71.5%) accepted and received PHECG, compared to 1,853 (99.6%) of the 1,861 patients approached by EMT-P. The rate of acceptance was significantly higher in the EMT-P teams than in the EMT-II teams (p < 0.001).
Figure 2.
The patient included in the study period from February 2019 to April 2021. ECG, electrocardiogram; EMT, emergency medical technician; EMT-P, EMT-paramedics.
The demographic and clinical information of the 2,617 patients who received and completed PHECG are shown in Table 1. The patients evaluated by EMT-II teams were younger, more often male, had more typical symptoms (such as chest pain, chest tightness and short of breath), underlying heart diseases and confirmed STEMI, but were less critical in clinical presentation. Regarding the prehospital service time, there were no significant differences in scene time (13.9 ± 5.1 min vs. 14.1 ± 5.7 min, p = 0.355) and scene-to-hospital time (21.0 ± 6.5 min vs. 20.6 ± 6.6 min, p = 0.118) between the EMT-II and EMT-P teams (Table 2). However, the transportation time was shorter (6.5 ± 3.5 min vs. 7.1 ± 4.3 min, p = 0.001; Table 2) and transportation speed higher in the EMT-P teams than in the EMT-II teams (0.53 ± 0.62 km/min vs. 0.46 ± 0.30 km/min, p < 0.001; Table 2).
Table 1. Characteristics of the patients, severity of illness, and diagnosis.
| EMT-P (n = 1853) | EMT-II (n = 764) | p | |
| Male (%) | 1033 (55.5%)0 | 519 (67.9%) | < 0.001 |
| Age (median/IQR) | 73 (58-85) | 67 (53-80) | < 0.001 |
| Symptom | |||
| Chest pain | 275 (14.8%) | 255 (33.4%) | < 0.001 |
| Chest tightness | 538 (29.0%) | 311 (40.7%) | < 0.001 |
| Short of breath | 209 (27.4%) | 609 (32.9%) | 0.006 |
| Cold sweating | 350 (18.9%) | 145 (19.0%) | 0.957 |
| Nausea or vomiting | 351 (18.9%) | 108 (14.1%) | 0.003 |
| Past history | |||
| Heart disease | 1156 (62.4%)0 | 544 (71.2%) | < 0.001 |
| Hypertension | 943 (50.9%) | 378 (49.5%) | 0.511 |
| Diabetes | 491 (26.5%) | 199 (26.0%) | 0.812 |
| Stroke | 147 (7.9%) | 32 (4.2%) | 0.001 |
| Severity of illness | |||
| Critical | 284 (15.3%) | 60 (7.9%) | < 0.001 |
| Non-critical | 1569 (84.7%) | 704 (92.1%) | < 0.001 |
| Suspected STEMI | 229 (12.4%) | 112 (14.7%) | 0.112 |
| Confirmed STEMI | 48 (2.6%) | 39 (5.1%) | 0.001 |
EMT, emergency medical technician; EMT-P, EMT-paramedics; STEMI, ST-elevation myocardial infarction.
Table 2. Prehospital service time and transportation speed.
| EMT-P (n = 1853) | EMT-II (n = 764) | p | |
| Scene time (min) | 14.1 ± 5.7 | 13.9 ± 5.1 | 0.355 |
| Transportation time (min) | 6.5 ± 3.5 | 7.1 ± 4.3 | 0.001 |
| Scene-to-hospital time (min) | 20.6 ± 6.6 | 21.0 ± 6.5 | 0.118 |
| Transport speed (km/min) | 0.53 ± 0.62 | 0.46 ± 0.30 | < 0.001 |
EMT, emergency medical technician; EMT-P, EMT-paramedics.
For gender disparities in the primary endpoints, the overall rate of accepting PHECG was lower in female patients (85.9% vs. 91.9% in male, p < 0.001; Table 3). The acceptance rates were also lower in female patients in other comparisons including presenting clinical symptoms, severity of illness, and past medical histories (Table 3). To determine whether there were differences when stratified by age, we further divided the patients into three groups, i.e. younger (< 55 years), middle (55-74 years), and older (> 75 years) groups. Interestingly, the gender disparity in PHECG acceptance was significant in the middle and older age groups, but not in the younger groups (Table 3).
