J A C C : C A R D I O V A S C U L A R I M A G I N G VO L . - , N O . - , 2 0 1 8
ª 2 0 1 8 T H E A U T H O R S . P U B L I S H E D B Y E L S E V I E R O N B E H A L F O F T H E A M E R I C A N
C O L L E G E O F C A R D I O L O G Y F OU N D A T I O N . T H I S I S A N O P E N A C C E S S A R T I C L E U N D E R
T H E C C B Y L I C E N S E ( h t t p : / / c r e a t i v e c o mm o n s . o r g / l i c e n s e s / b y / 4 . 0 / ) .
Myocardial Stiffness Evaluation UsingNoninvasive Shear Wave Imaging inHealthy and HypertrophicCardiomyopathic Adults
Olivier Villemain, MD,a,b Mafalda Correia, PHD,a Elie Mousseaux, MD, PHD,c Jérome Baranger, MS,aSamuel Zarka, MD,b Ilya Podetti, MS,a Gilles Soulat, MD,c Thibaud Damy, MD, PHD,d Albert Hagège, MD, PHD,b
Mickael Tanter, PHD,a Mathieu Pernot, PHD,a Emmanuel Messas, MD, PHDb
ABSTRACT
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OBJECTIVES The goal of our study was to investigate the potential of myocardial shear wave imaging (SWI) to
quantify the diastolic myocardial stiffness (MS) (kPa) noninvasively in adult healthy volunteers (HVs) and its physiological
variation with age, and in hypertrophic cardiomyopathy (HCM) populations with heart failure and preserved ejection
function (HFpEF).
BACKGROUND MS is an important prognostic and diagnostic parameter of the diastolic function. MS is affected by
physiological changes but also by pathological alterations of extracellular and cellular tissues. However, the clinical
assessment of MS and the diastolic function remains challenging. SWI is a novel ultrasound-based technique that has
the potential to provide intrinsic MS noninvasively.
METHODS Weprospectively included 80adults: 60HV (divided into 3 groups: 20- to 39-year old patients [n¼ 20]; 40- to
59-year-old patients [n¼ 20]; and 60- to 79-year-old patients [n¼ 20]) and 20 HCM-HFpEF patients. Echocardiography,
cardiac magnetic resonance imaging and biological explorations were achieved. MS evaluation was performed using an
ultrafast ultrasound scanner with cardiac phased array. The fractional anisotropy of MS was also estimated.
RESULTS MS increased significantly with age in the HV group (the mean MS was 2.59 � 0.58 kPa, 4.70 � 0.88 kPa, and
6.08 � 1.06 kPa for the 20- to 40-year-old, 40- to 60-year-old, and 60- to 80-year-old patient groups, respectively;
p < 0.01 between each group). MS was significantly higher in HCM-HFpEF patients than in HV patients (mean MS ¼12.68 � 2.91 kPa vs. 4.47 � 1.68 kPa, respectively; p < 0.01), with a cut-off at 8 kPa (area under the curve ¼ 0.993;
sensitivity ¼ 95%, specificity ¼ 100%). The fractional anisotropy was lower in HCM-HFpEF (mean ¼ 0.133 � 0.073) than
in HV (0.238 � 0.068) (p < 0.01). Positive correlations were found between MS and diastolic parameters in echocar-
diography (early diastolic peak/early diastolic mitral annular velocity, r ¼ 0.783; early diastolic peak/transmitral flow
propagation velocity, r ¼ 0.616; left atrial volume index, r ¼ 0.623) and with fibrosis markers in cardiac magnetic
resonance (late gadolinium enhancement, r ¼ 0.804; myocardial T1 pre-contrast, r ¼ 0.711).
CONCLUSIONS MS was found to increase with age in healthy adults and was significantly higher in HCM-HFpEF pa-
tients. Myocardial SWI has the potential to become a clinical tool for the diagnostic of diastolic dysfunction. (Non-invasive
Evaluation of Myocardial Stiffness by Elastography [Elasto-Cardio]; NCT02537041) (J Am Coll Cardiol Img 2018;-:-–-)
©2018TheAuthors. PublishedbyElsevier onbehalf of theAmericanCollegeofCardiologyFoundation. This is anopenaccess
article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
N 1936-878X https://doi.org/10.1016/j.jcmg.2018.02.002
m the aInstitut Langevin, ESPCI, CNRS, Inserm U979, PSL Research University, Paris, France; bHôpital Européen Georges
mpidou, Université Paris Descartes, Cardio-Vascular Departement, UMR 970, Paris, France; cHôpital Européen Georges
mpidou, Université Paris Descartes, Département de Radiologie, INSERM U970, Paris, France; and the dDepartment of
rdiology, AP-HP, Henri Mondor Teaching Hospital, Créteil, France. This study was supported by the European Research
uncil (ERC) under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC grant agreement 311025 and by
French Society of Cardiology. Dr. Damy has received support from Pfizer, GSK, Prothena, Novartis, and Resmed. Dr. Tanter is
ounder of and shareholder with SuperSonic Imagine. All other authors have reported that they have no relationships relevant
the contents of this paper to disclose. Drs. Pernot and Messas contributed to equally to this work, and are joint senior authors.
nuscript received November 26, 2017; revised manuscript received January 31, 2018, accepted February 1, 2018.
