Table 3. Clinical Evidences on IMR.
| Study (Year) | Study Population | Results |
|---|---|---|
| Studies about distribution of IMR | ||
| Melikian et al. (72) | 101 patients vs. 15 controls | IMR values of controls were lower than 25 U |
| Luo et al. (74) | 18 with CXS vs. 18 controls | IMR values of CXS were higher than controls (33.1 ± 7.9 vs. 18.8 ± 5.6, p < 0.001) |
| Echavarría-Pinto et al. (73) | 79 patients with FFR, CFR, and IMR | 75th percentile value of IMR was 29 U |
| Studies about clinical implication of IMR | ||
| Fearon et al. (76) | 29 patients with STEMI | Patients with IMR > 32 U had worse echocardiographic wall motion score than those with IMR ≤ 32. IMR was only significant predictor of recovery of left ventricular function |
| Cuisset et al. (75) | 50 patients with stable angina who underwent elective PCI | Patients with conventional stenting had significantly higher value of post-PCI IMR than direct stenting (24 ± 14 U vs. 13 ± 3 U, p < 0.01) |
| McGeoch et al. (77) | 57 patients with STEMI who underwent CMR | Patients with microvascular obstruction had higher IMR values than those without microvascular obstruction (38 U vs. 27 U, p = 0.003) |
| Fujii et al. (78) | 80 patients with stable angina with or without pravastatin therapy after PCI | Pravastatin therapy lowered IMR significantly after PCI (12.6 U vs. 17.6 U, p = 0.007) |
| Layland et al. (79) | 50 patients with elective PCI | IMR before PCI was higher in patients with PPMI (21.2 ± 2.1 vs. 15.6 ± 1.8, p = 0.02) and strongest predictor of PPMI (beta 0.7, p = 0.02) |
| Ng et al. (80) | 50 patients with elective PCI | IMR value of > 27 was independent predictor of PPMI (odds ratio, 22.7; 95% CI, 3.8–133.9) |
| Fearon et al. (81) | 254 patients with STEMI | Rate of death or re-hospitalization was higher in patients with IMR of > 40 U than those with IMR of ≤ 40 (17.1% vs. 6.6%, p = 0.027) |
CFR = coronary flow reserve, CMR = cardiac magnetic resonance imaging, CXS = cardiac X syndrome, FFR = fractional flow reserve, IMR = index of microcirculatory resistance, MACE = major adverse cardiovascular event, PCI = percutaneous coronary intervention, PPMI = peri-procedural myocardial infarction, STEMI = ST-elevation myocardial infarction