Role of pre-hospital emergency medical systems in the rescue of patients with ST-elevation myocardial infarction

Abstract

BACKGROUND:

Myocardial infarction (MI) is a series of clinical syndromes caused by ischemic necrosis of myocardial cells that results from severe and persistent acute ischemia of the myocardium due to a dramatic reduction or interruption of coronary blood supply.

OBJECTIVE:

In this study, we analyzed the role of pre-hospital emergency services in the rescue of patients suffering from ST-elevation myocardial infarction (STEMI).

METHODS:

We enrolled 229 patients with STEMI who were transported to the Second Hospital of Tianjin Medical University by Tianjin Emergency Center from January 2017 to June 2021. With the development of the pre-hospital emergency medical system in Tianjin (2019) as the time node, the patients were divided into three groups: A (87 cases), B (68 cases), and C (74 cases). The onset-to-call time, emergency response time, door-to-balloon (D-B) time, first medical contact to balloon dilation (FMC-B) time, symptom onset-to-balloon dilation (S-B) time, proportion of patients receiving prehospital administration of bispecific antibodies, number of days hospitalized, total hospitalization expenses, and in-hospital incidence and mortality of heart failure were compared between the three groups.

RESULTS:

Group C differed significantly from group A and group B in terms of emergency response time, D-B time, FMC-B time, S-B time, the proportion of patients who received prehospital administration of bispecific antibodies, and the number of days of hospitalization ( $P<$ 0.05), but there was no significant difference in the onset-to-call time ( $P>$ 0.05) and the decreasing trends in the in-hospital incidence and mortality of heart failure were not statistically significant (incidence: 9.50% vs. 13.23%, 12.64%; mortality: 4.10% vs. 5.90%, 4.60%).

CONCLUSION:

A reasonable pre-hospital emergency medical network layout and resource investment, as well as the strengthening of the interface between pre-hospital and in-hospital medical emergencies and pre-hospital standardized rescue, can shorten the emergency response time and the total ischemic time in patients with chest pain, which can improve patient prognosis to a certain extent.

Keywords

Chest pain center door-to-balloon time emergency response time pre-hospital medical emergency ST-elevation myocardial infarction

1. Introduction

Myocardial infarction (MI) is a series of clinical syndromes (including angina pectoris, arrhythmia, heart failure, and sudden death) caused by ischemic necrosis of myocardial cells that results from severe and persistent acute ischemia of the myocardium due to a dramatic reduction or interruption of coronary blood supply. The clinical mortality rate for this disease is high. Currently, MI is best treated by restoring coronary blood flow and saving the dying myocardium by opening the blocked coronary artery in time [1, 2, 3]. Emergency percutaneous coronary intervention (PCI) is currently the most effective technique for opening infarct-related vessels, with a 90 minute door-to-balloon (D-B) time limit as per international standards [4]. The pre-hospital emergency medical system regulates the amount of time between the call for an ambulance and the patient’s arrival at the hospital. Shorter time is associated with less myocardial damage and better prognosis for patients based on the characteristics of this disease, despite the lack of a clear international requirement for this period. Through the transmission of electrocardiograms and other medical records, the prehospital emergency medical system, as an important support for the chest pain center, can reduce the emergency response time (the time from call dispatch to ambulance arrival on-scene) and activate the Cardiac Catheterization Laboratory (CCL) [5]. As a result, this system can save valuable time for the resuscitation of acute and critically ill patients, as well as reduce the total myocardial ischemic time in patients with acute ST-elevation myocardial infarction (STEMI), thus improving the prognosis of patients [6, 7, 8]. Since 2019, Tianjin has aggressively promoted the development of a pre-hospital medical emergency system, which has yielded visible results, particularly in terms of reducing the emergency response time. From January 2017 to June 2021, we enrolled 229 STEMI patients who were transported by the Tianjin Emergency Center to the Chest Pain Center of the Second Hospital of Tianjin Medical University. These 229 STEMI patients were assigned to group A (pre-system implementation group, 87 patients from January 2017 to December 2018), group B (system under development group, 68 patients from January 2019 to December 2019), and group C (post-system implementation group, January 2020 to June 2021) with the development of the pre-hospital emergency system medical in Tianjin as the time node. Then, we compared the onset-to-call time, emergency response time, door-to-balloon (D-B) time, first medical contact to balloon dilation (FMC-B) time, symptom onset-to-balloon dilation (S-B) time, the number of days of hospitalization, total hospitalization expenses, and in-hospital incidence and mortality of heart failure among the three groups. Previous studies primarily focused on pre-hospital emergency treatment for ST-elevation myocardial infarction. In this study, we aimed to validate the effectiveness of Tianjin’s pre-hospital medical emergency system. Furthermore, we seek to emphasize the significance of pre-hospital care as a crucial component of the healthcare system and provide valuable insights for public health initiatives, particularly in areas where pre-hospital care is lacking.