ABBR EV I A T I ON S
AND ACRONYMS
DT = deceleration time
ECV = extracellular volume
FA = fractional anisotropy
HCM = hypertrophic
cardiomyopathy
HF = heart failure
HFpEF = heart failure with
preserved ejection function
HV = healthy volunteer
IVRT = isovolumic relaxation
time
LGE = late gadolinium
enhancement
MS = myocardial stiffness
SWI = shear wave imaging
Vp = transmitral flow
propagation velocity
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M yocardial stiffness (MS) is knownto play a key role in diastolic leftventricular (LV) function (1). Ab-
normalities in LV relaxation and MS are oneof the key pathophysiological mechanisms(2) in heart failure patients with preservedejection fraction (HFpEF). Hypertrophic car-diomyopathy (HCM) is also associated to se-vere diastolic dysfunction mainly due tofibrosis and fiber disarray (3). Moreover, MSis also affected by aging due to progressivephysiological changes and cellular and extra-cellular matrix alterations. However, as theclinical assessment of MS and of the diastolicfunction is still challenging (4), the studyof MS remained limited to invasiveexplorations (5).
In a general view, the assessments of dia-stolic function can be divided into those thatreflect the process of active/auxotonic relax-
ation (depending on filling load and afterload) andthose that reflect passive stiffness (independent ofload conditions) (6). In clinical practice, biologicalparameters are correlated with ventricular fillingpressures (e.g., brain natriuretic protein [BNP]) (7),echocardiographic parameters are identified to assessthe auxotonic relaxation and/or the filling pressure,and cardiac magnetic resonance (CMR) imaging offerstools to evaluate myocardial fibrosis (late enhance-ment gadolinium [LGE]) (8), or the collagen volumefraction (pre-post contrast T1 mapping or extracel-lular volume fraction [ECV]) (9,10). However, nonin-vasive estimation of passive stiffness remainschallenging. To date, cardiac catheterization is theonly validated option to assess the passive stiffnessclinically, through the compliance estimation thanksto the pressure-volume loops (11). But the risks for thepatients, the necessary equipment, and the costs ofthese interventions make this examination unfeasiblein daily clinical practice.
Shear wave imaging (SWI) is an ultrasound-basedtechnique for quantitative, local, and noninvasivemapping of soft tissue’s stiffness. The clinical impactof SWI has been shown during the last decade in thefield of breast lesions (12) and liver (13) imaging.Quantification of MS using SWI has also been investi-gated extensively on animal models in previousstudies (14). SWI was compared to invasive goldstandard parameters (15) derived from pressure-volume loops and was shown to quantify the end-diastolic MS (i.e., passive stiffness) accurately. Morerecently, the clinical feasibility and reproducibility oftransthoracic SWI was shown on a small group ofhealthy volunteers (HVs) (16) and on pediatric patients
(17). The next step is to show the clinical interest andcontribution of this technology for the assessment ofdiastolic MS in adults and its impact on diastolic LVfunction. Unlike other imaging techniques, echocar-diography is inexpensive, widely available, and can beperformed in real-time at the patient bedside allowingmonitoring of the heart structure and function.
In this study, we aimed to perform the first clinicalproof of concept of noninvasive MS evaluation onnormal and pathological patients. More specifically,the goals of our study were: 1) to quantify MS non-invasively with SWI in a healthy adult population toestablish values of MS and its dependence with age;2) to compare it to severely altered MS in HCM pa-tients with HFpEF; and 3) to investigate the correla-tion of MS with conventional echocardiography andCMR index of diastolic function.
METHODS
STUDY PATIENTS AND DESIGN. This was a prospec-tive study conducted at the Hôpital EuropéenGeorges Pompidou, Paris, France. A population ofHVs was contacted and recruited by the ClinicalInvestigation Center. HV-specific inclusion criteriawere: no history of heart failure symptoms, LV ejec-tion fraction (EF) >50%, early diastolic peak (E)/earlydiastolic mitral annular velocity (e0) <13, as well asnormal values of BNP (<35 pg/ml). Three age groupswere composed within the recruited HVs: 20- to39-year-old patients, 40- to 59-year-old patients, and60- to 79-year-old patients. Exclusion criteriaincluded systolic blood pressure (SBP) $140 mm Hgor/and diastolic blood pressure (DBP) $90 mm Hg,any persistent cardiac arrhythmia, more than mod-erate valvular disease, any relevant coronary arterydiseases, any contraindication to CMR, and anechogenicity.
Patients with clinical, genetic, and echocardio-graphic evidence for sarcomeric HCM with HFpEF(HCM-HFpEF group) were included. HCM-HFpEFpatients were identified according to the consensusof the European Society of Cardiology (18,19), usingspecific inclusion criteria: wall thickness $15 mm in 1or more LV myocardial segments; sarcomeric proteingene mutation identified; LVEF > 50%; New YorkHeart Association (NYHA) functional class $II; at least1 hospitalization for acute heart failure; and E/e0 $13or E/e0 8 to 13 combined with elevated BNP(>35 pg/ml).
