Circle Cardiovascular Imaging vs Heartflow (2026)
The deepest evidence base in the category against the only on premise architecture in it. Heartflow computes physiology: FFRCT estimates lesion significance, supported by the ACC AHA Chest Pain Guideline, the recognition no competitor holds, on more than 600 publications and 400,000 plus patients, delivered as a cloud service that transmits every scan out for processing. Circle keeps imaging inside the institution: cvi42 Plaque runs fully on premise, the clearest data residency position in the lane and effectively the only option for buyers under sovereignty constraints, on a scanner agnostic reading platform a clinician drives directly. The two barely compete on the same axis, Heartflow wins decisively on evidence and guideline status, Circle wins decisively on architecture and data control, and neither closes the other's gap. Circle also grades C on evidence, since no validation study specific to cvi42 Plaque was located, against Heartflow's A. If your failure mode is guideline backed physiology with the deepest evidence behind it, start with Heartflow. If your failure mode is imaging that cannot leave the enterprise, start with Circle.
- The strongest data residency position in the lane: cvi42 Plaque runs fully on premise, so imaging never leaves the institution, graded A on PHI stewardship and deployment, where Heartflow transmits every scan to vendor side processing.
- Scanner agnostic by heritage: cvi42 is a multi vendor cardiovascular reading platform compatible with all major systems, graded A on interoperability, spanning cardiac MRI and CT rather than a single disease pathway.
- Direct clinician control on premise: a Johns Hopkins user describes immediate and interactive control over the analysis, the counterpoint to a send out service with vendor side quality control of undisclosed extent.
- The recognition no one else holds: FFRCT is supported by the ACC AHA Chest Pain Guideline, a materially higher bar than a 510(k), graded A on regulatory status against Circle's single module B.
- Evidence depth without rival: more than 600 peer reviewed publications and clinical use across 400,000 plus patients, an A on clinical evidence, where no validation study specific to cvi42 Plaque was located and Circle grades C.
- Physiology plus the full pathway: FFRCT for lesion significance alongside plaque, stenosis detection, and intervention planning under one platform in cleared markets, a broader clinical span than plaque quantification alone.
This comparison is published by AI Health Index, an independent research platform that compares healthcare AI vendors objectively. Circle Cardiovascular Imaging and Heartflow are each graded against the same capability taxonomy, from each vendor's own public materials and the regulatory record, under the AI Health Index verification standard. No vendor pays for placement, and no vendor has reviewed this page. How this evidence is graded
Plain facts
| Fact | Circle Cardiovascular Imaging | Heartflow |
|---|---|---|
| Primary category | Radiology & Imaging AI | Radiology & Imaging AI |
| Founded | Not recorded | 2007 |
| Headquarters | Calgary, Alberta, Canada | Mountain View, California, United States |
| Website | circlecvi.com | heartflow.com |
Side by Side
Each record in one paragraph
Written to be quoted whole. Each paragraph states what the AI Health Index verified about the vendor, with the caveats attached. Generated from this pair’s live capability grades, so it moves when a grade moves.
The AI Health Index awards Circle Cardiovascular Imaging its top capability grade on several axes, including Model Supply Chain Disclosure, AI Safety and PHI Stewardship and FDA and Regulatory Status. Set against Heartflow, Circle Cardiovascular Imaging grades higher on several axes, including Model Supply Chain Disclosure, AI Safety and PHI Stewardship and AI Governance and Bias Disclosure. Its thinnest published disclosure sits on AI Liability and Recourse. Grades reflect evidence the AI Health Index could verify at the last review, so a low grade records disclosure the vendor has not published rather than a capability it has been shown to lack.
Source: AI Health Index, July 2026
The AI Health Index awards Heartflow its top capability grade on several axes, including AI Centrality, Clinical and Operational Evidence and Security Certifications and Trust Center. Set against Circle Cardiovascular Imaging, Heartflow grades higher on several axes, including AI Centrality, Model and Technology Transparency and Clinical and Operational Evidence. Grades reflect evidence the AI Health Index could verify at the last review, so a low grade records disclosure the vendor has not published rather than a capability it has been shown to lack.
Source: AI Health Index, July 2026
Questions buyers ask
Should we choose Circle Cardiovascular Imaging or Heartflow?
On the axes where the AI Health Index separates them, Circle Cardiovascular Imaging grades higher on several axes, including Model Supply Chain Disclosure, AI Safety and PHI Stewardship and AI Governance and Bias Disclosure, and Heartflow grades higher on several axes, including AI Centrality, Model and Technology Transparency and Clinical and Operational Evidence. Neither leads on the greater share of scored axes, so the decision turns on which constraint is binding rather than on an overall winner.
Where do Circle Cardiovascular Imaging and Heartflow differ most?
The widest separation the AI Health Index records between Circle Cardiovascular Imaging and Heartflow is on Clinical and Operational Evidence, where Circle Cardiovascular Imaging grades C and Heartflow grades A. That axis sits in the AI Capability group, so it should carry the most weight for a buyer whose binding constraint is how much of the work the model itself is trusted to do.
Where do Circle Cardiovascular Imaging and Heartflow grade the same?
The AI Health Index grades Circle Cardiovascular Imaging and Heartflow the same on several axes, including Autonomy and Oversight Model, HIPAA and BAA Posture and FDA and Regulatory Status. Neither holds an advantage the index can evidence on those axes, so they should not carry weight in a selection between these two.
What have Circle Cardiovascular Imaging and Heartflow not disclosed?
At the last review, at least one of Circle Cardiovascular Imaging and Heartflow published thin or absent detail on AI Liability and Recourse. The AI Health Index treats an absent disclosure as a gap in the public record rather than a failure of the product, so these are the axes to get in writing during diligence instead of inferring from the grade.
Related comparisons
Other published head to head assessments involving these vendors or their closest peers. The full set for this category is on the Clinical Decision Support page.
The two strongest strengths in this pairing sit on opposite vendors and rarely trade off directly. Heartflow holds A on regulatory status for ACC AHA guideline recognition of FFRCT and A on clinical evidence for the largest base in the index, but its Plaque and RoadMap functions are cleared in only five countries, and it transmits imaging out for processing whose human step is undisclosed.
Circle holds A on PHI stewardship, deployment, and interoperability for fully on premise, scanner agnostic analysis, but grades B on AI centrality as a platform with a plaque module and C on clinical evidence, since no validation study specific to cvi42 Plaque was located. Heartflow's own dossier candidly describes FFRCT reimbursement as inadequate, a disclosure this index credits. Neither publishes a licence price; Circle's on premise model resolves data residency structurally where Heartflow's terms are undisclosed.