The impact of microvascular resistance on the discordance between anatomical and functional evaluations of intermediate coronary disease

AIMS: In intermediate coronary artery disease, discordance between anatomical and functional assessments persists and the diagnostic accuracy of an anatomical evaluation is not satisfactory for determining functional significance. We aimed to evaluate the impact of microvascular resistance on "anatomical-functional discordance". METHODS AND RESULTS: In 97 intermediate coronary lesions of 83 patients, minimum lumen area (MLA), fractional flow reserve (FFR), Δ(Pd/Pa-FFR), and hyperaemic microvascular resistance index (hMVRI) were measured using intravascular ultrasound and an intracoronary dual pressure and Doppler sensor-tipped guidewire. hMVRI correlated with FFR and Δ(Pd/Pa-FFR) (r=0.611, p<0.001; r=-0.509, p<0.001; respectively). After the lesions were categorised into four groups based on functional significance (FFR 0.8) and the MLA cut-off for that (2.5 mm2), hMVRI was higher with a lower Δ(Pd/Pa-FFR) regardless of the MLA group in lesions with FFR >0.8, compared with those in lesions with FFR ≤0.8. hMVRI was independently associated with FFR and Δ(Pd/Pa-FFR) (β=0.443, p<0.001; β=-0.389, p<0.001; respectively). CONCLUSIONS: Coronary microvascular resistance is associated with anatomical-functional discordance and the ischaemic potential of intermediate epicardial stenosis. In determining a treatment strategy, anatomy alone is insufficient and an integrated physiologic approach is important.