Left Ventricular Chamber Stiffness Research Articles

Left ventricle function and post-transcriptional events with exercise training in pigs.

Standardized exercise protocols have been shown to improve overall cardiovascular fitness, but direct effects on left ventricular (LV) function, particularly diastolic function and relation to post-transcriptional molecular pathways (microRNAs (miRs)) are poorly understood. This project tested the central hypothesis that adaptive LV remodeling resulting from a large animal exercise training protocol, would be directly associated with specific miRs responsible for regulating pathways relevant to LV myocardial stiffness and geometry. Pigs (n = 9; 25 Kg) underwent a 4 week exercise training protocol (10 degrees elevation, 2.5 mph, 10 min, 5 days/week) whereby LV chamber stiffness (KC) and regional myocardial stiffness (rKm) were measured by Doppler/speckle tracking echocardiography. Age and weight matched non-exercise pigs (n = 6) served as controls. LV KC fell by approximately 50% and rKm by 30% following exercise (both p < 0.05). Using an 84 miR array, 34 (40%) miRs changed with exercise, whereby 8 of the changed miRs (miR-19a, miR-22, miR-30e, miR-99a, miR-142, miR-144, miR-199a, and miR-497) were correlated to the change in KC (r ≥ 0.5 p < 0.05) and mapped to matrix and calcium handling processes. Additionally, miR-22 and miR-30e decreased with exercise and mapped to a localized inflammatory process, the inflammasome (NLRP-3, whereby a 2-fold decrease in NLRP-3 mRNA occurred with exercise (p < 0.05). Chronic exercise reduced LV chamber and myocardial stiffness and was correlated to miRs that map to myocardial relaxation processes as well as local inflammatory pathways. These unique findings set the stage for utilization of myocardial miR profiling to identify underlying mechanisms by which exercise causes changes in LV myocardial structure and function.

Evaluation of left ventricular stiffness with echocardiography.

Half of patients with heart failure are presented with preserved ejection fraction (HFpEF). The pathophysiology of these patients is complex, but increased left ventricular (LV) stiffness has been proven to play a key role. However, the application of this parameter is limited due to the requirement for invasive catheterization for its measurement. With advances in ultrasound technology, significant progress has been made in the noninvasive assessment of LV chamber or myocardial stiffness using echocardiography. Therefore, this review aims to summarize the pathophysiological mechanisms, correlations with invasive LV stiffness constants, applications in different populations, as well as the limitations of echocardiography-derived indices for the assessment of both LV chamber and myocardial stiffness. Indices of LV chamber stiffness, such as the ratio of E/e' divided by left ventricular end-diastolic volume (E/e'/LVEDV), the ratio of E/SRe (early diastolic strain rates)/LVEDV, and diastolic pressure-volume quotient (DPVQ), are derived from the relationship between echocardiographic parameters of LV filling pressure (LVFP) and LV size. However, these methods are surrogate and lumped measurements, relying on E/e' or E/SRe for evaluating LVFP. The limitations of E/e' or E/SRe in the assessment of LVFP may contribute to the moderate correlation between E/e'/LVEDV or E/SRe/LVEDV and LV stiffness constants. Even the most validated measurement (DPVQ) is considered unreliable in individual patients. In comparison to E/e'/LVEDV and E/SRe/LVEDV, indices like time-velocity integral (TVI) measurements of pulmonary venous and transmitral flows may demonstrate better performance in assessing LV chamber stiffness, as evidenced by their higher correlation with LV stiffness constants. However, only one study has been conducted on the exploration and application of TVI in the literature, and the accuracy of assessing LV chamber stiffness remains to be confirmed. Regarding echocardiographic indices for LV myocardial stiffness evaluation, parameters such as epicardial movement index (EMI)/ diastolic wall strain (DWS), intrinsic velocity propagation of myocardial stretch (iVP), and shear wave imaging (SWI) have been proposed. While the alteration of DWS and its predictive value for adverse outcomes in various populations have been widely validated, it has been found that DWS may be better considered as an overall marker of cardiac function performance rather than pure myocardial stiffness. Although the effectiveness of iVP and SWI in assessing left ventricular myocardial stiffness has been demonstrated in animal models and clinical studies, both indices have their limitations. Overall, it seems that currently no echocardiography-derived indices can reliably and accurately assess LV stiffness, despite the development of several parameters. Therefore, a comprehensive evaluation of LV stiffness using all available parameters may be more accurate and enable earlier detection of alterations in LV stiffness.

