Design and Analysis of a Polymeric Left Ventricular Simulator via Computational Modelling

Preclinical testing of medical devices is an essential step in the product life cycle, whereas testing of cardiovascular implants requires specialised testbeds or numerical simulations using computer software Ansys 2016. Existing test setups used to evaluate physiological scenarios and test cardiac implants such as mock circulatory systems or isolated beating heart platforms are driven by sophisticated hardware which comes at a high cost or raises ethical concerns. On the other hand, computational methods used to simulate blood flow in the cardiovascular system may be simplified or computationally expensive. Therefore, there is a need for low-cost, relatively simple and efficient test beds that can provide realistic conditions to simulate physiological scenarios and evaluate cardiovascular devices. In this study, the concept design of a novel left ventricular simulator made of latex rubber and actuated by pneumatic artificial muscles is presented. The designed left ventricular simulator is geometrically similar to a native left ventricle, whereas the basal diameter and long axis length are within an anatomical range. Finite element simulations evaluating left ventricular twisting and shortening predicted that the designed left ventricular simulator rotates approximately 17 degrees at the apex and the long axis shortens around 11 mm. Experimental results showed that the twist angle is 18 degrees and the left ventricular simulator shortens 5 mm. Twist angles and long axis shortening as in a native left ventricle show it is capable of functioning like a native left ventricle and simulating a variety of scenarios, and therefore has the potential to be used as a test platform.

The Use of Global Longitudinal Strain to Detect Subclinical Reduction in Left Ventricular Pump Function

BACKGROUND

Left ventricular (LV) ejection fraction (LVEF) is not a sensitive marker of LV systolic function in a subset of patients with preserved EF. The relation between LV pump function and global longitudinal strain (GLS) has not been elucidated well in patients with objectively preserved EF and no apparent heart failure (HF). We aimed to detect whether LV GLS can discover impaired LV pump function [presented as low stroke volume index (SVI) and low cardiac output (COP)] in patients with objectively preserved EF and no apparent clinical HF and its practice utility.

METHODS

In total, 100 participants with LVEF of ≥50% were studied for demographic and echocardiographic data, including LVEF, stroke volume, SVI, COP, LV longitudinal strain assessments, apical 4-, 3-, and 2-chamber views averaged for GLS, and were classified into 2 groups: group 1: normal GLS (more negative than -18%) and group 2: low GLS (less negative than -18%).

RESULTS

Reduced LV GLS was associated with lower SVI (35.6 ± 13.6 vs. 43.8 ± 12.7 mL/m 2 ; P = 0.01), lesser COP (5.4 ± 1.9 vs. 6.5 ± 2.1 l/min; P = 0.02), GLS had strong positive correlations with SVI ( r = 0.75; P < 0.001), and COP ( r = 0.66; P < 0.001). LV GLS at a cutoff value less negative than -15% is a strong predictor of SVI ≤35 mL/m 2 (76% sensitivity and 79% specificity) and at a cutoff value less negative than -13.5% it is a strong predictor of COP ≤4 L/min (76% sensitivity and 73% specificity). LV GLS was the best independent predictor of low SVI (<35 mL/m 2 ) and low COP (<4 L/min).

CONCLUSION

Impaired LV strain is associated with lower LV pump function, presented as lower COP and lower SVI in patients with preserved EF even in the absence of clinical HF. It is of great importance to incorporate GLS in the routine evaluation of LV function hand-by-hand with the noninvasive assessment of LV stroke volume and COP that can replace GLS on evaluation of LV pump function in old machines with no GLS modalities, for early pick-up of patients with impaired LV pump function before apparent HF.

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.

Fast long-axis strain: a simple, automatic approach for assessing left ventricular longitudinal function with cine cardiovascular magnetic resonance

OBJECTIVES

In some cardiac pathologies, impairment of left ventricular (LV) longitudinal function may precede reduction in LV ejection fraction. This study investigates the effectiveness of a fast method to quantify long-axis LV function compared to conventional feature tracking and manual approaches.

METHODS

The study consisted of 50 normal controls and 100 heart failure (HF) patients including 40 with reduced ejection fraction (HFrEF), 30 with mid-range ejection fraction (HFmrEF), and 30 with preserved ejection fraction (HFpEF). Parameters including fast long-axis strain (FLAS) at end-systole and peak strain rates during systole (FLASR_s), early diastole (FLASR_e), and atrial contraction (FLASR_a) were derived by a fast semi-automated approach on cine cardiovascular magnetic resonance.

RESULTS

FLAS exhibited good agreement with strain values obtained using conventional feature tracking (bias - 2.9%, limits of agreement ± 3.0%) and the manual approach (bias 0.6%, limits of agreement ± 2.1%), where FLAS was more reproducible and required shorter measurement time. The mean FLAS (HFrEF < HFmrEF < HFpEF < controls; 6.1 ± 2.4 < 9.9 ± 2.4 < 11.0 ± 2.5 < 16.9 ± 2.3%, all p < 0.0001) was decreased in all the HF patient groups. A FLAS of 12.3% (mean-2SD of controls) predicted the presence of systolic dysfunction in 67% of patients with HFpEF, and 87% with HFmrEF. Strain parameters using the fast approach were superior to those obtained by conventional feature tracking and manual approaches for discriminating HFpEF from controls. Notable examples are area under the curve, sensitivity, and specificity for FLAS (0.94, 93%, and 86%) and FLASR_e (0.96, 90%, and 94%).

CONCLUSIONS

The fast approach-derived LV strain and strain rate parameters facilitate reproducible, reliable, and effective LV longitudinal function analysis.

KEY POINTS

• Left ventricular long-axis strain can be rapidly derived from cine CMR with shorter measurement time and higher reproducibility compared to conventional feature tracking and the manual approach. • Progressive reductions in left ventricular long-axis strain and strain rate measurements were observed from HFpEF, HFmrEF, to HFrEF group. • Based on long-axis strain, systolic abnormalities were evident in HFmrEF and HFpEF indicating common coexistence of systolic and diastolic dysfunction in the HF phenotypes.

Ivabradine improves left ventricular twist and untwist during chronic hypertension

BACKGROUND

Left ventricular (LV) dysfunction develops during LV hypertrophy and particularly during tachycardia. Thus we investigated the effects of heart rate (HR) reduction with ivabradine, an I_f-channel blocker, on LV twist and untwist which represents myocardial deformation occurring during the overall systole and diastole and therefore provide valuable evaluation of global LV systolic and diastolic function.

METHODS

Eight chronically instrumented pigs receiving continuous angiotensin II infusion during 28days to induce chronic hypertension and LV hypertrophy. Measurements were performed at Days 0 and 28 after stopping angiotensin II infusion in the presence and absence of ivabradine.

RESULTS

At Day 0, reducing HR from 75±3 to 55±2beats/min with ivabradine did not affect LV twist but slowed LV untwist along with an increase in LV end-diastolic pressure. At Day 28, LV posterior and septal wall thickness as well as the estimated LV mass increased, indicating LV hypertrophy. LV twist and untwist were significantly reduced by 33±4% from 16±1° and 32±6% from -154±9°/s, respectively, showing global LV systolic and diastolic dysfunction. In this context, ivabradine decreased HR by 25% from 86±5beats/min and significantly improved LV twist from 11±1 to 14±1° and LV untwist from -104±8 to -146±5°/s.

