• IRB approval, informed consent, and patient details
• Ethics Statements
• Animal studies
• Conflict of interest
• Submission declaration and verification
• Use of inclusive language
• Reporting sex- and gender-based analyses
• Authorship
• Clinical trial results
• Registration of clinical trials
• Article transfer service
• Copyright
• Preprints policy and sharing
• Role of the funding source
• Open access
• Language services
• Manuscript categories
• Peer Review
• Article structure
• Essential title page information
• Abstract
• Graphical abstract
• Keywords
• Abbreviations
• Artwork
• Tables
• References
• Data visualization
• Supplementary material
• Research data
• Submission checklist

Heart Rhythm O2 is an online-only, gold open access publication of the Heart Rhythm Society. With a focus on cardiac arrhythmias and electrophysiology, Heart Rhythm O2 publishes original Clinical and Experimental Research, Design Papers, Topics in Review, Brief Reports, Perspectives in Contrast, Editorial Commentaries, Letters to the Editor, and more. As an open access journal, Heart Rhythm O2 serves as a major venue for sharing information on the latest research and technologies for electrophysiologists, physicians, and allied health professionals who care for patients with rhythm disorders. All articles are peer reviewed. Editors are blinded from any submission where there is a real or perceived conflict of interest.

Heart Rhythm O2 is indexed in PubMed Central.

Manuscripts must be submitted online at https://www.editorialmanager.com/hroo/default.aspx

IRB approval, informed consent, and patient details

Studies on patients or volunteers require Institutional Review Board (IRB) approval, which must be documented in the Methods section of the paper.If the IRB waived the need for approval, please state this in the Methods, along with the reason for the waiver (e.g., IRB approval was waived due to the use of retrospective and de-identified data).
Appropriate consents, permissions and releases must be obtained where an author wishes to include case details or other personal information or images of patients and any other individuals in an Elsevier publication and this must be documented in the Methods section of the paper. Written consents must be retained by the author and copies of the consents or evidence that such consents have been obtained must be provided to Elsevier on request. For more information, please review the Elsevier Policy on the Use of Images or Personal Information of Patients or other Individuals, https://www.elsevier.com/patient-consent-policy. Unless you have written permission from the patient (or, where applicable, the next of kin), the personal details of any patient included in any part of the article and in any supplementary materials (including all illustrations and videos) must be removed before submission. If written informed consent is waived by the IRB, please state the reason why it was waived in the Methods.

Ethics Statements

Authors must attest that the research reported has adhered to relevant ethical guidelines and that the authors are in compliance with the regulations of their institutional review boards on human studies and animal care and use committees, including obtaining patient consent where appropriate. Examples of relevant guidelines are:

Animal studies

Animal Studies must conform to the Guide for the Care and Use of Laboratory Animals. Authors must include a statement in the Methods section confirming that the study conforms to these guidelines and was approved by the Institutional Animal Care and Use Committee (IACUC) at the authors' institution.

Conflict of interest

All authors must disclose any financial and personal relationships with other people or organizations that could inappropriately influence (bias) their work. Examples of potential conflicts of interest include employment, consultancies, stock ownership, honoraria, paid expert testimony, patent applications/registrations, and grants or other funding. If there are no conflicts of interest then please state this: 'Conflicts of interest: none'. See also https://www.elsevier.com/conflictsofinterest. Further information can be found at: https://service.elsevier.com/app/answers/detail/a_id/286/supporthub/publishing.

The corresponding author must upload a signed Heart Rhythm O2 conflict of interest form and include the conflicts of all authors on the title page of the article. The Heart Rhythm O2 conflict form can be found at the following link: https://www.elsevier.com/__data/promis_misc/HRO2_COI_Form.docx

Submission declaration and verification

Submission of an article implies that the work described has not been published previously (except in the form of an abstract, a published lecture or academic thesis, see 'Multiple, redundant or concurrent publication' for more information), that it is not under consideration for publication elsewhere, that its publication is approved by all authors and tacitly or explicitly by the responsible authorities where the work was carried out, and that, if accepted, it will not be published elsewhere in the same form, in English or in any other language, including electronically without the written consent of the copyright-holder. To verify compliance, your article may be checked by Crossref Similarity Check and other originality or duplicate checking software.

Please confirm in the cover letter with your submission that the manuscript is original and that all authors are responsible for the contents and have read and approved the manuscript for submission to Heart Rhythm O2.