Table 3. Comparison of the acceptance rates of prehospital ECG: male vs. female.
| Characteristics | Male (n = 1684) | Female (n = 1245) | p |
| Age | |||
| Age under 55 | 405/428 (94.6%) | 169/185 (91.4%) | 0.127 |
| Age 55-74 | 592/660 (89.7%) | 313/391 (80.1%) | < 0.001 |
| Age above 75 | 550/596 (92.3%) | 588/669 (87.9%) | 0.010 |
| Symptoms | |||
| Chest pain | 352/394 (89.3%) | 178/221 (80.5%) | 0.002 |
| Chest tightness | 498/551 (90.4%) | 351/418 (84.0%) | 0.003 |
| Short of breath | 472/515 (91.7%) | 345/408 (84.8%) | 0.001 |
| Cold sweating | 325/335 (97.0%) | 170/183 (92.9%) | 0.030 |
| Nausea or vomiting | 251/266 (94.4%) | 208/222 (89.3%) | 0.037 |
| Past history | |||
| Hypertension | 760/828 (91.8%) | 561/641 (87.5%) | 0.007 |
| Diabetes mellitus | 405/441 (91.8%) | 285/330 (86.4%) | 0.014 |
| Heart diseases | 989/1090 (90.7%) | 711/853 (83.4%) | < 0.001 |
| Stroke | 114/123 (92.7%) | 65/72 (90.3%) | 0.555 |
| Severity of illness | |||
| Critical | 217/227 (95.6%) | 127/146 (87.0%) | 0.002 |
| Non-critical | 1330/1457 (91.3%) | 943/1099 (85.8%) | < 0.001 |
ECG, electrocardiogram.
For gender comparisons in different levels of EMTs, there was no significant difference in acceptance rate in those approached by EMT-P (female 99.2% vs. male 99.9%, p = 0.087). In contrast, the acceptance rate was significantly lower in female patients approached by EMT-II (female 59.3% vs. male 79.2%, p < 0.001). When comparing the same gender between EMT-II and EMT-P teams, the PHECG acceptance rates were both lower in those approached by EMT-II, especially in the female patients (male 79.2% vs. 99.9, p < 0.001; female 59.3% vs. 99.2%, p < 0.0001).
Regarding prehospital service time, the scene time was significantly longer in the female patients in both those approached by EMT-II (female 15.2 ± 4.5 min vs. male 13.3 ± 5.2 min, p < 0.001) and EMT-P (female 14.6 ± 5.5 min vs. male 13.7 ± 5.8 min, p < 0.001; Table 4). No significant difference was noted between sexes in transportation time. Taken together, the overall scene-to-hospital time was significantly longer in the female patients, both in those approached by EMT-II (female 21.9 ± 5.7 min vs. male 20.6 ± 6.8 min, p < 0.001) and EMT-P (female 21.1 ± 6.4 min vs. male 20.2 ± 6.7 min, p < 0.001; Table 4).
Table 4. Comparisons of prehospital service time between male and female patients.
| Overall | EMT-P (n = 1853) | EMT-II (n = 764) | |||||||
| Male (n = 1547) | Female (n = 1070) | p | Male (n = 1028) | Female (n = 825) | p | Male (n = 519) | Female (n = 245) | p | |
| Scene time (min) | 13.6 ± 5.6 | 14.7 ± 5.3 | < 0.001 | 13.7 ± 5.8 | 14.6 ± 5.5 | < 0.001 | 13.3 ± 5.2 | 15.2 ± 4.5* | < 0.001 |
| Age under 55 | 12.0 ± 5.5 | 13.1 ± 5.4 | 0.019 | 11.6 ± 5.7 | 12.4 ± 5.2 | 0.192 | 12.4 ± 5.2 | 15.3 ± 5.1 | 0.001 |
| Age 55-74 | 12.8 ± 5.6 | 13.7 ± 5.4 | 0.022 | 12.8 ± 5.9 | 13.4 ± 5.7 | 0.187 | 12.9 ± 5.0 | 14.5 ± 4.2 | 0.011 |