CONCLUSIONS

Administration of ivabradine during chronic hypertension and LV hypertrophy improved LV twist and untwist. This further supports the beneficial effect of this drug on both LV systolic and diastolic function during the development of LV hypertrophy.

Normal Reference Ranges for Transthoracic Echocardiography Following Heart Transplantation

BACKGROUND

Heart function following heart transplantation (HTx) is influenced by numerous factors. It is typically evaluated using transthoracic echocardiography, but reference values are currently unavailable for this context. The primary aim of the present study was to derive echocardiographic reference values for chamber size and function, including cardiac mechanics, in clinically stable HTx patients.

METHODS

The study enrolled 124 healthy HTx patients examined prospectively. Patients underwent comprehensive two-dimensional echocardiographic examinations according to contemporary guidelines. Results were compared with recognized reference values for healthy subjects.

RESULTS

Compared with guidelines, larger atrial dimensions were seen in HTx patients. Left ventricular (LV) diastolic volume was smaller, and LV wall thickness was increased. With respect to LV function, both ejection fraction (62 ± 7%, P < .01) and global longitudinal strain (-16.5 ± 3.3%, P < .0001) were lower. All measures of right ventricular (RV) size were greater than reference values (P < .0001), and all measures of RV function were reduced (tricuspid annular plane systolic excursion 15 ± 4 mm [P < .0001], RV systolic tissue Doppler velocity 10 ± 6 cm/sec [P < .0001], fractional area change 40 ± 8% [P < .0001], and RV free wall strain -16.9 ± 4.2% [P < .0001]). Ejection fraction and LV global longitudinal strain were significantly lower in patients with previous rejection.

CONCLUSION

The findings of this study indicate that the distribution of routinely used echocardiographic measures differs between stable HTx patients and healthy subjects. In particular, markedly larger RV and atrial volumes and mild reductions in both LV and RV longitudinal strain were evident. The observed differences could be clinically relevant in the assessment of HTx patients, and specific reference values should be applied in this context.

Left ventricular longitudinal systolic function analysed by 2D speckle-tracking echocardiography in heart failure with preserved ejection fraction: a meta-analysis

BACKGROUND

The purpose of this meta-analysis was to confirm if the global longitudinal systolic function of the left ventricle (LV) is altered in patients with heart failure with preserved ejection fraction (HFpEF).

METHODS

We searched in different databases (Medline, Embase and Cochrane) studies that analysed LV global longitudinal systolic strain (GLS) in patients with HFpEF and in controls (such as healthy subjects or asymptomatic patients with arterial hypertension, diabetes mellitus or coronary artery disease).

RESULTS

Twenty-two studies (2284 patients with HFpEF and 2302 controls) were included in the final analysis. Patients with HFpEF had significantly lower GLS than healthy subjects (mean -15.7% (range -12% to -18.9%) vs mean -19.9% (range -17.1% to -21.5%), weighted mean difference -4.2% (95% CI -3.3% to -5.0%), p < 0.001, respectively). In addition, patients with HFpEF had also significantly lower GLS than asymptomatic patients (mean -15.5% (range -13.4% to -18.4%) vs mean -18.3% (range -15.1% to -20.4%), weighted mean difference -2.8%(95% CI -1.9% to -3.6%), p < 0.001, respectively). In line, 10 studies showed that the rate of abnormal GLS was significantly higher in patients with HFpEF (mean 65.4% (range 37%-95%)) than in asymptomatic subjects (mean 13% (range 0%-29.6%)). Regarding the prognostic relevance of abnormal GLS in HFpEF, two multicentre studies with large sample size (447 and 348) and high number of events (115 and 177) showed that patients with abnormal GLS had worse cardiovascular (CV) outcomes than those with normal GLS (HR for CV mortality and HF hospitalisation 2.14 (95% CI 1.26 to 3.66) and 1.94 (95% CI 1.22 to 3.07)), even adjusting these analyses for multiples clinical and echocardiographic variables.

CONCLUSION

The present meta-analysis analysing 2284 patients with HFpEF and 2302 controls confirms that the longitudinal systolic function of the LV is significantly altered in high proportion of patients with HFpEF. Further large multicentre studies with the aim to confirm the prognostic role of abnormal GLS in HFpEF are warranted.

Investigation on left ventricular multi-directional deformation in patients of hypertension with different LVEF

Background

This study is aimed at investigating myocardial multi-directional systolic deformation in hypertensive with different left ventricular ejection fraction (LVEF), and exploring its contribution to LVEF.

Methods

One hundred and twenty-three patients with primary hypertension (HT) were divided into group A (LVEF ≥ 55%), group B (45% ≤ LVEF < 50%, or 50% ≤ LVEF < 55% + LVEDVI ≥ 97 ml/m²), and group C (LVEF < 45%). Two-dimensional strain echocardiography (2DSE) including LV longitudinal strain (SL), radial strain (SR) and circumferential strain (SC) were measured.

Results

SL decreased gradually from group A, B to C (all p < 0.05) while SR and SC were reduced only in group B and C (all p < 0.05). All strain measurements correlated to LVEF, with the strongest correlation in SC (r = −0.82, p < 0.01) and the second in SL (r = −0.76). The diastolic E/e increased from group A, B to C.

Conclusions

Left ventricular multi-directional deformation correlated well to LVEF in hypertension and particularly SC, indicating that it was SC, not SL or SR, that makes the prominent contribution to left ventricular pump function.

Increased left ventricular extracellular volume and enhanced twist function in type 1 diabetic individuals

Individuals with type 1 diabetes (T1D) characteristically have high glycemic levels that over time can result in reactive fibrosis and abnormalities in myocardial function. T₁ mapping with magnetic resonance imaging (MRI) can estimate the extent of reactive fibrosis by measurement of the extracellular volume fraction (ECV). The extent of alterations in the ECV and associated changes in left ventricular (LV) function and morphology in individuals with T1D is unknown. Fourteen individuals with long-term T1D and 14 sex-, age-, and body mass index-matched controls without diabetes underwent MRI measurement of myocardial T₁ and ECV values as well as LV function and morphology. Ventricular mass, volumes, and global function (LVEF and circumferential/longitudinal/radial strain) were similar in those with T1D and controls. However, those with T1D had larger myocardial ECV (22.1 ± 1.8 vs. 20.1 ± 2.1, P = 0.008) and increased native (noncontrast) myocardial T₁ values (1,211 ± 44 vs. 1,172 ± 43 ms, P < 0.001) as compared with controls. Both the ECV and native T₁ values significantly correlated with several components of torsion and circumferential-longitudinal shear strain (E_cl, the shear strain component associated with twist). Individuals with T1D had increased systolic torsion (P = 0.035), systolic torsion rate (P = 0.032), peak E_cl (P = 0.001), and rates of change of systolic (P = 0.007) and diastolic (P = 0.007) E_cl Individuals with T1D, with normal structure, LVEF, and strain, have increased extracellular volume and increased native T₁ values with associated augmented torsion and E_cl These measures may be useful in detecting the early stages of diabetic cardiomyopathy and warrant larger prospective studies.NEW & NOTEWORTHY Individuals with type 1 diabetes, with normal left ventricular structure and function (ejection fraction and strain), have signs of interstitial fibrosis, measured with MRI as increased extracellular volume fraction and increased native myocardial T₁, which significantly correlated with a number of measures of augmented left ventricular twist function. These measures may be useful in detecting the early stages of diabetic cardiomyopathy.

