Magnetic resonance elastography as a method to estimate myocardial contractility.

Area of Science:

• Cardiovascular Imaging
• Biophysics
• Medical Engineering

Background:

• Assessing myocardial contractility is crucial for diagnosing cardiac conditions.
• Magnetic Resonance Elastography (MRE) is an emerging noninvasive imaging technique.
• Epinephrine is a known inotrope that increases myocardial contractility.

Purpose of the Study:

• To investigate the relationship between increasing epinephrine infusion and end-systolic effective stiffness derived from MRE.
• To evaluate MRE as a potential noninvasive method for assessing myocardial contractility in vivo.

Main Methods:

• Finite element modeling (FEM) determined optimal myocardial wall thickness for MRE analysis (≥1.5 cm).
• MRE was performed on five pigs, measuring end-systolic effective stiffness during stepwise intravenous epinephrine infusion.
• Student's t-test and least-squares linear regression analyzed stiffness changes and correlation with heart rate increases.

Main Results:

• FEM confirmed feasibility for wall thickness ≥1.5 cm.
• End-systolic effective stiffness significantly increased from baseline with initial epinephrine infusion (P=0.047).
• Strong linear correlations (R² 0.86-0.99) were observed between stiffness and heart rate increase in four pigs; pooled data showed R²=0.58.

Conclusions:

• Noninvasive MRE-derived end-systolic effective myocardial stiffness shows a significant increase with epinephrine infusion.
• MRE-derived myocardial stiffness may serve as a reliable noninvasive surrogate marker for myocardial contractility.