A Bibliometric Study on Junctional Ectopic Tachycardia: Time and Trends have much to Tell!

INTRODUCTION

Junctional ectopic tachycardia (JET), also known as junctional tachycardia, has been classically described as a paroxysmal, non-re-entrant supraventricular tachycardia that emanates from abnormal automaticity of the tissue located within the atrioventricular (AV) junction, especially the AV node and the His bundle.^[1] The previous studies report an incidence of JET to hover between 5.6% and 14%, entailing a mortality rate ranging from 8.3% to as high as 40%, depending on the patient subset involved.^[2,3] JET, however, based on etiology, can be broadly classified into two distinct subtypes, namely, congenital JET (CJET) and post-operative JET (POJET). CJET, which usually presents within the first 6 months of life as unexplained tachycardia, despite its’ rarity, often results in sudden cardiac death as well as cardiomegaly and heart failure in up to 60%.^[3,4] Conversely, POJET is more frequently observed within the first 24–48 hours following cardiac surgery, particularly in the pediatric population, secondary to direct surgical trauma, ischemia, and stretch of the AV conduction tissue.^[5] Over the years, various randomized control trials like the one published by Makhoul et al. in 2013 and even a meta-analysis conducted on the drugs for JET prophylaxis in 2022 by Mendel et al. have attempted to unravel this enigmatic complex arrhythmia and the associated debilitating impact.^[6,7]

Having said that diverse reported incidences, involvement of a multifaceted etiology, and an ongoing quest for preventative as well as therapeutic strategies make JET an interesting topic where perioperative factors are expected to play a pivotal role. Hence, we decided to conduct a bibliometric analysis to comprehensively elucidate the currently available knowledge network and the global research trends in JET.

MATERIAL AND METHODS

Data collection and search strategy

The data subset required for the bibliometric analysis was obtained through a Scopus (https://www.scopus.com/search/form.uri?display=basic#basic) search. The corresponding protocol is displayed below, wherein the keyword “Junctional Tachycardia” OR “Junctional Ectopic Tachycardia” was searched to obtain the preliminary results. These results were further refined by excluding the veterinary-related papers, which was followed by limiting the search further to the articles and reviews, giving the final paper count [Figure 1]. The metadata from the entire timeline, from January 1967 to May 2024, including the ahead-of-print versions, were considered, and a comma-separated value (.csv) file was downloaded for the subsequent analysis.

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Figure 1:

Flowchart of the literature search and screening process.

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RESULTS

Trends in publications

A total of 1065 papers were identified on Scopus during the preliminary search. These results were fine-tuned by excluding six veterinary-related papers, limiting to original articles and reviews, having excluded 34 book chapters, 28 conference papers, 25 notes, 17 editorials, 16 letters, 6 short surveys, 5 erratum, 1 conference review, and 1 retraction. Hence, a final paper count of 926 was included, of which 827 (89%) were original articles and 99 (11%) were reviews. First, a bubble map [Figure 2a] depicting the top 25 countries weighted to an overall number of documents produced over the years was created using Scimago Graphica. This outlined the United States of America (USA) to be leading the research front with a total of 339 articles during this study period. Figure 2b represents the top 25 journals based on the total number of papers published. Out of this, the journal Archives des Maladies du Cœur et des Vaisseaux topped the charts with 56 publications, which was closely followed by Pacing and Clinical Electrophysiology (PACE), having a grand total of 51 papers. Of the total of 926 articles, about eight articles had an excess of 200 citations each, which could arguably be labeled as landmark publications in the field. However, [Table 1] portrays a very different picture, with the Journal of American College of Cardiology (JACC) bagging the most number of citations, at 2683 from 20 papers, almost 13.5 times as many citations as Archives des Maladies du Cœur et des Vaisseaux.

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Figure 2:

Graphical representation of JET-related research output weighted to the number of documents using Scimago Graphica. (a) Bubble visualization of the top 25 countries superimposed over the world map. (b) Top 25 journals, along with citations received. (c) Timeline with a yearly output of articles and reviews. JET: Junctional ectopic tachycardia.

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Table 1: Top 10 journals weighted to number of JET-associated citations received.