Using a respiratory navigator significantly reduces variability when quantifying left ventricular torsion with cardiovascular magnetic resonance

BACKGROUND

Left ventricular (LV) torsion is an important indicator of cardiac function that is limited by high inter-test variability (50% of the mean value). We hypothesized that this high inter-test variability is partly due to inconsistent breath-hold positions during serial image acquisitions, which could be significantly improved by using a respiratory navigator for cardiovascular magnetic resonance (CMR) based quantification of LV torsion.

METHODS

We assessed respiratory-related variability in measured LV torsion with two distinct experimental protocols. First, 17 volunteers were recruited for CMR with cine displacement encoding with stimulated echoes (DENSE) in which a respiratory navigator was used to measure and then enforce variability in end-expiratory position between all LV basal and apical acquisitions. From these data, we quantified the inter-test variability of torsion in the absence and presence of enforced end-expiratory position variability, which established an upper bound for the expected torsion variability. For the second experiment (in 20 new, healthy volunteers), 10 pairs of cine DENSE basal and apical images were each acquired from consecutive breath-holds and consecutive navigator-gated scans (with a single acceptance position). Inter-test variability of torsion was compared between the breath-hold and navigator-gated scans to quantify the variability due to natural breath-hold variation. To demonstrate the importance of these variability reductions, we quantified the reduction in sample size required to detect a clinically meaningful change in LV torsion with the use of a respiratory navigator.

RESULTS

The mean torsion was 3.4 ± 0.2°/cm. From the first experiment, enforced variability in end-expiratory position translated to considerable variability in measured torsion (0.56 ± 0.34°/cm), whereas inter-test variability with consistent end-expiratory position was 57% lower (0.24 ± 0.16°/cm, p < 0.001). From the second experiment, natural respiratory variability from consecutive breath-holds translated to a variability in torsion of 0.24 ± 0.10°/cm, which was significantly higher than the variability from navigator-gated scans (0.18 ± 0.06°/cm, p = 0.02). By using a respiratory navigator with DENSE, theoretical sample sizes were reduced from 66 to 16 and 26 to 15 as calculated from the two experiments.

CONCLUSIONS

A substantial portion (22-57%) of the inter-test variability of LV torsion can be reduced by using a respiratory navigator to ensure a consistent breath-hold position between image acquisitions.

Incremental Value of Two Dimensional Speckle Tracking Echocardiography in the Functional Assessment and Characterization of Subclinical Left Ventricular Dysfunction

Subclinical left ventricular (LV) dysfunction refers to subtle abnormalities in LV function which typically precede a reduction in the left ventricular ejection fraction (LVEF). The assessment of myocardial function using LVEF, a radial metric of systolic function, is subject to load dependence, intra-observer and inter-observer variability. Reductions in LVEF typically manifest late in the disease process thus compromising the ability to intervene before irreversible impairment of systolic performance sets in. 2-Dimensional speckle tracking echocardiography (2D-STE), a novel strain imaging modality has shown promise as a sensitive indicator of myocardial contractility. It arms the clinician with a powerful and practical tool to rapidly quantify cardiac mechanics, circumventing several inherent limitations of conventional echocardiography. This article highlights the incremental utility of 2D-STE in the detection of subclinical LV dysfunction.

Real-time three-dimensional left ventricular contraction in patients with diastolic dysfunction

PURPOSE

Systolic alterations in left ventricular (LV) myocardial function have been reported previously in patients with diastolic dysfunction (DD). Recent advances in real-time three-dimensional echocardiography (3DE) enable the measurement of a set of parameters previously difficult to obtain with standard two-dimensional echocardiography (2DE). The aim of this study was to evaluate global 3DE LV contraction in patients with and without DD who had normal ejection fraction (EF).

METHODS

Sixty-five patients (average age 56 ± 6 years; 31 females and 34 males) with normal EF (>50 %) referred to echocardiographic examination for the evaluation of DD were included. In addition to measuring conventional echocardiographic parameters, they were also evaluated with 3DE. End diastolic volume, end systolic volume, EF, corrected standard deviation (SD) of time to minimal systolic volume for 16 segments its dispersion, average excursion of the segments and the SD of segmental motion (excursion-SD) were recorded.

RESULTS

When we tested the differences among three groups of diastolic function (normal, Grade 1, and Grade 2), the results showed that coronary artery disease, left atrial volume, septum, posterior wall, E, A, E/A, deceleration time, E' septum, E' lateral, and excursion-SD were significantly different. An ordered logistic regression analysis revealed that excursion-SD (p < 0.001) and septum (p < 0.001) measurements were statistically significant for predicting DD grade.

CONCLUSION

In our patient population, a decline in excursion-SD values was observed with increasing DD grade. In other words, the amount of segmental difference in terms of excursion was reduced.

Evaluation of the left ventricle longitudinal deformity using myocardial-tracking signals in severely obese adolescents

BACKGROUND

The global prevalence of obesity in school-age children and adolescents has increased in recent decades. Obesity modifies some aspects of the cardiovascular system in order to preserve the body homoeostasis. Echocardiography to study ventricular function plays an important role in the evaluation of pathological re-modelling associated with left ventricular dysfunction. The aim of this study was to evaluate the left ventricle function and structure with conventional echocardiography and to analyse the longitudinal deformity of the left ventricle using myocardial-tracking signals in a group of severely obese adolescents. Methods and results We carried out a descriptive cross-sectional study. We describe the evaluation of the left ventricle using conventional bi-dimensional echocardiography and the myocardial-tracking signals in severely obese adolescents. There were 34 severely obese adolescents included in our study; 52% had a left ventricular ejection fraction<55%, the left ventricular end-diastolic diameter was increased in 70.5% of patients, and 32.3% had an increase in left ventricular mass. On average, 78.9% had abnormal values of left ventricle longitudinal deformations. The number of segments affected per patient was, on average, 5.8, with the anterior apical segment being the most commonly affected. There was a decrease in global longitudinal deformity in 79.4% of the cases.

CONCLUSION

More than half of this group of asymptomatic severely obese adolescents showed abnormalities in left ventricular structure and function evaluated using traditional echocardiographic methods, but 100% of the cases showed abnormalities in longitudinal deformation in at least one of the 17 left ventricle segments evaluated using myocardial-tracking signals.

New diagnostic perspectives on heart failure with preserved ejection fraction: systolic function beyond ejection fraction

Although preserved ejection fraction is found in more than 50% of patients with heart failure, its acceptance as a specific clinical entity is limited. More understanding of the physiopathology, early diagnosis and medical management is needed. With no existing systematic information in the literature, the aim of this review is to provide a comprehensive overview of the new imaging techniques for diagnosing heart failure with preserved ejection fraction, particularly in the early stages of the disease, underlying the pivotal role of new technologies such as two-dimensional speckle tracking echocardiography and vascular stiffness.