Use of inclusive language

Inclusive language acknowledges diversity, conveys respect to all people, is sensitive to differences, and promotes equal opportunities. Content should make no assumptions about the beliefs or commitments of any reader; contain nothing which might imply that one individual is superior to another on the grounds of age, gender, race, ethnicity, culture, sexual orientation, disability or health condition; and use inclusive language throughout. Authors should ensure that writing is free from bias, stereotypes, slang, reference to dominant culture and/or cultural assumptions. We advise to seek gender neutrality by using plural nouns ("clinicians, patients/clients") as default/wherever possible to avoid using "he, she," or "he/she." We recommend avoiding the use of descriptors that refer to personal attributes such as age, gender, race, ethnicity, culture, sexual orientation, disability or health condition unless they are relevant and valid. When coding terminology is used, we recommend to avoid offensive or exclusionary terms such as "master", "slave", "blacklist" and "whitelist". We suggest using alternatives that are more appropriate and (self-) explanatory such as "primary", "secondary", "blocklist" and "allowlist". These guidelines are meant as a point of reference to help identify appropriate language but are by no means exhaustive or definitive.

Reporting sex- and gender-based analyses

Reporting guidance
For research involving or pertaining to humans, animals or eukaryotic cells, investigators should integrate sex and gender-based analyses (SGBA) into their research design according to funder/sponsor requirements and best practices within a field. Authors should address the sex and/or gender dimensions of their research in their article. In cases where they cannot, they should discuss this as a limitation to their research's generalizability. Importantly, authors should explicitly state what definitions of sex and/or gender they are applying to enhance the precision, rigor and reproducibility of their research and to avoid ambiguity or conflation of terms and the constructs to which they refer (see Definitions section below). Authors can refer to the Sex and Gender Equity in Research (SAGER) guidelines and the SAGER guidelines checklist. These offer systematic approaches to the use and editorial review of sex and gender information in study design, data analysis, outcome reporting and research interpretation - however, please note there is no single, universally agreed-upon set of guidelines for defining sex and gender.

Sex generally refers to a set of biological attributes that are associated with physical and physiological features (e.g., chromosomal genotype, hormonal levels, internal and external anatomy). A binary sex categorization (male/female) is usually designated at birth ("sex assigned at birth"), most often based solely on the visible external anatomy of a newborn. Gender generally refers to socially constructed roles, behaviors, and identities of women, men and gender-diverse people that occur in a historical and cultural context and may vary across societies and over time. Gender influences how people view themselves and each other, how they behave and interact and how power is distributed in society. Sex and gender are often incorrectly portrayed as binary (female/male or woman/man) and unchanging whereas these constructs actually exist along a spectrum and include additional sex categorizations and gender identities such as people who are intersex/have differences of sex development (DSD) or identify as non-binary. Moreover, the terms "sex" and "gender" can be ambiguous—thus it is important for authors to define the manner in which they are used. In addition to this definition guidance and the SAGER guidelines, the resources on this page offer further insight around sex and gender in research studies.


All authors should have made substantial contributions to all of the following: (1) the conception and design of the study, or acquisition of data, or analysis and interpretation of data, (2) drafting the article or revising it critically for important intellectual content, (3) final approval of the version to be submitted.

Changes to authorship

This policy concerns the addition, deletion, or rearrangement of author names:
Before an article is accepted for publication: If an author is removed, the corresponding author must upload with the resubmission a letter explaining (a) the reason the person is being removed and (b) written confirmation (e-mail, fax, letter) from all authors that they agree with the removal or rearrangement. In the case of removal of authors, this includes confirmation from the author being removed. All documentation should be collated into a single file (preferably PDF) and uploaded via the submission site as an "Author Change Documentation" submission item.
After acceptance, but before the accepted manuscript is published in an online issue: Requests to add or remove an author, or to rearrange the author names, must be sent to the Managing Editor ([email protected]) from the corresponding author and include the same information as above. Requests that are not sent by the corresponding author will be forwarded by the Managing Editor to the corresponding author. Note that: (1) Managing Editors will inform the Journal Editors of any such requests and (2) publication of the accepted manuscript in an online issue is suspended until authorship has been agreed.
After the accepted manuscript is published in an online issue: Any requests to add, delete, or rearrange author names in an article published in an online issue must be sent to the Journal Manager and follow the same policies as noted above; changes will result in a corrigendum.

Clinical trial results

In line with the position of the International Committee of Medical Journal Editors, the journal will not consider results posted in the same clinical trials registry in which primary registration resides to be prior publication if the results posted are presented in the form of a brief structured (less than 500 words) abstract or table. However, divulging results in other circumstances (e.g. investor's meetings) is discouraged and may jeopardize consideration of the manuscript. Authors should fully disclose all posting in registries of results of the same or closely related work.

Registration of clinical trials

Registration in a public trials registry is a condition for publication of clinical trials in this journal in accordance with International Committee of Medical Journal Editors (ICMJE, http://www.icmje.org) recommendations. Trials must register at or before the onset of patient enrolment. The clinical trial registration number should be included at the end of the abstract of the article. A clinical trial is defined as any research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects of health outcomes. Health-related interventions include any intervention used to modify a biomedical or health-related outcome (for example drugs, surgical procedures, devices, behavioral treatments, dietary interventions, and process-of-care changes). Health outcomes include any biomedical or health-related measures obtained in patients or participants, including pharmacokinetic measures and adverse events. Purely observational studies (those in which the assignment of the medical intervention is not at the discretion of the investigator) will not require registration.