2. Materials and methods

2.1 General information

Information source: From January 2017 through June 2021, we enrolled 229 patients with STEMI who were transported to the Second Hospital of Tianjin Medical University by the Tianjin Emergency Center. The following criteria were used to enroll patients: (1) Patients with chest pain or chest distress for more than 30 minutes; (2) Patients with ST elevation $>$ 0.1 mV in two or more adjacent leads on the electrocardiogram (ST elevation $>$ 0.3 mV in the chest leads V1–3); (3) Patients who met the indications for emergency PCI and underwent PCI. The exclusion and rejection criteria for patients were as follows: (1) Patients who were already on a ventilator or receiving cardiopulmonary resuscitation; (2) Patients with the unsuccessful opening of vessels through PCI; and (3) Patients with incomplete clinical data. When various indicators such as age and gender were compared among the 3 groups, the differences were not statistically significant ( $P>$ 0.05) (Table 1).

Table 1
Baseline information of the patients in the three groups

Groups	$n$	Male	Female	Age
Group A	87	66 (75.9)	21 (24.1)	65.70 $\pm$ 12.927
Group B	68	51 (75.0)	17 (25.0)	64.03 $\pm$ 14.466
Group C	74	60 (81.1)	14 (18.9)	63.42 $\pm$ 14.566
$x^{2}/t$		0.910		0.584
$P$		0.634		0.558

Data in the table are expressed as cases (%) or X $\pm$ S.

2.2 Methods

2.2.1 Study methods

The 3 groups were compared in terms of onset-to-call time, emergency response time (the time from call dispatch to ambulance arrival on-scene), D-B time, FMC-B time, S-B time, the proportion of patients who received prehospital administration of bispecific antibodies, the number of days of hospitalization, total hospitalization expenses, and in-hospital incidence and mortality of heart failure.

2.2.2 Resources and processes

(1) Resources: ⟀ Tianjin had 69 emergency stations prior to the development of the pre-hospital emergency medical system, with a mean emergency response time of about 27 minutes. ⟁ Tianjin had 204 emergency stations in the city after the implementation of the pre-hospital emergency medical system, and the average emergency response time was reduced to within 10 minutes.

(2) Processes: ⟀ Dispatchers manually dispatched orders prior to the development of the pre-hospital emergency medical system. However, because emergency physicians rarely communicated with on-scene personnel before patient arrival at the hospital, they lacked a thorough understanding of the situation. The interaction between pre-hospital and in-hospital medical emergency personnel was mostly conducted through telephone or WeChat, which took a long time for physicians and was inefficient. ⟁ After the implementation of the pre-hospital emergency medical system, orders were dispatched by the system based on the distance of the emergency unit team from the emergency site, with accurate distance measurement, which broke geographical boundaries, contributed to rapid and reasonable dispatch, and reduced unreasonable factors of manual dispatch. Before arriving at the site of the emergency, the emergency unit team can communicate with the on-site personnel to understand the situation and instruct them on handling the emergency. The relevant information about patients is then transmitted to the target hospital via the mobile terminal of the pre-hospital emergency notification system while the patient is being transported to the hospital. After the diagnosis of STEMI, physicians in the chest pain center immediately conduct a remote consultation and assessment and activate the Cardiac Catheterization Laboratory (CCL). When the ambulance arrived at the hospital, eligible patients were taken directly to the CLC for PCI, bypassing the emergency department and coronary care unit (CCU).

