Global research trends in cardiac arrest research: a visual analysis of the literature based on CiteSpace

Shi-jiao Yan, Mei Chen, Jing Wen, Wen-ning Fu,5, Xing-yue Song, Huan-jun Chen, Ri-xing Wang, Mei-ling Chen, Xiao-tong Han, Chuan-zhu Lyu

1School of Public Health, Hainan Medical University, Haikou 570100, China

2Research Unit of Island Emergency Medicine, Chinese Academy of Medical Sciences (No. 2019RU013), Hainan Medical University, Haikou 570100, China

3Guizhou Center for Disease Control and Prevention, Guiyang 550004, China

4School of Nursing, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430000, China

5Key Laboratory of Emergency and Trauma, Ministry of Education, College of Emergency and Trauma, Hainan Medical University, Haikou 571199, China

6Department of Emergency, Hainan Clinical Research Center for Acute and Critical Diseases, the Second Affiliated Hospital of Hainan Medical University, Haikou 570100, China

7Emergency and Trauma College, Hainan Medical University, Haikou 570100, China

8Department of Emergency Medicine, Hunan Provincial Institute of Emergency Medicine, Hunan Provincial Key Laboratory of Emergency and Critical Care Metabolomics, Hunan Provincial People's Hospital/the First Affiliated Hospital, Hunan Normal University, Changsha 410000, China

9Emergency Medicine Center, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu 610072, China

Corresponding Authors: Xiao-tong Han, Email: hanxiaotong2021@163.com; Chuan-zhu Lyu, Email: lvchuanzhu677@126.com

KEYWORDS: Cardiac arrest; Bibliometrics; CiteSpace; Research hotspots; Cardiopulmonary resuscitation

INTRODUCTION

Myocardial infarction and other unexpected cardiac occurrences are leading causes of increased cardiac arrest (CA) rates. Sudden cardiac death is a major global public health challenge and accounts for up to 20% of deaths in Western society.In China, more than 230 million people have cardiovascular disease, with 55,000 individuals experiencing CA every year, and less than 1% of out-of-hospital cardiac arrest (OHCA) patientsand 9.1% of in-hospital cardiac arrest (IHCA) patients survive until discharge.The high morbidity and mortality and low survival rate of CA are major global health and economic burdens.Many studies have been published in this area, but visual analysis research which could generate a more comprehensive understanding of CA research is rare. CiteSpace has been widely used in several disciplinary fields and is a literature visualization analysis software developed by researchers in the United States.The approach generates and analyzes networks of co-cited references based on bibliographic records from the Web of Science (WOS) by using dynamic graphs, which provide unique insights into particular research areas.

In this study, we investigated scientific research trends, hotspots, and frontiers in CA research based on CiteSpace’s literature visualization analysis tools, which focused on a 21-year CA literature research history (2000-2020) from the WOS database.

METHODS

Data sources

Data were collected for bibliometric and visualization analyses from Clarivate Analytics’s WOS Core Collection. We used “cardiac arrest” as the search term to retrieve CA-related studies from 2000 to 2020. To ensure the accuracy and objectivity of our literature analysis, the literature formats were limited to original articles and reviews and English-language only. From this, 30,564 related studies were retrieved.

Research methods

Exported records were analyzed for titles, authors, keywords, publication year, research institution, abstracts and journal names. Data were downloaded in TXT formats, and 500 pieces of data as one file were imported into CiteSpace software version 5.6 one by one for quantitative and qualitative analyses.

Parameter settings

Time-slicing was set between 2000 and 2020, where every 3 years was denoted as a time slice. The co-occurrence of keywords and co-cited documents were selected to generate a visual knowledge graph for analysis. The threshold (top N per slice) was set to 50, and the critical path (Pathfinder) and pruning graph (Pruning Sliced Networks) were selected as the pruning options.