Kiosk 6R-FB-10 - Non-invasive Prediction of Increased Left Ventricular Chamber Stiffness Using Echocardiography and Cardiac Magnetic Resonance Imaging

Kiosk 6R-FB-10 - Non-invasive Prediction of Increased Left Ventricular Chamber Stiffness Using Echocardiography and Cardiac Magnetic Resonance Imaging

Catestatin Protects Against Diastolic Dysfunction by Attenuating Mitochondrial Reactive Oxygen Species Generation.

Background Catestatin has been reported as a pleiotropic cardioprotective peptide. Heart failure with preserved ejection fraction (HFpEF) was considered a heterogeneous syndrome with a complex cause. We sought to investigate the role of catestatin in HFpEF and diastolic dysfunction. METHODS AND RESULTS Administration of recombinant catestatin (1.5 mg/kg/d) improved diastolic dysfunction and left ventricular chamber stiffness in transverse aortic constriction mice with deoxycorticosterone acetate pellet implantation, as reflected by Doppler tissue imaging and pressure-volume loop catheter. Less cardiac hypertrophy and myocardial fibrosis was observed, and transcriptomic analysis revealed downregulation of mitochondrial electron transport chain components after catestatin treatment. Catestatin reversed mitochondrial structural and respiratory chain component abnormality, decreased mitochondrial proton leak, and reactive oxygen species generation in myocardium. Excessive oxidative stress induced by Ru360 abolished catestatin treatment effects on HFpEF-like cardiomyocytes in vitro, indicating the beneficial role of catestatin in HFpEF as a mitochondrial ETC modulator. The serum concentration of catestatin was tested among 81 patients with HFpEF and 76 non-heart failure controls. Compared with control subjects, serum catestatin concentration was higher in patients with HFpEF and positively correlated with E velocity to mitral annular e' velocity ratio, indicating a feedback compensation role of catestatin in HFpEF. Conclusions Catestatin protects against diastolic dysfunction in HFpEF through attenuating mitochondrial electron transport chain-derived reactive oxygen species generation. Serum catestatin concentration is elevated in patients with HFpEF, probably as a relatively insufficient but self-compensatory mechanism.

Dantrolene improves left ventricular diastolic property in mineralcorticoid-salt-induced hypertensive rats

Left ventricular (LV) diastolic dysfunction is increasingly common in heart failure with preserved ejection fraction (HFpEF), and new drug therapy is desired. We recently reported that dantrolene (DAN) attenuates pressure-overload induced hypertrophic signaling through stabilization of tetrameric structure of cardiac ryanodine receptor (RyR2). Because cardiac hypertrophy substantially affects LV diastolic properties, we investigated the effect of DAN on LV diastolic properties in mineralocorticoid-salt–induced hypertensive rat model exhibiting the HFpEF phenotype.Male Sprague-Dawley (SD) rats (8 weeks old) received an uninephrectomy (UNX), subcutaneous implantation of a 200 mg pellet of deoxycorticosterone acetate (DOCA), and 0.9% NaCl water (UNX + DOCA-salt). UNX, a control pellet, and water without NaCl served as controls (UNX control). The effect of oral administration of 100 mg/kg/d DAN was examined in UNX control and UNX + DOCA-salt groups (UNX + DAN and UNX + DOCA-salt + DAN).UNX + DOCA-salt treatment resulted in mild hypertension. Chronic administration of DAN to UNX + DOCA-salt rats (UNX + DOCA-salt + DAN) did not affect blood pressure. DAN treatment increased the mitral annular early relaxation velocity in the UNX + DOCA-salt group. The size of cardiomyocytes increased in the UNX + DOCA-salt group, whereas the increase was suppressed by DAN treatment. LV fibrotic area was significantly smaller in the UNX + DOCA-salt + DAN group than in the UNX + DOCA-salt group (2.0 ± 0.2% vs 4.0 ± 0.4%). The LV chamber stiffness significantly increased in the UNX + DOCA-salt group, whereas the increase was suppressed by DAN treatment. DAN treatment normalized the CaM-RyR2 interaction and inhibited aberrant Ca2+ release.DAN improved left ventricular diastolic properties with respect to both myocardial relaxation and chamber stiffness. DAN may be a new treatment option for HFpEF.

