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\begin{document}

\title{Top 100 cited manuscripts in aortic valve replacement: A bibliometric
analysis}



\author[1]{Shwe Oo}%
\author[2]{Ka Hay Fan}%
\author[2]{Yuti Khare}%
\author[3]{Ka Siu Fan}%
\author[4]{Jeremy Chan}%
\author[5]{Chon Meng Lam}%
\author[3]{Sheung Heng Daniel Lai}%
\author[3]{Lok Yin Ada  Kwan}%
\affil[1]{Bristol Royal Infirmary}%
\affil[2]{Imperial College London Faculty of Medicine}%
\affil[3]{University of London}%
\affil[4]{University Hospitals Coventry and Warwickshire NHS Trust}%
\affil[5]{Cardiff and Vale University Health Board}%


\vspace{-1em}



  
  \date{May 23, 2024}


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\selectlanguage{english}
\begin{abstract}
Background: This bibliometric analysis is used to identify publications
and highlights the key areas that have significantly shaped modern
clinical practice for aortic valve replacement (AVR), which is becoming
increasingly relevant. The top 100 most cited manuscripts for AVR were
analysed. Method: The Thomson Reuters Web of Science database was
searched using the terms `aortic valve replacement', `replacement',
`aortic valve' and/or `AVR' for full manuscripts in English Language.
The results were ranked by citation number and the top 100 articles were
further analysed by subject, author, journal, year of publication,
institution and country of origin. Results: 26,782 eligible papers were
returned and accumulated 76,680 citations in total, with a mean citation
of 767 per manuscript (350-3667). The New England Journal of Medicine
accumulated the most citations whereas Circulation published the most
papers. Majority of manuscripts examined patients with aortic stenosis,
of which half also included aortic regurgitation. The United States of
America contributed 51 manuscripts, accumulating 43629 citations.
Conclusion: The most cited manuscript, by Leon et al., assessed the
outcomes of transcatheter aortic valve implantation in patients with
severe aortic stenosis who were unfit for surgical replacement. By
providing the most influential references this work serves as a guide to
topics of interest in the field of AVR.%
\end{abstract}%



\sloppy


\section*{Introduction}

{\label{introduction}}

The prevalence of aortic valve disease has been increasing due to the
ageing population. A corresponding rise in published literature is seen.
Hence, the identification of important works may become increasingly
difficult. Citations are received when a publication is referenced by
another peer-reviewed article and work with the greatest scientific
impact and significance are likely to be cited more. Similarly, the
citation counts of publications reflect its impact on scientific
progress as well as the influence of its journal of publication.

Bibliometric Citation analysis is a method of identifying significant
manuscripts amongst the plethora of publications whilst quantifying the
importance of each paper. Citation analysis involves ranking and
evaluating an article based on its number of citations, serving to rank
the scientific impact of both the article itself and its journal of
publication. Although there is no single best method of determining the
importance of a scientific publication, the use of bibliometric analysis
is generally accepted as an appropriate method. Many surgical
specialities have employed citation rank analysis to identify their most
influential papers, including paediatrics, general surgery and
cardiothoracic surgery.{[}1--3{]}

To date, there has not been a study to determine the top 100 manuscripts
on aortic valve replacement. Citation bibliometrics will provide insight
into how our understanding of aortic valve replacement, and its uses,
have evolved. Additionally, this paper will serve to reference the most
impactful papers on AVR to help identify the most relevant materials for
future authors.

\section*{Methods}

{\label{methods}}

A search was performed on the Thomson Reuters Web of Science citation
indexing database using the following terms 'aortic valve replacement',
'replacement', 'aortic valve' and/or 'AVR'. The search was limited to
full manuscripts in English Language and includes publications from 1970
to 2019. The returned list was sorted by the total number of citations.
This method was initially developed by Paladugu \emph{et al.} and
replicated by O'Sullivan, Kavanagh and Chan in various surgical
specialities. {[}2--5{]} The top 100 articles obtained were further
reviewed and analysed according to journal, authorship, institution,
country, year of publication, article type and topic. The generated
total citation count was inclusive of articles indexed by Web of Science
Core Collection, BIOSIS Citation Index, Chinese Science Citation
Database, Russian Science Citation Index and SciELO Citation Index.

