Microvascular resistance is not influenced by epicardial coronary artery stenosis severity: Experimental validation

William F. Fearon, Wilbert Aarnoudse, Nico H.J. Pijls, Bernard De Bruyne, Leora B. Balsam, David T. Cooke, Robert C. Robbins, Peter J. Fitzgerald, Alan C. Yeung, Paul G. Yock

Research output: Contribution to journalArticlepeer-review

135 Scopus citations


Background - The effect of epicardial artery stenosis on myocardial microvascular resistance remains controversial. Recruitable collateral flow, which may affect resistance, was not incorporated into previous measurements. Methods and Results - In an open-chest pig model, distal coronary pressure was measured with a pressure wire, and the apparent minimal microvascular resistance was calculated during peak hyperemia as pressure divided by flow, measured either with a flow probe around the coronary artery (Rmicro app) or with a novel thermodilution technique (apparent index of microcirculatory resistance [IMRapp]). These apparent resistances were compared with the actual Rmicro and IMR after the coronary wedge pressure and collateral flow were incorporated into the calculation. Measurements were made at baseline (no stenosis) and after creation of moderate and severe epicardial artery stenoses. In 6 pigs, 189 measurements of R micro and IMR were made under the various epicardial artery conditions. Without consideration of collateral flow, Rmicro app (0.43±0.12 to 0.46±0.10 to 0.51±0.11 mm Hg/mL per minute) and IMRapp (14±4 to 17±7 to 20±10 U) increased progressively and significantly with increasing epicardial artery stenosis (P<0.001 for both). With the incorporation of collateral flow, neither R micro nor IMR increased as a result of increasing epicardial artery stenosis. Conclusions - After collateral flow is taken into account, the minimum achievable microvascular resistance is not affected by increasing epicardial artery stenosis.

Original languageEnglish (US)
Pages (from-to)2269-2272
Number of pages4
Issue number19
StatePublished - May 18 2004
Externally publishedYes


  • Coronary disease
  • Microcirculation

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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