The influence of hemodialysis-induced preload changes on the propagation speed of natural shear waves

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation - Flanders (FWO) Background Shear wave elastography (SWE) is a novel ultrasound technique based on the detection of transverse waves travelling through the myocardium using high frame rate echocardiography. The propagation speed of these shear waves is dependent on the stiffness of the myocardium. Previous studies have shown the potential of SWE for the non-invasive assessment of myocardial stiffness. It is unclear, however, if preload changes lead to measurable changes in the shear wave propagation speed in the left ventricle. In patients undergoing hemodialysis, the volume status is acutely changed. In this way, the effect of preload changes on shear wave speed can be assessed. Purpose The aim of this study was to explore the influence of preload changes on end-diastolic shear wave propagation speed. Methods Until now, 6 patients (age: 80[53-85] years; female: n = 2) receiving hemodialysis treatment were included. Echocardiographic images were taken before and every hour during a 4 hour hemodialysis session. Left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (average frame rate: 1016[941-1310] Hz). Standard echocardiography was performed with a conventional ultrasound machine. Shear waves were visualized on tissue acceleration maps by drawing an M-mode line along the interventricular septum. Shear wave propagation speed after mitral valve closure (MVC) was calculated by measuring the slope of the wave pattern on the acceleration maps (Figure A). Results Over the course of hemodialysis, the systolic (141[135-156] mmHg vs. 165[105-176] mmHg; p = 0.35 among groups) and diastolic blood pressure (70[66-75] mmHg vs. 82[63-84] mmHg; p = 0.21 among groups), heart rate (56[54-73] bmp vs. 57[50-67] bpm; p = 0.76 among groups), E/A ratio (1.6[0.7-1.8] vs. 1.2[0.6-1.4]; p = 0.43 among groups) and E/e’ (14[9-15] vs. 9[8-13]; p = 0.24 among groups ) remained the same. The ultra-filtrated volumes are shown in Figure B. The shear wave propagation speed after MVC gradually decreased during hemodialysis (6.7[5.4-9.7] m/s vs. 4.4[3.6-9.0] m/s; p = 0.04 among groups) (Figure C). There was a moderate negative correlation between shear wave speed and the ultra-filtrated volume (r=-0.63; p < 0.01) (Figure D). Conclusion The shear wave propagation speed at MVC significantly decreased over the course of hemodialysis and correlated to the ultra-filtrated volume. These results indicate that alterations in left ventricular preload affect the speed of shear waves at end-diastole. End-diastolic shear wave speed might therefore be a potential novel parameter for the evaluation of the left ventricular filling state. More patients will be included in the future to further explore these findings. Abstract Figure.

Download Full-text

Natural shear wave propagation speed is influenced by both changes in myocardial structural properties as well as loading conditions

European Heart Journal - Cardiovascular Imaging ◽

10.1093/ehjci/jeaa356.146 ◽

2021 ◽

Vol 22 (Supplement_1) ◽

Author(s):

S Bezy ◽

J Duchenne ◽

M Orlowska ◽

M Amoni ◽

A Caenen ◽

...

Keyword(s):