\section*{Results}

{\label{results}}

The search terms yielded 26,782 manuscripts and were ranked in
descending order of total citations. The 100 top-ranked manuscripts had
a total of 76,680 citations and are shown in \textbf{Table 1} . The list
of manuscripts is ordered from most to least cited on PubMed.gov.{[}6{]}
The number of citations ranged from 3667 to 350, with a mean and median
citation count of 767 and 533 respectively. The manuscripts were
published across 16 journals shown in \textbf{Table 2} .

The journal \emph{New England Journal of Medicine} (NEJM) had the
highest impact factors and generated the highest number of citations, of
22,458 with 18 manuscripts. This is followed by Circulation with the
highest number of manuscripts, of 24, generating 14,719 citations. The
latest manuscript was on management guidelines for valvular heart
diseases by the European Society of Cardiology published in 2017 issue
of \emph{European Heart Journal} . The oldest manuscript was published
in Lancet in 1986 comparing percutaneous valvuloplasty against valve
replacement in patients with aortic stenosis.

The country with the most citations was the United States of America,
with 43,629 citations across 51 manuscripts. This is followed by France
and Canada, with 13,750 and 6579 citations respectively, generated by a
total of 26 manuscripts. Citations counts by country are shown
in\textbf{Figure 1} .

Of the top 10 authors, five have more than three authorships in the top
100 manuscripts (\textbf{Table 3} ). 8 of the top 10 cited authors have
multiple manuscripts and altogether generated a total of 36,578
citations. Nashimura had the most manuscripts in the top 100 (n=6),
totalling 4,583 citations. Vahanian generated the highest citation count
of 5,178 from four manuscripts in addition to being the senior author of
two other manuscripts within the top 100.

Of the top 100 manuscripts, 33 investigated aortic valve replacement for
both aortic regurgitation and stenosis whereas 32 were specific to
aortic stenosis alone, accumulating 33,336 and 22,638 citations
respectively. 29 manuscripts focussed specifically on the outcomes of
percutaneous or transcatheter approach to aortic valve replacement,
amounting to 20,702 citations. 18 of the top 100 were management
guidelines involving aortic valve replacement, resulting in 17,585
citations. Topics by citation are shown in \textbf{Table 4} .

\section*{Discussion}

{\label{discussion}}

Isolated aortic valve replacements comprised 10\% of cardiothoracic
operations in 2016, with 6\% performed alongside coronary artery bypass
grafting (CABG) and 1\% alongside mitral valve replacement (MVR).{[}7{]}
AVR surgery serves to provide symptomatic relief and improve prognosis
in patients with severe valve obstruction.{[}8{]} Hence, most common
indications for elective surgeries is aortic valve stenosis (AS) and
aortic regurgitation (AR). {[}9{]} As a result of an ageing population,
there has been an increasing incidence of AS and AR now with up to
275,000 to 370,000 per year who require AVR in the modern world.
{[}10{]} Most AVR are elective surgeries and are performed for AS, in
which the procedure currently provide a five-year survival rate of
78.4\% and fifteen-year survival rate of 39.7\%.{[}11{]} On the other
hand, the most common indications for emergency AVR surgery are critical
aortic stenosis and left ventricular failure, which typically presents
as cardiogenic shock and multiple organ failure.{[}12{]} Advances in
surgical techniques and understanding of the diseases produced notable
improvements in treatment outcomes, lowering mortality rates in hospital
from 6.4\% overall in 2000, to 3.1\% in 2015.{[}13,14{]}

The oldest manuscript was by Professor Alain Cribier who, in 1986, first
trialled the use of percutaneous transluminal balloon catheter aortic
valvuloplasty elderly patients with severe aortic valve stenosis in
1986.{[}15{]} This was introduced as an alternative intervention for
those who are unfit for the traumatic surgical approach. While it was
performed on only three patients and is too early to ascertain its
efficacy, it laid the foundation for researchers to eventually develop
the now widely used transcatheter aortic valve implantation (TAVI). This
is reflected in the ever-increasing amount of literature investigating
TAVI, with 29 of the top 100 specifically examining it alone. In
comparison, only 8 manuscripts focused solely on surgical techniques.
This increasing attention in AVR is reflected in the rising number of
top manuscripts per year, from less than 5 per year before 2000 to peak
in the 2010s, averaging more than 10 per year.

