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Published on: June 28, 2019
Prognostic value of microvascular resistance and its association to fractional flow reserve: a DEFINE-FLOW substudy
Ashkan Eftekhari1,2, Jelmer Westra3, Valérie Stegehuis4
1Department of Cardiology, Aarhus University Hospital Skejby, Aarhus, Denmark asef@rn.dk.
Insights
Hyperemic microvascular resistance (HMR) did not predict adverse events in stable coronary artery disease patients. Fractional flow reserve (FFR) can be represented by the ratio of HMR to total resistance, linking epicardial and microvascular measures.
Area of Science:
- Cardiovascular Medicine
- Interventional Cardiology
- Physiology
Background:
- Coronary artery disease (CAD) management relies on assessing stenosis severity.
- Fractional flow reserve (FFR) is a key metric, but microvascular function also impacts outcomes.
- Understanding the interplay between epicardial stenosis and microvascular resistance is crucial for prognosis.
Purpose of the Study:
- To investigate the prognostic value of hyperemic microvascular resistance (HMR).
- To explore the relationship between HMR, hyperemic stenosis resistance (HSR), and FFR.
- To determine if HMR predicts adverse clinical events in stable CAD.
Main Methods:
- Substudy of the DEFINE-FLOW cohort (NCT02328820) including 430 patients.
- Wire-based measurement of coronary pressure, flow, and resistance.
- Combined assessment of FFR, coronary flow reserve (CFR), HMR, and HSR.
Main Results:
- Mean FFR was 0.82±0.10 and mean CFR was 2.2±0.6.
- HMR was highest in lesions with FFR>0.80 and CFR<2.0 (2.92±1.2 mm Hg/cm/s).
- FFR correlated strongly with the HMR/(HMR+HSR) ratio (r²=0.98, p<0.0001).
- Increased HMR did not correlate with higher rates of target vessel failure (HR 1.51, p=0.10).
Conclusions:
- In stable CAD patients, elevated HMR was not associated with increased adverse clinical events.
- FFR can be conceptually reformulated as HMR/(HMR+HSR), integrating epicardial and microvascular resistance.
- This provides an alternative framework for understanding coronary lesion physiology.
Objective:
This study aimed to evaluate the prognostic value of hyperemic microvascular resistance (HMR) and its relationship with hyperemic stenosis resistance (HSR) index and fractional flow reserve (FFR) in stable coronary artery disease.
Methods:
This is a substudy of the DEFINE-FLOW cohort (NCT02328820), which evaluated the prognosis of lesions (n=456) after combined FFR and coronary flow reserve (CFR) assessment in a prospective, non-blinded, non-randomised, multicentre study in 12 centres in Europe and Japan. Participants (n=430) were evaluated by wire-based measurement of coronary pressure, flow and vascular resistance (ComboWire XT, Phillips Volcano, San Diego, California, USA).
Results:
Mean FFR and CFR were 0.82±0.10 and 2.2±0.6, respectively. When divided according to FFR and CFR thresholds (above and below 0.80 and 2.0, respectively), HMR was highest in lesions with FFR>0.80 and CFR<2.0 (n=99) compared with lesions with FFR≤0.80 and CFR≥2.0 (n=68) (2.92±1.2 vs 1.91±0.64 mm Hg/cm/s, p<0.001). The FFR value was proportional to the ratio between HMR and the HMR+HSR (total resistance), 95% limits of agreement (-0.032; 0.019), bias (-0.003±0.02) and correlation (r2=0.98, p<0.0001). Cox regression model using HMR as continuous parameter for target vessel failure showed an HR of 1.51, 95% CI (0.9 to 2.4), p=0.10.
Conclusions:
Increased HMR was not associated with a higher rate of adverse clinical events, in this population of mainly stable patients. FFR can be equally well expressed as HMR/HMR+HSR, thereby providing an alternative conceptual formulation linking epicardial severity with microvascular resistance.
Trial Registration Number:
NCT02328820.
