The performance of angiography-derived index of microcirculatory resistance for ischemia in angina with non-obstructive coronary artery disease: Validated by wire-based IMR and SPECT-MPI.

BACKGROUND

Coronary microvascular dysfunction (CMD) accounts for a significant part of angina with non-obstructive coronary artery (ANOCA). Angiography-derived index of microcirculatory resistance (angio-IMR) has been developed for the evaluation of CMD but not yet validated sufficiently in ANOCA.

AIMS: To validate angio-IMR against wire-based IMR and to investigate its diagnostic performance for ischemia in ANOCA patients.

METHODS

This study included two independent cohorts. The angio-IMR and wire-based IMR were measured in 74 patients (74 vessels) in the wire-based IMR validation cohort. The angio-IMR and single-photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) were successfully completed in 136 patients (408 vessels) in the SPECT-MPI validation cohort. The ischemia was defined as the myocardial perfusion defect on SPECT-MPI and a summed difference score (SDS) ≥ 2.

RESULTS

In the wire-based IMR validation cohort, the angio-IMR ≥ 25 had the high diagnostic efficiency (area under the receiver-operating characteristics curve (AUC): 0.917, 95 %CI: 0.843-0.922; p < 0.001) and classification agreement (CA) (91.9 %) with the referenced wire-based IMR ≥ 25. In the SPECT-MPI validation cohort, more ischemia was observed in the high angio-IMR group (angio-IMR ≥ 25) compared to the low angio-IMR group (angio-IMR < 25) (55.2 % vs 10.4 %, p < 0.001). The angio-IMR ≥ 25 had a moderate diagnostic performance for ischemia (AUC: 0.759, 95 %CI: 0.670-0.849; p < 0.001), and it could improve the ability to discriminate ischemia in ANOAC patients (integrated discrimination improvement (IDI): 0.184; p < 0.001; net reclassification improvement (NRI): 0.217; p < 0.001).

CONCLUSION

The study demonstrates that angio-IMR, validated through both wire-based IMR and SPECT-MPI, presents a promising and convenient diagnostic approach for identifying ischemia in patients with ANOCA.