Note that registering drug and biologics trials that are phase II – IV controlled investigations of a product subject to FDA regulation, and device trials including controlled trials of health outcomes of devices subject to FDA regulation, has become mandatory for trials started later than 12/26/07, or 21 days after the first patient is enrolled. Exceptions are for trials ongoing as of 9/27/07 that do NOT involve serious or life-threatening conditions; they may be submitted by 9/27/08. For example, all cardiology studies will be considered “serious conditions”. Trials involving serious conditions and initiated before 9/27/07 but completed prior to 12/26/07 are NOT subject to the new requirements. For any questions, consult: http://prsinfo.clinicaltrials.gov; http://grants.nih.gov/grants/guide/notice-files/NOT-OD-08-014.html

Article transfer service

This journal is part of our Article Transfer Service. This means that if the Editor feels your article is more suitable in one of our other participating journals, then you may be asked to consider transferring the article to one of those. If you agree, your article will be transferred automatically on your behalf with no need to reformat. Please note that your article will be reviewed again by the new journal. More information.


Upon acceptance of an article, authors will be asked to complete an 'Exclusive License Agreement' (more information). Permitted third party reuse of gold open access articles is determined by the author's choice of user license

Preprints policy and sharing

Authors may share preprints of their work at any time. Elsevier supports responsible sharing. Find out how you can share your research published in Elsevier journals here.

Role of the funding source

You are requested to identify who provided financial support for the conduct of the research and/or preparation of the article and to briefly describe the role of the sponsor(s), if any, in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. If the funding source(s) had no such involvement, it is recommended to state this.

Open access

As an open access journal with no subscription charges, a fee (Article Publishing Charge, APC) is payable by the author or research funder to cover the costs associated with publication. This ensures your article will be immediately and permanently free to access by everyone. The Article Publishing Charge for this journal is USD 2150, excluding taxes, and is applied to all article types except invited content and Letters/Replies to the Editor. There is a 25% discount for Heart Rhythm Society members.

Please visit our Open Access page for more information.

Language services

Please write your text in good English (American or British usage is accepted, but not a mixture of these). Authors who feel their English language manuscript may require editing to eliminate possible grammatical or spelling errors and to conform to correct scientific English may wish to use the English Language Editing service available from Elsevier's Author Services.


Our online submission system guides you stepwise through the process of entering your article details and uploading your files. The system converts your article files to a single PDF file used in the peer-review process. Editable files (e.g., Word) are required to typeset your article for final publication. All correspondence, including notification of the Editor's decision and requests for revision, is sent by e-mail.

Submit your article

Please submit your article via https://www.editorialmanager.com/hroo/default.aspx.Authors will be required to enter a Snapshot Summary of their article on the submission form. Snapshot Summaries should describe the take-home message of the article and should be no more and than 200 characters, including spaces.

Revision policy

Revised manuscripts must be received within 6 months of notification of a decision. If more time is needed, please notify the journal office at [email protected].

Manuscript categories

Authors should review and adhere to the following guidelines for reporting of research results and case reports.

Original Clinical or Original Experimental
5000 words; 8 figure/table (total); the abstract (250 words or fewer) is required and should be divided into the following 5 subsections: Background, Objective, Methods, Results, and Conclusion. Additional words and figures will be considered at the Editors' discretion.

Design Papers
Design papers should be ≤5000 words; the combined figure/table limit is 8. An abstract (250 words or fewer) is required and should be divided into 5 subsections: Background, Objective, Methods, Results, and Conclusion.
Ideally, the paper should describe a prospective, multicenter randomized trial or prospective registry studies that may answer important and novel questions in electrophysiology. There should be an in-depth discussion of the topic showing a need for this research with equipoise to do the study. A careful review of the literature with a succinct summary is desirable. The paper should provide a description of the knowledge gap the trial is intended to address, and what the results of this study will add to the currently available information. The paper should be written to engage readers to consider the impact of the trial and to describe the methodology clearly. If less common statistical analysis is to be used, the reason for this approach should be described. The study should be powered to achieve a clear achievable endpoint. The discussion should not repeat the introductory material but rather set the stage for the impact the authors believe the results will have for all possible outcomes. Early submissions are preferable to help provide feedback in methodology. The study must be ethical and have IRB approval. Investigators and centers are high quality (and may be looking for additional centers and investigators). Proper structures (DSMB, executive oversight committee, steering committee) should be carefully described. The trial should be listed on www.clinical trials.gov and structure and funding should be provided.

Topics in Review (Solicited and Unsolicited)
Review articles should be ≤8000 words; the combined figure/table limit is 8. Authors should include a brief, unstructured abstract (200 words).