Characterizing heart failure in the ventricular volume domain

Heart failure (HF) may be accompanied by considerable alterations of left ventricular (LV) volume, depending on the particular phenotype. Two major types of HF have been identified, although heterogeneity within each category may be considerable. All variants of HF show substantially elevated LV filling pressures, which tend to induce changes in LV size and shape. Yet, one type of HF is characterized by near-normal values for LV end-diastolic volume (EDV) and even a smaller end-systolic volume (ESV) than in matched groups of persons without cardiac disease. Furthermore, accumulating evidence indicates that, both in terms of shape and size, in men and women, the heart reacts differently to adaptive stimuli as well as to certain pharmacological interventions. Adjustments of ESV and EDV such as in HF patients are associated with (reverse) remodeling mechanisms. Therefore, it is logical to analyze HF subtypes in a graphical representation that relates ESV to EDV. Following this route, one may expect that the two major phenotypes of HF are identified as distinct entities localized in different areas of the LV volume domain. The precise coordinates of this position imply unique characteristics in terms of the actual operating point for LV volume regulation. Evidently, ejection fraction (EF; equal to 1 minus the ratio of ESV and EDV) carries little information within the LV volume representation. Thus far, classification of HF is based on information regarding EF combined with EDV. Our analysis shows that ESV in the two HF groups follows different patterns in dependency of EDV. This observation suggests that a superior HF classification system should primarily be founded on information embodied by ESV.

Evaluation of Right Ventricular Myocardial Mechanics Using Velocity Vector Imaging of Cardiac MRI Cine Images in Transposition of the Great Arteries Following Atrial and Arterial Switch Operations

OBJECTIVE

The aim of the study was to determine right and left ventricle deformation parameters in patients with transposition of the great arteries who had undergone atrial or arterial switch procedures.

SETTING

Patients with transposition are born with a systemic right ventricle. Historically, the atrial switch operation, in which the right ventricle remains the systemic ventricle, was performed. These patients have increased rates of morbidity and mortality. We used cardiac MRI with Velocity Vector Imaging analysis to characterize and compare ventricular myocardial deformation in patients who had an atrial switch or arterial switch operation.

DESIGN

Patients with a history of these procedures, who had a clinically ordered cardiac MRI were included in the study. Consecutive 20 patients (75% male, 28.7 ± 1.8 years) who underwent atrial switch operation and 20 patients (60% male, 17.7 ± 1.9 years) who underwent arterial switch operation were included in the study. Four chamber and short-axis cine images were used to determine longitudinal and circumferential strain and strain rate using Vector Velocity Imaging software.

RESULTS

Compared with the arterial switch group, the atrial switch group had decreased right ventricular ejection fraction and increased end-diastolic and end-systolic volumes, and no difference in left ventricular ejection fraction and volumes. The atrial switch group had decreased longitudinal and circumferential strain and strain rate. When compared with normal controls multiple strain parameters in the atrial switch group were reduced.

CONCLUSIONS

Myocardial deformation analysis of transposition patients reveals a reduction of right ventricular function and decreased longitudinal and circumferential strain parameters in patients with an atrial switch operation compared with those with arterial switch operation. A better understanding of the mechanisms of right ventricle failure in transposition of great arteries may lead to improved therapies and adaptation.

Assessment of Left Ventricular Diastolic Function by Doppler Echocardiography

Diastole is an essential part of the cardiac cycle, during which significant changes in myocardial function, ion and energy transfer, as well as coronary flow, occur. In contrast to systole, diastole consists of four phases, each of which has its distinguishing function and events. However, the four phases are inter-related with events in early diastole correlating with those in late diastole and those occurring during the isovolumic relaxation time predicting both. The complexity of diastolic phases is reflected in the ways by which diastolic function is assessed. While intra-cardiac flow velocities, into and out of the atria, are measured by pulsed-wave Doppler, those of wall motion are assessed by M-mode, myocardial Doppler velocities or, recently, speckle tracking technique. Optimum integration of various aspects of diastolic function should always be considered in order to obtain an accurate comprehensive assessment, bearing in mind factors that normally affect it, for example age.

Feasibility of radial and circumferential strain analysis using 2D speckle tracking echocardiography in cats

The purpose of the present study is to investigate the feasibility of strain analysis using speckle tracking echocardiography (STE) in cats and to evaluate STE variables in cats with hypertrophic cardiomyopathy (HCM). Sixteen clinically healthy cats and 17 cats with HCM were used. Radial and circumferential strain and strain rate variables in healthy cats were measured using STE to assess the feasibility. Comparisons of global strain and strain variables between healthy cats and cats with HCM were performed. Segmental assessments of left ventricle (LV) wall for strain and strain rate variables in cats with HCM were also performed. As a result, technically adequate images were obtained in 97.6% of the segments for STE analysis. Sedation using buprenorphine and acepromazine did not affect any global strain nor strain rate variable. In LV segments of cats with HCM, reduced segmental radial strain and strain rate variables had significantly related with segmental LV hypertrophy. It is concluded that STE analysis using short axis images of LV appeared to be clinically feasible in cats, having the possibility to be useful for detecting myocardial dysfunctions in cats with diseased heart.

Ejection fraction in patients with heart failure and preserved ejection fraction is greater than in healthy controls: a meta-analysis

BACKGROUND

Ejection fraction (EF) slightly declines with age in healthy control (HC) subjects. Yet, studies of heart failure with preserved ejection fraction (HFPEF) often report EF values which are surprisingly greater than those reported for HC of the same age. The goals of this study were to: (1) compare the EF, at rest, in subjects with HFPEF versus HC, and (2) compare how EF varies with age in HFPEF and HC.

METHODS

A systematic review and meta-analysis of the literature was performed. Studies were identified in the PUBMED and EMBASE databases until August 2013. A study reporting EF at rest in HFPEF and HC was included regardless of the aim of the primary study. In most of the primary studies (25 of 28 studies, 89%) EF was not a primary endpoint. A summary measure was the standardized mean difference (SMD) of the EF in HFPEF vs.

HC RESULTS

Twenty eight studies (1529 HFPEF and 1068 HC subjects) were included. SMD was 0.71 (95% CI: 0.31, 1.12, P<0.001) demonstrating a greater EF in HFPEF. Effect size of HFPEF on EF was moderate. A meta-regression showed a statistically non-significant trend of increased SMD with older age.

CONCLUSIONS

This analysis showed that EF in HFPEF is on average "greater-than-normal". This phenomenon may be related to an underlying adaptive mechanism occurring in HFPEF. Further research is needed.

Left atrial dysfunction relates to symptom onset in patients with heart failure and preserved left ventricular ejection fraction

AIMS

Pathophysiology of heart failure (HF) with preserved ejection fraction (HFPEF) remains unclear. Left atrial (LA) function has been related to HF symptoms. Our purpose is to analyse LA function in outpatients with new onset symptoms of HF.

