Diastolic Myocardial Mechanics in Hypertrophic Cardiomyopathy

Exaggerated myocardial torsion may contribute to dynamic left ventricular outflow tract obstruction in hypertrophic cardiomyopathy

Aims

Dynamic left ventricular (LV) outflow tract obstruction (LVOTO) is associated with symptoms and increased risk of developing heart failure in hypertrophic cardiomyopathy (HCM). The association of LVOTO and LV twist mechanics has not been well studied in HCM. The aim of the study was to compare the pattern of LV twist in patients with HCM associated with asymmetrical septal hypertrophy with and without LVOTO.

Methods and results

Echocardiography (including speckle tracking) was performed in 212 patients with HCM, divided according to the absence (n = 130) or presence (n = 82) of LVOTO (defined as peak pressure gradient ≥30 mmHg either at rest and/or with Valsalva manoeuvre). Patients with LVOTO were older, had smaller LV dimensions, a higher LV ejection fraction (LVEF), a longer anterior mitral valve leaflet length, and a higher early transmitral pulsed wave to septal tissue Doppler velocity ratio (E/E'). A univariate analysis showed that peak twist was significantly higher in patients with LVOTO compared with patients without LVOTO (19.7 ± 7.3 vs. 15.7 ± 6.0, P = 0.00015). Peak twist was similarly enhanced in patients with LVOTO, manifesting only during Valsalva (19.2 ± 5.6, P = 0.007) and patients with resting LVOTO (19.9 ± 8.0, P = 0.00004) compared with patients without LVOTO (15.7 ± 6.0). A stepwise forward logistic regression analysis showed that LVEF, LV end-systolic dimension indexed to body surface area, anterior mitral valve leaflet length, E/E', and peak twist were all independently associated with LVOTO.

Conclusion

This study demonstrates that increased peak LV twist is independently associated with LVOTO in patients with HCM. Peak twist was similarly exaggerated in patients with only latent LVOTO, suggesting that it may play a contributory role to LVOTO in HCM.

Left atrial function analysis in patients in sinus rhythm, normal left ventricular function and indeterminate diastolic function

Assessment of diastolic function by echocardiography may be indeterminate as demonstrated in previous studies where diastolic measurement is a discrepant. We aimed to assess whether left atrial (LA) function may contribute to left ventricle filling evaluation in patients with indeterminate diastolic function (IndtDFx). This retrospective study included 3 groups of patients based on diastolic function: normal diastolic function (NDFx), definite diastolic dysfunction (DDFx) and IndtDFx. All patients had sinus rhythm with left ventricular ejection fraction ≥ 45%. Diastolic function was determined according to the following echocardiographic parameters: mitral E', mitral E/E' ratio, LA maximal volume index, and pulmonary pressure. NDFx was defined as having less than 2 abnormal parameters, DDFx as more than 2 abnormal parameters, and IndtDFx as 2 abnormal parameters. LA function analysis was performed in all patients using echocardiographic 2D speckle tracking. Sixty seven patients were included in strain analysis. The DDFx group (n = 21) and IndtDFx (n = 19) were significantly different from NDFx (27) in some demographics, cardiovascular risk factors, presentation and echocardiographic parameters. Some of the phasic LA function (phasic LA volumes and strains) parameters in the IndtDFx group were similar to DDFx and significantly different from the NDFx group, while other parameters fell in between the two groups. Phasic LA minimal volume index was found to be associated with heart failure symptoms. The IndtDFx group is a heterogeneous group demonstrating clinical and echocardiographic profiles that closely resemble that of DDFx group. LA phasic function analysis may help in re-classification of patients with IndtDFx as actual DDFx or as NDFx.

