J Korean Med Sci.  2012 Sep;27(9):1044-1050. 10.3346/jkms.2012.27.9.1044.

Index of Microcirculatory Resistance as Predictor for Microvascular Functional Recovery in Patients with Anterior Myocardial Infarction

• Yoo SH
• Yoo TK
• Lim HS
• Kim MY
• Koh JH

• KMID: 1782137
• DOI: http://doi.org/10.3346/jkms.2012.27.9.1044

Abstract

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 (Pa), coronary wedge pressure (Pcw), mean aortic pressure (Pa), mean transit time (Tmn), and IMR (Pd * hyperemic Tmn) 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), Pcw (r = 0.404; P = 0.031), and Pcw/Pd of infarct-related arteries (r = 0.502; P = 0.016). The IMR was significantly correlated with the DeltaRegional wall motion score index (r = -0.61, P < 0.01) and DeltaLeft 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.

Keyword

Acute Anterior Wall Myocardial Infarction; Coronary Occlusion; Capillary Resistance; Magnetic Resonance Imaging

MeSH Terms

Adult
Aged
Aged, 80 and over
Anterior Wall Myocardial Infarction/*physiopathology
Arterial Pressure/physiology
Coronary Occlusion/pathology
Echocardiography
Female
Humans
Magnetic Resonance Imaging
Male
Microcirculation/*physiology
Middle Aged
Percutaneous Coronary Intervention
*Predictive Value of Tests
Prospective Studies
Recovery of Function
Risk Factors

Figure

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  Fig. 1 Correlation between intracoronary pressure parameters, index of microcirculatory resistance (IMR) and extent of microvascualr obstruction (MO). There was significant correlation between IMR, intracoronary pressure parameters and extent of MO. Open circles represent patients with MO as measured by cardiac MRI. CFR, coronary flow reserve; Pa, mean aortic pressure; Pcw, coronary wedge pressure.

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  Fig. 2 Correlation between ΔRWMSI and IMR (A) and Pcw/Pa (B). There was significant inverse correlation between ΔRWMSI and IMR. Thus, higher IMR is associated with the lower ΔRWMSI, implying the worse functional outcomes. Significant correlation was also found between ΔRWMSI and Pcw/Pa. Triangles indicate patients with MO, and circles represent patients with no MO. Δ (delta), the difference of the values at Follow up day minus at baseline day; RWMSI, regional wall motion score index; IMR, index of microcirculatory resistance; Pcw/Pa, coronary wedge pressure to mean aortic pressure ratio.

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