METHODS AND RESULTS

An observational study was performed including 138 consecutive outpatients with suspected HF referred to a one-stop clinic. Final diagnosis [HF with reduced EF (HFREF), HFPEF, or non-HF] was established according to current recommendations. Echocardiography was performed in all patients. LA function was analysed using strain derived from speckle tracking in sinus rhythm patients (n = 83). Results were analysed with ANOVA and Bonferroni statistical tests. Receiver operating characteristic (ROC) curves were constructed to investigate the predictive ability of LA parameters for the final diagnosis of HF. Patients were 75 ± 9 years and 63% women. Final diagnosis was 23.2% HFREF, 45.7% HFPEF, and 31.2% non-HF. Left ventricular strain rate showed no differences between non-HF and HFPEF groups, but both groups showed differences with the HFREF group. LA strain rate (A- and S-waves) was significantly reduced in both HF groups (without differences among them) when compared with the non-HF group. LA strain rate and indexed volume showed significant accuracy for HF diagnosis in ROC curves.

CONCLUSIONS

In outpatients with new-onset symptoms of HF, LA dysfunction was observed. It might be the initial mechanism in the development of symptoms in HFPEF patients. These findings support the relationship of LA dysfunction with HFPEF, suggesting that the analysis of LA function may be useful in sinus rhythm patients with new-onset dyspnoea.

A new twist on an old idea: a two-dimensional speckle tracking assessment of cyclosporine as a therapeutic alternative for heart failure with preserved ejection fraction

We recently reported that mitochondrial dysfunction, characterized by increased mitochondrial permeability transition (MPT), was present in a translational swine model of heart failure with preserved ejection fraction (HFpEF). Cyclophilin D is a key component of the MPT pore, therefore, the purpose of this study was to test the efficacy of a novel cyclosporine (CsA) dosing scheme as a therapeutic alternative for HFpEF. Computed tomography (CT), two‐dimensional speckle tracking two‐dimensional speckle tracking (2DST), and invasive hemodynamics were used to evaluate cardiac function. CT imaging showed 14 weeks of CsA treatment caused eccentric myocardial remodeling (contrasting concentric remodeling in untreated HF animals) and elevated systemic pressures. 2DST detected left ventricular (LV) mechanics associated with systolic and diastolic dysfunction prior to the onset of significantly increased LV end diastolic pressure including: (1) decreased systolic apical rotation rate, longitudinal displacement, and longitudinal/radial/circumferential strain; (2) decreased early diastolic untwisting and longitudinal strain rate; and (3) increased late diastolic radial/circumferential mitral strain rate. LV mechanics associated with systolic and diastolic impairment was enhanced to a greater extent than seen in untreated HF animals following CsA treatment. In conclusion, CsA treatment accelerated the development of heart failure, including dilatory LV remodeling and impaired systolic and diastolic mechanics. Although our findings do not support CsA as a viable therapy for HFpEF, 2DST was effective in differentiating between progressive gradations of developing HF and detecting diastolic impairment prior to the development of overt diastolic dysfunction.

We recently reported that mitochondrial dysfunction, characterized by increased mitochondrial permeability transition (MPT), was present in a translational swine model of heart failure with preserved ejection fraction (HFpEF). Cyclophilin D is a key component of the MPT pore, therefore, the purpose of this study was to test the efficacy of a novel cyclosporine (CsA) dosing scheme as a therapeutic alternative for HFpEF. CsA treatment accelerated the development of heart failure, including dilatory LV remodeling and impaired systolic and diastolic mechanics. Although our findings do not support CsA as a viable therapy for HFpEF, 2DST was effective in differentiating between progressive gradations of developing HF and detecting diastolic impairment prior to the development of overt diastolic dysfunction.

Current treatment of heart failure with preserved ejection fraction: should we add life to the remaining years or add years to the remaining life?

According to the ejection fraction, patients with heart failure may be divided into two different groups: heart failure with preserved or reduced ejection fraction. In recent years, accumulating studies showed that increased mortality and morbidity rates of these two groups are nearly equal. More importantly, despite decline in mortality after treatment in regard to current guideline in patients with heart failure with reduced ejection fraction, there are still no trials resulting in improved outcome in patients with heart failure with preserved ejection fraction so far. Thus, novel pathophysiological mechanisms are under development, and other new viewpoints, such as multiple comorbidities resulting in increased non-cardiac deaths in patients with heart failure and preserved ejection fraction, were presented recently. In this review, we will focus on the tested as well as the promising therapeutic options that are currently studied in patients with heart failure with preserved ejection fraction, along with a brief discussion of pathophysiological mechanisms and diagnostic options that are helpful to increase our understanding of novel therapeutic strategies.

Left ventricular twist and circumferential strain in dogs with myxomatous mitral valve disease

BACKGROUND

During the cardiac cycle, the ventricle undergoes a twisting motion because of the oblique orientation of the left ventricular (LV) myofibers. This can be quantified by speckle-tracking echocardiography (STE). In mitral regurgitation (MR) in humans, the short axis deformation has been suggested as being pivotal to LV function. Decreased and delayed LV twist has been described in experimental MR, but has not been studied in myxomatous mitral valve disease (MMVD).

HYPOTHESES

(1) Magnitude (CSt) and rate (CSRs) of systolic circumferential deformation decrease before the onset of congestive heart failure (CHF); (2) magnitude and rate of LV twist decrease, and onset of untwist is delayed, with increasing MMVD severity.

ANIMALS

A total of 97 privately owned small- to medium-sized dogs.

METHODS

Severity of MMVD was assessed by echocardiography and presence of clinical signs of CHF. Magnitude and rate of LV twist and circumferential deformation were evaluated by STE.

RESULTS

Dogs with CHF receiving treatment had increased CSt, CSRs, early diastolic untwisting rate, and delayed onset of untwist compared to dogs with minimal MMVD and increased systolic twist compared to dogs with mild MMVD (all P < .01). CSt and time to onset of untwist increased with echocardiographic variables of MR severity (all P < .002). CSRs and several LV twist variables decreased with increasing systolic LV internal diameter (all P < .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

No STE-derived variable was decreased before onset of CHF. In dogs with CHF receiving treatment, the delayed onset of relaxation might indicate LV dysfunction and the hyperdynamic CSt and LV twist reflect compensatory mechanisms.