The most cited paper, by Leon \emph{et al} ., investigated TAVI on high
risk, severe aortic stenosis candidates who are not suitable for
surgical replacement. This trial by PARTNER includes a specific cohort
of patients taking place in a multi-centre, randomized clinical trial.
Introduced in 1989 as a less invasive method of treatment for high-risk
patients, transfemoral TAVI is found to significantly reduced 1-year
mortality (30.7\% vs 49.7\%), cardiovascular-related mortality (19.6\%
vs 41.9\%), repeat hospitalisation (22.3\% vs 44.1\%) and significant
symptomatic relief {[}16{]}. However, the study also identified an
increased number of severe stroke (7.8\% vs 3.9\%) and vascular events
(32.4\% vs 7.3\%) in the 12 months following TAVI. Leon \emph{et
al.}concluded that such vascular complications may be attributed to
large femoral access sheath insertions and so novel lower profile valves
and support frames are being developed. This paper proposes TAVI as the
best treatment for high risk severe aortic stenosis patients with
complications unsuitable for standard surgery and identified the areas
of improvement to help perfect TAVI.

The second most cited study was a similar study by Smith \emph{et al.} ,
a randomised control trial comparing TAVI and standard approach but on
high-risk patients who are suitable for surgery. High risk severe aortic
stenosis patients showed similar 1-year mortality between standard
surgical replacement and TAVI. TAVI cohort had shorter ICU stays (3 vs 5
days) and as well as hospital stay (8 days vs 12 days). Major bleeding
was also less common in TAVI, with 14.7\% vs 25.7\%. However,
neurological events such as stroke and/or transient ischemic attacks are
nearly doubled in TAVI (8.3\% vs 4.3\%). This study also associated TAVI
with more procedural complications compared to normal surgery, with
increased vascular complications (18\% vs 4.8\%). The authors concluded
that the outcome of TAVI for male patients was similar to the surgical
approach but offers survival mortality benefits in women or patients
with a coronary bypass graft.

The third most cited study was by Birkmeyer \emph{et al.} , which
investigated the relationship between hospital volume, and the number of
procedures performed and their effects on postoperative mortality.
Analysis of 2.5 million procedures, including 6 types of cardiovascular
surgeries, revealed hospitals with larger volumes had lower mortality
rates. With higher hospital volumes, observed mortality rates of AVR
decreased: hospitals with very low, low, medium, high and very high
volume shown a decreasing mortality rate from 9.9\% to 7.6\%. Similar
trends can be seen in mitral valve replacements and carotid
endarterectomies. This study only included patients on Medicare within
the USA and the majority were above 65 years old. The authors concluded
that the apparent mortality reduction in specialised procedures may be
resultant of more specialised and experienced healthcare professions who
are equipped with greater resources.

Apart from the number of citations and manuscripts published under each
journal, the impact factor of the journals themselves also helps us
understand the quality and significance of the papers. The impact factor
is based on the citations of published articles in each journal,
specifically the average amount of citation by a journal's publications.
As such, journals with higher impact factor tends to publish work of
higher quality and importance which is cited more often. Hence, journals
with an impact factor above 45 (\emph{JAMA, Lancet} and \emph{NEJM} )
accounted with over a third of the total citation counts with 25
manuscripts. Furthermore, only 7\% and 16\% of articles from the list
were from journals with impact factors less than 5 and 10, respectively.
This demonstrates that research in aortic valve replacement is largely
dominated by publications in journals with high to very high impact
factors. However, it would be useful for future research to be able to
assess the clinical significance of these articles to determine the
correlation between citation count and clinical applicability.

\textbf{Limitations}

Citation analyses are prone to certain types of biases. Across many
institutions, particularly in the USA, some articles may receive
additional citations due to self-citations. This phenomenon has also
been noted in other citation analyses and was attributed to preferential
citation of 'local research' and tendency to integrate research in
clinical practice.{[}1{]} Similarly, by limiting the scope of our search
to the English language alone may further affect the self-citation
phenomenon.

