Conventionally, assessment of microvascular resistance requires a pressure wire and induction of maximal hyperemia with adenosine. This significantly increases the complexity of the procedure and procedural time. Angio-based Microvascular Resistance is a way to assess microvascular resistance from angiograms without the use of a pressure wire. The International Multicenter FAVOR Pilot Study [1] assessed a simple and fast fractional flow reserve (FFR) computation from radiographic coronary angiography. It was called quantitative flow ratio (QFR). The study compared the standard hyperemic FFR estimation with computed QFR estimation. They noted that QFR computation improved the diagnostic accuracy of three dimensional quantitative coronary angiography based identification of significance of stenosis.
While the initial study had 73 patients, another study with 200 patients validated the formula for calculation of microvascular resistance without the use of pressure wire and induction of hyperemia [2]. Another recent study compared Angio-based Microvascular Resistance from a single single angiographic projection to the index of microvascular resistance (IMR) and found good correlation [3]. Specialized software calculated QFR from a single angiographic image in this study. Flow velocity at maximal hyperemia was calculated by computer simulation. Angiographic microvascular resistance was the product of mean aortic pressure and the ratio of QFR to flow velocity.
References
- Tu S, Westra J, Yang J, von Birgelen C, Ferrara A, Pellicano M, Nef H, Tebaldi M, Murasato Y, Lansky A, Barbato E, van der Heijden LC, Reiber JHC, Holm NR, Wijns W; FAVOR Pilot Trial Study Group. Diagnostic Accuracy of Fast Computational Approaches to Derive Fractional Flow Reserve From Diagnostic Coronary Angiography: The International Multicenter FAVOR Pilot Study. JACC Cardiovasc Interv. 2016 Oct 10;9(19):2024-2035. doi: 10.1016/j.jcin.2016.07.013. PMID: 27712739.
- Tebaldi M, Biscaglia S, Di Girolamo D, Erriquez A, Penzo C, Tumscitz C, Campo G. Angio-Based Index of Microcirculatory Resistance for the Assessment of the Coronary Resistance: A Proof of Concept Study. J Interv Cardiol. 2020 Oct 25;2020:8887369. doi: 10.1155/2020/8887369. PMID: 33162844; PMCID: PMC7605930.
- Zhang Z, Dai Q, Zhang X, Qiao S, Bao X, Wang K, Xue P, Gao Y, Guo X, Xue Y, Wei Z, Xu B, Kang L. Microcirculatory resistance based on a single angiographic view in ST-segment elevation myocardial infarction patients. BMC Cardiovasc Disord. 2025 May 9;25(1):357. doi: 10.1186/s12872-025-04796-4. PMID: 40340800; PMCID: PMC12063289.