Echocardiographic evaluation of hypertrophic cardiomyopathy: A review of up-to-date knowledge and practical tips

Hypertrophic cardiomyopathy (HCM) is the most frequent cardiac disease with genetic substrate, affecting about .2%-.5% of the population. The proper diagnosis is important for optimal management and follow-up. Echocardiography plays an essential role in the assessment of patients with HCM including diagnosis, screening, management formulation, prognosis, and follow up. It also helps to differentiate HCM from other diseases. The advancement of software and probe technology added many echo modalities and techniques that helped in refining the diagnostic and assessing the prognosis of patients with HCM. In this review, we briefly summarize how to integrate the different echocardiographic modalities to obtain comprehensive assessment supported by an updated knowledge of the latest guidelines and recently published articles. Many practical tips and tricks are included in this review to improve the diagnostic accuracy of echocardiography and minimize errors during interpretation.

Altered regional myocardial velocities by tissue phase mapping and feature tracking in pediatric patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is associated with heart failure, atrial fibrillation and sudden death. Reduced myocardial function has been reported in HCM despite normal left ventricular (LV) ejection fraction. Additionally, LV fibrosis is associated with elevated T1 and might be an outcome predictor.

OBJECTIVE

To systematically compare tissue phase mapping and feature tracking for assessing regional LV function in children and young adults with HCM and pediatric controls, and to evaluate structure-function relationships among myocardial velocities, LV wall thickness and myocardial T1.

MATERIALS AND METHODS

Seventeen pediatric patients with HCM and 21 age-matched controls underwent cardiac MRI including standard cine imaging, tissue phase mapping (two-dimensional cine phase contrast with three-directional velocity encoding), and modified Look-Locker inversion recovery to calculate native global LV T1. Maximum LV wall thickness was measured on cine images. LV radial, circumferential and long-axis myocardial velocity time courses, as well as global and segmental systolic and diastolic peak velocities, were quantified from tissue phase mapping and feature tracking.

RESULTS

Both tissue phase mapping and feature tracking detected significantly decreased global and segmental diastolic radial and long-axis peak velocities (by 12-51%, P<0.001-0.05) in pediatric patients with HCM vs. controls. Feature tracking peak velocities were lower than directly measured tissue phase mapping velocities (mean bias = 0.3-2.9 cm/s). Diastolic global peak velocities correlated moderately with global T1 (r = -0.57 to -0.72, P<0.01) and maximum wall thickness (r = -0.37 to -0.61, P<0.05).

CONCLUSION

Both tissue phase mapping and feature tracking detected myocardial velocity changes in children and young adults with HCM vs. controls. Associations between impaired diastolic LV velocities and elevated T1 indicate structure-function relationships in HCM.

The role of echocardiography in management of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common non-ischemic cardiomyopathy, characterized by increased left ventricular wall thickness. Echocardiographic studies are essential for establishing the diagnosis, evaluating the extent of disease, and risk stratification. Echocardiography is also recommended in regular screening of the genotype-positive relatives. Two-dimensional, M-mode, and Doppler echocardiography are standard modalities in HCM diagnosis. Newer echocardiographic techniques as tissue Doppler, strain, and three-dimensional echocardiography are now widely used and can reveal subtle changes in the HCM patients. Echocardiography has given us a better understanding of the disease. In this review, we briefly profile the echocardiographic management of HCM in a clinical perspective.

Cardiovascular Magnetic Resonance Provides Evidence of Abnormal Myocardial Strain and Primary Cardiomyopathy in Marfan syndrome

OBJECTIVE

Marfan syndrome is an autosomal-dominant genetic disorder caused by mutations in the fibrillin-1 gene. The condition is a connective tissue disease that frequently involves the cardiovascular system. The existence of a primary cardiomyopathy in Marfan syndrome, however, is controversial. The aims of this study were to investigate the prevalence of left ventricular dysfunction with both transthoracic echocardiography and cardiovascular magnetic resonance (CMR) in a cohort of Marfan syndrome patients and to investigate patterns of myocardial strain across the cohort.

METHODS

We used an institutional database to identify all patients with a firm diagnosis of Marfan syndrome based on Ghent criteria. Inclusion required left ventricular ejection fraction (LVEF) to have been measured by both CMR and transthoracic echocardiography within 12 months of each other. Normal LVEF was defined as a value of >55% when measured by CMR. Velocity vector imaging was used to measure left ventricular longitudinal strain patterns by application of feature tracking to cine magnetic resonance images. Results were compared with data from 20 age-matched control subjects.

