Vessel-specific angiography-derived index of microcirculatory resistance in an all-comer population undergoing percutaneous coronary intervention, a PIONEER IV trial substudy

BACKGROUND: Recently, angiography-derived index of microvascular resistance (angio-IMR) has emerged as a less invasive alternative to estimate CMD during cardiac catheterization. Whether CMD differs across vessel territories and populations remains disputed. METHODS: Consecutive all-comer patients undergoing coronary angiography for chronic coronary syndrome (CCS) or non-ST-elevation myocardial infarction (NSTEMI) enrolled in the PIONEER-IV trial at the University Medical Center Groningen were included. Angio-IMR was retrospectively calculated using quantitative flow ratio (QFR) software in all three major coronary vessel territories pre- and post-PCI, if applicable. Angio-IMR levels were compared between coronary vessels, indication, and sex. The association between angio-IMR and LV function on AI-derived echocardiography analyses were assessed. RESULTS: In 220 patients, mean age was 65 ± 9 years, 18.3 % were women, and 20.3 % presented with NSTEMI. CMD was common: 80.0 % had baseline angio-IMR ≥25 mmHg·s/cm. Angio-IMR was similar in the LAD, RCA and LCX in both target and non-target vessels (p > 0.05). In the LAD, angio-IMR increased significantly post-PCI (p < 0.001), while RCA and LCX showed no significant change. Whilst NSTEMI patients showed similar baseline angio-IMR as CCS patients, they had lower post-PCI angio-IMR (p = 0.011). Women had lower average post-PCI angio-IMR (27 vs. 37 mmHg·s/cm, p < 0.001) and showed improved microvascular resistance post-PCI. Angio-IMR was not associated with cardiac function overall, but in NSTEMI patients, higher baseline angio-IMR correlated with worse LV function. CONCLUSION: Angio-IMR is similar in all coronary vessels, but lower in NSTEMI patients than in CCS and lower in women. In NSTEMI patients, higher IMR was associated with worse LV function.