{
  "abstract": "Introduction: Discordance between resting and hyperemic epicardial physiology is commonbut mechanistically unclear. Microvascular resistance reserve (MRR), a novelindex of vasodilatory capacity, may provide insight. We aimed to characterizethe prevalence and microvascular substrate of FFR/RFR discordance, andwhether MRR is independently associated with discordant phenotypes.\n\nMethods: We retrospectively analyzed 891 vessels from 723 consecutive patients with paired resting full-cycle ratio (RFR) and fractional flow reserve (FFR) measurements (June 2018–October 2024). Vessels were categorized as concordant or discordant. An operator-selected subset of 210 underwent coronary flow reserve (CFR), index of microvascular resistance (IMR), and MRR assessment. Multivariable logistic regression identified predictors of each discordant phenotype (FFR−/RFR+ and FFR+/RFR−).\n\nResults: Discordance was present in 195 vessels (22%); 121 (13.6%) FFR−/RFR+ and 74 (8.3%) FFR+/RFR−. Discordance was more common in the LAD (25% vs. 17%, OR 1.68, 95% CI 1.20–2.36, p = 0.003), driven predominantly by the FFR−/RFR+ phenotype (OR 2.43, 95% CI 1.56–3.78, p < 0.001). In the microvascular subset ( n = 210), reduced CFR (OR 0.77, 95% CI 0.59–0.97, p = 0.039) and reduced MRR (OR 0.81, 95% CI 0.65–0.97, p = 0.037) were independently associated with the FFR−/RFR+ phenotype, while neither predicted the FFR+/RFR− phenotype. However, among 45 discordant vessels with microvascular data, MRR provided greater discrimination than CFR (AUC 0.712, 95% CI 0.539–0.884 vs. 0.608, 95% CI 0.434–0.783, p = 0.018).\n\nDiscussion: These exploratory, hypothesis-generating findings suggest that impaired microvascular vasodilatory reserve, expressed predominantly as elevated resting flow, may contribute mechanistically to the FFR−/RFR+ phenotype.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Cardiology, Royal Perth Hospital, Perth, WA, Australia.",
    "School of Medicine, University of Western Australia, Perth, WA, Australia."
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 17,
  "authors": [
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        0,
        1
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      "name": "Aswin Babu"
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        0
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      "name": "Isobelle Goldrick"
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    {
      "affs": [
        1
      ],
      "name": "Billy Broadbent",
      "orcid": "0009-0002-0737-8033"
    },
    {
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        1
      ],
      "name": "Rania Faeq"
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    {
      "affs": [
        1
      ],
      "name": "Charley Budgeon"
    },
    {
      "affs": [
        0
      ],
      "name": "Roopa Krishnamoorthy"
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    {
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        0
      ],
      "name": "Primero Ng"
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    {
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        0
      ],
      "name": "Cara Barnes"
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    {
      "affs": [
        0
      ],
      "name": "Dipen Sankhesara"
    },
    {
      "affs": [
        0
      ],
      "name": "Avadhesh Saraswat"
    },
    {
      "affs": [
        0
      ],
      "name": "Imran Shiekh"
    },
    {
      "affs": [
        0
      ],
      "name": "James Marangou"
    },
    {
      "affs": [
        0
      ],
      "name": "Richard Alcock"
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    {
      "affs": [
        0
      ],
      "name": "Rachel Orme"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Carl Schultz"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Graham S Hillis"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Jon Spiro"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/41aqswwemkcd1.bib",
  "cited_by": 0,
  "doi": "10.3389/fcvm.2026.1929694",
  "fulltext_url": "https://europepmc.org/articles/PMC13714799",
  "id": "41aqswwemkcd1",
  "issns": [
    "2297-055X"
  ],
  "landing_url": "https://www.frontiersin.org/articles/10.3389/fcvm.2026.1929694/full",
  "language": "eng",
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "heading",
      "Original Research"
    ],
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      "openalex",
      "2746|Coronary Interventions and Diagnostics"
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  "pdf_url": "https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2026.1929694/pdf",
  "pmcid": "PMC13714799",
  "pmid": "42953518",
  "published": "2026-10-14",
  "publisher": "Frontiers Media SA",
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      "field": "medicine",
      "origin": "openalex:2746|Coronary Interventions and Diagnostics",
      "subfield": "surgery"
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  "title": "Microvascular resistance reserve: insights into discordant resting and hyperemic epicardial coronary physiology",
  "title_text": "Microvascular resistance reserve: insights into discordant resting and hyperemic epicardial coronary physiology",
  "type": "peer-reviewed",
  "updated_at": "2026-11-01T12:22:13Z",
  "url": "https://research.draconitic.com/paper/41aqswwemkcd1",
  "venue": "Frontiers in Cardiovascular Medicine",
  "versions": []
}