RESULTS

Sixty-nine Marfan syndrome patients met the inclusion criteria. The mean age was 35.4 ± 15.0 years, and 56.5% were male. The mean LVEF was 59.0% ± 7.0% by CMR and 59.1% ± 5.8% by echo. One-fifth of Marfan syndrome patients (15/69; 21.7%) had reduced function with LVEF ≤55% by CMR, but only 5 of these were identified by echo. Furthermore, echo identified 5 Marfan syndrome patients as having reduced LVEF in the presence of a normal LVEF by CMR. Some Marfan syndrome patients had abnormal longitudinal strain patterns even with LVEF within the reference range.

CONCLUSIONS

These data provide support for a primary cardiomyopathy in some Marfan syndrome patients. Cardiovascular magnetic resonance is more sensitive than echo for identifying cases with mild systolic dysfunction. Strain analysis may be more sensitive than simple LVEF assessment for identifying at-risk individuals.

Differences in the extent of fibrosis in obstructive and nonobstructive hypertrophic cardiomyopathy

AIMS

Left ventricular outflow tract (LVOT) obstruction is a key feature of hypertrophic cardiomyopathy (HCM) that identifies patients at increased risk of adverse outcomes. Previous studies have hypothesized that LVOT obstruction enhances myocardial fibrosis and increases left ventricular (LV) filling pressures, producing greater clinical deterioration. However, this hypothesis has not been demonstrated in a clinical cohort comparing obstructive and nonobstructive patients.

METHODS

Patients with HCM in whom Doppler echocardiography was performed within 30 days of cardiac MRI were enrolled, using the E/e' ratio to assess LV diastolic function and late gadolinium enhancement to evaluate the extent of fibrosis. Data were assorted according to LVOT obstruction status at rest.

RESULTS

The current study enrolled 67 patients who were mostly middle-aged (56.8 ± 13.2 years old) men (75%) with preserved ejection fraction. Obstructive HCM presented a significant association with a high fibrosis extent [odds ratio (OR) 3.33; P = 0.034] which was maintained after adjusting for sex and age (OR 4.37; P = 0.016) but not for maximum LV wall thickness (OR 2.13; P = 0.225). Obstructive HCM was also associated with a clinically significant E/e' ratio more than 14 (OR 7.8; P = 0.001) which decreased slightly after adjusting for age, sex and maximum LV thickness (OR 6.54; P = 0.014). There was a significant association between an E/e' ratio more than 14 and the extent of fibrosis (OR 1.29; P < 0.001) which was maintained after adjusting for age, sex and maximum LV wall thickness (OR 1.36; P = 0.001).

CONCLUSION

LVOT obstruction may play a role in the extent of fibrosis in HCM, possibly conditioning greater diastolic dysfunction.

Echocardiography in the Diagnosis and Management of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an inherited condition present in about 1/500 individuals with more than 1500 causative mutations identified in primarily 10 sarcomeric proteins. Although HCM is inherited in an autosomal dominant way, there is often incomplete penetrance and variable phenotype even with the same genotype. It is characterized by a degree of hypertrophy (usually asymmetric), that is, not due to another identifiable cause, as well as variable degrees of myocardial fibrosis and microvascular abnormalities.

Impaired left ventricular mechanics and functional reserve are associated with reduced exercise capacity in patients with hypertrophic cardiomyopathy

BACKGROUND

Reduced metabolic equivalents (METs) are an indicator of exercise intolerance, which predicts poor prognosis in hypertrophic cardiomyopathy (HCM) patients. We sought to evaluate the changes in left ventricular (LV) mechanics and functional reserves, as well as their association with functional capacity in HCM patients.

METHODS

Seventy HCM patients and thirty controls were included in this study. LV mechanics were evaluated at rest and during exercise by echocardiography and two-dimensional speckle-tracking imaging to obtain parameters of functional reserve, LV global longitudinal strain (LVGLS), strain rate (SR), and circumferential strain.