Wave Propagation ◽

Structural Properties ◽

Shear Wave ◽

Wave Speed ◽

Propagation Speed ◽

Left Ventricular ◽

Balloon Occlusion ◽

Frame Rate ◽

Shear Wave Speed ◽

Wave Propagation Speed

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation - Flanders (FWO) Background Shear wave elastography (SWE) is a promising tool for the non-invasive assessment of myocardial stiffness. It is based on the evaluation of the propagation speed of shear waves by high frame rate echocardiography. These waves can be induced by for instance mitral valve closure (MVC) and the speed at which they travel is related to the instantaneous stiffness of the myocardium. Myocardial stiffness is defined by the local slope of the stress-strain relation and can therefore be altered by both changes in structural properties of the myocardium as well as loading conditions. Purpose The aim of this study was to investigate how changes in myocardial structural properties as well as loading conditions affect shear wave speed after MVC. Methods Until now, 8 pigs (weight: 33.6 ± 5.4 kg) were included. The following interventions were performed: 1) preload was reduced by balloon occlusion of the vena cava inferior, 2) afterload was increased by balloon occlusion of descending aorta, 3) preload was increased by intravenous administration of 500 ml of saline and 4) ischemia/reperfusion injury (I/R injury) was induced in the septal wall by balloon occlusion of the LAD for 90 min. with subsequent reperfusion for 40 min. Echocardiographic and left ventricular pressure recordings were simultaneously obtained during each intervention. Left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (average frame rate: 1279 ± 148 Hz). Shear waves were visualized on tissue acceleration maps by drawing an M-mode line along the interventricular septum. Shear wave propagation speed after MVC was calculated by assessing the slope of the wave pattern on the tissue acceleration map (Figure A). Results The change in left ventricular end-diastolic pressure (LVEDP) and shear wave speed after MVC between baseline and each intervention are shown in Figure B and C, respectively. Preload reduction resulted in significant lower LVEDP compared to baseline (p < 0.01), while the other loading changes did not have a significant effect. Shear wave speed after MVC significantly increased by afterload and preload increase (p < 0.01). I/R injury resulted in increased shear wave speed (p < 0.01) without significantly altering LVEDP. There was a good positive correlation between the change in LVEDP and the change in shear wave speed induced by loading changes (r = 0.76; p < 0.001) (Figure D). However, the correlation became less strong if data of I/R injury was taken into account as well (r = 0.63; p < 0.001). Conclusion Our results suggest that SWE is capable to characterize myocardial tissue properties and besides has the potential as a novel method for the estimation of left ventricular filling pressures. However, in the presence of structural changes of the myocardium, care should be taken when estimating filling pressures based on shear wave propagation speed. Abstract Figure.

Download Full-text

Myocardial stiffness assessed by natural shear wave elastography is related to pressure-volume loop derived parameters

European Heart Journal ◽

10.1093/eurheartj/ehab724.034 ◽

2021 ◽

Vol 42 (Supplement_1) ◽

Author(s):

S Bezy ◽

A Caenen ◽

J Duchenne ◽

M Orlowska ◽

M Amoni ◽

...

Keyword(s):

Shear Wave ◽

Wave Speed ◽

Propagation Speed ◽

Shear Wave Elastography ◽

Frame Rate ◽

Myocardial Stiffness ◽

High Frame Rate ◽

Shear Wave Speed ◽

Non Invasive ◽

Operating Chamber

Abstract Background Several cardiovascular disorders are accompanied by a stiffening of the myocardium and may result in diastolic heart failure. The non-invasive assessment of myocardial stiffness could therefore improve the understanding of the pathophysiology and guide treatment. Shear wave elastography (SWE) is a recent technique with tremendous potential for evaluating myocardial stiffness in a non-invasive way. Using high frame rate echocardiography, the propagation speed of shear waves is evaluated, which is directly related to the stiffness of the myocardium. These waves are induced by for instance mitral valve closure (MVC) and propagate throughout the cardiac muscle. However, validation of SWE against an invasive gold standard method is lacking. Purpose The aim of this study was to compare echocardiographic shear wave elastography against invasive pressure-volume loops, a gold standard reference method for assessing chamber stiffness. Methods In 15 pigs (31.2±4.1 kg) stiffness of the myocardium was acutely changed by inducing ischemia/reperfusion (I/R) injury. For this, the proximal LAD was balloon occluded for 90 minutes with subsequent reperfusion for 40 minutes. Conventional and high frame rate echocardiographic images were acquired simultaneously with pressure-volume loops during baseline conditions and after the induction of the I/R injury. Preload was reduced in order to acquire a set of pressure-volume loops to derive the end-diastolic pressure volume relation (EDPVR). From the EDPVR, the stiffness coefficient β and the operating chamber stiffness dP/dV were obtained. High frame rate echocardiographic datasets of the parasternal long axis view were acquired with an experimental ultrasound scanner (HD-PULSE) at an average frame rate of 1304±115 Hz. Tissue acceleration maps were obtained by drawing an M-mode line along the interventricular septum in order to visualize shear waves after MVC (at end-diastole). The propagation speed was assessed by semi-automatically measuring the slope (Figure A). Results I/R injury led to an elevated chamber stiffness constant β (0.09±0.03 1/ml vs. 0.05±0.01 1/ml; p<0.001) and operating chamber stiffness dP/dV (1.09±0.38 mmHg/ml vs. 0.50±0.18 mmHg/ml; p<0.01). Likewise, shear wave speed after MVC increased after the induction of the I/R injury in comparison to baseline (6.1±1.2 m/s vs. 3.2±0.8 m/s; p<0.001). Shear wave speed had a moderate positive correlation with β (r=0.63; p<0.001) (Figure B) and a strong positive correlation with dP/dV (r=0.81; p<0.001) (Figure C). Conclusion End-diastolic shear wave speed is strongly related to chamber stiffness, assessed invasively by pressure-volume loops. These results indicate that shear wave propagation speed could be used as a novel non-invasive measurement of the mechanical properties of the ventricle. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FWO - Research Foundation Flanders