Research Letters (≤ 800 words, 1 figure or table)
Research Letters provide a brief description of a focused topic or phenomenon. Articles are limited to 800 words, including references (5 refs maximum) and legends. No abstract should be included. Authors must include a conclusion statement at the end of the article. Headings, such as Introduction, Methods, Results, and Conclusions, should not be included. Authors may include up to 1 figure or 1 table. Supplementary data is not permitted. All research letters will be peer-reviewed. Research Letters will be published under the heading "Letters" along with Letters to the Editor.

Brief Reports (≤ 1500 words, up to 4 figures/tables)
Submissions to this section are for articles that contain untested or unproven new ideas with limited supporting evidence but must have compelling rationale. The idea should be one that is difficult or impossible to test definitively or would take a long time or significant resources to do so. Additional articles that can be considered are those with novel or incremental value, but are of small sample size, represent preliminary data, or are of limited content, both in methodology and results. Articles must be <1500 total words, including references and tables, and a combined total of 4 figures and/or tables. No abstract should be included. Supplementary data are permitted.

Case Reports
Submissions are limited to 6 authors and 2500 words, including text, references (≤15), figure legends, and ≤3 figures. No abstract should be included. All case reports will be considered. Selection priority will be based upon the reporting of new therapies, new complications of therapies, or new mechanisms of diseases. A statement regarding patient consent should be included in the article

Allied Health Professionals Section
This section of the journal is intended for Allied Health Professionals (AHP) to submit articles on topics of particular interest to AHPs. The first or corresponding author must be an AHP.
Submissions can include original research, practice-improvement topics, or review articles. For articles regarding research and practice improvement, topics may include process improvement, patient care, and patient education. Some examples include workflow, care pathways, best practices for care of patients with CIEDs and arrhythmias, reimbursement, team-based-practice models, optimizing the use of nurse practitioners and physician assistants, shared decision making, ablation techniques, imaging/mapping, quality of life, device troubleshooting, and remote monitoring. Articles should be between 2500 - 3000 words and should be divided into the following five subsections: Background, Objectives, Methods, Results, and Conclusion. A brief abstract (200 words or fewer) summarizing key concepts is required. References (15 max) are required and figures, tables, graphic and electronic video clips are also encouraged. While figures/tables are not strictly limited, we encourage the inclusion of up to 5 figures and 3 tables.
Review articles submitted to the AHP section should include a brief unstructured abstract (200 words); the word count is flexible. Proposals for review article topics should be submitted to [email protected].

Global Voices
This section of the journal features original research, topical reviews and brief reports, representing electrophysiology (EP) and arrhythmia care around the world. Submissions will be considered that focus on health disparities, racial/ethnic or sex-specific outcomes, and arrhythmias and outcomes in unique patient populations, including health resource-constrained populations.
Review articles submitted to the Global Voices section should include a brief abstract (200 words). The word count is flexible. Original research submissions should include a structured abstract (with headings Background, Objective, Methods, Results, and Conclusions; 250 words max), and should be limited to 5000 words.
Proposals for Global Voices articles should be submitted to [email protected]. If approved, the journal office will forward an invitation link for authors to upload the manuscript to the journal submission site. All articles will be peer reviewed. If accepted for publication the Open Access fees will be waived.

Perspectives in Contrast (Invited)
This submission category is focused on providing contrasting opinions, perspectives, clinical value, scientific value and future adoption of new therapy or approach to patient management. Two authors are selected by invitation only to provide the contrasting perspectives. Each author should provide a strong summary of their position regarding the topic. Each author is limited to 2000 words.

Fellows Corner
The Fellows Corner highlights selected case reports, providing an opportunity for fellows to introduce an educational or innovative case in the field of cardiac arrhythmias and electrophysiology. The case report should be a succinct description (1100 words max, including references) of the clinical scenario, the teaching point(s) or innovations, and potential implications of the case, and it can be accompanied by one small figure. At the end of the article, authors should include a section called "What We Learned From This Case," and list 3 brief bullets with the key take-home messages that other fellows would appreciate. Occasionally, an opinion piece can also be considered that is related to fellowship and early career training and discusses pertinent issues. Submissions are limited to 4 authors. Authors should state what fellowship program they belong to in the cover letter.

Letters to the Editor
Letters should not exceed 400 words (excludes title page) and are limited to 10 references. Letters may refer to papers published in an issue within 6 months. Letters regarding articles posted outside this time frame will not be eligible for consideration. Letters will be reviewed and are subject to editing. They should not contain original data or figures.

All articles by invitation only. Point of Views should be limited to 1000 words, including references (10 refs max). Up to one figure or table may be included. Authors should present a review of a medical problem or challenge for which the authors have a viewpoint, or hypothesis. The latter should be supported by preliminary data, case reports, or prior public discourse on the topic. The strengths and weaknesses of the viewpoint or hypothesis should be discussed and a carefully considered proposal for exploring the authors ideas further. Articles should not have an abstract, but they should include a Summary section with 3-4 brief bullets summarizing the key take-home messages of the article.