All subjects included in the study underwent clin-ical explorations, biological explorations (hematocrit,C-reactive protein, BNP), an echocardiography, a CMRand a cardiac SWI. All explorations were performed
FIGURE 1 Myocardial Shear Wave Imaging
0Anterior wall
Anteriorwall
Inferior wall
Inferior wall
RV
RVOT
RVOT
LVOTAV
LVLA
MV
Septum
LVSeptum
Time = 0s10
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th [m
m]
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B-mode SA Shear wave propagation
20 400
X [mm]
0Time = 1.1 ms
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th [m
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B-mode and shear wave elastography imaging examples of a healthy volunteer (HV). Shear wave propagation in short- and long-axis views of a HV (tissue axial
velocity images). AV ¼ atrioventricular; LA ¼ left atrium; LV ¼ left ventricle; LVOT ¼ left ventricular outflow tract; MV ¼ mitral valve; RV ¼ right ventricle;
RVOT ¼ right ventricular outflow tract; SA ¼ short axis view.
J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . - , N O . - , 2 0 1 8 Villemain et al.- 2 0 1 8 :- –- Transthoracic Myocardial Stiffness Assessment in Adults
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on the same day. Three months later and if no clinicalevent was noted (symptoms of heart failure, hospi-talization for cardiac cause, modification of weight orblood pressure), a second echocardiography, andcardiac SWI were realized to estimate the reproduc-ibility on 5 patients per HV subgroup, randomlyselected (n ¼ 15).
The study was approved by the local ethics com-mittee, and all patients gave written informed con-sent (Non-Invasive Evaluation of Myocardial Stiffnessby Elastography [Elasto-Cardio]; NCT02537041).
IMAGING PROCEDURES. Echocardiography. Echocardio-graphic explorations were performed on a Vivid 9system (General Electric Healthcare, Chalfont St.Giles, Great Britain). Mitral valve inflow pattern (Eand A velocity), E-wave deceleration time (E-waveDT), isovolumic relaxation time (IVRT), transmitralflow propagation velocity (Vp), septal mitral valveannular velocities (e0 and a0), as well as pulmonaryveins S-wave on D-wave ratio (PV S/D ratio) wererecorded in an apical 4-chamber view, to assess themarkers of diastolic function according to AmericanSociety of Echocardiography guidelines (20). Globaland septal longitudinal strain was also performed bythe Speckle Tracking 2D Strain software of GeneralElectrics, directly on the Vivid 9 system. Data were
analyzed from stored images by experienced opera-tors (O.V. and A.H.) who were unaware of other testresults. Measurements were made over 3 cardiac cy-cles; the average was used for statistical analysis.
CMR. The CMR protocol consisted of cine-sequences,T1-weighted spin-echo, and 2-dimensional inversionrecovery gradient echo sequences for late enhance-ment assessment after gadobutrol administration(LGE). Post contrast T1 times (T1 mapping) was per-formed with a modified Look-Locker inversion re-covery sequence with a 3(3)5 scheme before and 15min after contrast application (21). Mapping wasperformed over all available short-axis slices. Extra-cellular volume (ECV) fraction was calculated on thebasis of the combination of pre- and post-contrast T1mapping data according to the approach proposed byRommel et al. (10). All acquisitions were consistentwith the Society for Cardiovascular Magnetic Reso-nance published guidelines (22). Data were inter-preted by 2 experienced readers (E.M. and G.S.) whowere unaware of the subjects’ clinical informationand the results of other diagnostic tests.
MS measured by SWI. SWI is based on the remote gen-eration of shear waves in soft tissue by acoustic radi-ation force combined with ultrasonic ultrafast imagingof the shear wave propagation (5,000 images/s), using
FIGURE 2 Study Flowchart
Population screened (n = 93)
IncludedHCM-HFpEF group (n = 20)
Healthy Volunteer (HV) group (n = 69)
IncludedHV group (n = 60)
HV group(n = 20)
20 – 39 yo
HV group(n = 20)
40 – 59 yo
3 months later: re-evaluation of Cardiac Elastography andEchocardiography (n = 15)
HV group(n = 20)
60 – 79 yo
Exclusion (n = 9)- 1 congenital heart disease- 1 valvulopathy on echocardiography- 1 doubt with infarct scar on CMR- 6 anechoic
Total included: n = 80- Clinical exam- Biological explorations- Echocardiography- CMR- Cardiac Elastography
Exclusion (n = 4)- 2 infarct scars seen on CMR- 2 anechoic
Sarcomeric hypertrophic cardiomyopathy with heart failurepreserved ejection fraction (HCM-HFpEF) group (n = 24)
The study was performed on 60 healthy volunteer and 20 HCM patients. CMR ¼ cardiac magnetic resonance; HCM ¼ hypertrophic cardiomyopathy; HFpEF ¼ heart
failure with preserved ejection fraction.
Villemain et al. J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . - , N O . - , 2 0 1 8
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the same ultrasonic transducer (Figure 1, OnlineVideo 1) (23). This modality has already beendescribed in previous works (14,15), and is alsodescribed in more details in the Online Appendix. Inthis study, a phased array probe (2.75-MHz centralfrequency, SuperSonic Imagine, Aix-en-Provence,France) connected to an ultrafast ultrasound scanner(Aixplorer, SuperSonic Imagine) was used. A conven-tional real-time echocardiographic image was used toposition the probe. The focus of the acoustic radiationforce generation was adjusted manually by the oper-ator on the myocardial wall. The operator thanlaunched the SWI acquisition that lasted approxi-mately 1 s.