Prognostic value of left ventricular chamber stiffness and heart failure in patients with severe aortic stenosis undergoing aortic valve replacement

Abstract Background Increased left ventricular (LV) stiffness (LVStiffn) was shown to be associated with mortality in patients with severe aortic stenosis (AS), despite aortic valve replacement (AVR), and may contribute to future heart failure (HF) symptoms. The aim was to assess whether preoperative LVStiffn is a risk factor of HF in these patients. Methods A retrospective analysis was done in patients with severe AS who underwent AVR (93% surgical). LV end-diastolic pressure-volume relations (P=aVb) were reconstructed from LV end-diastolic volumes and estimated end-diastolic pressures (from E/e'); LVStiffn at 30 mmHg (CS30) and capacitance (V30) were then derived. Primary endpoint was development of symptomatic HF at &amp;gt;1 month post AVR. Results 1,837 patients were studied (age 76±10 years, 62% males, LVEF 61±12%; Table). Mean CS30 was 2.2±1.3 mmHg/mL and V30 64±17 mL/m2. Patients with higher CS30 ≥3 mmHg/mL were older, more frequently female, and had more comorbidities. During a median follow-up of 5.0 [3.0–7.9] years, 607 (33%) patients developed HF. A higher CS30 (≥3 mmHg/mL), but not V30 (P=0.32), was associated with higher risk of HF events (HR 1.86 [95% CI 1.52–2.27], P&amp;lt;0.0001), along with other clinical and echo predictors (Table). In multivariate analysis, adjusting for age, sex, comorbidities, advanced NYHA class III–IV, creatinine &amp;gt;1.5 mg/dL, medication use, severity of AS, reduced LVEF &amp;lt;50%, diastolic dysfunction grade ≥2, right ventricular size and pulmonary hypertension, a higher CS30 ≥3 mmHg/mL remained independently associated with HF events (adjusted HR 1.61 [1.29–2.01], P&amp;lt;0.0001; Figure). Conclusion Increased LVStiffn in patients with severe AS undergoing AVR is associated with HF at follow-up, despite the benefits brought by AVR, and can help identify patients with poorer outcomes who may need closer monitoring/more intensive treatment of comorbidities Funding Acknowledgement Type of funding sources: None.

Myocardial stiffness assessed by shear wave elastography relates to pressure-volume loop derived measurements of chamber stiffness

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundations Flanders Background Increased myocardial stiffness is an important cause of diastolic dysfunction. Currently, invasive pressure-volume loop analysis is the gold standard method for the assessment of the left ventricular (LV) chamber stiffness. Its non-invasive assessment in the clinic is cumbersome, requires the combination of several parameters and has limited reliability. Shear wave elastography (SWE) is a novel method that evaluates the propagation of shear waves travelling along the myocardium using high frame rate echocardiography. The propagation speed is directly related to myocardial stiffness. Shear waves can be induced naturally by mitral valve closure (MVC). So far, the in vivo validation of SWE against an invasive gold standard reference method is still lacking. Purpose To compare myocardial stiffness assessed by shear wave propagation speed after MVC to invasive pressure-volume loop derived measurements of chamber stiffness. Methods Fifteen pigs (31.2 ± 4.1 kg) were included in the study. The instantaneous stiffness of the myocardium was altered by performing the following interventions: 1) preload reduction, 2) afterload increase, 3) preload increase and 4) induction of ischemia/reperfusion (I/R) injury by balloon occlusion of the proximal LAD for 90 min. with subsequent reperfusion of 40 min. To obtain the end-diastolic pressure-volume loop relation (EDPVR), a set of pressure-volume loops was acquired under preload reduction. From the EDPVR, the chamber stiffness constant β and operating chamber stiffness dP/dV were derived. SWE datasets in a parasternal long-axis view were acquired with an experimental ultrasound scanner at an average frame rate of 1304 ± 115 Hz. Shear waves after MVC were visualized on tissue acceleration maps by drawing an M-mode line along the interventricular septum (Figure 1A). The propagation speed was calculated by semi-automatically measuring the spatiotemporal slope. Results The chamber stiffness constant β significantly increased after the induction of the I/R injury (0.05 ± 0.01 1/ml vs. 0.09 ± 0.03 1/ml; p &amp;lt; 0.001). The operating chamber stiffness dP/dV decreased by reducing preload and increased by increasing afterload, increasing preload or by inducing an I/R injury (0.50 ± 0.18 mmHg/ml vs. 0.09 ± 0.05 mmHg/ml, 0.67 ± 0.19 mmHg/ml, 0.78 ± 0.35 mmHg/ml and 1.09 ± 0.38 mmHg/ml, respectively; p &amp;lt; 0.01). Likewise, shear wave propagation speed after MVC increased by increasing pre- and afterload (p = 0.001) and by inducing I/R injury (p &amp;lt; 0.001) (Figure 1B). Preload reduction had no significant influence (p = 0.118). Shear wave speed had a strong positive correlation with β (r = 0.63; p &amp;lt; 0.001) (Figure 1C) and dP/dV (r = 0.81; p &amp;lt; 0.001) (Figure 1D). Conclusions Shear wave speed after MVC is strongly related to invasive pressure-volume loop derived measures of chamber stiffness. The results of this study indicate the potential of SWE as a novel non-invasive method for the assessment of the instantaneous stiffness of the myocardium. Abstract Figure.