Editorial Commentary
All articles by invitation only. Articles are limited to 1500 words, including references.

Peer Review

This journal operates a single blind review process. All contributions will be initially assessed by the editor for suitability for the journal. Papers deemed suitable are then sent to a minimum of two independent expert reviewers to assess the scientific quality of the paper, frequently under the direction of a section editor with expertise in the manuscript topic. The Editor is responsible for the final decision regarding acceptance or rejection of articles. The Editor's decision is final. Editors are blinded from any submission where there is a real or perceived conflict of interest: specifically, editors are not involved in decisions about papers that they have written themselves, that have been written by family members or colleagues, or that relate to products or services in which the editor has an interest. Any such submission is subject to all of the journal's usual procedures, with peer review handled independently of the relevant editor and their research groups. For more information on the types of peer review, please visit: https://www.elsevier.com/reviewers/peer-review

Use of word processing software

It is important that the file be saved in the native format of the word processor used. The text should be in single-column format. Keep the layout of the text as simple as possible. Most formatting codes will be removed and replaced on processing the article. In particular, do not use the word processor's options to justify text or to hyphenate words. However, do use bold face, italics, subscripts, superscripts etc. When preparing tables, if you are using a table grid, use only one grid for each individual table and not a grid for each row. If no grid is used, use tabs, not spaces, to align columns. The electronic text should be prepared in a way very similar to that of conventional manuscripts (see also the Guide to Publishing with Elsevier). Note that source files of figures, tables and text graphics will be required whether or not you embed your figures in the text. See also the section on Electronic artwork.
To avoid unnecessary errors you are strongly advised to use the 'spell-check' and 'grammar-check' functions of your word processor.

Article structure

Original Clinical and Experimental articles should be divided into the following sections: Introduction, Methods, Results, Discussion, and Conclusions, with appropriate subheadings to make the sections easily understood. A section on Clinical Implications for Experimental articles may be worthwhile.


State the objectives of the work and provide an adequate background, avoiding a detailed literature survey or a summary of the results.


Provide sufficient detail to allow the work to be reproduced. Methods already published should be indicated by a reference: only relevant modifications should be described. Articles should include a statement regarding research guidelines, and, if applicable, an ethics statement regarding IRB approval and patient consent; animal studies must include statements regarding IACUC approval and guidelines.


Results should be clear and concise.


This should explore the significance of the results of the work, not repeat them. Avoid extensive citations and discussion of published literature.


The main conclusions of the study should be presented in a short Conclusion.

Key Findings

Please provide a bulleted list of the Key Findings from the article. The Key Findings should briefly summarize the most important information from the article. The Key Findings should be submitted in MS Word format as a separate file, rather than embedded in the main manuscript document. Include a minimum of 3 Key Findings (no more than 5).


If there is more than one appendix, they should be identified as A, B, etc. Formulae and equations in appendices should be given separate numbering: Eq. (A.1), Eq. (A.2), etc.; in a subsequent appendix, Eq. (B.1) and so on. Similarly for tables and figures: Table A.1; Fig. A.1, etc.

Essential title page information

  • Title. Concise and informative. Titles are often used in information-retrieval systems. Avoid abbreviations and formulae where possible. Do not include trade names in titles.
  • Short title. Include a short title of 50 or fewer characters.
  • Author names, academic degrees, and affiliations. Please include academic degrees after each author’s name. Fellows of the Heart Rhythm Society (FHRS) should be identified by including FHRS after the degree. Where the family name may be ambiguous (e.g., a double name), please indicate this clearly. Present the authors' affiliation addresses (where the actual work was done) below the names. Indicate all affiliations with a lower-case superscript letter immediately after the author's name and in front of the appropriate address. Provide the full postal address of each affiliation, including the country name.
  • Corresponding author. Clearly indicate who will handle correspondence at all stages of refereeing and publication, also post-publication. Ensure that the e-mail address and the complete postal address is included. Contact details must be kept up to date by the corresponding author.Please do not include telephone or fax numbers
  • Conflict of interest statement.Conflicts of all authors must be included on the title page. If there are no conflicts, please state on the title page that the authors have no conflicts to disclose
  • Present/permanent address. If an author has moved since the work described in the article was done, or was visiting at the time, a 'Present address' (or 'Permanent address') may be indicated as a footnote to that author's name. The address at which the author actually did the work must be retained as the main, affiliation address. Superscript Arabic numerals are used for such footnotes.


Clinical and Experimental articles and Design Papers should include a structured abstract (without references) of fewer than 250 words. Divide the abstract into sections: Background, Objective, Methods, Results, and Conclusion that state the importance and potential implications of the observations. Review articles and Allied Health Professionals articles should have an unstructured abstract.