2.3 Observation indexes

The onset-to-call time, emergency response time (the time from call dispatch to ambulance arrival on-scene), D-B time, FMC-B time, S-B time, the proportion of patients who received prehospital administration of bispecific antibodies, the number of days of hospitalization, total hospitalization expenses, and in-hospital incidence and mortality of heart failure were all observed.

2.4 Data processing

SPSS 25.0 statistical software was used for data processing. The groups were compared. Measurement data conforming to a normal distribution are expressed as mean $\pm$ standard deviation ( $\bar{x}\pm s$ ) and analyzed with the $t$ -test. Measurement data that did not conform to a normal distribution are expressed as the median M (P25, P75) and were analyzed using the rank sum test. Count data are expressed as percentages (%) and analyzed using the chi-squared test. A statistically significant difference was defined as $P<$ 0.05.

3. Results

There were statistically significant differences in the emergency response, D-B, FMC-B, and S-B times among the three groups ( $P<$ 0.05), but no significant differences in the onset-to-call time (Table 2).

Table 2
Comparison of different time periods in the three groups

Group	$n$	Onset-to-call time	Emergency response time	D-B	FMC-B	S-B
Group A	87	35.00 (10.00, 79.50)	20.00 (15.00, 25.00)	67.00 (56.50, 80.00)	102.00 (89.50, 120.00)	174.00 (140.00, 254.00)
Group B	68	49.50 (14.75, 105.00)	13.00 (10.00, 15.75)	61.00 (51.00, 74.00)	92.00 (80.00, 98.75)	148.00 (117.75, 191.00)
Group C	74	43.00 (14.00, 109.25)	10.00 (8.00, 12.00)	57.00 (43.00, 65.25)	86.50 (78.00, 98.00)	151.00 (110.00, 206.50)
$H$		1.406	89.409	22.179	35.447	10.240
$P$		0.495	$<$ 0.01 ${}^{*}$	$<$ 0.01 ${}^{*}$	$<$ 0.01 ${}^{*}$	0.006 ${}^{*}$

Data in the table are expressed as M (P ${}_{25}$ , P ${}_{75}$ ). ${}^{*}P<$ 0.05.

There were significant differences between the three groups in the proportion of patients receiving remote electrocardiograms and patients receiving prehospital administration of bispecific antibodies ( $P<$ 0.05), but no statistically significant difference in the proportion of patients bypassing CCU (Table 3).

Table 3

Comparison of remote electrocardiogram transmission, bypassing of CCU, and bispecific antibody administration in the three groups

Groups	$n$	Remote electrocardiogram transmission	Bypassing CCU	Bispecific antibody
Group A	87	46 (52.9)	78 (90.7)	72 (82.8)
Group B	68	62 (91.2)	62 (91.2)	56 (82.4)
Group C	74	65 (87.8)	72 (97.3)	70 (94.6)
$x^{2}/F$		39.252	3.139	6.182
$P$		0.000 ${}^{*}$	0.208	0.045

Data in the table are expressed as cases (%). ${}^{*}P<$ 0.05.

The number of days spent in the hospital varied significantly between the three groups ( $P<$ 0.05), but there was no statistically significant difference in total hospitalization expenses (Table 4).

Table 4

Comparison of the days and expenses of hospitalization among the three groups

Group	$n$	Number of days of hospitalization	Total hospitalization expenses
Group A	87	7.52 $\pm$ 3.788	38671.00 (32847.68, 46593.50)
Group B	68	6.91 $\pm$ 1.818	39592.22 (32664.38, 46859.98)
Group C	74	6.05 $\pm$ 2.093	36032.21 (30665.39, 3797.63)
$t/H$		5.464	3.548
$P$		0.005 ${}^{*}$	0.170

Data in the table are expressed as M (P ${}_{25}$ , P ${}_{75}$ ). ${}^{*}P<$ 0.05.

Table 5

Comparison of major adverse cardiac and cerebrovascular events in patients in the three groups

Groups	$n$	Heart failure	Mortality
Group A	87	11 (12.64)	4 (4.60)
Group B	68	9 (13.23)	4 (5.90)
Group C	74	7 (9.50)	3 (4.10)
$x^{2}/F$		0.584	0.272
$P$		0.747	0.873

Data in the table are expressed as cases (%).