Mild aortic valve disease and the diastolic pressure–volume relationship in heart failure with preserved ejection fraction

ObjectiveMild aortic valve stenosis (AS) and aortic valve (AV) sclerosis are associated with diastolic dysfunction and increased mortality in the general population. This study specifically investigated the impact of mild...

Paired Pressure-Volume Loop Analysis and Biaxial Mechanical Testing Characterize Differences in Left Ventricular Tissue Stiffness of Volume Overload and Angiotensin-Induced Pressure Overload Hearts.

Pressure overload (PO) and volume overload (VO) of the heart result in distinctive changes to geometry, due to compensatory structural remodeling. This remodeling potentially leads to changes in tissue mechanical properties. Understanding such changes is important, as tissue modulus has an impact on cardiac performance, disease progression, and influences on cell phenotype. Pressure-volume (PV) loop analysis, a clinically relevant method for measuring left ventricular (LV) chamber stiffness, was performed in vivo on control rat hearts and rats subjected to either chronic PO through Angiotensin-II infusion (4-weeks) or VO (8-weeks). Immediately following PV loops, biaxial testing was performed on LV free wall tissue to directly measure tissue mechanical properties. The β coefficient, an index of chamber stiffness calculated from the PV loop analysis, increased 98% in PO (n = 4) and decreased 38% in VO (n = 5) compared to control (n = 6). Material constants of LV walls obtained from ex vivo biaxial testing (n = 9-10) were not changed in Angiotensin-II induced PO and decreased by about half in VO compared to control (47% in the circumferential and 57% the longitudinal direction). PV loop analysis showed the expected increase in chamber stiffness of PO and expected decrease in chamber stiffness of VO. Biaxial testing showed a decreased modulus of the myocardium of the VO model, but no changes in the PO model, this suggests the increased chamber stiffness in PO, as shown in the PV loop analysis, may be secondary to changes in tissue mass and/or geometry but not an increase in passive tissue mechanical properties.

Myocardial Native T1 Predicts Load-Independent Left Ventricular Chamber Stiffness In Patients With HFpEF

ObjectivesThis study sought to evaluate the potential of cardiac magnetic resonance T1 mapping to detect load-independent left ventricular (LV) chamber stiffness by histological confirmation. BackgroundAccurate noninvasive diagnosis of LV diastolic dysfunction in heart failure with preserved ejection fraction (HFpEF) remains challenging. MethodsNineteen HFpEF patients (14 female, 65 ± 16 years of age) without primary cardiomyopathy were prospectively enrolled. Cine, late gadolinium enhancement cardiac magnetic resonance, and triple-slice T1 mapping using a modified Look-Locker inversion recovery sequence were performed at 3-T. Extracellular volume (ECV) was quantified from pre- and post-contrast T1 values of the blood and myocardium with hematocrit correction. LV stiffness constant (beta) was assessed by calculating the slope of the end-diastolic pressure–volume relationship curve during vena cava occlusion. Biopsy samples were used for quantification of collagen volume fraction (CVF) and myocardial cell size. ResultsSix patients showed focal scar on late gadolinium enhancement. There was no significant difference in histological CVF between patients with and without focal myocardial scarring (p = 0.2). Septal ECV rather than native T1 was a better surrogate marker for detecting histological CVF (r = 0.54; p = 0.02, and r = 0.44; p = 0.06, respectively). Global native T1 and ECV, but not native T1 and ECV in the septal myocardium, correlated well with the beta of passive LV stiffness, and had similar ability for predicting LV stiffness to histological CVF (r = 0.54, 0.50, 0.53, all p < 0.05, respectively). When the beta ≥0.054 was considered as moderately increased LV stiffness, global native T1 ≥1,362 ms provided 88% sensitivity and 64% specificity with the C-statistic of 0.81 (95% confidence interval: 0.56 to 0.95). ConclusionsMyocardial native T1 provides comparable ability in predicting LV stiffness to ECV and histological CVF and may be useful for monitoring patients with HFpEF who have renal dysfunction, allergy to gadolinium, or wheezing that can simulate asthma. Our feasibility study shows the potential of native T1 to allow for insight of heterogeneous pathophysiology and better risk stratification of HFpEF.