Download Full-text

The behaviour of natural shear waves under different loading conditions

European Heart Journal ◽

10.1093/ehjci/ehaa946.0127 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

S Bezy ◽

J Duchenne ◽

M Orlowska ◽

L Wouters ◽

A Caenen ◽

...

Keyword(s):

Wave Propagation ◽

Shear Wave ◽

Propagation Velocity ◽

Shear Waves ◽

Left Ventricular ◽

Balloon Occlusion ◽

Frame Rate ◽

Funding Source ◽

Preload Reduction ◽

Propagation Velocities

Abstract Background Shear wave imaging (SWI) is a novel ultrasound technique based on the detection of transverse waves traveling through the myocardium using high frame rate echocardiography. These waves can be naturally induced e.g. by mitral valve closure (MVC). Their propagation velocity is dependent on the stiffness of the myocardium. Previous studies have shown the potential of SWI for the non-invasive assessment of myocardial stiffness. So far, the influence of loading on shear wave propagation velocities has not been extensively investigated. Purpose The aim of this study was to explore how loading changes affect shear wave propagation velocities after MVC. Methods Until now, 5 pigs (weight: 33.5±6.9 kg) were included. Echocardiographic images and left ventricular pressure recordings were simultaneously acquired during acute loading alterations: 1) preload was reduced by balloon occlusion of the vena cava inferior, 2) afterload was increased by balloon occlusion of the descending aorta and 3) preload was increased by intra-venous administration of 500 ml of saline. Left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (average frame rate: 1247±179 Hz). Shear waves were visualized on tissue acceleration maps by drawing an M-mode line along the interventricular septum. Shear wave propagation velocities after MVC were calculated by measuring the slope of the wave front on the acceleration maps (Figure A). Results The changes in left ventricular end-diastolic pressures (LV EDP) between baseline and each intervention are shown in Figure B. Preload reduction resulted in significantly reduced LV EDP (p<0.01). The shear wave propagation velocities after MVC dropped with preload reduction and increased significantly by increasing afterload as well as preload (both p<0.05) (Figure C). There was a good positive correlation between the change in LV EDP and the change in shear wave velocities (r=0.83; p<0.001) (Figure D). Conclusion The shear wave propagation velocity after MVC was significantly influenced by alterations in left ventricular loading conditions and changes in these velocities were related to changes in LV EDP. These results indicate that shear wave measurements at MVC might be a potential novel parameter for the estimation of left ventricular filling pressures. More pigs will be included in the future to further confirm these findings. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fonds Wetenschappelijk Onderzoek - Vlaanderen

Download Full-text

Sensitivity of the Shear Wave Speed-Stress Relationship to Soft Tissue Material Properties and Fiber Alignment

10.31224/osf.io/54btr ◽

2021 ◽

Author(s):

Jonathon Blank ◽

Darryl Thelen ◽

Matthew S. Allen ◽

Joshua Roth

Keyword(s):