The explored myocardial segment was the ante-roseptal basal segment (ASB segment). It was evalu-ated in 2 orthogonal axes (short- and long-axis views)(Figure 1). Short-axis measurements were used toderive the shear modulus, whereas long-axis andshort-axis values were used to compute the fractionalanisotropy. All acquisitions were performed at
end-diastole and triggered by an electrocardiogram.The 30 frames recorded after the push were post-processed to visualize the shear wave and computethe speed.
Data were interpreted off-line by 1 experiencedreader (O.V.) who was unaware of the subjects’ clin-ical information and the results of other diagnostictests.Fractional anisotropy. Similar to any fiber-composedmuscular tissue, the myocardium presents a signifi-cant anisotropy of its elastic properties. Consequently,MS is expected to be higher when measured along thefibers, which are mainly oriented along the circum-ferential direction in the mid-wall layer. To evaluatethe degree of anisotropy in the myocardium, thefractional anisotropy (FA) was computed. FA wasdefined using two shear wave speed measurementsperformed in orthogonal propagation directions (long-axis and short-axis views) using the formula publishedby Lee et al. (24). More details on the method are givenin the Online Appendix.
TABLE 1 Population Characteristics
Healthy Volunteer(n ¼ 60)
HCM-HFpEF(n ¼ 20) p Value
Patient
Age, yrs 50.6 � 16.9 57 � 17.5 0.22
Sex, M/F 31/29 17/3 <0.01
BMI, kg/m2 23.6 � 2.9 24.8 � 3.6 0.74
Systolic BP, mm Hg 117 � 10 115 � 11 0.41
Diastolic BP, mm Hg 70 � 7 75 � 6 0.47
NYHA functional class I 52 0 <0.01
NYHA functional class II 8 14 <0.01
NYHA functional class III to IV 0 6 <0.01
Biology (blood explorations)
CRP, mg/l 1.4 � 1.1 1.9 � 0.8 0.55
NTproBNP, pg/ml 16 � 9 365 � 144 <0.01
Hematocrit, % 43 � 2 40 � 2 0.03
Echocardiography parameters
LA surface, 4 cavities view, cm2 16.1 � 4 29.3 � 7.1 <0.01
LAVI, ml/m2 25.9 � 8.7 43.3 � 18.6 <0.01
LAVI > 34 ml/m2, % 12/60 (20) 15/20 (75) <0.01
LVEF, % 68 � 9.9 66 � 7.9 0.67
LVEDD, mm 45.9 � 4.8 49.9 � 5.7 0.47
LVESD, mm 28.3 � 4.8 24.6 � 3.2 0.22
LV mass/BSA, g/m2 70.6 � 20 125 � 34 <0.01
LV GS, % 17.4 � 2.4 14.6 � 3.1 <0.01
ASB segment GS, % 16.9 � 2.2 6.4 � 3.6 <0.01
ASB segment enddiastolic thickness, mm
5.9 � 1.4 20.8 � 5.1 <0.01
Peak E-wave, cm/s 74.8 � 17.6 88.3 � 30.2 <0.01
E/A 1.4 � 0.5 1.1 � 0.4 <0.01
e’ septal, cm/s 13.8 � 4.1 5.8 � 1.9 <0.01
E/e’ 5.9 � 2.4 16.1 � 6.5 <0.01
e’/a’ septal 1.6 � 0.8 1.3 � 0.9 0.29
E-wave DT, ms 179 � 60 238 � 62 <0.01
IVRT, ms 94 � 17 144 � 31 <0.01
Vp, cm/s 50.4 � 7.4 29.2 � 5.5 <0.01
E/Vp 1.3 � 0.3 3.4 � 1.5 <0.01
PV S/D ratio 1.2 � 0.3 0.7 � 0.3 <0.01
Cardiac magnetic resonance
ASB segment enddiastolic thickness, mm
5.7 � 1.4 18.3 � 3.4 <0.01
LV mass/LVED volume, g/ml 0.75 � 0.17 2.1 � 0.51 <0.01
Myocardial T1 pre-contrast, ms 1,217 � 49 1,299 � 80 <0.01
Blood T1 pre-contrast, ms 1,738 � 102 1,694 � 67 0.17
Myocardial T1 post-contrast, ms 440 � 52 395 � 60 0.02
Blood T1 post-contrast, ms 247 � 41 230 � 50 0.08
Focal LGE present (ASB segment), % 0/60 (0) 16/20 (80) <0.01
Extracellular volume fraction, % 24.5 � 3.7 27.2 � 4.1 <0.01
Values are mean � SD or n/n (%).
A ¼ late diastolic peak (pulsed-wave Doppler); a’ ¼ late diastolic mitral annular velocity by Doppler tissueimaging; ASB ¼ anteroseptal basal; BMI ¼ body mass index; BP ¼ blood pressure; BSA ¼ body surface area;CRP ¼ C-reactive protein; DT ¼ deceleration time; E ¼ early diastolic peak (pulsed-wave Doppler); e’ ¼ earlydiastolic mitral annular velocity by Doppler tissue imaging; GS ¼ global strain; HCM ¼ hypertrophic cardiomy-opathy; HFpEF ¼ heart failure with preserved ejection fraction; IVRT ¼ isovolumic relaxation time; LA ¼ leftatrium; LAVI ¼ left atrium volume index; LGE ¼ late gadolinium enhancement; LVEF ¼ left ventricle ejectionfraction; LVEDD ¼ left ventricle end-diastolic diameter; LVESD ¼ left ventricle end-systolic diameter; NYHA ¼New York Heart Association; NTproBNP ¼ N-terminal pro brain natriuretic peptide; PV S/D ratio ¼ pulmonaryveins velocities; Vp ¼ transmitral flow propagation velocity.