Figure 1.

Comparison of major adverse cardiac and cerebrovascular events in patients in the three groups

Although the incidence and mortality rates of heart failure were not statistically significantly different between the three groups (Table 5), they showed a decreasing trend after the implementation of the system (Fig. 1).

4. Discussion

Patients with high-risk chest pain, such as those with acute pulmonary embolism or acute MI, are characterized by their challenging pre-hospital diagnosis, short treatment time, rapid disease progression, and strong correlation between prognosis and the beginning of rescue [9]. Furthermore, acute MI accounts for a large proportion of high-risk patients with chest pain and has a high mortality rate. After years of research and practice, the establishment of chest pain centers in China has yielded remarkable results, contributing to the development of standardized diagnosis and treatment processes for the rescue of STEMI patients and more mature regional collaborative rescue networks [10, 11, 12, 13]. The establishment of the Chest Pain Center in the Second Hospital of Tianjin Medical University was associated with an increase in the proportion of patients with infarct-related coronary artery reperfusion and significant reductions in the mortality of acute heart failure incidents during hospitalization, as well as the mean time and expense of hospitalization [14].

The pre-hospital emergency medical system plays a pivotal role in the rescue of patients with chest pain as an essential support for the chest pain center. In February 2019, the Tianjin government issued the Implementation Plan for Strengthening the Construction of Pre-Hospital Emergency Medical System in Tianjin, which effectively advanced the development of the pre-hospital emergency medical system with a top-level design of unified planning, unified reporting, unified quality control, clear staffing, and a clear funding guarantee. Six emergency centers were built in 5 suburbs and the Binhai new area, and 204 emergency stations were built in Tianjin, with 1 emergency station for every 80,000 people and 1 ambulance for every 40,000 people. The staffing of ambulances was clarified to include doctors, nurses, drivers, and stretcher bearers, as well as a funding guarantee standard for pre-hospital medical emergencies was established. Through multiple promotions, the implementation of the pre-hospital emergency medical system in Tianjin has yielded visible results, significantly reducing the radius of emergency services and response time [15].

At the same time, information technology has strengthened the interface between pre-hospital and in-hospital medical emergencies. Specifically, 44 medical institutions above the second level in Tianjin that are primarily responsible for the rescue of acutely ill patients are linked to the pre-hospital emergency notification system of the emergency center, forming a seamless emergency medical network. Before arriving at the target hospital, the emergency physician can transmit the condition, vital signs, electrocardiogram, and real-time audio and video information of patients to the in-hospital physician and activate the in-hospital CCL in time to allow the in-hospital physicians to prepare for treatment in advance, thereby realizing information flow before patient arrival and moving the treatment gateway forward [16, 17, 18, 19].

In this study, we discovered that the key time nodes such as the emergency response, D-B, FMC-B, and S-B times were significantly shorter after system implementation than before system development, which was accompanied by significant elevations in the proportion of remote electrocardiogram transmission, slight increases in the proportion of patients bypassing CCU (97.3% vs. 90.7%), reductions in the number of days of hospitalization, and a decreasing trend of the in-hospital incidence and mortality of heart failure, similar to the related studies [19, 20].

This study has several limitations. Firstly, the sample size in this study was relatively small, which may impact the generalizability of the results to larger populations. Additionally, the scope of this study was limited to examining the incidence and mortality of heart failure during hospitalization. This narrow focus may not capture the full picture of heart failure outcomes, as factors beyond the hospital stay can significantly influence long-term prognosis and patient outcomes. The lack of long-term follow-up of patients’ prognosis was also a limitation of this study. Including long-term follow-up would allow for a more comprehensive understanding of the outcomes and effectiveness of interventions in managing heart failure. Further research with a larger sample size and longer follow-up time are needed to provide more comprehensive and reliable data. In addition to the limitations mentioned, it is worth considering the potential application of advanced techniques, such as artificial intelligence, in the context of pre-hospital emergency medical networks [21, 22, 23, 24]. While this study focused on evaluating the effectiveness of the existing pre-hospital medical emergency system, future research could investigate the integration of AI technologies to enhance its capabilities.