Heart failure with preserved ejection fraction: chronic low-intensity interval exercise training preserves myocardial O2 balance and diastolic function

We have previously reported chronic low-intensity interval exercise training attenuates fibrosis, impaired cardiac mitochondrial function, and coronary vascular dysfunction in miniature swine with left ventricular (LV) hypertrophy (Emter CA, Baines CP. Am J Physiol Heart Circ Physiol 299: H1348-H1356, 2010; Emter CA, et al. Am J Physiol Heart Circ Physiol 301: H1687-H1694, 2011). The purpose of this study was to test two hypotheses: 1) chronic low-intensity interval training preserves normal myocardial oxygen supply/demand balance; and 2) training-dependent attenuation of LV fibrotic remodeling improves diastolic function in aortic-banded sedentary, exercise-trained (HF-TR), and control sedentary male Yucatan miniature swine displaying symptoms of heart failure with preserved ejection fraction. Pressure-volume loops, coronary blood flow, and two-dimensional speckle tracking ultrasound were utilized in vivo under conditions of increasing peripheral mean arterial pressure and β-adrenergic stimulation 6 mo postsurgery to evaluate cardiac function. Normal diastolic function in HF-TR animals was characterized by prevention of increased time constant of isovolumic relaxation, normal LV untwisting rate, and enhanced apical circumferential and radial strain rate. Reduced fibrosis, normal matrix metalloproteinase-2 and tissue inhibitors of metalloproteinase-4 mRNA expression, and increased collagen III isoform mRNA levels (P < 0.05) accompanied improved diastolic function following chronic training. Exercise-dependent improvements in coronary blood flow for a given myocardial oxygen consumption (P < 0.05) and cardiac efficiency (stroke work to myocardial oxygen consumption, P < 0.05) were associated with preserved contractile reserve. LV hypertrophy in HF-TR animals was associated with increased activation of Akt and preservation of activated JNK/SAPK. In conclusion, chronic low-intensity interval exercise training attenuates diastolic impairment by promoting compliant extracellular matrix fibrotic components and preserving extracellular matrix regulatory mechanisms, preserves myocardial oxygen balance, and promotes a physiological molecular hypertrophic signaling phenotype in a large animal model resembling heart failure with preserved ejection fraction.

The effects of serum potassium and magnesium levels in a patient with Gitelman's syndrome on the timing of ventricular wall motion and the pattern of ventricular strain and torsion

Gitelman's syndrome is a primary renal tubular hypokalemic metabolic alkalosis. Hypokalemia and hypomagnesemia can cause cardiac tissue excitability and conduction. Global ventricular mechanical function is directly related to the contractile properties of cardiac myocytes, which are largely dependent on the flow of ions such as potassium and magnesium. Here, we show that increased levels of potassium, in addition to magnesium, in a patient with Gitelman's syndrome significantly impacts the timing of ventricular wall motion and the pattern of ventricular strain and torsion. Two-dimensional speckle tracking echocardiography was used for evaluation of the hypokalemic-hypomagnesemic period (first day) and third day after potassium chloride and magnesium replacement therapy. The transthoracic echocardiography showed that the percent ejection fraction was similar in hypokalemic-hypomagnesemic (63%) and normokalemic-normomagnesemic (after potassium and magnesium therapy, 67%) hearts. However, decreased left ventricular apical 4-chamber peak systolic longitudinal strain, left ventricle global peak systolic strain, and global torsion values increased after potassium chloride and magnesium replacement therapy.

Progression of myocardial remodeling and mechanical dysfunction in the spontaneously hypertensive rat

The progression of hypertensive heart disease (HHD) to heart failure (HF) is associated with myocardial remodeling. Corresponding changes in three-dimensional organization of cardiac extracellular matrix have not been quantified or related fully to the development of HF. Spontaneously hypertensive rats (SHRs) and Wistar-Kyoto controls were studied at 3, 12, 18, and 24 mo. Hemodynamic and morphological data, brain natriuretic peptide levels, and echocardiography demonstrate four distinct disease stages: systemic hypertension, diastolic dysfunction, early systolic failure, and decompensated HF. Passive left ventricular (LV) pressure-volume relationships were determined in vitro. Transmural specimens from the anterior LV free wall were imaged using extended-volume confocal microscopy, and three-dimensional myocardial architecture was quantified. In SHRs, LV compliance was reduced at 12 mo and increased progressively thereafter. However, it was less than in controls for filling pressures <10 mmHg and not significantly different at ≥10 mmHg. Myocyte cross section was enlarged, with increased variability from 12 mo, while collagen fraction increased progressively. Perimysial collagen fraction remained unchanged with age, although endomysial collagen increased from 12 mo. Perimysial collagen between adjacent muscle layers fused at 12 mo and continued to thicken subsequently, while muscle layers became more dispersed and disordered. We conclude that LV dilatation, which accompanies decompensated HF in this model of HHD, is not due to LV "softening." While perimysial (and endomysial) collagen networks are substantially remodeled, they are not dissolved, as has been proposed. We argue that progressive disruption of the laminar organization of LV myocardium may contribute to impaired systolic function in HHD.

Myocardial systolic and diastolic performance derived by 2-dimensional speckle tracking echocardiography in heart failure with normal left ventricular ejection fraction

BACKGROUND

The aim of this study was to investigate the myocardial systolic and diastolic performance of the left ventricle (LV) in patients with heart failure with normal LV ejection fraction (HFNEF) through novel LV myocardial indices, which assess the systolic and diastolic function of the whole myocardium of the LV.

METHODS AND RESULTS

LV myocardial systolic and diastolic performance were assessed as the average value of peak systolic strain and peak early-diastolic strain rate, respectively, in longitudinal, circumferential, and radial directions from all LV segments using 2-dimensional speckle-tracking echocardiography. We studied patients with HFNEF and a control group consisting of asymptomatic subjects with LV diastolic dysfunction of similar age, sex, and LV ejection fraction. A total of 322 patients were included (92 with HFNEF and 230 with asymptomatic LV diastolic dysfunction). Myocardial systolic and diastolic LV performance were significantly lower in HFNEF (20.13±6.02% and 1.14±0.27 s(-1)) than in patients with asymptomatic LV diastolic dysfunction (25.33±6.06% and 1.37±0.33 s(-1), respectively; all P<0.0001). In addition, patients with HFNEF with low systolic and diastolic LV myocardial performance had significantly higher LV filling pressures (17.1±6.6 and 17.6±6.3 versus 12.0±5.1 and 11.7±4.7, respectively; all P<0.001) and lower cardiac output (4.8±1.0 L/min and 4.9±1.1 L/min versus 5.7±1.2 L/min and 5.8±1.1 L/min, respectively; all P<0.001) than patients with normal LV myocardial performance. In relation to these findings, the symptomatic status (ie, New York Heart Association functional class) was significantly altered in those patients with low systolic and diastolic LV myocardial performance.

CONCLUSIONS

In patients with HFNEF, both systolic and diastolic LV myocardial performance are impaired, which is associated with increased LV filling pressures, decreased cardiac output, and worse New York Heart Association functional class. Therefore, the measurement of these myocardial parameters could be of great importance in HFNEF because these echocardiographic indices assess the multidirectional function of the whole myocardium of the LV, thereby allowing detection of an alteration of the global function of the LV which is associated with a worse symptomatic status in these patients.

Heart disease and left ventricular rotation - a systematic review and quantitative summary

Background

Left ventricular (LV) rotation is increasingly examined in those with heart disease. The available evidence measuring LV rotation in those with heart diseases has not been systematically reviewed.

Methods

To review systematically the evidence measuring LV rotational changes in various heart diseases compared to healthy controls, literature searches were conducted for appropriate articles using several electronic databases (e.g., MEDLINE, EMBASE). All randomized-controlled trials, prospective cohort and case–controlled studies that assessed LV rotation in relation to various heart conditions were included. Three independent reviewers evaluated each investigation’s quality using validated scales. Results were tabulated and levels of evidence assigned.

