Abstract Body (Do not enter title and authors here): Background: Mechanical complications following Myocardial Infarction (MI), such as ventricular rupture, significantly impact patient morbidity and mortality. Reperfused MI characterized by intramyocardial hemorrhage (hMI), has been identified to be the most severe form of myocardial injury. However, whether hMI portends a higher risk for mechanical complications is not known. The Wall Strain Index (WSI) Ratio, which is a measure of myocardial deformation and one that has been previously validated for cardiac rupture, is a desirable biomarker for examining the potential mechanical differences in strain development in hMI vs. non-hMI.
Research Question: Do patients with hMIs have a higher radial and circumferential Wall Strain Index (WSI) Ratio compared to patients without hMI?
Methods: We performed a retrospective cohort study (MIRON-STRAIN, NCT06450912) in mechanically revascularized STEMI patients (n=181) who underwent CMR (cine, T2* and LGE) approximately 2 days after PCI. WSI Ratio was computed using the 2D-strain module in CVI⁴² (circumferential & longitudinal). Parametric statistics was performed using Shapiro-Wilk test and non-parametric statistics was performed using Mann-Whitney U test.
Results: Patients with hMI (n=104) showed significantly higher radial and circumferential WSI Ratios compared to non-hMI patients. The radial WSI Ratio was approximately 58% higher in hMI relative to non-hMI patients (1.36±0.72 in hMI vs. 0.86±0.55 in non-hMI (p<0.001)). The circumferential WSI Ratio was 103% higher in hMI patients compared to those with non-hMI (1.22±0.87 in hMI vs. 0.60±0.44 in non-hMI (p<0.001)). Median and IQR values for radial and circumferential WSI ratios showed significant differences, indicating the development of higher myocardial stress in hMI. Additional findings in hMI included higher LV EDV (122.08±33.22 ml vs. 100.78±31.92 ml, p<0.001), and Infarct Size (%LV, 38.69±14.27% vs. 16.20±12.11%, p<0.001).
Conclusion: The Wall Strain Index Ratio is significantly elevated in hMI patients, indicating hMI patients carry a significant risk for mechanical complications. Our findings suggest that WSI Ratio can serve as a valuable biomarker for enabling timely and targeted monitoring and critical care.