S. No.	Journal	TC	TD	IF
1.	Journal of the American College of Cardiology	2683	20	24.4
2.	The American Journal of Cardiology	1738	37	2.8
3.	Circulation	1523	29	37.8
4.	PACE	1082	51	1.8
5.	Pediatric Cardiology	766	36	1.6
6.	American heart journal	754	17	4.8
7.	Journal of thoracic and cardiovascular surgery	736	15	6
8.	Heart rhythm	490	23	5.5
9.	Annals of thoracic surgery	376	12	4.6
10.	Anesthesia and analgesia	355	3	5.9

TC: Total number of citations, TD: Total number of documents, IF: Impact factor of the journal for the year 2022, JET: Junctional ectopic tachycardia, PACE: Pacing and clinical electrophysiology

The earliest metadata observed during the index study was from 1967, while the latest was published in April 2024 with few still in ahead of print. The timeline of JET research papers based on yearly frequency has been rendered in Figure 2c as a bar graph. Since 1967, the research interest in the topic has gradually risen, with 2008 seeing 26 papers a year, to a recent spike in output seen in 2022, which witnessed 43 articles, of which 39 were original research and four were reviews.

Keyword and author analysis

The search generated a total of 1038 author keywords, which was narrowed down to 79 keyword co-occurrences, as per the set minimum keyword co-occurrence limit of 5. Network visualization analysis of these 79 selected keywords was plotted using the VOSviewer [Figure 3a]. The resulting map further classified these keywords into seven distinct clusters [Figure 3b], each color-coded for easy delineation. The node size within the hotspot connotes the frequency of keyword occurrence, with the inter-connecting line thickness representing the co-occurrence of keywords. Arrhythmia, congenital heart disease, supraventricular tachycardia, catheter ablation, tachycardia, pediatrics, children, arrhythmias, amiodarone, and tetralogy of Fallot were among the ten most frequently used author keywords in decreasing frequency of co-occurrences.

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Figure 3:

(a) Network visualization analysis (weighted-to-co-occurrences) of the selected author keywords from Scopus search. (b) Scimago Graphica representation of individual author keyword clusters (in no specific order of frequency) and color-coded to match network visualization.

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The cluster density visualization analysis and the overlay analysis of the co-occurred keywords for a period of 15 years (2005–2020), during which significant shifts in keywords were observed by the VOSviewer algorithm, are depicted in Figure 4a and b. The network analysis with a filter of authors with at least five publications on JET found 45 individual authors delineated in [Figure 4c]. Among the authors, B Brembilla-Perrot (CHU de Brabois, France) had the highest number of published papers related to JET at 22 articles and 129 citations, while Bruce B. Lerman (Weill Cornell Medicine, USA) was cited the most, with a citation count of 1120 from 5 JET-related papers.

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Figure 4:

(a) Keyword cluster density visualization. (green to red transition denoting increased frequency of co-occurred keyword). (b) Overlay visualization analysis (weighted to co-occurrences) of author keywords related to Scopus search along the timeline. (c) Network visualization analysis of the related authors (weighted to number of documents).

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DISCUSSION

The analysis meticulously assessed the patterns and trends in JET publications, alongside endeavoring to map the future directions of JET research. Among 83 countries across the globe contributing research papers on JET during the study timeline, 37% of the papers with around 9299 citations happened to be contributed by the USA, followed by France and Germany [Figure 2a]. This trend bespeaks the medical research facilities in high-income nations with an early history of conducting pediatric cardiac surgeries dating back to 1938.^[8,9] The majority were in English (765), French (90), and German (22), with a few in other languages, including Italian, Spanish, Chinese, and Japanese, again reflecting similar trends regarding nationalities of the paper’s origin, in addition to the universal acceptance of English in scientific publications.^[10]

The cardiology journals had the maximum share of JET-related publications, followed by allied branches such as cardiac surgery and cardiac anesthesia [Figure 2b]. The Société Française de Cardiologie journal Archives des Maladies du Cœur et des Vaisseaux, although with the highest number of publications, had fewer citations [Table 1]. When compared to the impact factor (IF) of 1.8 for the former French language journal, higher IF English journals such as the JACC, the American Journal Of Cardiology, and the American Heart Association journal Circulation with respective IF’s (as of 2022) 24.4, 2.8, and 37.4, despite of fewer overall publications, led the way in terms of the citation received.^[11] Fortunately, the interest in JET has steadily increased [Figure 2c], with the first spike seen around the mid-90s, primarily corresponding to the advancements in cardiopulmonary bypass (CPB) techniques. Furthermore, the availability of endocardial mapping as a diagnostic and therapeutic modality probably contributed to this spike.^[12]

