Continuous shear wave measurements for dynamic cardiac stiffness evaluation in pigs

Area of Science:

• Cardiovascular imaging
• Biomedical engineering
• Myocardial mechanics

Background:

• Ultrasound shear wave elastography (SWE) non-invasively assesses dynamic myocardial stiffness by tracking shear wave propagation.
• Interpreting SWE measurements is complex due to influences from cardiac loading and contractility.
• Understanding these dependencies is crucial for accurate clinical application of SWE.

Purpose of the Study:

• To investigate the relationship between shear wave speed and pressure-volume loop-derived indices of loading, myocardial stiffness, and contractility.
• To assess the impact of altered loading and ischemia/reperfusion injury on these relationships.
• To evaluate the potential of SWE-derived parameters as non-invasive biomarkers for cardiac function.

Main Methods:

• Transthoracic shear wave elastography was performed in 13 pigs.
• Cardiac loading was manipulated, and myocardial ischemia/reperfusion injury was induced.
• Shear wave propagation speed (diastolic and systolic) was correlated with pressure-volume loop-derived indices.

Main Results:

• Diastolic shear wave speed showed a strong correlation with operational myocardial stiffness (R=0.75, p<0.001), indicating influence from both loading and intrinsic tissue properties.
• The ratio of systolic to diastolic shear wave speed correlated significantly with contractility (preload-recruitable stroke work, R=0.67, p<0.001).
• These findings suggest SWE parameters can reflect changes in myocardial mechanics under various physiological and pathological conditions.

Conclusions:

• Diastolic shear wave speed is influenced by cardiac loading and intrinsic myocardial stiffness.
• The shear wave speed ratio may serve as a non-invasive index of cardiac contractility, particularly during conditions like ischemia/reperfusion injury.
• SWE holds promise for non-invasive assessment of myocardial mechanical properties and function.