J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . - , N O . - , 2 0 1 8 Villemain et al.- 2 0 1 8 :- –- Transthoracic Myocardial Stiffness Assessment in Adults
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STATISTICAL ANALYSIS. Data for continuous vari-ables are presented as mean � SD, if normallydistributed, or as median and interquartile range ifnon-normally distributed. Categorical variables arepresented as frequencies and percentages. Compari-sons between groups were made using chi-squaretests for categorical variables. Continuous variableswere compared with unpaired Student t tests or thenonparametric Mann-Whitney U test where appro-priate. Univariate and stepwise multivariate linearregression analyses were performed to identify pre-dictors of r (standardized coefficient of linearregression). Receiver-operating characteristic (ROC)curves and area under the curve (AUC) werecomputed to assess the effectiveness of MS to predicthealthy or pathologic subjects. Reproducibility of MSestimation (3 months after the first estimation) wastested by the Bland-Altman limits of agreement. Thereproducibility coefficient was calculated as 1.96 �the SD of the differences, as proposed by Bland andAltman (25). All the analyses were conducted usingMedcalc (MedCalc Software, Mariakerke, Belgium).
RESULTS
POPULATION CHARACTERISTICS. A total of 93 sub-jects (69 HV and 24 HCM-HFpEF) were prospectivelyscreened for inclusion into the study (Figure 2). Eightpatients from the HV group were excluded based onthe exclusion criteria (1 congenital heart disease and 1valvulopathy on echocardiography, 1 doubt on infractscar on CMR, 6 anechoic). Two patients of the HCM-HFpEF group were excluded based on the exclusioncriteria (2 infarct scars seen on CMR, 2 anechoic).Finally, 80 subjects were included: HCM-HFpEFgroup (n ¼ 20), HV 20-year-old to 39-year-old group(n ¼ 20), HV 40- to 59-year-old group (n ¼ 20), and HV60- to 79-year-old group (n ¼ 20) (Figure 2).
The molecular genetic causes for the HCM-HFpEFgroup were: 8 mutations of MYH7, 6 mutations ofMYBPC3, 2 mutations of TNNT2, 1 mutation of TPM1, 1mutation of TNNI3, 1 mutation of MYL3, and 1 muta-tion of MYL2.
The subjects’ baseline characteristics includingclinical characteristics, laboratory data, echocardio-graphic results, and CMR results are shown in Table 1.
There is no statistical difference between the HVgroup and the HCM-HFpEF group in terms of age (p ¼0.22), body mass index (BMI) (p ¼ 0.74), and BP (SBP,p ¼ 0.41; DBP, p ¼ 0.47). In both groups, there was nodiabetic patient.
FIGURE 3 Myocardial Stiffness for Healthy Volunteers
0,000
1
2
3
4
5
6
7
8
9
10
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p < 0.01
p < 0.01 p < 0.01
Mean = 4.70 ± 0.88
Mean = 6.08 ± 1.06
Total Mean = 4.47 ± 1.68
HV Linear (HV)
Mean = 2.59 ± 0.58
Age (Years)
Myo
card
ial S
tiffne
ss (k
Pa)
50,00 60,00 70,00 80,00 90,00
Myocardial Stiffness - Healthy Volunteer
y = 0,087x + 0,1248R2 = 0,7722
Myocardial stiffness measured in HV as a function of age. Abbreviation as in Figure 1.
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Concerning theHCM-HFpEF group, 6 patients (30%)had a New York Heart Association (NYHA) functionalclass$III (4 patientswere class III, 2 patientswere classIV). Twenty patients (100%) had a BNP >35 pg/ml.Regarding echocardiographic results, LV mass indexwas significantly higher than the HV group (125 � 34g/m2 vs. 70.6� 20 g/m2; p<0.01), the ASB segmentwassignificantly thicker than the HV group (20.8 � 5.1 mmvs. 5.9� 1.4 mm; p< 0.01), with a segment strain lowerthan the HV group (�6.4 � 3.6% vs. �16.9 � 2.2%; p <
0.01). All the main diastolic function parameters weresignificantly different (p < 0.01) than those of the HVgroup (E/A; e0, E/e0, E-wave DT, IVRT, Vp, E/Vp, PV S/Dratio). Regarding CMR results, 16 of 20 (80%) had anLGE on the ASB segment (p < 0.01). There was a dif-ference between HV and HCM-HFpEF groups con-cerningmyocardial T1 post-contrast (p¼0.02) and ECV(p < 0.01).
MYOCARDIAL STIFFNESS RESULTS. HV group. Themean MS for the HV group was 4.47 � 1.68 kPa(Figure 3). No patient from the HV group had an MSlarger than 8 kPa. The mean MS was 2.59 � 0.58 kPa forthe 20- to 39-year-old HV group, 4.70�0.88 kPa for the40- to 59-year-oldHVgroup, and6.08� 1.06 kPa for the60- to 79-year-old HV group. There was a statisticalsignificant difference between all age groups (p<0.01).