Wave Propagation ◽

Shear Modulus ◽

Shear Wave ◽

Wave Speed ◽

Axial Stress ◽

Beam Model ◽

Fiber Alignment ◽

Wave Speeds ◽

Shear Wave Speed ◽

Constitutive Properties

The use of shear wave propagation to noninvasively gauge material properties and loading in tendons and ligaments is a growing area of interest in biomechanics. Prior models and experiments suggest that shear wave speed primarily depends on the apparent shear modulus (i.e., shear modulus accounting for contributions from all constituents) at low loads, and then increases with axial stress when axially loaded. However, differences in the magnitudes of shear wave speeds between ligaments and tendons, which have different substructures, suggest that the tissue’s composition and fiber alignment may also affect shear wave propagation. Accordingly, the objectives of this study were to (1) characterize changes in the apparent shear modulus induced by variations in constitutive properties and fiber alignment, and (2) determine the sensitivity of the shear wave speed-stress relationship to variations in constitutive properties and fiber alignment. To enable systematic variations of both constitutive properties and fiber alignment, we developed a finite element model that represented an isotropic ground matrix with an embedded fiber distribution. Using this model, we performed dynamic simulations of shear wave propagation at axial strains from 0% to 10%. We characterized the shear wave speed-stress relationship using a simple linear regression between shear wave speed squared and axial stress, which is based on an analytical relationship derived from a tensioned beam model. We found that predicted shear wave speeds were both in-range with shear wave speeds in previous in vivo and ex vivo studies, and strongly correlated with the axial stress (R2 = 0.99). The slope of the squared shear wave speed-axial stress relationship was highly sensitive to changes in tissue density. Both the intercept of this relationship and the apparent shear modulus were sensitive to both the shear modulus of the ground matrix and the stiffness of the fibers’ toe-region when the fibers were less well-aligned to the loading direction. We also determined that the tensioned beam model overpredicted the axial tissue stress with increasing load when the model had less well-aligned fibers. This indicates that the shear wave speed increases likely in response to a load-dependent increase in the apparent shear modulus. Our findings suggest that researchers may need to consider both the material and structural properties (i.e., fiber alignment) of tendon and ligament when measuring shear wave speeds in pathological tissues or tissues with less well-aligned fibers.

Download Full-text

P1501Can we measure the stiffening of hypertensive hearts non-invasively? A shear wave imaging study using ultra-high frame rate echocardiography

European Heart Journal ◽

10.1093/eurheartj/ehz748.0264 ◽

2019 ◽

Vol 40 (Supplement_1) ◽

Author(s):

M Cvijic ◽

P Santos ◽

A M Petrescu ◽

S Bezy ◽

M Orlowska ◽

...

Keyword(s):

Left Atrium ◽

Shear Wave ◽

Interventricular Septum ◽

Left Ventricular ◽

Frame Rate ◽

Volume Index ◽

Healthy Controls ◽

Myocardial Stiffness ◽

High Frame Rate ◽

Concentric Hypertrophy

Abstract Background Cardiac shear wave (SW) elastography is a novel technique based on high-frame-rate (HFR) echocardiography which has been shown to be related to myocardial stiffness. In this study we explore the relation between myocardial SW velocity and myocardial remodelling in remodelled hearts of patients with arterial hypertension (AH). Methods We prospectively included 33 treated AH patients with hypertrophic left ventricular (LV) remodelling (59±14 years, 55% male) and 26 aged matched healthy controls (55±15 years, 77% male). AH patients were further divided according to their LV geometric pattern into a concentric remodelling (CR) group (13 patients) and a concentric hypertrophy (CH) group (20 patients). LV parasternal long axis views were acquired with an experimental HFR ultrasound scanner (HD-PULSE) at 1266±317 frames per seconds. Myocardial acceleration maps were created from the HFR-datasets and an anatomical M-mode line was drawn along the midline of the interventricular septum (IVS). The propagation velocity of natural SWs occurring at mitral valve closure (MVC) was measured on these M-modes (Figure A) in order to assess passive myocardial stiffness. Standard echocardiography using a commercial scanner was performed to evaluate LV remodelling. Results SW velocities at MVC differed significantly between AH patients and controls (5.83±1.20 m/s vs. 4.04±0.96 m/s; p<0.001). Within the patient group, patients with CH had highest SW velocities at MVC (p<0.001), whereas values between controls and patients with CR were comparable (p=0.075) (Figure B). In AH patients, significant positive correlations were found between SW velocity at MVC and parameters of LV remodelling (IVS thickness: r=0.728, p<0.001; LV mass index: r=0.780, p<0.001, LV end-diastolic volume: r=0.604, p=0.008) (Figure C) and also parameters of diastolic function (E/e': r=0.495, p=0.005, left atrium diameter: r=0.866, p<0.001, left atrium volume index: r=0.661, p<0.001). Figure A, B, C Conclusions SW velocity – and therefore myocardial stiffness – is higher in AH patients compared to healthy controls and increases with increasing severity of hypertensive heart disease. Patients with concentric remodelling have still close-to-normal passive myocardial properties while patients with concentric hypertrophy show significant stiffening. Echocardiographic shear wave elastography is a promising new technique for the non-invasive assessment of myocardial stiffness and might provide valuable new insights into myocardial function and the pathophysiology of myocardial disease.

