Comparative Evaluation of Resting and Hyperemic Angiography-Derived Index of Microcirculatory Resistance in Chronic Coronary Syndrome.

Background: Angiography-derived index of microcirculatory resistance (IMR) has emerged as a feasible alternative to wire-based IMR, due to the elimination of specialized wire and simplifying of the procedure. However, the differences in diagnostic accuracy between hyperemic and resting angiography with this technology remain underexplored.

Methods: This prospective, multicenter study was conducted to evaluate the feasibility and diagnostic accuracy of x-ray angiography-derived IMR (xaIMR) in patients with chronic coronary syndrome using wire-based functional indices as the reference. Angiography-derived functional indices were calculated using a computational fluid dynamics model. The xaIMR indices were derived from hyperemic and resting angiography, respectively.

Results: A total of 139 vessels were included in the analysis of the present study. Both hyperemic xaIMR (r=0.82; P<0.001) and resting xaIMR (R-xaIMR) (r=0.25; P=0.003) exhibited positive linear correlations with wire-based IMR. Notably, hyperemic xaIMR was associated with a higher diagnostic yield (area under the receiver operating characteristic curve) than resting xaIMR (area under the receiver operating characteristics curve, 0.95 versus 0.72; P<0.001). Significant differences in diagnostic yield between these modalities were observed in vessels with compromised coronary flow reserve (<2.0). In contrast, such differences were not observed in vessels with normal coronary flow reserve (≥2.0).

Conclusions: xaIMR, especially derived from hyperemic angiography, is a reliable, noninvasive alternative to wire-based IMR for assessing coronary microcirculatory resistance in chronic coronary syndrome. However, resting angiography-derived xaIMR may have limited diagnostic accuracy in patients with reduced coronary flow reserve. Further studies are warranted to validate these findings in broader populations.