Related Experiment Video
Updated: May 19, 2026
Interventional Diagnostic Procedure: A Practical Guide for the Assessment of Coronary Vascular Function
Published on: March 15, 2022
The index of microvascular resistance identifies patients with periprocedural myocardial infarction in elective
Jamie J Layland1, Robert J Whitbourn, Andrew T Burns
1Department of Cardiology, St Vincent's Hospital, Fitzroy, Victoria, Australia. jamie.layland@svhm.org.au
Background:
This study was designed to assess whether measurement of the index of microvascular resistance (IMR) could help prospectively identify patients who develop periprocedural myocardial infarction (PPMI).
Methods And Results:
IMR was measured in 54 patients before and following percutaneous coronary intervention (PCI) in a culprit vessel with a PressureWire using the equation IMR = Pa(Hyp) × Tmn(Hyp) (Pd(Hyp)-Pw/Pa(Hyp)-Pw). IMR was also measured in an angiographically normal reference vessel. The relative pre-IMR ratio (rPIMR) defined as IMR Culprit divided by IMR Non-Culprit was also calculated. Troponin was sequentially sampled up to 24 h following PCI. Mean troponin post-PCI was 0.37±0.8 ng/ml. 33 (61%) patients fulfilled the criteria for PPMI. IMR pre-PCI was the most significant correlate of post-PCI troponin (r=0.43 p=0.001), however, the number of balloon inflations (r=0.3, p=0.02) and rPIMR (r=0.33 p=0.017) were also correlated. IMR pre-PCI was higher in patients with periprocedural myocardial infarction compared with patients without PPMI (IMR pre-PCI 21.2±2.1 PPMI vs 15.6±1.8 No PPMI, p=0.02). The strongest predictor of troponin post-PCI was IMR pre-PCI (β 0.7, p=0.02). Both IMR pre- and rPIMR were predictive of PPMI (OR 11 (1.3 to 90.5) p=0.026, OR 1.09 (1 to 1.19) p=0.03, respectively).
Conclusion:
Microvascular function prior to PCI is an important determinant of PPMI. Measuring IMR pre-PCI and rPIMR may allow prospective identification of patients at risk of periprocedural myocardial infarction. Future studies in a larger cohort are required to establish the predictive ability of IMR in PPMI.
Insights
Measuring microvascular resistance (IMR) before percutaneous coronary intervention (PCI) can help identify patients at risk of developing periprocedural myocardial infarction (PPMI). This index, along with the relative pre-IMR ratio (rPIMR), shows predictive ability for PPMI.
Area of Science:
- Cardiology
- Interventional Cardiology
- Vascular Physiology
Background:
- Periprocedural myocardial infarction (PPMI) is a complication of percutaneous coronary intervention (PCI).
- Identifying patients at risk for PPMI is crucial for improving outcomes.
- The role of microvascular function in predicting PPMI requires further investigation.
Purpose of the Study:
- To assess if the index of microvascular resistance (IMR) can prospectively identify patients who develop PPMI.
- To evaluate the correlation between pre-PCI IMR and post-PCI troponin levels.
- To determine the predictive value of IMR and related indices for PPMI.
Main Methods:
- IMR was measured in 54 patients before and after PCI using a PressureWire.
- IMR was assessed in both the culprit vessel and a non-culprit reference vessel.
- The relative pre-IMR ratio (rPIMR) was calculated, and troponin levels were monitored post-PCI.
Main Results:
- IMR before PCI was the most significant correlate of post-PCI troponin.
- Patients who developed PPMI had a higher IMR before PCI compared to those who did not.
- Both pre-PCI IMR and rPIMR were found to be predictive of PPMI.
Conclusions:
- Microvascular function assessed by IMR prior to PCI is a key determinant of PPMI.
- Measuring pre-PCI IMR and rPIMR may enable prospective identification of patients at risk for PPMI.
- Larger cohort studies are needed to confirm the predictive ability of IMR in PPMI.