Download Full-text

Shear wave elastography: can we estimate filing pressures?

European Heart Journal ◽

10.1093/ehjci/ehaa946.1025 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

A.E Werner ◽

S Bezy ◽

M Orlowska ◽

G Kubiak ◽

W Desmet ◽

...

Keyword(s):

Diastolic Function ◽

Shear Wave ◽

Propagation Velocity ◽

Shear Wave Elastography ◽

Left Ventricular ◽

Filling Pressure ◽

Frame Rate ◽

Funding Source ◽

High Frame Rate ◽

Non Invasive

Abstract Background The assessment of the left ventricular diastolic function is complex, as there is no single non-invasive parameter that provides a direct measurement of myocardial relaxation, myocardial compliance, or – as a surrogate - LV filling pressure. Estimation of diastolic function is therefore based on the combination of many parameters. Shear wave (SW) elastography (SWE) is a novel method based on high frame rate echocardiography. SWs occur after mechanical excitation of the myocardium, e.g. after mitral valve closure (MVC), and their propagation velocity is directly related to myocardial stiffness (MS). Purpose The aim of this study was to investigate if velocities of natural shear waves are related to MS at end diastole (ED) and, thus, could be used to estimate left ventricular end-diastolic pressures (LVEDP) as marker of diastolic function. Methods So far, we have prospectively enrolled 30 patients with a wide range of diastolic function, scheduled for heart catheterization so that LV filling pressures could be invasively measured. Patients with severe aortic stenosis, mitral stenosis of any degree and a more than moderate mitral regurgitation, as well as regional myocardial abnormalities or dysfunction in the anteroseptal wall were excluded. Echocardiography was performed immediately after catheterization. SW elastography in parasternal long axis views of the left ventricle (LV) was performed using an experimental scanner (HD-PULSE) at 1100±250 frames per second. Tissue acceleration maps were extracted from an anatomical M-mode line along the midline of the LV septum. The SW propagation velocity at MVC was measured as the slope on the M-mode acceleration map (Figure A). Results SW velocities at ED correlated very well with the invasively measured LVEDP (r=0.815, p<0.001, Figure B). In comparison, classical echocardiographic parameters correlated only weakly or not with LVEDP (E/A: r=0.528, p=0.036, Figure C; E/e': r=−0.169, p=0,531, Figure D) with LVEDP. For the detection of an elevated LVEDP above 15 mmHg, a cut off value for the SW velocity at MVC of 3.75 m/s was associated with a Sensitivity of 92.9% and a Specificity of 83.3%. Conclusions End-diastolic shear wave velocities, measured by high frame rate shear wave elastography, showed a significant correlation with the end-diastolic filling pressure of the LV indicating a potential clinical value of the new method for a non-invasive and direct assessment of LV diastolic function. More patients will be included to confirm these findings. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fonds Wetenschappelijk Onderzoek Flanderen (Research Foundation Flanders)

Download Full-text

Shear wave cardiovascular MR elastography using intrinsic cardiac motion for transducer-free non-invasive evaluation of myocardial shear wave velocity

Scientific Reports ◽

10.1038/s41598-020-79231-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Marian Amber Troelstra ◽

Jurgen Henk Runge ◽

Emma Burnhope ◽

Alessandro Polcaro ◽

Christian Guenthner ◽

...

