Background:
Myocardial infarction (MI) leads to gradually decreased cardiac contractility that can ultimately cause heart failure or sudden death. One potential therapy to recover this MI-impaired contractile function is the regenerative approach that integrates both tissue engineering and exogenously produced cardiomyocytes. Although this contractile recovery has been assessed by different imaging methods in previous studies, these assessments in global cardiac performance are plagued by their relatively low sensitivity. As this treatment is locally performed, the sensitivity of its therapeutic assessment can be improved by myocardial strain imaging that assesses regional contractility.
Methods:
We first made tissue engineered heart muscles (EHMs) by casting human embryonic stem cell-derived cardiomyocytes (ESC-CMs) with collagen in preformed molds. Then we transplanted these EHMs (n=12) into the post-MI rat hearts one month after this injure. We also performed sham surgeries on a control group (n=9) without EHM transplantation. Meanwhile, strain imaging from cardiac magnetic resonance imaging (MRI) and ultrasound were performed prior to and four weeks after EHM transplantations. In addition, global cardiac performance such as left ventricular ejection fraction (EF) was estimated from cardiac MRI.
Results:
Based on the measurements, regional myocardial strain measured from tagged MRI detected the preserved systolic function in the EHM-treated group compared to control group (P=0.04). In contrary, the global function EF was unable to detect this significant difference between both groups (P=0.38). Similarly, myocardial strain measured from cardiac ultrasound also failed to detect the significance between both treatment and control groups (P=0.24).
Conclusions:
This study for the first time confirmed that regional assessment of contractile function offered higher sensitivity compared to the conventional measure of global systolic performance. This finding highlights the feasibility and sensitivity of cardiac strain derived from tagged MRI as a sensitive method to assess the efficacy of regenerative therapies in both preclinical and clinical studies.
Multi-oriented windowed harmonic phase reconstruction for robust cardiac strain imaging