Additionally, the earliest assessed manuscript dates back to 1982; older
publications would have had a longer duration to accumulate citations
and it may take a certain amount of time for an influential manuscript
to accrue citations due to lead time. However, given that the top 10
cited manuscripts were all published between 2002 and 2015, publication
time bias might not be a significant limitation. Finally, certain
authors may be under-represented as only first and the senior author is
assessed despite most manuscripts being authored by multiple
researchers.

\section*{Conclusion}

{\label{conclusion}}

The most cited manuscript by Leon \emph{et al.} highlighted the
treatment and outcomes of transcatheter aortic valve implantation for
aortic stenosis patients who were not suitable for AVR surgery. The
majority of the manuscripts used were presented in acclaimed,
high-impact journals, and this particular work provided a reference for
the most influential papers in AVR surgery. Indeed it reflected quality
and significance as well as served as a marker for what makes a paper
'citable'. Conducting this investigation, it was made clear that the
ongoing research into surgical techniques proves that this top 100 most
cited papers list will likely change in the coming years, warranting
future analyses.

\emph{Bibliography}

{[}1{]} Ellul T, Bullock N, Abdelrahman T, Powell AGMT, Witherspoon J,
Lewis WG. The 100 most cited manuscripts in emergency abdominal surgery:
A bibliometric analysis. Int J Surg. 2017 Jan 1;37:29--35.

{[}2{]} Chan J, Mak TLA, Chu TSM, Hui TLY, Kwan LYA. The 100 most cited
manuscripts in coronary artery bypass grafting. J Card Surg. 2019 Sep
1;34(9):782--7.

{[}3{]} Kavanagh RGG, Kelly JCC, Kelly PMM, Moore DPP. The 100 classic
papers of pediatric orthopaedic surgery a bibliometric analysis
{[}Internet{]}. Journal of Bone and Joint Surgery - Series A Journal of
Bone and Joint Surgery Inc.; Sep 18, 2013 p. e134.

{[}4{]} Paladugu R, Schein M, Gardezi S, Wise L. One Hundred Citation
Classics in General Surgical Journals. World J Surg. 2002 Sep
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{[}5{]} O'Sullivan KE, Kelly JC, Hurley JP. The 100 most cited
publications in cardiac surgery: a bibliometric analysis. Irish J Med
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{[}6{]} Fan KS. Top 100 cited manuscripts in aortic valve replacement: A
bibliometric analysis {[}Internet{]}. 2019.
https://www.ncbi.nlm.nih.gov/myncbi/browse/collection/59183764/

{[}7{]} D'Agostino RS, Jacobs JP, Badhwar V, Fernandez FG, Paone G,
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2018 Jan 1;105(1):15--23.

{[}8{]} Rashedi N, Otto C. When Should We Operate in Asymptomatic Severe
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{[}9{]} M\selectlanguage{romanian}ǎrgulescu AD. Assessment of aortic valve disease - a clinician
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{[}10{]} Manji RA, Menkis AH, Ekser B, Cooper DKC. The future of
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{[}11{]} Foroutan F, Guyatt GH, O'Brien K, Bain E, Stein M, Bhangra S,
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{[}12{]} Christ G, Zehetgruber M, Mundigler G, Coraim F, Laufer G,
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{[}13{]} Kvidal P, Bergstr\selectlanguage{ngerman}öm R, Hörte LG, Stahle E. Observed and
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{[}14{]} Takano H, Miyata H, Motomura N, Yamauchi T, Shirakawa Y,
Takamoto S. Analysis of Risk Factors for Mortality and Morbidity of
Surgical Aortic Valve Replacement for Aortic Stenosis: Risk Models From
a Japanese Database. Circulation. 2015;132:A16999.

{[}15{]} Cribier A, Saoudi N, Berland J, Savin T, Rocha P, Letac B.
Percutaneous transluminal valvuloplasty of acquired aortic stenosis in
elderly patients: An alternative to valve replacement? Lancet.
1986;1(8472):63--7.

{[}16{]} Nielsen H. Transcatheter aortic valve implantation. Dan Med J.
2012;59(12):B4556.\selectlanguage{english}
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