Phosphodiesterase 9a Inhibition in Mouse Models of Diastolic Dysfunction.

Low myocardial cGMP-PKG (cyclic guanosine monophosphate-protein kinase G) activity has been associated with increased cardiomyocyte diastolic stiffness in heart failure with preserved ejection fraction. Cyclic guanosine monophosphate is mainly hydrolyzed by PDE (phosphodiesterases) 5a and 9a. Importantly, PDE9a expression has been reported to be upregulated in human heart failure with preserved ejection fraction myocardium and chronic administration of a PDE9a inhibitor reverses preestablished cardiac hypertrophy and systolic dysfunction in mice subjected to transverse aortic constriction (TAC). We hypothesized that inhibiting PDE9a activity ameliorates diastolic dysfunction. To examine the effect of chronic PDE9a inhibition, 2 diastolic dysfunction mouse models were studied: (1) TAC-deoxycorticosterone acetate and (2) Leprdb/db. PDE9a inhibitor (5 and 8 mg/kg per day) was administered to the mice via subcutaneously implanted osmotic minipumps for 28 days. The effect of acute PDE9a inhibition was investigated in intact cardiomyocytes isolated from TAC-deoxycorticosterone acetate mice. Atrial natriuretic peptide together with PDE9a inhibitor were administered to the isolated intact cardiomyocytes through the cell perfusate. For acute inhibition, no cellular stiffness reduction was found, whereas chronic PDE9a inhibition resulted in reduced left ventricular chamber stiffness in TAC-deoxycorticosterone acetate, but not in Leprdb/db mice. Passive cardiomyocyte stiffness was reduced by chronic PDE9a inhibition, with no differences in myocardial fibrosis or cardiac morphometry. PDE9a inhibition increased the ventricular-arterial coupling ratio, reflecting impaired systolic function. Chronic PDE9a inhibition lowers left ventricular chamber stiffness in TAC-deoxycorticosterone acetate mice. However, the usefulness of PDE9a inhibition to treat high-diastolic stiffness may be limited as the required PDE9a inhibitor dose also impairs systolic function, observed as a decline in ventricular-arterial coordination, in this model.

Changes in Myocardial Microstructure and Mechanics With Progressive Left Ventricular Pressure Overload

This study assessed the regional changes in myocardial geometry, microstructure, mechanical behavior, and properties that occur in response to progressive left ventricular pressure overload (LVPO) in a large animal model. Using an index of local biomechanical function at early onset of LVPO allowed for prediction of the magnitude of left ventricular chamber stiffness (Kc) and left atrial area at LVPO late timepoints. Our study found that LV myocardial collagen content alone was insufficient to identify mechanisms for LV myocardial stiffness with progression to heart failure with preserved ejection fraction (HFpEF). Serial assessment of regional biomechanical function might hold value in monitoring the natural history and progression of HFpEF, which would allow evaluation of novel therapeutic approaches.

Predictive value of left ventricular diastolic chamber stiffness in patients with severe aortic stenosis undergoing aortic valve replacement.

Despite improvements in cardiac haemodynamics and symptoms, long-term mortality remains increased in some patients after aortic valve replacement (AVR). Limited data exist on the prognostic role of left ventricular (LV) chamber stiffening in these patients. We performed a retrospective analysis in 1893 patients with severe aortic stenosis (AS) referred for AVR. LV end-diastolic pressure-volume relations (EDPVR, P = αV^β) were reconstructed from echocardiographic measurements of end-diastolic volumes and estimates of end-diastolic pressure (EDP). The impact of EDPVR-derived LV chamber stiffness (CS30, at 30 mmHg EDP) on all-cause mortality after AVR was evaluated. Mean age was 76 ± 10 years, 39% were females, and ejection fraction (EF) was 61 ± 12%. The mean LV chamber stiffness (CS30) was 2.2 ± 1.3 mmHg/mL. A total of 877 (46%) patients had high LV stiffness (CS30 >2 mmHg/mL). In these patients, the EDPVR curves were steeper and shifted leftwards, indicating higher stiffness at all pressure levels. These patients were slightly older, more often female, and had more prevalent comorbidities compared to patients with low stiffness. At follow-up [median 4.2 (interquartile range 2.8-6.3) years; 675 deaths], a higher CS30 was associated with lower survival (hazard ratio: 2.7 for severe vs. mild LV stiffening; P < 0.0001), both in patients with normal or reduced EF. At multivariate analysis, CS30 remained an independent predictor, even after adjusting for age, sex, comorbidities, EF, LV remodelling, and diastolic dysfunction. Higher preoperative LV chamber stiffening in patients with severe AS is associated with poorer outcome despite successful AVR.