| Age above 75 | 15.6 ± 5.0 | 15.7 ± 5.1 | 0.669 | 15.8 ± 5.0 | 15.7 ± 5.2 | 0.945 | 15.1 ± 5.0 | 15.7 ± 4.5 | 0.326 |
| Transportation time (min) | 6.7 ± 3.9 | 6.6 ± 3.6 | 0.305 | 6.4 ± 3.4 | 6.5 ± 3.6 | 0.731 | 7.3 ± 4.6 | 6.7 ± 3.5 | 0.430 |
| Age under 55 | 6.4 ± 3.7 | 6.1 ± 3.5 | 0.456 | 6.3 ± 3.7 | 5.9 ± 3.3 | 0.341 | 6.5 ± 3.5 | 6.7 ± 4.1 | 0.674 |
| Age 55-74 | 6.9 ± 3.8 | 6.8 ± 3.9 | 0.679 | 6.6 ± 3.4 | 6.6 ± 4.0 | 0.767 | 7.4 ± 4.3 | 7.0 ± 3.2 | 0.479 |
| Age above 75 | 6.9 ± 4.1 | 6.6 ± 3.4 | 0.302 | 6.4 ± 3.2 | 6.6 ± 3.5 | 0.279 | 8.3 ± 5.9 | 6.5 ± 3.3 | 0.004 |
| Scene-to-hospital time (min) | 20.3 ± 6.8 | 21.3 ± 6.3 | < 0.001 | 20.2 ± 6.7 | 21.1 ± 6.4 | < 0.001 | 20.6 ± 6.8 | 21.9 ± 5.7# | < 0.001 |
| Age under 55 | 18.3 ± 6.8 | 19.3 ± 6.5 | 0.127 | 17.9 ± 7.1 | 18.3 ± 6.2 | 0.571 | 18.9 ± 6.2 | 22.1 ± 6.9 | 0.004 |
| Age 55-74 | 19.7 ± 6.7 | 20.5 ± 6.4 | 0.095 | 19.4 ± 6.7 | 20.0 ± 6.6 | 0.191 | 20.3 ± 6.6 | 21.5 ± 5.6 | 0.143 |
| Age above 75 | 22.5 ± 6.2 | 22.3 ± 5.9 | 0.770 | 22.2 ± 5.9 | 22.3 ± 6.1 | 0.583 | 23.4 ± 7.0 | 22.2 ± 5.3 | 0.140 |
| Transportation speed (km/min) | 0.51 ± 0.57 | 0.51 ± 0.52 | 0.808 | 0.54 ± 0.65 | 0.53 ± 0.58 | 0.579 | 0.47 ± 0.34 | 0.43 ± 0.17 | 0.618 |
| Age under 55 | 0.53 ± 0.56 | 0.54 ± 0.60 | 0.811 | 0.58 ± 0.68 | 0.58 ± 0.68 | 0.985 | 0.47 ± 0.32 | 0.43 ± 0.16 | 0.466 |
| Age 55-74 | 0.51 ± 0.69 | 0.49 ± 0.28 | 0.629 | 0.54 ± 0.83 | 0.51 ± 0.30 | 0.628 | 0.46 ± 0.32 | 0.44 ± 0.16 | 0.483 |
| Age above 75 | 0.50 ± 0.40 | 0.50 ± 0.59 | 0.840 | 0.51 ± 0.40 | 0.52 ± 0.65 | 0.611 | 0.48 ± 0.40 | 0.43 ± 0.17 | 0.216 |
* p < 0.05 compared to scene time of the female patients in EMT-P; # p < 0.05 compared to scene-to-hospital time of the female patients in EMT-P.
EMT, emergency medical technician; EMT-P, EMT-paramedics.
To determine whether there were gender disparities when stratified by age, we also compared different age groups. As shown in Table 4, the difference in scene time between male and female patients resulted mainly from the younger (< 55 years) and middle (55-74 years) age groups, especially in those approached by EMT-II. For the older age group (> 75 years), the scene time was generally longer compared to the younger and middle age groups. However, there were no significant differences between sexes, either in EMT-II or EMT-P teams.
When comparing the prehospital service time between EMT-II and EMT-P teams in each gender, there were no significant differences in male patients regarding scene time (EMT-II 13.3 ± 5.2 min vs. EMT-P 13.7 ± 5.8 min, p = 0.119) and scene-to-hospital time (EMT-II 20.6 ± 6.8 min vs. EMT-P 20.2 ± 6.7 min, p = 0.518; Table 4). For female patients, however, the EMT-II teams spent significantly longer time at the scene (15.2 ± 4.5 min vs. 14.6 ± 5.5 min in EMT-P, p < 0.05; Table 4). Since there was no significant difference in transportation time, the scene-to-hospital time was thus longer in the EMT-II teams (21.9 ± 5.7 min vs. 21.1 ± 6.4 min in EMT-P, p < 0.05; Table 4).