Myocardial stiffness dependence on age. A strong in-crease in MS with age was found (Figure 3). Thecorrelation between age (x) and MS (y) values wasrobust (y ¼ 0.087x þ 0.1248; r2 ¼ 0.77; p < 0.01). Amultivariate linear regression analysis (includingsex, age, BMI, hazard ratio SBP, and DBP) showedthat age was the only clinical parameter correlatedwith MS (age, p < 0.01; sex, p ¼ 0.77; BMI, p ¼0.98; HR, p ¼ 0.88; SBP, p ¼ 0.33; DBP, p ¼ 0.63).The correlation of echocardiographic parametersand age was lower: E/A, r2 ¼ 0.30; E/e0, r2 ¼ 0.23;E/Vp r2 ¼ 0.01 (Online Figure 1). In univariateanalysis for the HV group, there was nocorrelation between LV mass and MS (r ¼ 0.21, p ¼0.44).
HCM-HFpEF group. The mean MS for the HCM-HFpEFgroup was 12.68 � 2.91 kPa. Only 2 patients had anMS value less than 8 kPa (6.46 kPa and 7.97 kPa).The correlation between age and MS values for thispathological group was low (r2 ¼ 0.14, r ¼ 0.37, p <
0.01). We found no difference between MYH7 andMYBPC3 mutation subgroups (p ¼ 0.34).
Comparison between MS healthy and MS HCM-HFpEFgroups. There was a significant statistical differencebetween the MS healthy group and the MS HCM-HFpEF group (p < 0.01) (Figure 4). Based on the
FIGURE 4 Myocardial Stiffness in HCM and HV Groups
0,00 10,00 20,00 30,00 40,00Age (Years)
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ss (k
Pa)
y = 0,087x + 0,1248R2 = 0,7722
y = 0,0631x + 9,1113R2 = 0,1357
Mean = 4.47 ± 1.68
Mean = 12,68 ± 2.91
p < 0.01
HV Versus HCM
HV HCM0123456789
10111213141516
Myo
card
ial S
tiffne
ss (k
Pa)
Mean = 4.47± 1.68
p < 0.01
HV Versus HCM
Mean = 12.68± 2.91
0 20 40 60 80 100100-Specificity
0
20
40
60
80
100
Sens
itivi
ty
MS = 8kPaSe = 95%Sp = 100%AUC = 0.993
ROC Curves for Healthy Volunteer and HCM-HFpEF
HCM Linear(HV)Linear(HCM)HV
Comparison of Myocardial Stiffness between healthy volunteer group (HV) and hypertrophic cardiomyopathy with HFpEF group (HCM group).
AUC ¼ area under the curve; MS ¼ myocardial stiffness; Se ¼ sensitivity; Sp ¼ specificity; ROC ¼ receiver-operating curve; other abbrevi-
ations as in Figures 1 and 2.
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7
ROC curve analysis, the optimal cut-off value of MSfor detection of HCM-HFpEF was 8 kPa (AUC ¼0.993, sensitivity ¼ 95%, specificity ¼ 100%).Correlation of MS with measures of diastolic functionand other parameters. Positive correlations were foundbetween MS and parameters in echocardiography(E/e0, r ¼ 0.783, p < 0.01; E/Vp, r ¼ 0.616, p < 0.01;
left atrial volume index [LAVI], r¼ 0.623, p< 0.01) andCMR (LGE, r ¼ 0.804, p < 0.01; myocardial T1 pre-contrast, r ¼ 0.711, p < 0.01; myocardial T1 post-contrast, r ¼ 0.595, p ¼ 0.01; ECV fraction, r ¼ 0.447,p ¼ 0.03). Correlation of MS with other parameters issummarized in Table 2. There was no correlation be-tween MS and the global strain (r ¼ 0.37, p ¼ 0.27) or
TABLE 2 Myocardial Stiffness Correlations
r p Value
Patient
Age, yrs 0.881 <0.01
Sex, M/F NA NA
BMI, kg/m2 0.089 0.98
Systolic BP, mm Hg 0.207 0.33
Diastolic BP, mm Hg 0.154 0.63
NYHA functional class 0.677 0.02
Biology (blood explorations)
CRP, mg/l 0.217 0.36
NTproBNP, pg/ml 0.413 0.06
Hematocrit, % 0.299 0.15
Echocardiography parameters
LA surface, 4 cavities view, cm2 0.378 0.21
LAVI, ml/m2 0.623 <0.01
LVEF, % 0.204 0.45
LVEDD, mm 0.266 0.51
LVESD, mm 0.178 0.76
LV mass/BSA, g/m2 0.329 0.23
LV GS, % 0.378 0.27
ASB segment GS, % 0.420 0.09
ASB segment end diastolic thickness, mm 0.277 0.31
Peak E-wave, cm/s 0.304 0.30
E/A 0.506 0.01
e’ septal, cm/s 0.365 0.39
E/e’ 0.783 <0.01
e’/a’ septal 0.452 0.07
E-wave DT, ms 0.511 0.02
IVRT, ms 0.361 0.14
Vp, cm/s 0.219 0.55
E/Vp 0.616 <0.01
PV S/D ratio 0.422 0.10
Cardiac magnetic resonance
ASB segment end diastolic thickness, mm 0.325 0.17
LV mass/LVED volume, g/ml 0.388 0.11
Myocardial T1 pre-contrast, ms 0.711 <0.01
Blood T1 pre-contrast, ms 0.195 0.67
Myocardial T1 post-contrast, ms 0.595 0.01
Blood T1 post-contrast, ms 0.101 0.77
Focal LGE present, ASB segment 0.804 <0.01
Extracellular volume fraction, % 0.447 0.03
NA ¼ not available; other abbreviations as in Table 1.