P4351Validation by cardiac catheterization of noninvasive evaluation of left ventricular chamber and myocardial stiffness as a diastolic function using speckle tracking echocardiography

Abstract Background Left ventricular (LV) diastolic function is mainly composed of LV relaxation and LV stiffness. We reported that pulmonary capillary wedge pressure (ePCWP) and LV relaxation assessed by Tau (eTau) are noninvasively evaluated by speckle tracking echocardiography (STE). The minimum LV diastolic pressure (mLVP) was reported to have a strong correlation with Tau. Therefore, LV chamber stiffness (c-stiffness) may be assessed with the use of two LV diastolic pressure-volume coordinates: the mLVP and volume and the end-diastolic pressure (EDP) and volume. Purpose We sought to noninvasively assess LV stiffness using STE and validate the value by cardiac catheterization. Methods Echocardiography and catheterization were performed in 124 patients (age 72±8) (70 angina pectoris, 20 prior myocardial infarction, 19 hypertensive heart disease, 11 congestive heart failure and 4 paroxysmal atrial fibrillation). The ePCWP (mmHg) is noninvasively obtained as 10.8 − 12.4 × Log (left atrial active emptying function/minimum volume) and the eTau (ms) is obtained as isovolumic relaxation time/(ln 0.9 × systolic blood pressure − ln ePCWP) as previously reported. The mLVP (e-mLVP) was estimate using Tau. The estimated EDP (e-EDP) was calculated as 12.3 − 10.1 × Log (left atrial active emptying function / minimum volume). LV c-stiffness (mmHg/ml) was calculated as LV pressure change (from mLVP to EDP) obtained by catheterization divided by LV volume change during diastole which equals to stroke volume by echocardiography. Estimated c-stiffness (e-c-stiffness) was noninvasively obtained using e-mLVP and e-EDP. Furthermore, LV myocardial stiffness (m-stiffness) was calculated by LVED stress / LV longitudinal strain by STE, where LV stress (kdynes/cm2) was calculated as 0.334 × pressure × dimension / [thickness (1 + thickness/dimension)]. The estimated m-stiffness (e-m-stiffness) was calculated using e-EDP. Results The eTau and e-EDP estimated by STE had a good correlation with Tau and EDP invasively obtained by catheterization (r=0.75 and 0.63, respectively, both p&lt;0.001). There was a good correlation between Tau and mLVP (Tau = 2.06 mLVP + 33.7, r=0.70). The estimated LVED stress had good correlation with ED stress obtained by catheterization (r=0.77, p&lt;0.001). The e-c-stiffness and e-m-stiffness had a good correlation with those obtained by catheterization (e-c-stiffness; 0.116±0.07 and c-stiffness; 0.115±0.06, r=0.603, e-m-stiffness; 0.81±0.41 and m-stiffness; 0.85±0.45, r=0.89, respectively). Bland-Altman analysis revealed a good agreement between e-c-stiffness and c-stiffness, and between e-m-stiffness and m-stiffness without fixed and proportional bias. Conclusion This study demonstrated that LV stiffness may be noninvasively assessed by STE with reasonable accuracy and may have utility and value in the routine clinical practice for the diagnosis and treatment in patients with diastolic dysfunction.

Metformin improves diastolic function in an HFpEF-like mouse model by increasing titin compliance.

Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome characterized by a preserved ejection fraction but increased diastolic stiffness and abnormalities of filling. Although the prevalence of HFpEF is high and continues to rise, no effective therapies exist; however, the diabetic drug metformin has been associated with improved diastolic function in diabetic patients. Here we determine the therapeutic potential of metformin for improving diastolic function in a mouse model with HFpEF-like symptoms. We combine transverse aortic constriction (TAC) surgery with deoxycorticosterone acetate (DOCA) supplementation to obtain a mouse model with increased diastolic stiffness and exercise intolerance. Echocardiography and pressure-volume analysis reveal that providing metformin to TAC/DOCA mice improves diastolic function in the left ventricular (LV) chamber. Muscle mechanics show that metformin lowers passive stiffness of the LV wall muscle. Concomitant with this improvement in diastolic function, metformin-treated TAC/DOCA mice also demonstrate preserved exercise capacity. No metformin effects are seen in sham operated mice. Extraction experiments on skinned ventricular muscle strips show that the metformin-induced reduction of passive stiffness in TAC/DOCA mice is due to an increase in titin compliance. Using phospho-site-specific antibodies, we assay the phosphorylation of titin's PEVK and N2B spring elements. Metformin-treated mice have unaltered PEVK phosphorylation but increased phosphorylation of PKA sites in the N2B element, a change which has previously been shown to lower titin's stiffness. Consistent with this result, experiments with a mouse model deficient in the N2B element reveal that the beneficial effect of metformin on LV chamber and muscle stiffness requires the presence of the N2B element. We conclude that metformin offers therapeutic benefit during HFpEF by lowering titin-based passive stiffness.

Novel echocardiographic method to assess left ventricular chamber stiffness and elevated end-diastolic pressure based on time-velocity integral measurements of pulmonary venous and transmitral flows.

The detection of increased left ventricular (LV) chamber stiffness may play an important role in assessing cardiac patients with potential but not overt heart failure. A non-invasive method to estimate it is not established. We investigated whether the echocardiographic backward/forward flow volume ratio from the left atrium (LA) during atrial contraction reflects the LV chamber stiffness. We studied 62 patients who underwent cardiac catheterization and measured their left ventricular end-diastolic pressure (LVEDP) and pressure increase during atrial contraction (ΔPa) from the LV pressure waveform. Using the echocardiographic biplane method of disks, we measured the LV volume change during atrial contraction indexed to the body surface area (ΔVa), and ΔPa/ΔVa was calculated as a standard for the LV operating chamber stiffness. Using pulsed Doppler echocardiography, we measured the time-velocity integral (TVI) of the backward pulmonary venous (PV) flow during atrial contraction (IPVA) and the ratio of IPVA to the PV flow TVI throughout a cardiac cycle (FPVA). We also measured the TVI of the atrial systolic forward transmitral flow (IA) and the ratio of the IA to the transmitral TVI during a cardiac cycle (FA) and calculated IPVA/IA and FPVA/FA. IPVA/IA and FPVA/FA were well correlated with ΔPa/ΔVa (r = 0.79 and r = 0.81) and LVEDP (r = 0.73 and r = 0.77). The areas under the ROC curve to discriminate LVEDP >18 mmHg were 0.90 for IPVA/IA and 0.93 for FPVA/FA. The FPVA/FA, the backward/forward flow volume ratio from the LA during atrial contraction, is useful for non-invasive assessments of LV chamber stiffness and elevated LVEDP.

Increased Left Ventricular Diastolic Stiffness Is Associated With Heart Failure Symptoms in Aortic Stenosis Patients With Preserved Ejection Fraction

BackgroundClinical risk factors associated with heart failure (HF) symptoms in aortic stenosis (AS) patients with preserved ejection fraction (EF) have not been fully identified. We hypothesized that left ventricular (LV) diastolic stiffness is associated with HF symptoms in patients with AS. Methods and ResultsWe retrospectively evaluated 275 patients with at least moderate AS (aortic valve area <1.5 cm2) and preserved EF (≥50%). LV diastolic stiffness was evaluated with the use of echocardiographic parameters, diastolic wall strain (DWS, a measure of LV wall stiffness), and KLV (a marker of LV chamber stiffness). There were 69 patients with HF. Patients with HF were older, were more likely to be African American, had a higher body mass index, and had more hypertension and coronary artery disease (P < .05 for all). Aortic valve area index and mean pressure gradient across the aortic valve were not different between patients with and without HF. Despite similar echocardiographic parameters of AS severity, patients with HF had stiffer LV (DWS 0.21 ± 0.06 vs 0.25 ± 0.06 [P < .01], KLV 0.17 ± 0.11 vs 0.13 ± 0.08 [P < .01]). Logistic regression analyses revealed that after adjusting for age, race, body mass index, history of hypertension, and coronary artery disease, LV diastolic stiffness parameters remained significantly associated with HF symptoms. ConclusionsLV diastolic stiffness is independently associated with HF in AS patients with preserved EF.

Experimentally Increasing the Compliance of Titin Through RNA Binding Motif-20 (RBM20) Inhibition Improves Diastolic Function In a Mouse Model of Heart Failure With Preserved Ejection Fraction.