5. Conclusion

Our study demonstrates that a reasonable pre-hospital emergency medical network layout that is coupled with appropriate resource investment, strengthened collaboration between pre-hospital and in-hospital medical emergencies, and pre-hospital standardized rescue may reduce emergency response and total ischemic time for patients with chest pain, and therefore improve patient’s prognosis. To enhance the treatment of critically ill patients, such as those suffering from chest pain, and ensure public physical health, we highly recommend integrating the pre-hospital emergency network and increasing investment in pre-hospital medical care.

Ethics approval and consent to participate

This study was approved by the Ethics Committee of the Second Hospital of Tianjin Medical University and conducted in accordance with the Declaration of Helsinki. Written, informed consent was obtained from all participants.

Competing interests

The authors declare that they have no competing interests.

Funding

Sponsored by Tianjin Health Research Project (No. TJWJ2023MS043).

Availability of data and materials

All data generated or analysed during this study is included in this article. Further enquiries can be directed to the corresponding author.

Footnotes

Acknowledgments

We would like to acknowledge the hard and dedicated work of all staff that implemented the intervention and evaluation components of the study.

References

Choudhury

West

El-Omar

. ST elevation myocardial infarction. Clin Med (Lond). 2016 Jun; 16(3): 277-82. doi: 10.7861/clinmedicine.16-3-277. PMID: 27251920; PMCID: PMC5922709.

Neumann

Sousa-Uva

. ‘Ten commandments’ for the 2018 ESC/EACTS guidelines on myocardial revascularization. Eur Heart J. 2018 Nov 7; 39(42): 3759. doi: 10.1093/eurheartj/ehy658. PMID: 30403801.

Lin

Chen

. Interim analysis report of kuanxiong aerosol in improving angina and quality of life after percutaneous coronary intervention. World J Tradit Chin Med. 2022; 8: 87-91. doi: 10.4103/wjtcm.wjtcm_26_21.

Levine

Bates

Blankenship

Bailey

Bittl

Cercek

Chambers

Ellis

Guyton

Hollenberg

Khot

Lange

Mauri

Mehran

Moussa

Mukherjee

Ting

O’Gara

Kushner

Ascheim

Brindis

Casey

Jr Chung

de Lemos

Diercks

Fang

Franklin

Granger

Krumholz

Linderbaum

Morrow

Newby

Ornato

Radford

Tamis-Holland

Tommaso

Tracy

Woo

Zhao

. 2015 ACC/AHA/SCAI Focused Update on Primary Percutaneous Coronary Intervention for Patients With ST-Elevation Myocardial Infarction: An Update of the 2011 ACCF/AHA/SCAI Guideline for Percutaneous Coronary Intervention and the 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction. J Am Coll Cardiol. 2016 Mar 15; 67(10): 1235-1250. doi: 10.1016/j.jacc.2015.10.005. Epub 2015 Oct 21. Erratum in: J Am Coll Cardiol. 2016 Mar 29; 67(12): 1506. PMID: 26498666.

Kontos

Gunderson

Zegre-Hemsey

Lange

French

Henry

McCarthy

Corbett

Jacobs

Jollis

Manoukian

Suter

Travis

Garvey

. Prehospital Activation of Hospital Resources (PreAct) ST-Segment-Elevation Myocardial Infarction (STEMI): AÂ Standardized Approach to Prehospital Activation and Direct to the Catheterization Laboratory for STEMI Recommendations From the American Heart Association’s Mission: Lifeline Program. J Am Heart Assoc. 2020 Jan 21; 9(2): e011963. doi: 10.1161/JAHA.119.011963. Epub 2020 Jan 20.

Chen

Liu

. Reperfusionof time and prognosis of pre-hospital emergency transport system in treatmentof patients with acute STEMI. Lingnan Journal of Emergenc Medicine. 2021; 26(3): 235-237. doi: 10.3969/j.issn.1671-301X.2021.03.005.

Liu

. Analysis of the value of pre-hospital emergency medical service in patients with acute chest pain. Journal of Hunan Normal University (Medical Sciences). 2019; 16(4): 108-111. doi:CNKI:SUN:HNYG0.2019-04-036.