Villemain et al. J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . - , N O . - , 2 0 1 8
Transthoracic Myocardial Stiffness Assessment in Adults - 2 0 1 8 :- –-
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the septal strain (r ¼ 0.4, p ¼ 0.09). There wasno correlation between MS and BNP (r ¼ 0.41, p ¼0.06).Reproducibility. Among the 15 HV patients who were re-evaluated 3 months later, there was no statistical dif-ference with the initial assessment (mean MS ¼ 4.26 �1.36 kPa; p ¼ 0.67). Moreover, Bland-Altman analysisshowed good agreement between measurements:MS þ0.08 kPa (upper limit of agreement: þ0.89 kPa;lower limit of agreement:�0.73 kPA) (Online Figure 2).
FRACTIONAL ANISOTROPY. The mean FA for the HVgroup (0.238 � 0.068) was higher than that for the
HCM-HFpEF group (0.133 � 0.073; p < 0.01). Eighteenof 20 patients (90%) from the HCM-HFpEF group hadan FA less than 0.155 whereas 56 of 60 patients (93%)from the HV group had an FA larger than this cut-off(AUC ¼ 0.891, sensibility ¼ 90%, specificity ¼ 91.2%)(Figure 5).
DISCUSSION
In this study, MS was assessed quantitatively usingnoninvasive SWI in HV and HCM patients with HFpEF.To our knowledge, this is the first study to assess MSquantitatively and noninvasively in both HV andpathological cases (HCM-HFpEF). This study showedthat SWI allows us to establish values of MS in a HVpopulation, MS increases strongly with age in thenormal heart, and there is a large difference in MSbetween HV and HCM-HFpEF groups (cutoff ¼ 8 kPa).
In this study we were able to quantify MS aging. Inthe NORRE (Normal Reference Ranges for Echocardi-ography) study, Caballero et al. (26) also found agradual change with age of the main echocardio-graphic parameters of the diastolic function. In thisstudy, which analyzed 449 HV echocardiographs, theE/e0 ratio increased from an average of 6.9 � 1.6 in 20-to 39-year-old subjects to an average of 9.7 � 2.8 in 60-to 79-year-old subjects, a change of approximately50% with a fairly linear evolution. Myocardial agingwas also evaluated by CMR on a human population(27) or by invasive estimation on animal study (28). In1991, Weger et al. (29) have well demonstrated that theage-induced physiological myocardial fibrosis impactson the cardiac function, including the ability of theventricle to relax during the diastolic filling (auxotonicrelaxation). Regarding HV patients who participatedin our study, we also found a linear evolution of MS,allowing us to establish the change of MS with age.
We also showed an MS difference between HV andHCM-HFpEF noninvasively. Zile et al. (30) have shownon myocardial histologic explorations of HFpEF pa-tients that an increase in passive MS is due to anarchitectural modification (increase of collagen andtitin). Moreover, in a systematic review on HCM pub-lished in 2002, Barry J. Maron (3) noted that the “LVmyocardial architecture is disorganized [.] withmultiples intercellular connections often arranged onchaotic alignment and with expanded interstitial(matrix) collagen,” which is supported by previouswork that tried to link myocardial histological explo-rations and MS (31). Our study shows that theabnormal MS of this characteristic pathological group(HCM-HFpEF) can be quantified noninvasively. Inaddition, SWI provided information on myocardialarchitecture through the analysis of the FA which
FIGURE 5 Fractional Anisotropy
HCM Linear(HCM)Linear(HV)HV
Mean = 0.238 ± 0.068
Mean = 0.133 ± 0.073
p < 0.01
y = 0,0006x + 0,102R2 = 0,0166
y = 0,0009x + 0,1914R2 = 0,052
0,00 10,00 20,00 30,00 40,00Age (Years)
Frac
tiona
l Ani
sotr
opy
(Equ
atio
n 2)
Fractional Anisotropy of HV and HCM
50,00 60,00 70,00 80,00 90,000
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
0,45
Frac
tiona
l Ani
sotr
opy
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
HV HCM
Mean = 0.238± 0.068
Mean = 0.133± 0.073
p < 0.01
FA - HV Versus HCM
Comparison of fractional anisotropy (FA) between healthy volunteer group (HV) and hypertrophic cardiomyopathy with HFpEF group (HCM group).
J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . - , N O . - , 2 0 1 8 Villemain et al.- 2 0 1 8 :- –- Transthoracic Myocardial Stiffness Assessment in Adults
9
revealed differences between the tissue architectureof the 2 groups, with a decrease of the physiologicalanisotropy in the HCM-HFpEF group. However, theclinical interest of this parameter must be furtherinvestigated and analyzed on more patients and otherpathological groups.
