Functional assessment in angina and non-obstructive coronary arteries: from microvascular resistance reserve to subtypes of coronary microvascular dysfunction.

Aims: Coronary microvascular dysfunction (CMD) is a heterogeneous condition defined by reduced coronary flow reserve (CFR). The new index 'microvascular resistance reserve' (MRR) has been developed, but its role is unclear. We investigate the relationships between functional indices in ANOCA (angina and non-obstructive coronary arteries) patients and evaluate the hemodynamic features of different CMD subtypes.

Fractional flow reserve (FFR) and index of microcirculatory resistance (IMR) relationship in patients with chronic or stabilized acute coronary syndromes.

Aims: To investigate the influence of index of microcirculatory resistance (IMR) on fractional flow reserve (FFR) and adenosine-induced hyperemia (ΔPd/Pa-FFR) in patients with chronic (CCS) or stabilized acute coronary syndromes (ACS), utilizing various IMR threshold values.

Methods: Data were extracted from two ongoing Italian registries involving patients with CCS or stabilized ACS who underwent a #FullPhysiology approach [Pd/Pa, FFR, IMR, coronary flow reserve (CFR)] by bolus thermodilution technique in the left anterior descending artery. Correlations between IMR and both FFR and ΔPd/Pa-FFR were analyzed both globally and within three IMR-defined groups: Group 1 (IMR <25), Group 2 (25 ≤ IMR <40), and Group 3 (IMR ≥40).