Results

A total of 1,782 studies were found through the systematic literature search. Upon review of the articles, 47 were included. The articles were separated into those investigating changes in LV rotation in participants with: aortic stenosis, myocardial infarction, hypertrophic cardiomyopathy, dilated cardiomyopathy, non-compaction, restrictive cardiomyopathy/ constrictive pericarditis, heart failure, diastolic dysfunction, heart transplant, implanted pacemaker, coronary artery disease and cardiovascular disease risk factors. Evidence showing changes in LV rotation due to various types of heart disease was supported by evidence with limited to moderate methodological quality.

Conclusions

Despite a relatively low quality and volume of evidence, the literature consistently shows that heart disease leads to marked changes in LV rotation, while rotational systolic-diastolic coupling is preserved. No prognostic information exists on the potential value of rotational measures of LV function. The literature suggests that measures of LV rotation may aid in diagnosing subclinical aortic stenosis and diastolic dysfunction.

Inter-study reproducibility of cardiovascular magnetic resonance myocardial feature tracking

BACKGROUND

Cardiovascular magnetic resonance myocardial feature tracking (CMR-FT) is a recently described method of post processing routine cine acquisitions which aims to provide quantitative measurements of circumferentially and radially directed ventricular wall strain. Inter-study reproducibility is important for serial assessments however has not been defined for CMR-FT.

METHODS

16 healthy volunteers were imaged 3 times within a single day. The first examination was performed at 0900 after fasting and was immediately followed by the second. The third, non-fasting scan, was performed at 1400.CMR-FT measures of segmental and global strain parameters were calculated. Left ventricular (LV) circumferential and radial strain were determined in the short axis orientation (Ecc(SAX) and Err(SAX) respectively). LV and right ventricular longitudinal strain and LV radial strain were determined from the 4-chamber orientation (Ell(LV), Ell(RV), and Err(LAX) respectively). LV volumes and function were also analysed.Inter-study reproducibility and study sample sizes required to demonstrate 5% changes in absolute strain were determined by comparison of the first and second exams. The third exam was used to determine whether diurnal variation affected reproducibility.

RESULTS

CMR-FT strain analysis inter-study reproducibility was variable. Global strain assessment was more reproducible than segmental analysis. Overall Ecc(SAX) was the most reproducible measure of strain: coefficient of variation (CV) 38% and 20.3% and intraclass correlation coefficient (ICC) 0.68 (0.55-0.78) and 0.7 (0.32-0.89) for segmental and global analysis respectively. The least reproducible segmental measure was Ell(RV): CV 60% and ICC 0.56 (0.41-0.69) whilst the least reproducible global measure was Err(LAX): CV 33.3% and ICC 0.44 (0-0.77). Variable reproducibility was also reflected in the calculated sample sizes, which ranged from 11 (global Ecc(SAX)) to 156 subjects (segmental Ell(RV)). The reproducibility of LV volumes and function was excellent. There was no diurnal variation in global strain or LV volumetric measurements.

CONCLUSIONS

Inter-study reproducibility of CMR-FT varied between different parameters, as summarized above and was better for global rather than segmental analysis. It was not measurably affected by diurnal variation. CMR-FT may have potential for quantitative wall motion analysis with applications in patient management and clinical trials. However, inter-study reproducibility was relatively poor for segmental and long axis analyses of strain, which have yet to be validated, and may benefit from further development.

Structural remodeling and mechanical function in heart failure

The cardiac extracellular matrix (ECM) is the three-dimensional scaffold that defines the geometry and muscular architecture of the cardiac chambers and transmits forces produced during the cardiac cycle throughout the heart wall. The cardiac ECM is an active system that responds to the stresses to which it is exposed and in the normal heart is adapted to facilitate efficient mechanical function. There are marked differences in the short- and medium-term changes in ventricular geometry and cardiac ECM that occur as a result of volume overload, hypertension, and ischemic cardiomyopathy. Despite this, there is a widespread view that a common remodeling "phenotype" governs the final progression to end-stage heart failure in different forms of heart disease. In this review article, we make the case that this interpretation is not consistent with the clinical and experimental data on the topic. We argue that there is a need for new theoretical and experimental models that will enable stresses acting on the ECM and resultant deformations to be estimated more accurately and provide better spatial resolution of local signaling mechanisms that are activated as a result. These developments are necessary to link the effects of structural remodeling with altered cardiac mechanical function.

Cardiovascular magnetic resonance myocardial feature tracking for quantitative viability assessment in ischemic cardiomyopathy

BACKGROUND

Low dose dobutamine stress magnetic resonance imaging is valuable to assess viability in patients with ischemic cardiomyopathy. Analysis is usually qualitative with considerable operator dependency. The aim of the current study was to investigate the feasibility of cine images derived quantitative cardiac magnetic resonance (CMR) myocardial feature tracking (FT) strain parameters to assess viability in patients with ischemic cardiomyopathy.

METHODS

15 consecutive patients with ischemic cardiomyopathy referred for viability assessment were studied at 3T at rest and during low dose dobutamine stress (5 and 10μg/kg/min of dobutamine). Subendocardial and subepicardial circumferential (Eccendo and Eccepi) and radial (Err) strains were assessed using steady state free precession (SSFP) cine images orientated in 3 short axis slices covering 16 myocardial segments.

RESULTS

Dysfunctional segments without scar (n=75) improved in all three strain parameters: Eccendo (Rest: -10.5±6.9; 5μg: -12.1±6.9; 10μg: -14.1±9.2; p<0.05), Eccepi (Rest: -7±4.8; 5μg: -8.2±5.5; 10μg: -9.1±5.9; p<0.05) and Err (Rest: 11.7±8.3; 5μg: 16±10.9; 10μg: 16.5±12.8; p<0.05). There was no response to dobutamine in dysfunctional segments with scar transmurality above 75% (n=6): Eccendo (Rest: -4.7±3.0; 5μg: -2.9±2.5; 10μg: -6.6±3.3; p=ns), Eccepi (Rest: -2.9±2.9; 5μg: -5.4±3.9; 10μg: -4.5±4.2; p=ns) and Err (Rest:9.5±5; 5μg:5.4±6.2; 10μg:4.9±3.3; p=ns). Circumferential strain (Eccendo, Eccepi) improved in all segments up to a transmurality of 75% (n=60; p<0.05). Err improved in segments <50% transmurality (n=45; p<0.05) and remained unchanged above 50% transmurality (n=21; p=ns).

CONCLUSIONS

CMR-FT is a novel technique, which detects quantitative wall motion derived from SSFP cine imaging at rest and with low dose dobutamine stress. CMR-FT holds promise of quantitative assessment of viability in patients with ischemic cardiomyopathy.

Epidemiology and diagnosis of heart failure with preserved left ventricular ejection fraction: rationale and design of the study

AIMS

Despite major advances in our understanding of 'systolic' heart failure, at present the epidemiology, pathophysiology, and therapy of heart failure with preserved left ventricular ejection fraction (HFpEF) is poorly understood, in large part because of the lack of robust and widely accepted diagnostic criteria. Although there is a good evidence base for the treatment of systolic heart failure, similar data are lacking for the treatment of HFpEF. Methods In our study, we will screen a consecutive series of 5000 subjects aged ≥60 from the community. Following symptom questionnaire and echocardiography, metabolic exercise testing will be used to confirm whether or not patients thought clinically to have HFpEF are in fact exercise limited and that this limitation is cardiac in origin. Blood samples for plasma brain natriuretic peptide (BNP) will be taken at rest and following exercise in symptomatic patients and matching controls.