RESULTS

Hypertrophic cardiomyopathy (HCM) patients had lower LVGLS, systolic SR, early and late diastolic SR at rest and during exercise, and reduced absolute and relative systolic and diastolic reserve compared to controls. LV circumferential strain was significantly higher at rest but lower during exercise in HCM patients. Exercise capacity was markedly reduced in HCM patients, and peak exercise LVGLS (LVGLS-exe) significantly correlated with exercise capacity. Multivariate regression analyses showed that LVGLS-exe, LV filling pressure during exercise (E/e'-exe), and LV mass index (LVMI) were independent predictors of exercise capacity. Moreover, LVGLS-exe displayed incremental predictive value over E/e'-exe and LVMI for exercise intolerance. Receiver operating characteristic curve analysis showed LVGLS-exe had optimal accuracy for predicting exercise intolerance in HCM patients.

CONCLUSIONS

Hypertrophic cardiomyopathy (HCM) patients have reduced LV mechanics at rest and during exercise and impaired mechanical reserve. LVGLS-exe is associated with exercise capacity and is an optimal predictive value for reduced exercise capacity in HCM patients.

Multilayer Myocardial Mechanics in Genotype-Positive Left Ventricular Hypertrophy-Negative Patients With Hypertrophic Cardiomyopathy

It is unknown whether the presence of a sarcomeric mutation alone is sufficient to result in abnormal myocardial force generation, or whether additional changes in myocardial architecture (hypertrophy, disarray, and fibrosis) are required to impair systolic function. Speckle tracking echocardiography allows quantification of global strain/strain rates, twist, and dyssynchrony. In the present study we sought to further elucidate early abnormalities of myocardial mechanics in sarcomeric mutation carriers without evidence of clinical disease. Sixty genotype-positive left ventricular hypertrophy-negative (G+left ventricular hypertrophy [LVH]-) patients and 60 normal controls were studied. Velocity vector imaging was applied retrospectively to echocardiographic images to quantify global longitudinal and circumferential strain/strain rate, and rotation parameters. The G+LVH- group demonstrated both smaller left ventricular diastolic cavity dimensions (4.5 ± 0.6 cm vs 4.8 ± 0.4 cm) and a higher LVEF (66 ± 6% vs 60 ± 5%) compared with controls. An increase in circumferential subendocardial systolic strain (-30 ± 5 vs -27 ± 3%) and both systolic and diastolic subendocardial strain rate was seen in the G+LVH- group. Peak rotation angles were higher at the base and apex, with an increase in total twist (9.0 ± 3.8 vs 6.9 ± 2.9). In the control group, global and average segmental strain were similar, suggesting no/minimal dyssynchrony (global mechanical synchrony index [GMSi] 0.97-0.98). In the G+LVH- group GMSi was significantly lower (subendocardial GMSi 0.95; subepicardial GMSi 0.60), suggesting increasing subendocardial to subepicardial dyssynchrony. In conclusion, utilizing multilayer strain analysis, we demonstrate that G+LVH- subjects have enhanced subendocardial systolic strain rate and twist, as well as mechanical dyssynchrony within the left ventricular myocardium. These results demonstrate that abnormalities in myocardial mechanics precede the development of clinical hypertrophy.

Layer-specific strain analysis of left ventricular myocardium after alcohol septal ablation for hypertrophic obstructive cardiomyopathy

INTRODUCTION

We aimed to explore the layer-specific systolic strain of left ventricular (LV) myocardium in patients with hypertrophic obstructive cardiomyopathy (HOCM) before and after alcohol septal ablation (ASA).The routine 2D (frame rate: >50 Hz) data sets were acquired using GE Vivi7 system for 44 consecutive HOCM patients and 21 matched normal subjects. Fifteen of HOCM patients had serial echocardiograms available for speckle tracking analyses before and 1 year after ASA. 2D strain was analyzed by EchoPAC software.The layer strain from inner to mid-myocardial and outer layers in basal and middle segments in HOCM patients continuously declined. The absolute values of peak systolic strains from the endocardium to mid-myocardium and epicardium in the basal septum of the HOCM group were significantly lower than those of the normal group (P <.01). Meanwhile, the layer systolic strain of LV endocardium in the basal septum increased significantly during a 1-year follow-up (P <.05).