Graphical abstract

Authors are encouraged to submit a graphical abstract, as it draws more attention to the online article. Graphical abstracts are optional and should not be identical to any figures from the article or supplemental data. The graphical abstract should summarize the contents of the article in a concise, pictorial form designed to capture the attention of a wide readership. Legends should not be included. Graphical abstracts should be submitted as a separate file in the online submission system. Image size: Please provide an image with a minimum of 531 × 1328 pixels (h × w) or proportionally more. The image should be readable at a size of 5 × 13 cm using a regular screen resolution of 96 dpi. Preferred file types: TIFF, EPS, PDF or MS Office files. See https://www.elsevier.com/graphicalabstracts for examples.
Authors can make use of Elsevier's Illustration and Enhancement service to ensure the best presentation of their images and in accordance with all technical requirements: Illustration Service.


Immediately after the abstract, provide 5-10 keywords, using American spelling and avoiding general and plural terms and multiple concepts (avoid, for example, 'and', 'of'). Be sparing with abbreviations: only abbreviations firmly established in the field may be eligible. These keywords will be used for indexing purposes.


Avoid ALL abbreviations other than standard units of measurement and common abbreviations, such as RV, LV, etc. Such abbreviations that are unavoidable should be spelled out at first mention in both the abstract and the text. Ensure consistency of abbreviations throughout the article.


Collate acknowledgements in a separate section at the end of the article before the references and do not, therefore, include them on the title page, as a footnote to the title or otherwise. List here those individuals who provided help during the research (e.g., providing language help, writing assistance or proof reading the article, etc.).

Formatting of funding sources

List funding sources in this standard way to facilitate compliance to funder's requirements:

Funding: This work was supported by the National Institutes of Health [grant numbers xxxx, yyyy]; the Bill & Melinda Gates Foundation, Seattle, WA [grant number zzzz]; and the United States Institutes of Peace [grant number aaaa].

It is not necessary to include detailed descriptions on the program or type of grants and awards. When funding is from a block grant or other resources available to a university, college, or other research institution, submit the name of the institute or organization that provided the funding.

If no funding has been provided for the research, it is recommended to include the following sentence:

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.


Follow internationally accepted rules and conventions: use the international system of units (SI). If other units are mentioned, please give their equivalent in SI.

Math formulae

Please submit math equations as editable text and not as images. Present simple formulae in line with normal text where possible and use the solidus (/) instead of a horizontal line for small fractional terms, e.g., X/Y. In principle, variables are to be presented in italics. Powers of e are often more conveniently denoted by exp. Number consecutively any equations that have to be displayed separately from the text (if referred to explicitly in the text).


Footnotes should be used sparingly. Number them consecutively throughout the article. Many word processors build footnotes into the text, and this feature may be used. Should this not be the case, indicate the position of footnotes in the text and present the footnotes themselves separately at the end of the article. Do not include footnotes in the Reference list.


For the ease of reviewers, please include figures and legends at the end of the main manuscript MS Word file. Each legend should appear on the same page as the figure it describes. For revised submissions, please also upload each figure as a separate, high resolution figure file. Acceptable file formats are noted below.

Electronic artwork

General points
• Make sure you use uniform lettering and sizing of your original artwork.
• Embed the fonts used if the application provides that option.
• Aim to use the following fonts in your illustrations: Arial, Courier, Times New Roman, Symbol, or use fonts that look similar.
• Number the illustrations according to their sequence in the text.
• Use a logical naming convention for your artwork files.
• Size the illustrations close to the desired dimensions of the published version.
• Submit each illustration as a separate file.
A detailed guide on electronic artwork is available on our website:
You are urged to visit this site; some excerpts from the detailed information are given here.
If your electronic artwork is created in a Microsoft Office application (Word, PowerPoint, Excel) then please supply 'as is' in the native document format.
Regardless of the application used other than Microsoft Office, when your electronic artwork is finalized, please 'Save as' or convert the images to one of the following formats (note the resolution requirements for line drawings, halftones, and line/halftone combinations given below):
EPS (or PDF): Vector drawings, embed all used fonts.
TIFF (or JPEG): Color or grayscale photographs (halftones), keep to a minimum of 300 dpi.
TIFF (or JPEG): Bitmapped (pure black and white pixels) line drawings, keep to a minimum of 1000 dpi.
TIFF (or JPEG): Combinations bitmapped line/half-tone (color or grayscale), keep to a minimum of 500 dpi.
Please do not:
• Supply files that are optimized for screen use (e.g., GIF, BMP, PICT, WPG); these typically have a low number of pixels and limited set of colors;
• Supply files that are too low in resolution;
• Submit graphics that are disproportionately large for the content.

Color artwork

Please make sure that artwork files are in an acceptable format (TIFF (or JPEG), EPS (or PDF), or MS Office files) and with the correct resolution. For further information on the preparation of electronic artwork, please see https://www.elsevier.com/artworkinstructions.