Marcolino

Ribeiro

. Focusing on prehospital care to improve ST elevation myocardial infarction care. Heart. 2020 Mar; 106(5): 323-324.

Pandie

Hellenberg

Hellig

Ntsekhe

. Approach to chest pain and acute myocardial infarction. S Afr Med J. 2016 Mar; 106(3): 239-45. doi: 10.7196/samj.2016.v106i3.10323. PMID: 27303759.

10.

Huo

. Chinese chest pain center construction theory and medical model. Chinese Journal of Interventional Cardiology. 2021; 29(1): 1-3. doi: 10.3969/j.issn.1004-8812.2021.01.001.

11.

Gulati

Levy

Mukherjee

Amsterdam

Bhatt

Birtcher

Blankstein

Boyd

Bullock-Palmer

Conejo

Diercks

Gentile

Greenwood

Hess

Hollenberg

Jaber

Jneid

Joglar

Morrow

O’Connor

Ross

Shaw

. 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2021 Nov 30; 144(22): e368-e454. doi: 10.1161/CIR.0000000000001029. Epub 2021 Oct 28. Erratum in: Circulation. 2021 Nov 30; 144(22): e455. PMID: 34709879.

12.

, et al. Chest pain centers contribute to decrease in acute cardiac complications and better short-term prognosis for patients with AMI. International Journal of Clinical and Experimental Medicine. 2018; 11(8): 8487-8494.

13.

Zhang

, et al. Effect of regional cooperative rescue systems based on chest pain centers for patients with acute myocardial infarction in a first-tier city in China. Internal and Emergency Medicine. 2021; 16(8): 1-8.

14.

Wang

Feng

Che

. The influence of chest pain center establishment on treatment for patients with ST-segment elevation myocardial infarction. Tianjin Medical Journal. 2018; 46(4): 400-405. doi: 10.11958/20171165.

15.

Shao

Liu

Chang

Zhang

. [Thinking and practice on the construction of pre-hospital first aid system in Tianjin. Chinese Journal of Urban and Rural Enterprise Hygiene. 2021; 36(05): 91-94. doi: 10.16286/j.1003-5052.2021.05.031.

16.

Kotelnik

Pesce

Masterton

Marshall

Pigott

Bialek

Maloney

, et al. 12-lead electrocardiograms acquired and transmitted by emergency medical technicians are of diagnostic quality and positively impact patient care. Prehospital and Disaster Medicine.Â 2021; 36(1): 47-50.

17.

Liu

Zeng

. Practice of pre-hospital first aid standardization System construction – Exploration of large emergency first aid platform construction. China Medical News. 2021; 36(18): 5-5. doi: 10.3760/cma.j.issn.1000-8039.2021.18.107.

18.

Pavlopoulos

Berler

Kyriacou

Koutsouris

. Design and development of a multimedia database for emergency telemedicine. Technol Health Care. 1998 Sep; 6(2–3): 101-10. PMID: 9839856.

19.

Brunetti

Dell’Anno

Martone

Natale

Rizzon

, Cillo

Russo

. Prehospital ECG transmission results in shorter door-to-wire time for STEMI patients in a remote mountainous region. Am J Emerg Med. 2020 Feb; 38(2): 252-257.

20.

Cheung

Leung

Siu

Tsang

Tsui

MSH

Tam

Chan

RHW

. Prehospital electrocardiogram shortens ischaemic time in patients with ST-segment elevation myocardial infarction. Hong Kong Med J. 2019 Oct; 25(5): 356-362.

21.

Badnjevic

Gurbeta

Boskovic

Dzemic

. Measurement in medicine – Past, present, future. Folia Medica. 2015; 50(1): 43-46.

22.

et al.Review of Artificial Intelligence Application in Cardiology, 2020 9th Mediterranean Conference on Embedded Computing (MECO), Budva, Montenegro. 2020, pp. 1-5. doi: 10.1109/MECO49872.2020.9134333.

23.

Badnjević

Avdihodžić

Gurbeta Pokvić

. Artificial intelligence in medical devices: Past, present and future. Psychiatria Danubina. 2021; 33(3): 336-341.

24.

Aba

Lgpa

. Inspection of medical devices. Clinical Engineering Handbook (Second Edition). 2020; 491-497.