Keyword(s):

Healthy Volunteers ◽

Shear Wave ◽

Wave Speed ◽

Shear Waves ◽

Valve Closure ◽

Limits Of Agreement ◽

Wave Speeds ◽

Shear Wave Speed ◽

Non Invasive ◽

Aortic Valve Closure

AbstractChanges in myocardial stiffness may represent a valuable biomarker for early tissue injury or adverse remodeling. In this study, we developed and validated a novel transducer-free magnetic resonance elastography (MRE) approach for quantifying myocardial biomechanics using aortic valve closure-induced shear waves. Using motion-sensitized two-dimensional pencil beams, septal shear waves were imaged at high temporal resolution. Shear wave speed was measured using time-of-flight of waves travelling between two pencil beams and corrected for geometrical biases. After validation in phantoms, results from twelve healthy volunteers and five cardiac patients (two left ventricular hypertrophy, two myocardial infarcts, and one without confirmed pathology) were obtained. Torsional shear wave speed in the phantom was 3.0 ± 0.1 m/s, corresponding with reference speeds of 2.8 ± 0.1 m/s. Geometrically-biased flexural shear wave speed was 1.9 ± 0.1 m/s, corresponding with simulation values of 2.0 m/s. Corrected septal shear wave speeds were significantly higher in patients than healthy volunteers [14.1 (11.0–15.8) m/s versus 3.6 (2.7–4.3) m/s, p = 0.001]. The interobserver 95%-limits-of-agreement in healthy volunteers were ± 1.3 m/s and interstudy 95%-limits-of-agreement − 0.7 to 1.2 m/s. In conclusion, myocardial shear wave speed can be measured using aortic valve closure-induced shear waves, with cardiac patients showing significantly higher shear wave speeds than healthy volunteers. This non-invasive measure may provide valuable insights into the pathophysiology of heart failure.

Download Full-text

Relationship between myocardial properties and myocardial stiffness in hearts with thick walls: a shear wave imaging study using ultra-high frame rate echocardiography

European Heart Journal - Cardiovascular Imaging ◽

10.1093/ehjci/jeaa356.182 ◽

2021 ◽

Vol 22 (Supplement_1) ◽

Author(s):

M Cvijic ◽

A Petrescu ◽

S Bezy ◽

P Santos ◽

M Orlowska ◽

...

Keyword(s):

Shear Wave ◽

Systolic Pressure ◽

Left Ventricular ◽

Frame Rate ◽

Local Geometry ◽

Cavity Pressure ◽

Invasive Approach ◽

Tissue Properties ◽

Myocardial Stiffness ◽

High Frame Rate

Abstract Funding Acknowledgements Type of funding sources: None. Background Shear wave (SW) imaging, based on high frame rate (HFR) echocardiography, is a new non-invasive approach for assessing myocardial stiffness. Operating myocardial stiffness increases with increasing wall stress, therefore measured myocardial stiffness does not necessarily reflect intrinsic myocardial properties only, but can be influenced by cavity pressure and chamber geometry. Purpose To explore the relationship between local myocardial geometry, cavity pressure and pathological substrate with SW velocity and to determine to which extent the above mentioned factors influence SW velocity. Methods We included 26 healthy controls (55 ± 14 years, 77 % male) and 61 patients with thick heart (24 patients with cardiac amyloidosis (AML) [70 ± 9 years, 52 % male], 37 patients with hypertrophic cardiomyopathy (HCM) [54 ± 14 years, 78 % male]). Left ventricular (LV) parasternal long axis views were acquired with an experimental HFR scanner at 1142 ± 282 frames per seconds. Propagation velocity of the SW occurring after mitral valve closure in the interventricular septum (IVS) served as measure of myocardial stiffness (Figure A). While conventional echocardiographic measurements were used to evaluate local myocardial geometry (LV end-diastolic diameter [EDD], IVS thickness) and LV cavity pressure (LV diastolic pressure-estimated by E/e` and LV systolic pressure-estimated by systolic blood pressure and potential LV outflow gradient in HCM). Results LV cavity pressure and local geometry differed significantly between controls and patients (p < 0.05, for all, Figure B). SW velocity correlated with cavity pressure (E/e`: r = 0.375, p < 0.001, LV systolic pressure: r = 0.264, p = 0.020) and local geometry (IVS thickness: r = 0.700, p < 0.001; EDD: r=-0.307, p = 0.007) and differed significantly among groups (Figure C). Multivariate analysis revealed that SW velocity was independently related only with the pathological substrate and IVS thickness (p = 0.006 and p < 0.001, respectively). In a regression model, the pathological substrate, cavity pressure and local geometry accounted for 56% of variation in SW velocity (p < 0.001), while the pathological substrate alone accounted for nearly half of the variance (R2 = 0.44, p < 0.001) (Figure D). Conclusions Our study demonstrated that SW velocity is related to both pathological substrate and local geometry and LV pressures. Additionally, our results suggest that variations in myocardial tissue properties had the most influence on SW velocity, while LV pressure and local geometry played a minor role. Therefore, the changes in SW velocity reflect predominantly tissue properties that are altered by underlining disease rather than cavity pressure and morphological abnormalities. Thus, SW elastography could provide useful novel diagnostic information in the evaluation of cardiomyopathies. Abstract Figure A, B, C, D

