The Role of Index of Microcirculatory Resistance in Left Anterior Descending Artery ST Segment Elevation Myocardial Infarction Patients after Primary Percutaneous Coronary Intervention
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Published on: June 28, 2019
Seong Huan Choi1, Sung Gyun Ahn2, Myeong Ho Yoon3
1Division of Cardiology, Department of Medicine, Inha University Hospital, Incheon 22332, Republic of Korea.
Insights
An elevated index of microvascular resistance (IMR) in patients with ST-elevation myocardial infarction (STEMI) indicates larger infarct size, worse left ventricular function, and increased mortality after percutaneous coronary intervention.
Area of Science:
- Cardiology
- Interventional Cardiology
- Cardiovascular Research
Background:
- Microvascular dysfunction is a critical factor in ST-elevation myocardial infarction (STEMI) outcomes.
- The index of microvascular resistance (IMR) is a key metric for assessing microvascular function.
- Understanding the prognostic implications of IMR in Left Anterior Descending (LAD) artery STEMI is crucial.
Purpose of the Study:
- To evaluate the relationship between the index of microvascular resistance (IMR) and clinical outcomes in patients with LAD artery STEMI.
- To determine if elevated IMR is associated with infarct size, left ventricular function, and mortality.
- To identify IMR as a potential prognostic marker in STEMI patients post-primary percutaneous coronary intervention (PCI).
Main Methods:
- Retrospective analysis of 316 STEMI patients undergoing primary PCI from 2005-2015.
- Enrollment of 246 patients with LAD STEMI for IMR evaluation.
- Stratification into two groups based on an IMR cut-off value of 30, comparing all-cause mortality, left ventricular function, and cardiac biomarkers.
Main Results:
- Patients with IMR > 30 exhibited significantly higher peak Creatinine Kinase (CK) and CK-MB levels.
- Lower left ventricular ejection fraction (LVEF) and impaired LVEF improvement were observed in the IMR > 30 group.
- All-cause mortality was significantly higher in the IMR > 30 group (7.5% vs. 1.3%), with IMR > 30 identified as an independent poor prognostic factor (HR: 5.151).
Conclusions:
- An elevated IMR (>30) in LAD STEMI patients post-PCI is linked to larger infarct size.
- Higher IMR values correlate with more severe left ventricular dysfunction.
- Elevated IMR is a significant predictor of increased all-cause mortality in this patient population.
Abstract:
Background: Our aim was to assess the relationship of the index of microvascular resistance (IMR) in left anterior descending (LAD) artery involved STEMI patients. Methods: Data of 316 STEMI patients who had undergone primary percutaneous coronary intervention (PCI) were collected from three cardiovascular centers from 2005 to 2015. In total, 246 patients with LAD STEMI were enrolled for IMR evaluation. Patients were divided into two groups respective of the cut-off IMR value of 30. All-cause mortality, left ventricular function, improvement of systolic function, and cardiac biomarkers were analyzed and compared. Results: A total of 246 patients were enrolled. The number of patients in the IMR above 30 group was 93 and below 30 was 153. The mean ages for each group were 57.91 ± 11.99 and 54 ± 10.63, respectively. The peak creatinine kinase (CK) (3936.85 ± 2827.32 IU/L vs. 2218.08 ± 2310.41 IU/L, p < 0.001) and CKmb (336.15 ± 195.08 mg/mL vs. 231.53 ± 179.53 mg/mL, p < 0.001) levels were higher for an IMR above the 30 group. The left ventricular ejection fraction (LVEF) (44.57 ± 6.685% vs. 47.35 ± 8.17%, p = 0.006) and improvement of LVEF (2.81 ± 7.135% vs. 5.88 ± 7.65%, p = 0.004) was lower in the IMR above 30 group. All-cause mortality (7.5% vs. 1.3%, p = 0.012) was higher in the IMR above 30 group, and a Cox regression analysis showed that an IMR above 30 was a poor prognostic factor regarding all-cause mortality (HR: 5.151, 95% CI 1.062-24.987, p = 0.042) even after adjusting for classical clinical risk factors. Conclusions: An elevated IMR value represented larger infarct size, more severe LV dysfunction, and higher mortality in LAD STEMI patients after successful PCI.
