Angiography-Derived Index of Microvascular Resistance and its Prognostic Value in Patients with NSTEMI

Acute myocardial infarction (AMI) continues to be associated with high morbidity and mortality, despite significant advancements in its treatment over the years. Patients with non-ST-segment-elevation myocardial infarction (NSTEMI) are quite varied as regards their characteristics, clinical manifestations, and outcomes, which highlights the importance of identifying those at high risk. Several studies have shown that the prognosis of these patients is significantly affected by coronary microvascular damage.

The index of microvascular resistance (IMR) is a reliable and reproducible technique for the quantitative assessment of microvascular function. However, its application remains limited due to the complexity and cost of its measurement. 

Angiography-derived IMR (angio IMR), an innovative wire-free technology, has been developed to facilitate the rapid calculation of IMR in patients undergoing coronary angiography, allowing for the quantification of microcirculation in these patients. Several studies have demonstrated the prognostic value of angio IMR in predicting outcomes in patients with AMI with coronary arteries without obstructive lesions, as well as in those with chronic coronary syndromes. However, there is no data on this tool in patients with NSTEMI.

The aim of this multicenter retrospective study was to assess the prognostic impact of angio IMR in patients with NSTEMI after a percutaneous intervention. The primary endpoint (PEP) was the 2-year rate of major adverse cardiac events (MACE), defined as a composite of cardiac death, heart failure rehospitalization, reinfarction, and treated-vessel revascularization.

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The study included a total of 2212 patients, of which 206 had an angio IMR >25, while 2006 had an angio IMR ≤25. The mean age was approximately 63 years, and most subjects were men. The mean angio IMR after angioplasty was 20.63. Patients with an angio IMR >25 experienced a higher rate of MACE compared with those with an angio IMR ≤25 (32.52% vs. 9.37%; P < 0.001). After angioplasty, an angio IMR >25 was an independent predictor of MACE (hazard ratio [HR]: 4.230; 95% confidence interval [CI]: 3.151-5.679; P < 0.001) and showed incremental prognostic value compared with conventional risk factors (area under the curve [AUC]: 0.774 vs. 0.716; P < 0.001).

Conclusion

This study has shown that angio IMR is an independent predictor of MACE in patients undergoing angioplasty in a setting of NSTEMI. Incorporating angio IMR into conventional clinical risk factors significantly increased the ability to estimate MACE risk.

Original Title: Prognostic Value of Coronary Angiography–Derived Index of Microcirculatory Resistance in Non–ST-Segment Elevation Myocardial Infarction Patients.

Reference: Yuxuan Zhang, MD et al J Am Coll Cardiol Intv 2024.