Figure captions

Ensure that each illustration has a caption. A caption should comprise a brief title and a description of the illustration. Keep text in the illustrations themselves to a minimum but explain all symbols and abbreviations used. Figure captions must be included in the manuscript file; the text of the caption should be editable.


Number tables consecutively in accordance with their appearance in the text. Each table should be included on a separate page and designed for economy of space and readability. Notes designated in the tables and all abbreviations should be defined in a footnote. Abbreviations should be identified in alphabetical order. Footnotes should be used in the following order: †, ‡, §, ¶, #. Avoid vertical rules. Be sparing in the use of tables and ensure that the data presented in tables do not duplicate results described elsewhere in the article.


Citations in text

Please ensure that every reference cited in text is also present in the reference list (and vice versa). Unpublished results and personal communications are not recommended in the reference list but may be mentioned in the text in parentheses. Citation of a reference as 'in press' implies that the item has been accepted for publication.

Reference links

Increased discoverability of research and high high-quality peer review are ensured by online links to the sources cited. In order to allow us to create links to abstracting and indexing services, such as Scopus, CrossRef and PubMed, please ensure that data provided in the references are correct. Please note that incorrect surnames, journal/book titles, publication year and pagination may prevent link creation. When copying references, please be careful as they may already contain errors. Use of the DOI is highly encouraged.

A DOI is guaranteed never to change, so you can use it as a permanent link to any electronic article. An example of a citation using DOI for an article not yet in an issue is: VanDecar J.C., Russo R.M., James D.E., Ambeh W.B., Franke M. (2003). Aseismic continuation of the Lesser Antilles slab beneath northeastern Venezuela. Journal of Geophysical Research, https://doi.org/10.1029/2001JB000884. Please note the format of such citations should be in the same style as all other references in the paper

Web references

As a minimum, the full URL should be given and the date when the reference was last accessed. Any further information, if known (DOI, author names, dates, reference to a source publication, etc.), should also be given. Web references can be listed separately (e.g., after the reference list) under a different heading if desired, or can be included in the reference list.

Data references

This journal encourages you to cite underlying or relevant datasets in your manuscript by citing them in your text and including a data reference in your Reference List. Data references should include the following elements: author name(s), dataset title, data repository, version (where available), year, and global persistent identifier. Add [dataset] immediately before the reference so we can properly identify it as a data reference. The [dataset] identifier will not appear in your published article.

Preprint references

Where a preprint has subsequently become available as a peer-reviewed publication, the formal publication should be used as the reference. If there are preprints that are central to your work or that cover crucial developments in the topic, but are not yet formally published, these may be referenced. Preprints should be clearly marked as such, for example by including the word preprint, or the name of the preprint server, as part of the reference. The preprint DOI should also be provided.

References in a special issue

Please ensure that the words 'this issue' are added to any references in the list (and any citations in the text) to other articles in the same Special Issue.

Reference management software

Most Elsevier journals have their reference template available in many of the most popular reference management software products. These include all products that support Citation Style Language styles, such as Mendeley. Using citation plug-ins from these products, authors only need to select the appropriate journal template when preparing their article, after which citations and bibliographies will be automatically formatted in the journal's style. If no template is yet available for this journal, please follow the format of the sample references and citations as shown in this Guide. If you use reference management software, please ensure that you remove all field codes before submitting the electronic manuscript. More information on how to remove field codes from different reference management software.

Reference style

Text: Indicate references by (consecutive) superscript Arabic numerals in the order in which they appear in the text. The numerals are to be used outside periods and commas, inside colons and semicolons.
List: Number the references in the list in the order in which they appear in the text. Please list the first 6 authors in each reference. If there are more than 6 authors, list the first 3 followed by et al. The references should be double spaced and use the same font size as the remainder of the manuscript.

Reference to a journal publication:
1. Kim YG, Shim J, Oh S, Lee K, Choi J, Kim Y. Electrical isolation of the left atrial appendage increases the risk of ischemic stroke and transient ischemic attack regardless of postisolation flow velocity. Heart Rhythm 2018;15:1746-1753.
2. Calkins H, Kuck KH, Cappato R, et al. 2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: Recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design. Heart Rhythm 2012;9:632-696.

Reference to a book:
3. Strunk W Jr, White EB. The Elements of Style. 4th ed. New York, NY: Longman; 2000.

Reference to a chapter in an edited book:
4. Mettam GR, Adams LB. How to prepare an electronic version of your article. In: Jones BS, Smith RZ, eds. Introduction to the Electronic Age. New York, NY: E-Publishing Inc; 2009:281-304.

Abbreviations for periodicals cited in the references should follow the style of Index Medicus and can also be accessed at http://www.nlm.nih.gov.

Data visualization

Include interactive data visualizations in your publication and let your readers interact and engage more closely with your research. Follow the instructions here to find out about available data visualization options and how to include them with your article.