Main observation index

The main observation indicators, such as annual publications, author publication amount, and institution publication amount, could reflect the more representative research authors, institutions and the trend of publication volume in the field of CA. The analysis of emerging keywords and article co-citations intuitively reflected current research hotspots and common concerns of researchers. Potential relationships between studies were also identified through keywords clustering, keywords emergence, keywords timeline views, etc., and thus, future research directions were ascertained.

RESULTS

Articles published in CA-related research

In total, 30,564 CA-related publications were retrieved. After preprocessing by CiteSpace software, 2,252 literature records unrelated to the subject, such as call for papers and statements, were excluded, and 28,312 articles were finally included. From 2000 to 2020, the research interest in CA in the WOS database increased significantly. The average annual number of published articles was 1,348 (Figure 1).

Literature sources

Journal co-citation analysis clarified the distribution of key knowledge sources in the CA research field. After statistical analysis, 1,904 journals were involved in this subject area, from which the top 10 journals were screened out (supplemental Figure 1). Research results for CA were mainly distributed in the “Circulation” and “Resuscitation” areas, and the average impact factors of related journals (impact factor 26.25) suggested that CA research was a highly topical, global subject area.

Figure 1. The growth in literature related to cardiac arrest research showing annual publication numbers between 2000 and 2020. The horizontal axis represents the publication year. The vertical axis represents the number of publications.

Bibliometric analysis of countries/regions

The country/region cooperation network map is shown in Supplemental Figure 2. Node number and size indicate the publications volume generated by countries/regions, and the connections between nodes indicated close cooperation between them. The main CA research outputs were derived from diff erent regions of the Americas, Europe, and Asia (Table 1). The graph network density was 0.0315, suggesting a weak to moderate cooperative relationship between countries/regions.

Bibliometric analysis of institutions

Several research institutions and affiliated hospitals of universities contributed to the main CA literature, of which the University of Pittsburgh ranked first with 732 articles, followed by the universities of Washington, and Pennsylvania (supplemental Table 1). The top 10 institutions published 17.71% of CA studies, and the vast majority was from the United States. The network density in this study was 0.0079 (＞0.5 denotes a tight network), which indicated that the global CA research cooperation network was relatively evacuated. The cooperation relationships of the top five institutions are shown in supplemental Figure 3, of which the Mayo Medical Center displayed a good domestic cooperation relationship.

Table 1. Top 20 countries/regions generating CA research publications

Bibliometric analysis of authors

The top 10 authors involved in CA research are listed in Supplemental Table 2. These authors have collectively published a total of 1,472 papers, accounting for 5.20% of all published papers on CA research. Robert A. Berg was identified as the most active author in the field of CA research, with 228 publications, followed by Clitton W. Callaway, and Vinay M. Nadkarni. Author co-citation levels could, to a certain degree, objectively reflect their academic influence in the field. Author co-citations in the field of CA are shown in supplemental Figure 4.

Analysis of CA research hotspots

A cluster analysis of CA publications was performed to generate a keyword cluster map consisting of 130 nodes and 141 links (supplemental Figure 5). The top 10 high-frequency keywords and centrality indices are shown in Table 2. As shown Figure 2, the closer to the warm colors (yellow, orange, and red) the research timeline view is, the more recent the study. Of these, cardiopulmonary resuscitation (CPR), CA, OHCA, extracorporeal membrane oxygenation (ECMO), and management is the focus of the current research.

Keywords with the strongest citation burst often referred to subjects that appeared more frequently in a particular period, which potentially reflected development trends in the research field. Thus, the larger the citation burst value is, the greater the research innovation outcome, representing frontiers in the research field.In recent years, basic life support, targeted temperature management (TTM), ECMO, and cardiogenic shock have become major research frontiers (supplemental Figure 6).