Beyond the analysis of viscoelastic properties and oftissue structure, the comparison of MS with the rec-ommended ultrasound parameters used to assess thediastolic function seems to show that this quantitativeparameter could help to distinguish patients withdiastolic dysfunction from others. Obviously, the dia-stolic function analysis remains complex and it wouldbe unrealistic to think that 1 quantitative parametercould define the LV diastolic function. For example,LAVI >34 ml/m2 is a key structural alteration allowingthe definition the diagnostic of HFpEF (19), but Ca-ballero et al. (26) have also clarified that 15.1% of hea-thy people have a LAVI >34 ml/m2 whereas only 0.5%have an E/e0 ratio >15. Nevertheless, the MS assess-ment of patients with HFpEF has clearly helped toimprove understanding of this disease (32). Perform-ing the assessment noninvasively would refine ourdiagnostic capabilities and may help us to understanddisease “at the bedside,”with a noninvasive approach.
Beyond the diagnostic contribution that the evalu-ation of MS by SWI could represent, the prospects oftherapeutic follow-up could be interesting. The cur-rent finding is that there is no specific medical treat-ment of diastolic dysfunction in HCM. This is probablydue to the fact that there is as yet nomedical treatment
with a high expected efficacy in HFpEF, as recalled inthe recent European guidelines: “No treatment has yetbeen shown, convincingly, to reduce morbidity ormortality in patients with HFpEF” (19). NoninvasiveMS assessment could be a major tool for the develop-ment of novel treatments of HCM and/or HFpEF.Thanks to this noninvasive MS marker, the impact ofcertain treatments (angiotensin-converting enzymeinhibitors or mineralocorticoid/aldosterone receptorantagonists, for example) could be evaluatedquantitatively.
Finally, we have observed a good reproducibilityof the MS assessment. Despite the small size of thisanalysis group (n ¼ 15), which limits its interpreta-tion, these results indicate that this technique couldbe used to evaluate a patient through longitudinalfollow up. We did not re-evaluate the reproducibilityof this technique on HCM-HFpEF groups because it isstill difficult to estimate the impact of the diseaseevolution on the MS results, and the treatments ofthese patients were modified after the initial evalu-ation and could change their diastolic function (andmaybe their myocardial structure).
STUDY LIMITATIONS. This was a monocentric study,and on a small sample. Therefore, it is difficult toextrapolate these results to a general population,which would require larger population groups. Thegold standard of MS assessment remains an invasivemeasurement with a conductance catheter. From aregulatory point-of-view, this exploration could not beachieved on HV patients recruited exclusively for this
PERSPECTIVES
COMPETENCY IN MEDICAL KNOWLEDGE: This
study is the first, to our knowledge, to quantify MS in
patients using noninvasive SWI. It opens the path to
the clinical evaluation of LV function using a new
parameter relatively independent of loading. We
expect this parameter to be robust, stable, and
representative of the myocardial LV diastolic function.
TRANSLATIONAL OUTLOOK: Future studies
should address the evaluation of this new parameter
in systolic and diastolic heart failure patients and
whether this parameter could improve the diagnosis
and prognosis of this population.
Villemain et al. J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . - , N O . - , 2 0 1 8
Transthoracic Myocardial Stiffness Assessment in Adults - 2 0 1 8 :- –-
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study, notably because of the risks inherent to thisinvasive exploration. However, previous work on ananimal model had shown a strong correlation betweenMS estimated by SWI and MS estimated through theend-diastolic strain-stress relationship (14,15). Inaddition, the noninvasive echocardiographic evalua-tion of MS has been shown possible by extrapolatingthe LV volume-pressure curve (end-diastolic pressurevolume relationship) knowing a single-beat point,based on Doppler and bidimensional data (volume)(33–35). It will be interesting in future studies tocompare the MS estimated by SWI with this noninva-sive method. Concerning the HCM-HFpEF group, nocatheterization was provided in the management ofthese patients during the time of the study. Anotherlimitation of our study is the local evaluation of MS bythe SWI. Indeed, we compared global functionalparameter (E/e0, E/Vp, or LAVI) with a segmentalparameter (MS of the ASB segment). Nonetheless, thesame segment was analyzed for all people included inthe study. This study was limited to the basal septum.Themain reason is that we used a conventional phasedarray with an elevation focus at 70 mm which limitedthe generation of the shear waves at higher depth. Toaddress other segments, the development of dedicatedprobes will be required.
CONCLUSIONS
In this study, we quantitatively assessed the end-diastolic MS in adult HV patients using SWI in the HVand sarcomeric HCM with HFpEF patients. MS wasfound to increase with age, and a cut-off of 8 kPaallowed clear differentiation of these 2 groups. The FAobtained by SWI reflected the underlying tissuestructure modifications. Thanks to this ultrasound
technology, the noninvasive assessment of MS en-ables a new diagnostic option in cardiology. Futurestudies will aim to evaluate MS on other heart dis-eases, such as isolated HFpEF, HF with reduced EF,hypertension, diabetes cases with HFpEF, or othercardiomyopathies to determine the impact of thisparameter in clinical practice.
ACKNOWLEDGEMENTS The authors thank the FrenchSociety of Cardiology and the team of the ClinicalInvestigation Center (Centre d’Investigation Clinique,HEGP, INSERM) and the Clinical Research Unity (Unitéde Recherche Clinique, URC-HEGP) for their support.
ADDRESS FOR CORRESPONDENCE: Dr. MathieuPernot, Institut Langevin, ESPCI, CNRS, Inserm U979,PSL Research University, 17 rue Moreau, 75012 Paris,France. E-mail: [email protected].
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KEY WORDS diastolic function,echocardiography, myocardial stiffness,myocardium
APPENDIX For supplemental methods,figures, and a video, please see the onlineversion of this article.
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