Circulation Formatting Requirements: Complete Author Guide

Circulation requires a structured abstract for Original Research and Review articles. The structure follows the standard clinical research format.

• Word limit: 250 words maximum
• Structure: Background, Methods, Results, Conclusions
• Clinical trial registration: If the paper reports a clinical trial, the registration number and registry name must appear at the end of the abstract
• Citations: Not permitted in the abstract
• Abbreviations: Define abbreviations at first use within the abstract, even if they're defined again in the main text

The Results section of your abstract should include actual numbers, not just qualitative statements. Write "The intervention reduced LDL-C by 38% (95% CI: 32-44%, P<0.001)" instead of "The intervention significantly reduced LDL-C." Circulation reviewers are quantitative, and vague abstracts signal weak data.

For Research Letters, no abstract is required. For Brief Communications, the abstract is shorter at 150 words but still needs to follow the structured format.

A formatting quirk specific to Circulation: the Background section should be only 1-2 sentences. Don't waste abstract space on general epidemiology. "Coronary artery disease remains the leading cause of death worldwide" is filler that every reviewer has read thousands of times.

Circulation enforces a combined limit of 7 figures and tables for Original Research. Planning your display items early matters because running out of slots mid-revision is a common problem.

Figure specifications:

Central Illustration: Circulation strongly encourages (and for some article types requires) a Central Illustration. This is a single graphical summary that captures the main finding or concept. It appears prominently in the published article and is used for social media promotion. The Central Illustration counts as one of your 7 display items, so plan accordingly.

Data Supplement: Additional figures, tables, videos, and datasets can be uploaded as an online-only Data Supplement. There's no strict limit on the number of supplementary items, but they should be clearly referenced in the main text with the prefix "Supplemental" (e.g., Supplemental Figure 1, Supplemental Table 1).

Tables in Circulation must be submitted as editable text, not as images. Each table needs a title (placed above the table) and footnotes for abbreviations and statistical details. Use horizontal rules only at the top, below the header row, and at the bottom. Vertical rules are not permitted.

Circulation uses the AHA reference style, which is a numbered sequential system based on the Vancouver format with AHA-specific modifications.

In-text citations: Superscript numbers (e.g., "as previously demonstrated^1,2"). Multiple references are separated by commas with no spaces. Ranges use a hyphen (e.g., "^3-7"). Numbers are assigned in order of first appearance.

Reference list format:

1. Smith JA, Johnson BC, Williams DE. Title of the article in sentence case. Circulation. 2025;151:e123-e135. doi:10.1161/CIRCULATIONAHA.124.000000

Key formatting details:

• Author names: Last name followed by initials, no periods between initials (e.g., "Smith JA")
• List all authors for papers with 6 or fewer; for 7+ authors, list the first 3 followed by "et al."
• Journal titles are abbreviated per NLM/MEDLINE standards
• Volume and page numbers separated by a colon
• DOIs are required for all references that have them
• Year follows the journal abbreviation with a period and semicolon

Circulation's reference cap for Original Research is approximately 40. This is enforced editorially. Reviews get around 75, which is relatively generous. Don't pad your reference list with tangential citations just to show breadth. Reviewers notice, and it signals insecurity about the work.

One AHA-specific detail: references to AHA scientific statements and guidelines should use the full committee name as author (e.g., "American Heart Association Council on Clinical Cardiology") rather than individual author names, unless only individual authors are listed.

Circulation's supplementary material is called the "Data Supplement" and lives online only.

What goes in the Data Supplement:

• Additional figures and tables that support but don't drive the main narrative
• Detailed methods descriptions that exceed main text space
• Videos, audio files, and large datasets
• STROBE, CONSORT, or PRISMA checklists (often required)

Formatting rules:

• Supplementary items must be cited in the main text in numerical order
• Label as "Supplemental Figure 1" (not "Supplementary" or "S1")
• Provide titles and legends for all supplementary display items
• Videos should be MP4 format, under 50 MB per file
• All supplementary material undergoes peer review

A practical tip: Circulation reviewers regularly request that authors move main-text figures into the supplement (or vice versa). Build your manuscript with this flexibility in mind. If Figure 3 is a supporting experiment rather than a core result, it's safer in the supplement from the start.

The Data Supplement is also where you should include the full, unedited statistical output for clinical trials. AHA journals have been increasingly strict about data transparency since 2020, and having raw statistical tables in the supplement strengthens your position during review.

Circulation requires a cover page (also called a title page) as the first page of the manuscript file. This isn't optional, and missing elements will trigger a desk return.

Required cover page elements:

• Full title (no more than 120 characters for Original Research)
• Short title / running head (maximum 40 characters)
• All author names with degrees and institutional affiliations
• Corresponding author name, mailing address, phone, fax, and email
• Total word count of the body text
• Total word count of the abstract
• Number of figures and tables
• Journal subject terms (select from AHA's standardized list)
• Conflict of interest disclosures for all authors
• Sources of funding with grant numbers

Conflict-of-interest disclosure: Every author must provide a disclosure statement. "None" is acceptable, but the statement must be present. AHA uses its own disclosure format, which categorizes relationships by type (consultant, speaker, equity, etc.) and whether they're relevant to the manuscript content.

This is a genuine formatting trap: AHA's disclosure format is different from ICMJE's standard disclosure form. Even if you've completed an ICMJE form, you still need to fill out the AHA-specific version through the journal's submission portal.

Circulation has several formatting and submission details that aren't obvious from a quick read of the author guidelines.

1. Clinical trial registration is mandatory. Any study that prospectively assigns participants to an intervention must be registered in a public registry (ClinicalTrials.gov, ISRCTN, etc.) before the first patient is enrolled. The registration number must appear in the abstract and on the title page. Papers without registration will be rejected outright.

2. ORCID requirement. The corresponding author must have a verified ORCID iD linked to their ScholarOne account. This became mandatory in 2023. Co-authors are encouraged but not required to provide ORCIDs.

3. The "What Is New?" and "What Are the Clinical Implications?" boxes. Original Research articles must include two text boxes at the end of the manuscript. "What Is New?" (3-5 bullet points) describes the novel findings. "What Are the Clinical Implications?" (3-5 bullet points) describes the practical significance. These boxes appear in the published article and are heavily used by readers. Write them carefully; they're not an afterthought.

4. Data sharing statement. Circulation requires a data availability statement describing whether and how the study data can be accessed by other researchers. This goes on the title page.

5. Dual submission monitoring. AHA journals actively cross-check for simultaneous submission to multiple AHA titles. Submitting the same manuscript to Circulation and Circulation Research at the same time will result in rejection from both.

6. Statistical review. All Original Research articles undergo a separate statistical review in addition to scientific peer review. Your methods section should include enough statistical detail to survive this dedicated scrutiny. Name the software, version, and specific tests used. If you ran a mixed-effects model, specify the random and fixed effects, the correlation structure, and how you handled missing data.

Formatting a Circulation manuscript correctly takes attention to detail across dozens of requirements, from the AHA-specific disclosure format to the Central Illustration specifications and the "What Is New?" boxes. A single oversight can add weeks to your timeline.

Manusights' AI-powered manuscript review checks your formatting against journal-specific requirements before you submit, catching problems like incorrect reference style, missing structural elements, and word count overruns. It's faster than manually cross-referencing the author guidelines, and it catches the non-obvious issues that trip up even experienced authors.

If you're preparing a submission for Circulation or any of the other AHA journals, running your manuscript through an automated check is the simplest way to avoid a desk return. You can also explore our journal submission guides for related journals in cardiology and clinical medicine.