CONCLUSIONS

At the end of our study we will establish community prevalence and population characteristics of HFpEF, and also evaluate the diagnostic accuracy of current echocardiography parameters and BNP for the diagnosis of the condition.

The pathophysiology of heart failure with preserved ejection fraction: from molecular mechanisms to exercise haemodynamics

The pathophysiology of HfpEF is complex. In this review we discuss the molecular aspects of HfpEF as well as the profoundly disturbed haemodynamics with particular focus on exercise haemodynamic abnormalities.

Assessment of myocardial mechanics using speckle tracking echocardiography: fundamentals and clinical applications

The authors summarize the recent developments in speckle-tracking echocardiography (STE), a relatively new technique that can be used in conjunction with two-dimensional or three-dimensional echocardiography for resolving the multidirectional components of left ventricular (LV) deformation. The tracking system is based on grayscale B-mode images and is obtained by automatic measurement of the distance between 2 pixels of an LV segment during the cardiac cycle, independent of the angle of insonation. The integration of STE with real-time cardiac ultrasound imaging overcomes some of the limitations of previous work in the field and has the potential to provide a unified framework to more accurately quantify the regional and global function of the left ventricle. STE holds promise to reduce interobserver and intraobserver variability in assessing regional LV function and to improve patient care while reducing health care costs through the early identification of subclinical disease. Following a brief overview of the approach, the authors pool the initial observations from clinical studies on the development, validation, merits, and limitations of STE.

Kinetics of Left Ventricular Strains and Torsion During Incremental Exercise in Healthy Subjects

Background—

The dynamics of systolic and diastolic strains and torsional mechanics of the left ventricle (LV) and their relation to diastolic filling never have been evaluated at various exercise intensities.

Methods and Results—

Speckle tracking echocardiography was performed in 20 healthy sedentary subjects at rest and during a progressive submaximal exercise test at 20%, 30%, and 40% of maximal aerobic power. LV twist increased progressively with exercise intensity (10.5±3.2 to 15.8±4.5°; P <0.001), whereas longitudinal strain remained unchanged after the first workload, underlining the key role of torsional reserve in systolic-diastolic coupling during exercise. The increase in diastolic untwisting (−88.7±34.2 to −182.9±53.5 deg · s −1 ; P <0.01) was correlated to enhanced systolic twist ( R =0.61; P <0.001), and its magnitude of increase was significantly higher compared to diastolic longitudinal and circumferential strain rates (119±64% versus 65±44% and 57±24%, respectively), emphasizing its contribution to diastolic filling. The timing of peak untwisting and the chronology of diastolic mechanical events were unchanged during effort. Untwisting was driven mainly by apical rotation and determined mitral opening and isovolumic relaxation time ( R =0.47 and 0.61, respectively; P <0.001), whereas basal rotation and longitudinal and circumferential diastolic strain rates were major determinants of increased early diastolic filling ( R =0.64, 0.79, and 0.81, respectively; P <0.001).

Conclusions—

The use of speckle tracking echocardiography gives new insights into physiological adaptive LV mechanics during incremental exercise in healthy subjects, underlining the key role of torsional mechanics. It might be useful to better understand the mechanisms of diastolic dysfunction and exercise intolerance in various pathological conditions.

Global strain rate imaging for the estimation of diastolic function in HFNEF compared with pressure-volume loop analysis

AIMS

Strain rate imaging provides direct information on intrinsic myocardial function and may improve the diagnostic of diastolic dysfunction in heart failure with normal ejection fraction (HFNEF). We therefore correlated global strain with pressure-volume (PV) loop analysis and compared it with flow and tissue Doppler measurements.

METHODS AND RESULTS

Longitudinal two-dimensional strain rate and flow and tissue Doppler (TDI) indices were measured simultaneously and correlated with diastolic indices of PV relationship obtained by a conductance catheter in 21 patients with HFNEF and 12 controls. HFNEF patients showed a reduced global strain rate during isovolumetric relaxation (SR(IVR)) [0.27 (0.12-0.39) vs. 0.44 (0.29-0.56) s(-1), P = 0.028]. Global strain rate during early (SR(E)) and late (SR(L)) diastole did not defer from controls. Their ratios with early transmitral flow, E/SR(IVR) and E/SR(E), were both elevated in HFNEF [3.68 (2.57-7.52) vs. 1.73 (1.47-2.37) m, P = 0.007 and 1.13 (0.76-1.36) vs. 0.83 (0.57-1.04) m, P = 0.030]. SR(E) and SR(IVR) correlated with left ventricular (LV) relaxation τ (r = 0.40 and 0.47, P < 0.05); E/SR(IVR) and E/SR(E) with LV end-diastolic pressure (r = 0.49 and 0.57, P < 0.01) and LV stiffness constant β (r = 0.42 and 0.43, P < 0.01). Neither of the strain rate indices were significantly more accurate than TDI (area under the curve: SR(E) 0.55, SR(IVR) 0.70, E'/A' 0.72, E/SR(E) 0.75, E/SR(IVR) 0.80, and E/E' 0.83).

CONCLUSION

Strain rate imaging is accurate in detecting increased LV stiffness in HFNEF, but it is not superior to already established TDI analysis including E/E' in patients with only mild degree of disease.

Left ventricular strain and untwist in hypertrophic cardiomyopathy: relation to exercise capacity

Background

Nonobstructive hypertrophic cardiomyopathy (nHCM) is often associated with reduced exercise capacity despite hyperdynamic systolic function as measured by left ventricular ejection fraction. We sought to examine the importance of left ventricular strain, twist, and untwist as predictors of exercise capacity in nHCM patients.

Methods

Fifty-six nHCM patients (31 male and mean age of 52 years) and 43 age- and gender-matched controls were enrolled. We measured peak oxygen consumption (peak Vo₂) and acquired standard echocardiographic images in all participants. Two-dimensional speckle tracking was applied to measure rotation, twist, untwist rate, strain, and strain rate.

Results

The nHCM patients exhibited marked exercise limitation compared with controls (peak Vo₂ 23.28 ± 6.31 vs 37.70 ± 7.99 mL/[kg min], P < .0001). Left ventricular ejection fraction in nHCM patients and controls was similar (62.76% ± 9.05% vs 62.48% ± 5.82%, P = .86). Longitudinal, radial, and circumferential strain and strain rate were all significantly reduced in nHCM patients compared with controls. There was a significant delay in 25% of untwist in nHCM compared with controls. Both systolic and diastolic apical rotation rates were lower in nHCM patients. Longitudinal systolic and diastolic strain rate correlated significantly with peak Vo₂ (r = −0.34, P = .01 and r = 0.36, P = .006, respectively). Twenty-five percent untwist correlated significantly with peak Vo₂ (r = 0.36, P = .006).

Conclusions

In nHCM patients, there are widespread abnormalities of both systolic and diastolic function. Reduced strain and delayed untwist contribute significantly to exercise limitation in nHCM patients.