Left ventricular (LV) stiffening contributes to heart failure with preserved ejection fraction (HFpEF), a syndrome with no effective treatment options. Increasing the compliance of titin in the heart has become possible recently through inhibition of the splicing factor RNA binding motif-20. Here, we investigated the effects of increasing the compliance of titin in mice with diastolic dysfunction. Mice in which the RNA recognition motif (RRM) of one of the RNA binding motif-20 alleles was floxed and that expressed the MerCreMer transgene under control of the αMHC promoter (referred to as cRbm20ΔRRM mice) were used. Mice underwent transverse aortic constriction (TAC) surgery and deoxycorticosterone acetate (DOCA) pellet implantation. RRM deletion in adult mice was triggered by injecting raloxifene (cRbm20ΔRRM-raloxifene), with dimethyl sulfoxide (DMSO)-injected mice (cRbm20ΔRRM-DMSO) as the control. Diastolic function was investigated with echocardiography and pressure-volume analysis; passive stiffness was studied in LV muscle strips and isolated cardiac myocytes before and after elimination of titin-based stiffness. Treadmill exercise performance was also studied. Titin isoform expression was evaluated with agarose gels. cRbm20ΔRRM-raloxifene mice expressed large titins in the hearts, called supercompliant titin (N2BAsc), which, within 3 weeks after raloxifene injection, made up ≈45% of total titin. TAC/DOCA cRbm20ΔRRM-DMSO mice developed LV hypertrophy and a marked increase in LV chamber stiffness as shown by both pressure-volume analysis and echocardiography. LV chamber stiffness was normalized in TAC/DOCA cRbm20ΔRRM-raloxifene mice that expressed N2BAsc. Passive stiffness measurements on muscle strips isolated from the LV free wall revealed that extracellular matrix stiffness was equally increased in both groups of TAC/DOCA mice (cRbm20ΔRRM-DMSO and cRbm20ΔRRM-raloxifene). However, titin-based muscle stiffness was reduced in the mice that expressed N2BAsc (TAC/DOCAcRbm20ΔRRM-raloxifene). Exercise testing demonstrated significant improvement in exercise tolerance in TAC/DOCA mice that expressed N2BAsc. Inhibition of the RNA binding motif-20-based titin splicing system upregulates compliant titins, which improves diastolic function and exercise tolerance in the TAC/DOCA model. Titin holds promise as a therapeutic target for heart failure with preserved ejection fraction.

Abstract 76: Experimentally Increasing Titin’s Compliance in a Mouse Model of Heart Failure with Preserved Ejection Fraction Ameliorates Diastolic Dysfunction

Increasing titin length in the heart through functional deletion of the RNA recognition motif (RRM) of RBM20 protein leads to a reduction of left ventricular (LV) chamber stiffness in sedentary mice. We tested the therapeutic effect of upregulating compliant titins by creating diastolic dysfunction in a mouse model with inducible RBM20 inhibition (MerCreMer;cRbm20ΔRRM). Under transcriptional control of an MHC6 promoter, RBM20 function of MerCreMer;cRbm20ΔRRM mice was inhibited in time- and cardiac-specific manners. Adult male MerCreMer;cRbm20ΔRRM mice had undergone transaortic constriction (TAC) surgery with Deoxycorticosterone acetate (DOCA) pellet implantation. Two weeks after TAC+DOCA surgery, mice developed LV hypertrophy and diastolic dysfunction as demonstrated by echocardiography. Four weeks after surgery, pressure volume analysis revealed that LV chamber stiffness was markedly increased in TAC+DOCA mice (140% increased versus sham). However, the TAC+DOCA mice with RBM20 inhibition developed less severe LV chamber stiffness (29% increased versus sham). Passive stiffness measurements showed a reduction of cardiomyocyte stiffness in TAC+DOCA mice with RBM20 inhibition. Inhibition of the RBM20-based splicing system results in expression of compliant mutant N2BA titin which consequently lead to reduction of cardiomyocyte stiffness and LV chamber stiffness in a mouse model with diastolic dysfunction.

LEFT VENTRICULAR DIASTOLIC STIFFNESS IS ASSOCIATED WITH HEART FAILURE SYMPTOMS IN AORTIC STENOSIS PATIENTS WITH PRESERVED EJECTION FRACTION

Clinical risk factors associated with heart failure (HF) development in aortic stenosis (AS) patients with preserved ejection fraction (EF) have not been clarified yet. We hypothesized that left ventricular (LV) myocardial and chamber stiffness are associated with symptomatic HF. We evaluated 256