ISMRM - SCMR Workshop

ISMRM - SCMR Workshop: Oral Session 4: Clinical Applications of Microstructure, Strain and Motion Encoding

Oral Abstract 1: Changes in Remote and Border Zone Strain and Twist after a Myocardial Infarction

Wednesday, January 29, 2025

1:45 PM – 1:55 PM East Coast USA Time

Location: Blue Room

Presenting Author(s)

TH

Tawfik Hussein, MSc

Ph.D. Candidate
Emory University & Georgia Institute of Technology

Primary Author(s)

TH

Tawfik Hussein, MSc

Ph.D. Candidate
Emory University & Georgia Institute of Technology

Co-Author(s)

JO

John Oshinski, PhD

Professor of Radiology and Biomedical Engineering
Emory University
MR

Manas Reddy, N/A

Undergraduate
Georgia Institute of Technology
MP

Muralidhar Padala, PhD

Associate Professor of Cardiothoracic Surgery
Emory University

Background: Global indices of ventricular function fail to capture the local adaptive remodeling that occurs in the heart post-myocardial infarction (MI). Local indices, such as strain and twist, could provide insights into early changes in myocardial function. The goal of this work was to quantify the local changes in circumferential and longitudinal Green strain (E_CC and E_RR, respectively) in both ventricles as well as twist in a porcine infarct model using tagged MRI [1]. The hypothesis is that MI will cause differential changes in strain and twist in the regions adjacent and remote to the myocardial infarct in proportion to the size of infarct.

Methods: A postero-lateral MI was induced in 5 healthy Yorkshire pigs by injecting ethanol into the left circumflex artery (LCX). ECG-gated cine tagged MRI was acquired in the basal short axis (SA) to measure LV strain (i.e., E_CC and E_RR), RV E_CC, and LV twist at baseline (pre-MI) and 3 months post-MI. The SA images were divided into 3 zones (infarcted, border, remote), based on late Gadolinium enhancement (LGE) images assessed on an AHA 17-segment model (Figure 1). LGE images were used to quantify the size of the infarct by area. Measured strain and twist were averaged for each zone, and their respective mean and standard deviation over time was calculated. Finally, the peak systolic strains and twist were calculated for both timepoints and averaged over all 5 animals. A paired t-test was used to assess if the difference between the mean baseline and post-MI strains per zone was significant. Pearson’s correlation test was conducted to determine if the infarct size is correlated to each local parameter in each zone.

Results: E_CC and E_RR changed pre- to post-MI in all three zones. Peak systolic E_CC and E_RR in the remote zone increased by – 3.96 ± 0.01% and 10.00 ± 0.01%, respectively, (from baseline to MI) with p-values = 0.038 & 0.018 while it did not change significantly in the border zone (Figure 2). Interestingly, RV E_CC increased in both the lateral wall septum, which may imply RV compensation. Finally, twist did not change from baseline to MI (p = 0.23). The size of the infarct was correlated with a reduction in E_CC and E_RR in the remote zone, with the greatest correlation with remote E_RR, indicating that a greater infarct size inhibits the over-compensation of the remote zone (Figure 3).

Conclusion: Radial and circumferential myocardial strains in areas remote to the infarct increase post-MI while twist does not change. Additionally, E_CC increases in both the septum and lateral wall of the RV. Hence, measurements of myocardial strain can provide more mechanistic insights into the LV remodeling process and may serve as predictive markers of adverse remodeling.