Co-citation analysis

Co-citation relationships indicated that two or more articles were cited by one or more articles at the same time. The relationship was expressed as a connection between nodes on the knowledge graph, which can be mined the contents of common concern of the literature. The co-citation analysis for CA is shown in supplemental Table 3 and supplemental Figure 7. The top five citations were Nielsen et al, who introduced target temperature management for CA; Holzer et aland Bernard et al, who proposed that mild hypothermia therapy eff ectively improved prognosis in CA patients; Nichol et al, who identified regional differences in the incidence and outcomes of OHCA in ten North American regions; and Sasson et al, who published a meta-analysis summarizing how factors and effective interventions provided by witnesses of OHCA patients were associated with survival rates.

Table 2. High-frequency keywords and centrality indices in CA research (top 10)

Figure 2. Top timeline view of CA research hotspots.

DISCUSSION

During the preceding 21 years covered by this study, the number of annual publications in CA research increased gradually. The curve indicates that CA continues to be a research hotspot and that publications related to CA might continue to increase in the years ahead. Over the past 21 years, the United States has an leading position in the field of CA research. Many core institutions focusing on CA research came from university and affiliated hospitals in the United States. However, there is less cooperation among various countries, and research results cannot be shared efficiently, which seriously affects the efficiency of global CA research. Increased attention has been given to CA due to its high morbidity and mortality rates, which has provided solid foundations for the establishment of research partnerships, thereby enhancing the efficiency of international CA research.

The research hotspots in the fields of CA over the last two decades were summarized based on the results of keywords analyses. Analysis of high-risk populations for CA, preventing the occurrence of CA and improving the prognosis and outcome of patients with CA are the principal research directions in this field. Cardiac surgery patients are high-risk populations for CA. Previous studies showed that CA is one of the critical peri-anesthetic complications in general surgery.In the United States, more than 250,000 cardiac surgery operations is performed annually, and the incidence of postoperative CA ranges from 0.7% to 5.2%.The results of bibliometric analysis also suggest that related studies are more closely concentrated on the keyword “cardiac surgery”. Emerging keywords at different periods could reflect hotspot changes in this area. Our study showed that global CA research was more concentrated and focused on high-incidence and therapy themes; emerging therapy keywords referred to “CPR”, “hypothermia”, and “ECMO” indicated the keyword clustering and timeline view highlights.

The early identification and prevention of CA is important to eff ectively reduce the incidence of CA. The priority target of CA prevention is high-risk populations, and appropriate preventive measures should be taken. Medications, implantable cardioverter devices (ICDs), catheter ablation, revascularization, targeted temperature management and prognostic factors after CA are key points in the preventive management of individuals at high risk of CA.Generating good treatment effects for CA patients involves every link of the survival chain. Previous studies showed that the implementation rate of CPR from bystanders at OHCA events was 5.58%-36.00%, with less than 3% of patients receiving defibrillation.Therefore, an important goal of current CA research is to improve bystander rescue and CPR implementation capabilities, as well as improving automated external defibrillator (AED) availability. The establishment of high-quality CPR and AED systems is vital rescue measures that improve patients’ survival rates.

The treatment has always been an important part of CA research. The fundamentals of cardiac resuscitation include the immediate provision of high-quality CPR combined with rapid defibrillation (as appropriate).These mainstays of therapy set the groundwork for other possible interventions, such as medications, extracorporeal cardiopulmonary resuscitation (ECPR), and post-cardiac arrest care, including TTM and cardiorespiratory support. High-quality CPR should include minimizing interruptions in chest compressions, providing compressions of adequate rate and depth, avoiding leaning on the chest between compressions and avoiding hyperventilation, and optimal hand compression position and compression posture.A study showed that the effect of CPR appeared to be maximized when the rescuer kneels beside the victim’s chest (e.g., outside the hospital) or stands at the bedside (e.g., in the hospital) while the patient is lying on his back.Defibrillation is the most eff ective method of terminating CA and achieving return of spontaneous circulation (ROSC) in a shockable rhythm. According to the 2020 American Heart Association (AHA) guidelines for CPR and emergency cardiovascular care (ECC), the ROSC and survival rate of patients with CA were significantly increased after the teams with advanced cardiovascular life support (ACLS) certification resuscitated and treated them.Therefore, there is a positive correlation between better ACLS training for emergency service providers and the improvement of the ROSC rate. Over the past 20 years, the outcomes of IHCA in adults and children have improved due to the promotion and improvement of high-quality CPR, aggressive postresuscitation care, and extracorporeal life support. However, survival rates for OHCA were not significantly increased. Therefore, continuous improvement in the care of CA high-risk patients and their quality of life is still a topic of common concern among acute and critical care research all over the world.

