A Comparison of Acoustic Radiation Force-Derived Indices of Cardiac Function in the Langendorff Perfused Rabbit Heart

Abstract

In the past decade, there has been an increased interest in characterizing cardiac tissue mechanics utilizing newly developed ultrasound-based elastography techniques. These methods excite the tissue mechanically and track the response. Two frequently used methods, acoustic radiation force impulse and shear wave elasticity imaging (ARFI and SWEI), have been considered qualitative and quantitative techniques providing relative and absolute measures of tissue stiffness respectively. Depending on imaging conditions, it is desirable to identify indices of cardiac function that could be measured by ARFI and SWEI and to characterize the relationship between the measures. In this study, we have compared two indices (i.e. relaxation time constant used for diastolic dysfunction assessment and systolic/diastolic stiffness ratio) measured nearly simultaneously by M-mode ARFI and SWEI techniques. We additionally correlated ARFI-measured inverse displacements with SWEI measured values of the shear modulus of stiffness. For the eight animals studied, the average relaxation time constant ( ) measured by ARFI and SWEI were (69±18 ms, R2=0.96) and (65±19 ms, R2=0.99), (ARFI-SWEI inter-rater agreement = 0.90). Average systolic/diastolic stiffness ratio for ARFI, and SWEI measurements were 6.01±1.37 and 7.12±3.24 respectively (agreement=0.70). Shear modulus of stiffness (SWEI) was linearly related to inverse displacement values (ARFI) with a 95% CI for the slope of 0.010–0.011 (1/μm)/(kPa) (R2=0.73). In conclusion, the relaxation time constant and the systolic/diastolic stiffness ratio were calculated with good agreement between the ARFI and SWEI derived measurements. ARFI relative and SWEI absolute stiffness measurements were linearly related with varying slopes based on imaging conditions and subject tissue properties.

Measuring Intraventricular Pressure Using Ultrasound Elastography

“…If we can identify the ARFI measurements at the time of the opening of the aortic valve, for example, based on the electrocardiogram signal or the derivative of the SWEI curve, and using systolic and diastolic peripheral blood pressure measurements, ARFI measurements could also be used to estimate IVP. These results are consistent with the result of our previous publication regarding the linear relationship between ARFI and SWEI measurements . Because of technical limitations, ARFI might be the first cardiac stiffness measurement technique to become practical transthoracically …”

“…These results are consistent with the result of our previous publication regarding the linear relationship between ARFI and SWEI measurements. 19 Because of technical limitations, ARFI might be the first cardiac stiffness measurement technique to become practical transthoracically. 20 There has been an effort in the field to correlate the IVP and the intramyocardial pressure.…”

Non-invasive Measurement of Dynamic Myocardial Stiffness Using Acoustic Radiation Force Impulse Imaging

“…Short-term changes in ARFI-and SWEI-derived myocardial stiffness in response to inotropic agents and variations in coronary perfusion pressure have also been demonstrated using rodent hearts in Langendorff set-ups (Pernot et al, 2011;Vejdani-Jahromi et al, 2015). ARFI-and SWEI-derived indices of dynamic myocardial stiffness have also shown to be well correlated to each other (Vejdani-Jahromi et al, 2016).…”

Recent technological advancements in cardiac ultrasound imaging

“…Acoustic radiation force is one of the non-thermally mediated bioeffects of ultrasound, which is generated by a change in the density of energy and momentum of the propagating waves due to the absorption, reflection and scattering from inclusions or from spatial variations in propagation velocity [109]. ARFI imaging is considered a qualitative elastography technique, as it can provide relative measures of tissue stiffness, while SWEI is considered a quantitative elastography technique that can provide absolute measures of tissue stiffness [109, 110]. The third imaging technique, SSI, is also quantitative, as it can map the stiffness of soft tissue characterized by the Young modulus defined by the slope of the stress/strain curve [108].…”