Supplementary material

Elsevier accepts electronic supplementary material to support and enhance your scientific research. Supplementary files offer the author additional possibilities to publish supporting applications, high-resolution images, background datasets, sound clips and more. Supplementary files supplied will be published online alongside the electronic version of your article in Elsevier Web products, including ScienceDirect: http://www.sciencedirect.com. In order to ensure that your submitted material is directly usable, please provide the data in one of our recommended file formats. Authors should submit the material in electronic format together with the article and supply a concise and descriptive caption for each file. Supplemental material should be referred to in the main text in sequential order. For more detailed instructions please visit our artwork instruction pages at https://www.elsevier.com/artworkinstructions.

Supplementary material is scientific evidence and assumed to be original. If published previously the source must be cited with permission exactly as required for previously published material and should not include logos, symbolic landmarks, or any other identification of the origin.

Research data

This journal encourages and enables you to share data that supports your research publication where appropriate, and enables you to interlink the data with your published articles. Research data refers to the results of observations or experimentation that validate research findings. To facilitate reproducibility and data reuse, this journal also encourages you to share your software, code, models, algorithms, protocols, methods and other useful materials related to the project.

Below are a number of ways in which you can associate data with your article or make a statement about the availability of your data when submitting your manuscript. If you are sharing data in one of these ways, you are encouraged to cite the data in your manuscript and reference list. Please refer to the "References" section for more information about data citation. For more information on depositing, sharing and using research data and other relevant research materials, visit the research data page.

Data linking

If you have made your research data available in a data repository, you can link your article directly to the dataset. Elsevier collaborates with a number of repositories to link articles on ScienceDirect with relevant repositories, giving readers access to underlying data that gives them a better understanding of the research described.

There are different ways to link your datasets to your article. When available, you can directly link your dataset to your article by providing the relevant information in the submission system. For more information, visit the database linking page.

For supported data repositories a repository banner will automatically appear next to your published article on ScienceDirect.

In addition, you can link to relevant data or entities through identifiers within the text of your manuscript, using the following format: Database: xxxx (e.g., TAIR: AT1G01020; CCDC: 734053; PDB: 1XFN).

Data statement

To foster transparency, we encourage you to state the availability of your data in your submission. This may be a requirement of your funding body or institution. If your data is unavailable to access or unsuitable to post, you will have the opportunity to indicate why during the submission process, for example by stating that the research data is confidential. The statement will appear with your published article on ScienceDirect. For more information, visit the Data Statement page.

Submission checklist

The following list will be useful during the final checking of an article prior to sending it to the journal for review. Please consult this Guide for Authors for further details of any item.

Ensure that the following items are present:
  • HRO2 conflict form has been uploaded
  • One author has been designated as the corresponding author on the title page with contact details (E-mail address and full postal address). Telephone/fax numbers are not included.
  • All necessary files have been uploaded, and:
  • The title page includes all author names/affiliations
  • Conflicts of all authors are listed on the title page
  • Information on IRB, patient consent, and ethical guidelines is included in the Methods (where applicable)
  • Total word count is noted on the title page
  • Keywords (5-10)are included
  • Each figure has a legend; figures and legends should be included after the reference section

  • Further considerations:
  • Manuscript has been 'spell-checked' and 'grammar-checked'
  • Manuscript includes continuous line numbering
  • Manuscript is double-spaced, single columned, and pages are numbered
  • References are in the correct format for this journal and are cited numerically, not alphabetically.
  • All references mentioned in the Reference list are cited in the text, and vice versa
  • Permission has been obtained for use of copyrighted material from other sources (including the Web)

For any further information please visit our customer support site at https://service.elsevier.com.


To ensure a fast publication process of the article, we kindly ask authors to provide us with their proof corrections within two days. Corresponding authors will receive an e-mail with a link to our online proofing system, allowing annotation and correction of proofs online. The environment is similar to MS Word: in addition to editing text, you can also comment on figures/tables and answer questions from the Copy Editor. Web-based proofing provides a faster and less error-prone process by allowing you to directly type your corrections, eliminating the potential introduction of errors. If preferred, you can still choose to annotate and upload your edits on the PDF version. All instructions for proofing will be given in the e-mail we send to authors, including alternative methods to the online version and PDF.
We will do everything possible to get your article published quickly and accurately. Please use this proof only for checking the typesetting, editing, completeness and correctness of the text, tables and figures. Significant changes to the article as accepted for publication will only be considered at this stage with permission from the Editor. It is important to ensure that all corrections are sent back to us in one communication. Please check carefully before replying, as inclusion of any subsequent corrections cannot be guaranteed. Proofreading is solely your responsibility.

Journal does not give free offprints.

Visit the Elsevier Support Center to find the answers you need. Here you will find everything from Frequently Asked Questions to ways to get in touch.
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