Nervous system injury caused by CA is one of the main causes of death in patients.TTM effectively improves the prognosis of neurological function and survival rates and plays an important role in the comprehensive treatment of CA patients after ROSC. A recent trial published in 2019 including 581 comatose CA survivors with nonshockable initial rhythm (27.4% of the patients had IHCA) showed that moderate hypothermia at 33 °C led to a better neurologic outcome at 90 d compared with normothermia.Regarding the duration of TTM, it has been demonstrated to have similar outcomes for 24 and 48 h. Based on currently available evidence, the International Liaison Committee on Resuscitation and the American Heart Associationsuggested considering the use of TTM, targeting a constant temperature between 32 ℃ and 36 ℃, in patients who remain comatose after resuscitation from either OHCA or IHCA with any initial rhythm. Induction, maintenance and rewarming are the three crucial tenets of TTM; however, the best standard for the implementation of target temperature has not been determined. Therefore, the induction times, cooling rates, target temperature, and duration still require further research. Similarly, a lack of clinical implementation strategies and related experience in the treatment of complications might limit the application of TTM.Therefore, optimizing TTM strategies is a key research direction for improving CA patient prognoses.

CiteSpace visualization data suggested that CA research was closely linked with all aspects of the survival chain, including scientific research of early identification and prevention, emergency response system, high-quality CPR, defibrillation, treatment and rehabilitation after ROSC; however, being more inclined to CPR, ECMO and TTM. The survival rate of patients with CA has a global research focus and is also the fundamental goal of AHA and its guidelines.Thus, more comprehensive follow-up research should be conducted to improve and optimize the current survival chain to ensure CA patient with satisfactory prognosis.

There were some limitations of the present study. First, bibliometrics is a cross-sectional analysis. Second, citations for the latest publications were limited because of the short study period. Finally, visualization of the research output by CiteSpace software is limited to a single database and English-language only; therefore, partial analysis or literature omissions may have inadvertently occurred.

CONCLUSIONS

From our bibliometric analysis, we deconstructed CA research history over the past 21 years using the visualization software CiteSpace. We identified CA research strengths, research hotspots, and importantly, future thematic areas for CA research. The main study outcomes were as follows: (1) described the overall imaging of the main research forces to provide references for strengthening international cooperation and exchange; (2) provided new ideas for CA prognoses by following up frontiers and emerging trends in this area; (3) CPR, ECMO, survival rate and target temperature management are still the research hotspots of scholars at home and abroad, especially the implementation of highquality CPR; and (4) focused on the clinical application of CA prevention measures and TTM strategies.

Funding: This study was supported by the National Natural Science Foundation of China (8216120150); Hainan Provincial Key Research and Development Project (ZDYF2020112); Hainan Provincial Science and Technology Major Project (ZDKJ202004); Key Laboratory of Emergency and Trauma (Hainan Medical University); Ministry of Education (Grant.KLET-202002).

Ethical approval: Ethical approval is not required for this study.Conflicts of interest: The authors declare that they have no conflicts of interest.

Contributors: MC, SJY, WNF, and CZL conceived and designed the study. MC, SJY, WNF, JW, XYS, MLC and HJC participated in the acquisition and analysis of data. SJY and MC drafted the manuscript, and XYS, HJC, MLC, XTH and CZL revised the manuscript. All authors read and approved the final manuscript. CZL is the guarantor of this work, has full access to all the data in the study and takes responsibility for its integrity and the accuracy of the data analysis. SJY and MC contributed equally to this work.

All the supplementary files in this paper are available at http://wjem.com.cn.