Intracardiac Echocardiography Measurement of Dynamic Myocardial Stiffness with Shear Wave Velocimetry

Abstract

Acoustic Radiation Force (ARF)-based methods have been demonstrated to be a viable tool for noninvasively estimating tissue elastic properties, and shear wave velocimetry has been used to quantitatively measure the stiffening and relaxation of myocardial tissue in open-chest experiments. Dynamic stiffness metrics may prove to be indicators for certain cardiac diseases, but a clinically-viable means of remotely generating and tracking transverse wave propagation in myocardium is needed. Intracardiac echocardiography (ICE) catheter-tip transducers are demonstrated here as a viable tool for making this measurement. ICE probes achieve favorable proximity to the myocardium, enabling the use of shear wave velocimetry from within the right ventricle throughout the cardiac cycle. This work describes the techniques used to overcome the challenges of using a small probe to perform ARF-driven shear wave velocimetry, and presents in vivo porcine data showing the effectiveness of this method in the interventricular septum. Acoustic Radiation Force (ARF)-based methods have been demonstrated to be a viable tool for noninvasively estimating tissue elastic properties, and shear wave velocimetry has been used to quantitatively measure the stiffening and relaxation of myocardial tissue in open-chest experiments. Dynamic stiffness metrics may prove to be indicators for certain cardiac diseases, but a clinically-viable means of remotely generating and tracking transverse wave propagation in myocardium is needed. Intracardiac echocardiography (ICE) catheter-tip transducers are demonstrated here as a viable tool for making this measurement. ICE probes achieve favorable proximity to the myocardium, enabling the use of shear wave velocimetry from within the right ventricle throughout the cardiac cycle. This work describes the techniques used to overcome the challenges of using a small probe to perform ARF-driven shear wave velocimetry, and presents in vivo porcine data showing the effectiveness of this method in the interventricular septum.

Myocardial passive shear wave detection

“…The relative standard deviation in the full dataset (assuming normal distribution) was 25% for both the end-systolic and enddiastolic dataset, which is similar to that found in literature within a group of 6 pigs [6]. [6]. The difference between the work reported by Hollender et al [6] and this work is the moment in which the shear wave velocity is measured.…”

“…The relative standard deviation in the full dataset (assuming normal distribution) was 25% for both the end-systolic and enddiastolic dataset, which is similar to that found in literature within a group of 6 pigs [6]. [6].…”

“…[6]. The difference between the work reported by Hollender et al [6] and this work is the moment in which the shear wave velocity is measured. In this work, the end-diastolic shear wave velocity is measured when the heart starts to contract, as the contraction is the cause of the closing of the mitral valve.…”

“…The expected correlation between diastolic dysfunction and myocardial stiffness led to several studies on shear waves to measure the myocardial stiffness non-invasively [4][5][6][7]. For the method to produce robust outcome values, determination of the propagation velocity needs to be accurate.…”

Intracardiac shear wave velocimetry using Acoustic Radiation Force (ARF) excitations: In vivo results

“…Intracardiac Echocardiography (ICE) holds promise for obtaining the proximity to the tissue needed to generate ARF excitations. ICE is commonly used for function assessment and therapy guidance [5], [6], and has already been shown to be feasible for cardiac ARFI imaging [7], [8]. The small size of ICE transducer arrays introduces challenges such as limited acoustic output and relatively large physiological motion [9].…”