Higher Index of Microcirculatory Resistance (IMR) significantly predicted worse functional recovery at 6 months, correlating inversely with the change in Regional Wall Motion Score Index (r = -0.61).
Observational (n=34)
Blinded observers
No
Does the index of microcirculatory resistance (IMR) predict microvascular obstruction and left ventricular functional recovery in patients with anterior myocardial infarction undergoing primary PCI?
Intracoronary measurement of the index of microcirculatory resistance (IMR) immediately after primary PCI for anterior AMI is a reliable predictor of microvascular obstruction and short-term left ventricular functional recovery.
Effect estimate: r = -0.61
p-value: p=< 0.01
IMR is useful for assessing the microvascular dysfunction after primary percutaneous coronary intervention (PCI). It remains unknown whether index of microcirculatory resistance (IMR) reflects the functional outcome in patients with anterior myocardial infarction (AMI) with or without microvascular obstruction (MO).This study was performed to evaluate the clinical value of the IMR for assessing myocardial injury and predicting microvascular functional recovery in patients with AMI undergoing primary PCI. We enrolled 34 patients with first anterior AMI. After successful primary PCI, the mean distal coronary artery pressure (P(a)), coronary wedge pressure (P(cw)), mean aortic pressure (P(a)), mean transit time (T(mn)), and IMR (P(d)* hyperemic T(mn)) were measured. The presence and extent of MO were measured using cardiac magnetic resonance image (MRI). All patients underwent follow-up echocardiography after 6 months. We divided the patients into two groups according to the existence of MO (present; n = 16, absent; n = 18) on MRI. The extent of MO correlated with IMR (r = 0.754; P < 0.001), P(cw) (r = 0.404; P = 0.031), and P(cw)/P(d) of infarct-related arteries (r = 0.502; P = 0.016). The IMR was significantly correlated with the ΔRegional wall motion score index (r = -0.61, P < 0.01) and ΔLeft ventricular ejection fraction (r = -0.52, P < 0.01), implying a higher IMR is associated with worse functional improvement. Therefore, Intracoronary wedge pressures and IMR, as parameters for specific and quantitative assessment of coronary microvascular dysfunction, are reliable on-site predictors of short-term myocardial viability and Left ventricle functional recovery in patients undergoing primary PCI for AMI.
Yoo et al. (Sun,) conducted a observational in Anterior Myocardial Infarction (n=34). Index of Microcirculatory Resistance (IMR) vs. Microvascular Obstruction (MO) vs No MO was evaluated on Correlation between IMR and Δ Regional wall motion score index (ΔRWMSI) (r = -0.61, p=< 0.01). Higher Index of Microcirculatory Resistance (IMR) significantly predicted worse functional recovery at 6 months, correlating inversely with the change in Regional Wall Motion Score Index (r = -0.61).