DISCUSSION
EMTs play an important role in prehospital care and serve as the backbone of the EMS system. Being the first medical contact of patients with a variety of critical illnesses in the community, the ability and performance of EMT in the field are crucial in the systems of care, and can significantly impact the fluency of medical care and outcomes of the patients.13-17 EMTs can be divided into three levels: EMT-I, EMT-II, and EMT-P. In Taiwan, the training time of the three levels of EMTs are 40, 280, and 1280 hours, respectively. Theoretically the higher the level of the EMT, the more knowledge and experience they have, and hence better performance in prehospital medical care. Many studies have compared the abilities and performance among different levels of EMTs.13-15 For PHECG, the current study is, to the best of our knowledge, one of the first to compare the performance between EMT-II and EMT-P.
The results of this study showed that the rate of completing PHECG was high (2617 of 2679, 97.7%) once the suggestion had been accepted by the patient. This indicates that technically there were no difficulties in operating the ECG machine and transmitting the ECG data in the prehospital setting, either in the EMT-II or EMT-P teams. This is consistent with previous studies suggesting that transmission of PHECG is feasible in EMT-basic and EMT-intermediate.15 Further, since the identification of STEMI and disposition of the patient were based on computerized ECG interpretation and predesignated algorithm, there was no significant difference in scene time between the EMT-II and EMT-P teams. This suggests that the execution of PHECG was equally efficient at these two levels of EMTs. Computerized ECG interpretation has been reported to provide an immediate diagnosis with acceptable accuracy, significantly decrease the time required for manual interpretation, standardize various ECG classifications, and reduce interpretation discrepancies among different individuals.18,19 Although computerized ECG still needs to be over-read and confirmed by authorized physicians, its application in prehospital chest pain algorithms is justified and can help to reduce the stress and responsibility burden of first-line EMTs. In this era when artificial intelligence (AI) interpretation of ECG is rapidly progressing and increasingly applied, the incorporation of AI in PHECG interpretation can not only provide more timely and precise judgement, but also help optimize prehospital triage and care of chest pain patients.20,21
Even though the execution of PHECG was comparable between EMT-II and EMT-P teams in this study, there was a significant difference in the acceptance of PHECG by the patients and families. In contrast to EMT-P in which the acceptance rate was as high as 99.6%, only 71.5% of the patients approached by EMT-II accepted and received PHECG. Many factors may affect decision-making, including the attitude and explanation of the EMT. With more knowledge, training and experience, EMT-P may be more confident and active in encouraging the acceptance of PHECG. Similarly, the patients and families may have been more likely to accept PHECG due to the EMT-P’s professionalism and on-site explanation.
Other important findings in this study include gender differences in the acceptance of PHECG and prehospital service time. Gender disparities in health care have long been an issue of interest.22,23 Several factors may contribute to the gender disparity in PHECG acceptance. For example, awareness of a possible heart attack may have been lower in the female patients when they have symptoms, since cardiovascular risk is generally lower in women. This in turn may have reduced the willingness to accept PHECG. As shown in Table 3, even in the patients with typical symptoms such as chest pain, tightness, shortness of breath and cold sweating, the acceptance of PHECG was significantly lower in the female patients compared to the male patients. Similarly, the acceptance rate was also lower in the female patients even with risk factors such as hypertension, diabetes mellitus and heart diseases (Table 3). Another factor may be reluctance of the female patients to expose their chest for the application of ECG leads, especially if PHECG was to be done in a public place. These factors may explain why the acceptance of PHECG in this study was lower in the female patients. Interestingly, when stratifying the patients into three age groups, we found that the acceptance of PHECG was significantly lower in the female patients only in the middle and older age groups (Table 3). This could be explained in part by the conservative attitude of older females in Asian societies. Nevertheless, poorer disease knowledge and atypical clinical presentations may also have played roles.
Regarding the longer scene time in the female patients, the higher percentage of atypical presentations and lower number of cardiovascular risk factors may have led to a longer time required for evaluation and explanation.24-28 Meanwhile, it may also have taken a longer time to prepare and perform PHECG, which taken together may have prolonged the total time spent at the scene for both the EMT-II and EMT-P teams (Table 4). While no difference was noted in transportation time, the scene-to-hospital time was thus longer in the female patients (all p < 0.001 compared to the male patients, Table 4). These results are consistent with previous studies in Western societies,29 suggesting a fundamental gender difference in prehospital management of patients receiving PHECG. Of note, when stratifying the patients into three age groups, the longer scene time in the female patients appeared to be significant only in the younger and middle age groups, especially in those approached by EMT-II (Table 4). In patients older than 75 years, the scene time was generally longer than in the younger and middle age groups, both in those approached by EMT-II and EMT-P, but there was no significant difference between sexes (Table 4). This could be due to the complexity in disease presentation, clinical evaluation and on-site management of the elderly, making the scene time longer with no gender disparity in receiving PHECG.
