TABLE 2.
Non-randomized controlled trials of microvascular resistance indices in acute MI associated with clinical outcomes.
| First author/Study | Sample size | Index | Follow-up time | Association with clinical outcomes |
| Scarsini et al. (4) | 198 STEMI |
IMR after PPCI |
Median 40.1 months | At 1 year and at long term follow-up, group with IMR > 40 and MVO had a significantly higher risk of adverse clinical outcomes than group with IMR ≤ 40 and no MVO (HR 12.6; p = 0.017 and HR 5.2; p = 0.004). At 1 year follow-up, group with IMR > 40 or MVO showed no significant differences compared to group with IMR ≤ 40 and no MVO, however, at long term follow-up, adverse clinical outcomes were higher in the first group (HR 4.2; p = 0.009) and similar to those with IMR > 40 and MVO |
| Fukunaga et al. (13) | 88 STEMI |
IMR after PPCI |
6 months | Optimal cut-off of IMR for cardiac death, non-fatal MI and HHF was 37U (AUC 0.68, sensitivity 75%, specificity 61%). IMR > 37 was associated with a higher incidence of MACE versus IMR ≤ 37 (p = 0.007). IMR was not an independent predictor of MACE (HR 0.99; p = 0.59) |
| Maznyczka et al. (17) | 144 STEMI |
IMR after PPCI |
1 year | IMR, IMR > 40U and IMR > 44U were associated with HHF (OR 1.02, p < 0.001; OR 5.34, p = 0.002; OR 6.92; p = 0.001, respectively) IMR (OR 1.02, p = 0.001), IMR > 40U (OR 4.08, p = 0.005) and IMR > 44U (OR 5.33, p = 0.001) were also associated with death and HHF |
| Fearon et al. (18) | 253 STEMI |
IMR after PPCI |
Median 2.8 years | IMR > 40U was a predictor of death (HR 4.30; p = 0.02) and death or HHF (HR 2.20; p = 0.03) |
| Carrick et al. (19) | 283 STEMI |
IMR after PPCI |
Median 845 days | IMR > 40U associated with all-cause death or HHF (OR 4.36; p < 0.001) |
| De Waard et al. (20) | 176 acute MI |
IMR after PPCI |
Median 3.2 years | HMR > 3.0 mmHgcm–1s was associated with death (HR 6.4, 95%CI: 1.3–32.0) and HHF (HR 7.0; 95%CI: 1.5–33.7) |
| Jin et al. (21) | 145 STEMI |
IMR after PPCI |
Mean 85 ± 43 months | HMR optimal cut-off of 2.82 mmHgcm–1s (AUC 0.82; p = 0.006) predicted cardiac death and HHF HMR > 2.82 mmHgcm–1s was associated with MACE (HR 1.74; p < 0.001) |
| Maznyczka et al. (45) | 271 STEMI |
IMR after PPCI |
5 years | IMR was a predictor of death or HHF and MACE at 30 days (AUCIMR 0.74; p < 0.001 and AUCIMR 0.74, p = 0.002, respectively) and 5 years after MI (AUCIMR 0.64, p = 0.002 and AUCIMR 0.66, p < 0.001, respectively) |
| Fahrni et al./Insights from OxAMI cohort (46) | 260 STEMI |
IMR after PPCI |
30 days | IMR was a predictor of MACE (AUC 0.90; 95% CI 0.85–0.93); IMR ≤ 40U identified all patients free of major cardiac events (100% sensitivity, 62% specificity) |
AUC, area under the curve; CI, confidence interval; HHF, hospitalization for heart failure; HMR, hyperemic microvascular resistance; IMR, index of microvascular resistance; MACE, major adverse cardiac events; MI, myocardial infarction; PPCI, primary percutaneous coronary intervention; STEMI, ST segment elevation myocardial infarction.