Speaking strictly in reference to bibliometric analysis, keywords, especially the author keywords, capture the essence of an article and provide sentinel insights into the author’s research vision.^[13] They are handpicked specifically during the manuscript drafting to ensure optimal indexing and searchability. Bibliometric analysis of these keywords [Figure 3a] helps comprehend the very bleeding edge of a research topic. The selected keywords were grouped into seven clusters by VOSviewer [Figure 3b], based on the common theme of keywords involved, such as #1 Non-pharmacological options, #2 CPB, #3 Congenital heart disease, #4 Pharmacotherapy, #5 CJET, #6 Diagnostic modalities for JET, and #7 POJET. The clusters #1 and #4 represent the nonpharmacological and pharmacological management options available for the treatment of JET. Here, non-pharmacological ablative techniques, radiofrequency and cryo-catheter ablation, are at the cornerstone of managing recurrent-resistant JET, targeting the ectopic foci or aberrant pathways, thereby destroying the arrhythmogenic tissue or isolating it from the rest of the conduction system.^[14] Pharmacological therapy initiated with amiodarone, later incorporated newer agents such as α2-adrenergic agonists like dexmedetomidine, pacemaker “funny” current inhibitor, namely, ivabradine, and ultra-short-acting beta-blockers such as esmolol and landiolol have been demonstrated to be helpful in rate control with minimal hemodynamic fluctuations.^[15] Having said that, being a perioperative arrhythmia featuring amidst wide fluctuations in homeostatic variables, preventative strategies such as temperature regulation, electrolyte correction, and inotrope down titration continue to be a pivotal part of the standard management protocol for JET.

Clusters #2 and #7, containing keywords such as “pediatrics,” “cardiopulmonary bypass,” and “post-operative complication”, highlight the risk of JET in children exposed to CPB. The Ismail et al. study on JET in post-operative patients with tetralogy of Fallot reveals an incidence of JET in the operating room and ICU to be 30.25% and 68.75%, respectively.^[16] Congenital heart diseases such as heterotaxy syndromes, single ventricle disease, and surgeries like Fontan operation are also associated with an accentuated incidence of JET, as seen in cluster #3. Izumi et al. found heterotaxy syndrome as an independent risk factor for JET (odds ratio 4.83; 95% confidence interval 2.18– 10.07).^[17] Cluster #5 highlights various aspects of CJET, such as fetal tachycardia, cardiomyopathy, and the possible requirement of extracorporeal membrane oxygenation in case of incessant JET to allow time for rate and rhythm control.^[18] Keywords nonetheless in the cluster #6 represent the diagnostic modalities available, such as echocardiography and electrophysiological studies, required for ruling out morphologically similar arrhythmias and confirming the diagnosis.^[19]

The density and network overlay analysis [Figure 4a and b] of keywords depicted in terms of frequency and temporal trends show the evolution of JET research. At the same time, the author analysis [Figure 4c] mirrors the patterns observed in the nationality and language trends, with minimal author networks beyond the constraints of individual institutions and national borders. As for the timeline, the initial papers appearing in the 1960s were mostly etiologycentric. The research perspective shifted toward electrical pacing (Montoyo et al.) and beta-blockers (Aronow et al.) as treatment modalities for JET in 1973.^[20,21] Special interest in amiodarone, as a broad-spectrum anti-arrhythmic, saw the rise ever since its 1985 United States Food and Drug Administration approval.^[22,23] At the turn of the millennium, the primary area of interest was pediatric cardiac surgery, with the incorporation of mini bypass circuits, heparin-coated circuits, ultrafiltration devices, and the use of albumin in priming solutions. In the following years, ablation-associated complications, as well as acute myocarditis of viral origin, such as Echovirus 6, came into the limelight.^[19,24,25] While pharmacological agents such as dexmedetomidine, esmolol, ivabradine, landiolol, magnesium, and nifekalant happen to be employed in JET successfully,^[15] the molecular-level studies are accruing to identify connexin 43, junctophilin-2, ryanodine receptors, SCN5A mutation (D1275N), and TNNI3K as important genomic targets.^[26-28]

The main limitation of our present study was restricting the bibliometric analysis only to Scopus-indexed titles. Multiple source analysis using different indexing options like Web of Science (Clarivate PLC, United Kingdom) and the use of other bibliometric software such as CiteSpace (Chaomei Chen, USA) may have added layers. The former was limited nonetheless by the lack of access to those data sets and the sheer complexity of the analytical software. Although veterinary-related studies were broadly excluded, the possibility of some early trials involving animal models cannot be entirely ruled out. The inclusion of review papers could have interestingly resulted in the repetition of keywords, however, buttressing the heightened interest in the subject.

CONCLUSION

As a maiden evaluation of the research trends in the topic, the index bibliometric analysis (VOSviewer and Scimago Graphica) of the JET papers from 1967 to 2024 delineates growing interest in the topic. That being said, the considerable morbidity-mortality burden attributable to JET in pediatric cardiac surgery calls for future research to focus on the molecular mechanisms of the intriguing arrhythmia, aimed at refining the existing preventative treatment strategies.