When we focused on female patients only and compared those approached by EMT-II and EMT-P, the scene time (15.2 ± 4.5 vs. 14.6 ± 5.5, p < 0.05) and scene-to-hospital time (21.9 ± 5.7 vs. 21.1 ± 6.4, p < 0.05) in those approached by EMT-II were both significantly longer than in those approached by EMT-P. On the other hand, no such differences were noted in the male patients (Table 4). This implies that although EMT-II carried out PHECG as efficiently as EMT-P, EMT-II may have taken longer to evaluate, explain, prepare, and execute PHECG in the female patients.
As shown in Table 1, there were significantly more confirmed STEMI patients in the EMT-II groups. Although this could be due to a random effect, it is plausible that EMT-II were more consistent with the criteria of PHECG when making suggestions, while EMT-P had a lower threshold to activate PHECG when they had any suspicions. This is in part supported by the findings that the incidences of typical symptoms such as chest pain, chest tightness and cold sweating were all significantly higher in patients approached by EMT-II (Table 1). Although the lower threshold of PHECG activation in the EMT-P teams may have decreased the detection rate of STEMI, this may also have reduced the missed rate, especially in those with atypical signs or symptoms.
Another interesting finding in this study is that the transportation time was shorter and transportation speed higher in the EMT-P teams (Table 2). Many factors may influence the transportation speed of a patient, including traffic conditions, time of the event, and location of the scene, etc. Given that there was no significant difference in the 24-hour distribution of the calls, it is possible that the traffic conditions were better for most of the calls in the responsible areas of the EMT-P teams. Another possibility is positivity of the EMT-P, which may have increased the speed of transportation of the patients. When comparing the transportation speed between sexes or among different age groups, however, there were no significant differences, either in EMT-P or EMT-II teams (Table 4).
Limitations
There are a number of limitations in this study. First, this is a single-city study in which PHECG was done exclusively by EMT-II or EMT-P teams. The results may not be applicable to other EMS systems in which EMT-II and EMT-P are mixed in the same team. However, with understanding of basic differences in training and experience, cooperation and compensation between different levels of EMTs in the same team may improve the overall performance. Second, there were no data in this study showing potential delays of the prehospital service time with the use of PHECG, since the goal was to compare the performance between EMT-II and EMT-P teams. The differential impacts of PHECG on door-to-balloon time and clinical outcomes were not available, either. Third, only scene time was used as an indicator of the overall on-site performance. Detailed information regarding evaluation and management at the scene, such as the time used for history taking, physical examination, explanation, PHECG execution, transmission of ECG, and medical management were not recorded and compared. Therefore, the exact factors increasing the scene time in the EMT-II teams could not be clarified. Fourth, the transportation speed was a rough estimate rather than the actual speed recorded in the ambulance. In addition, the actual route to the hospital and distance were not available, and the speed would not be consistent during the entire transportation process. Even with these limitations, however, this study is one of the first to compare the performance of PHECG and gender differences at different levels of EMTs. Based on these limitations, improvements in the design of flowcharts, training of EMTs, and implementation of PHECG in existing EMS systems can be done.
CONCLUSIONS
PHECG has become an important link in the systems of care for patients with acute coronary syndrome. The initiation and performance of PHECG by EMTs play a central role in prehospital triage as well as early activation of the PCI team. While we found that the EMT-II teams were fully competent in executing PHECG and generally showed no significant differences compared to the EMT-P teams, there was room for improvement in the suggestion and performance of PHECG in certain age groups of patients, and especially in females. Moreover, both EMT-II and EMT-P teams can manage to shorten the time spent at the scene for female and elderly patients receiving ECG in the pre-hospital settings. Although the systems of care and composition of EMT teams may vary in different cities and areas, the results from the current study provide valuable and important information when implementing or improving PHECG in prehospital care.
DECLARATION OF CONFLICT OF INTEREST
All the authors declare no conflict of interest.
Acknowledgments
This authors and study group would express special thanks to the Taipei City Fire Department for the great support provided in the establishment of the system, training of the EMTs, collection of data, and analysis of the results.
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