Download Full-text

Differentiation of hypertensive heart disease and hypertrophic cardiomyopathy with myocardial stiffness measurements: a shear wave imaging study using ultra-high frame rate echocardiography

European Heart Journal ◽

10.1093/ehjci/ehaa946.0087 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

M Cvijic ◽

S Bezy ◽

A Petrescu ◽

P Santos ◽

M Orlowska ◽

...

Keyword(s):

Hypertrophic Cardiomyopathy ◽

Shear Wave ◽

Interventricular Septum ◽

Hypertensive Heart Disease ◽

Wall Stress ◽

Left Ventricular ◽

Frame Rate ◽

Invasive Technique ◽

Myocardial Stiffness ◽

High Frame Rate

Abstract Background Recently, cardiac shear wave (SW) elastography, based on high frame rate (HFR) echocardiography, has been proposed as new non-invasive technique for assessing myocardial stiffness. As myocardial stiffness increases with increasing wall stress, differences in measured operating myocardial stiffness do not necessarily reflect differences in intrinsic myocardial properties, but can also be caused by mere changes in loading or chamber geometry. This complicates myocardial stiffness interpretation for different types of pathologic hypertrophy. Purpose To explore the relationship between myocardial stiffness and underlying pathological substrates for cardiac hypertrophy. Methods We included 20 patients with hypertension (HT) and myocardial remodelling (59±14 years, 75% male), 20 patients with hypertrophic cardiomyopathy (HCM) (59±16 years, 60% male) and 20 healthy controls (56±14 years, 75% male). Left ventricular (LV) parasternal long axis views were acquired with an experimental HFR scanner at 1293±362 frames per seconds. Propagation velocity of SW occurring after mitral valve closure in the interventricular septum (IVS) served as measure of operating myocardial stiffness (Figure A). To compare myocardial stiffness among hearts with differing loading conditions and chamber geometry, SW velocities were normalized to end-diastolic wall stress, estimated at IVS from regional wall thickness, longitudinal and circumferential regional radii of curvature, and non-invasively estimated LV end-diastolic pressure (EDP). Results SW velocities differed significantly between groups (p<0.001). The controls had the lowest SW velocities (4.02±0.97 m/s), whereas values between HT and HCM group were comparable (6.46±0.99 m/s vs. 7.00±2.10 m/s; p=0.738). Considering end-diastolic wall stress, HCM patients had the same SW velocity at lower wall stress compared to HT (Figure B), indicating higher myocardial stiffness in the HCM group. SW velocities normalized for wall stress indicated significantly different myocardial stiffness among all groups (p<0.001) (Figure C). In a multiple linear regression model, the underlying pathological substrate independently influenced SW velocity (beta 1.37, 95% CI (0.78–1.96); p<0.001), while wall stress did not significantly affect its value (p=0.479). Conclusions Our study demonstrated that SW elastography can detect differences in myocardial stiffness in hypertensive heart and hypertrophic cardiomyopathy. Additionally, our results suggest that SW velocity is dominated by underlying myocardial tissue properties. We hypothesize that differential changes in cardiomyocytes and/or the extracellular matrix contribute to the differential myocardial stiffening in different pathologic entities of LV hypertrophy. Thus, SW elastography could provide useful novel diagnostic information in the evaluation of LV hypertrophy. Figure A, B, C Funding Acknowledgement Type of funding source: None

Download Full-text