Related Experiment Video
Updated: Jul 13, 2025
Real-Time Assessment of Spinal Cord Microperfusion in a Porcine Model of Ischemia/Reperfusion
Published on: December 10, 2020
The Index of Microcirculatory Resistance After Primary PCI: A Pooled Analysis of Individual Patient Data
Mohamed El Farissi1, Frederik M Zimmermann1, Giovanni Luigi De Maria2
1Department of Cardiology, Catharina Hospital, Eindhoven, the Netherlands.
Insights
Index of microcirculatory resistance (IMR) after primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI) independently predicts cardiac death. Elevated IMR identifies high-risk patients needing further monitoring and therapies.
Area of Science:
- Cardiology
- Interventional Cardiology
- Cardiovascular Research
Background:
- ST-segment elevation myocardial infarction (STEMI) patients treated with primary percutaneous coronary intervention (PCI) face persistent risks of heart failure and mortality.
- Microvascular dysfunction, indicated by the index of microcirculatory resistance (IMR), is linked to poorer outcomes post-PCI for STEMI.
- The predictive value of IMR for cardiac death following primary PCI remains uncertain.
Purpose of the Study:
- To ascertain if IMR serves as an independent predictor of cardiac death.
- To determine the optimal IMR cutoff value for predicting outcomes in STEMI patients.
- To compare the predictive capabilities of IMR against cardiac magnetic resonance imaging (CMR) parameters like infarct size.
Main Methods:
- A pooled analysis of individual patient data from six cohorts measuring IMR post-primary PCI in STEMI.
- Kaplan-Meier analyses were employed to estimate cardiac mortality up to five years.
- The primary endpoint was cardiac death, assessed against a predefined IMR cutoff of 40.
Main Results:
- In 1,265 patients, cardiac death occurred in 4.9% of those with IMR >40 versus 2.2% with IMR ≤40 (HR: 2.81).
- IMR was an independent predictor of cardiac death, with an optimal cutoff of 70 (HR: 4.73).
- Higher IMR correlated with increased infarct size, microvascular obstruction, and intramyocardial hemorrhage.
Conclusions:
- Post-primary PCI IMR in STEMI is an independent predictor of long-term cardiac death.
- IMR can identify high-risk patients amenable to intensified cardioprotective strategies and monitoring.
- IMR offers valuable prognostic information beyond traditional risk factors.
Background:
Despite treatment with primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI), the risk of heart failure and late death remains high. Microvascular dysfunction, as assessed by the index of microcirculatory resistance (IMR), after primary PCI for STEMI has been associated with worse outcomes. It is unclear whether IMR after primary PCI predicts cardiac death.
Objectives:
The aims of this analysis were: 1) to determine if IMR is an independent predictor of cardiac death; 2) to assess the optimal cutoff value of IMR after STEMI; and 3) to compare IMR with several cardiac magnetic resonance parameters, including infarct size.
Methods:
In a collaborative, pooled analysis of individual patient data from 6 cohorts that measured IMR directly after primary PCI, cardiac mortality up to 5 years was estimated using Kaplan-Meier analyses. The primary endpoint was cardiac death using the predefined IMR cutoff value of 40.
Results:
In total, 1,265 patients were included in this study with a median follow-up of 2.8 years (IQR: 1.2-5.0 years). Cardiac death at 5 years occurred in 2.2% and 4.9% of patients (HR: 2.81; 95% CI: 1.34-5.88; P = 0.006) in the IMR ≤40 and IMR >40 groups, respectively. The composite of cardiac death or hospitalization for heart failure occurred in 4.9% and 8.9% (HR: 1.98; 95% CI: 1.20-3.29; P = 0.008) in the IMR ≤40 and IMR >40 groups, respectively. IMR was an independent predictor of cardiac death, whereas coronary flow reserve was not. The optimal cutoff value of IMR for the prediction of cardiac death in this cohort was 70 (HR: 4.73; 95% CI: 2.27-9.83; P < 0.001). Infarct size was 17.6% ± 13.3% and 23.9% ± 14.6% of the left ventricular mass in the IMR ≤40 and IMR >40 groups, respectively (P < 0.001). Microvascular obstruction and intramyocardial hemorrhage occurred more frequently in the IMR >40 group than in the IMR ≤40 group.
Conclusions:
In this large, pooled analysis of individual patient data, IMR measured directly after primary PCI in STEMI was an independent predictor of cardiac death. IMR may be used as a tool to identify patients at the time of primary PCI who are at highest risk for late cardiac mortality and who might benefit most from additional cardioprotective therapies and monitoring.