CONCLUSIONS

The layer-specific strains of HOCM patients measured by tissue Doppler echocardiography decreased significantly compared to those of normal individuals. The increased specific layer strain of LV endocardium in the basal septum may be a valid marker of echocardiographic improvement in HOCM patients receiving ASA.

Challenging the complementarity of different metrics of left atrial function: insight from a cardiomyopathy-based study

Aims

Left ventricular (LV) strain provides incremental values to LV ejection fraction (LVEF) in predicting outcome. We sought to investigate if similar relationship is observed between left atrial (LA) emptying fraction and LA strain.

Methods and results

In this study, we selected 50 healthy subjects, 50 patients with dilated, 50 hypertrophic, and 50 infiltrative (light-chain (AL) amyloidosis) cardiomyopathy (CMP). Echocardiographic measures included LVEF and LA emptying fraction as well as LV and LA longitudinal strain (LVLS and LALS). After regression analysis, comparison of least square means of LA strain among aetiologies was performed. Intraclass correlation coefficient (ICC) and coefficient of variation (COV) were used in the assessment of variability and reproducibility of LV and LA metrics. The mean LVLS and all LA metrics were impaired in patients with all CMP compared with healthy subjects. In contrast to the moderate relationship between LVEF and LVLS (r = -0.51, P < 0.001), there was a strong linear relationship between LA emptying fraction and LA strain (r = 0.87, P < 0.001). In multiple regression analysis, total LA strain was associated with LVLS (β = -0.48, P < 0.001), lateral E/e' (β = -0.24, P < 0.001), age (β = -0.21, P < 0.001), and heart rate (β = -0.14, P = 0.02). The least square mean of LA strain adjusted for the parameters was not different among aetiologies (ANOVA P = 0.82). The ICC (>0.77) and COV (<13) were acceptable.

Conclusion

In contrast to LV measures, there is a strong linear relationship between volumetric and longitudinal deformation indices of left atrium irrespective of CMP aetiology. Either LA emptying fraction or LA strain could be used as an important parameter in predictive models.

Left Ventricular Wall Stress Is Sensitive Marker of Hypertrophic Cardiomyopathy With Preserved Ejection Fraction

Hypertrophic cardiomyopathy (HCM) patients present altered myocardial mechanics due to the hypertrophied ventricular wall and are typically diagnosed by the increase in myocardium wall thickness. This study aimed to quantify regional left ventricular (LV) shape, wall stress and deformation from cardiac magnetic resonance (MR) images in HCM patients and controls, in order to establish superior measures to differentiate HCM from controls. A total of 19 HCM patients and 19 controls underwent cardiac MR scans. The acquired MR images were used to reconstruct 3D LV geometrical models and compute the regional parameters (i.e., wall thickness, curvedness, wall stress, area strain and ejection fraction) based on the standard 16 segment model using our in-house software. HCM patients were further classified into four quartiles based on wall thickness at end diastole (ED) to assess the impact of wall thickness on these regional parameters. There was a significant difference between the HCM patients and controls for all regional parameters (P < 0.001). Wall thickness was greater in HCM patients at the end-diastolic and end-systolic phases, and thickness was most pronounced in segments at the septal regions. A multivariate stepwise selection algorithm identified wall stress index at ED (σ_i,ED) as the single best independent predictor of HCM (AUC = 0.947). At the cutoff value σ_i,ED < 1.64, both sensitivity and specificity were 94.7%. This suggests that the end-diastolic wall stress index incorporating regional wall curvature—an index based on mechanical principle—is a sensitive biomarker for HCM diagnosis with potential utility in diagnostic and therapeutic assessment.

Hypertrophic cardiomyopathy and left ventricular hypertrophy in hypertensive heart disease with mildly reduced or preserved ejection fraction: insight from altered mechanics and native T1 mapping

AIM

To explore the relationship between extracellular volume (ECV), native T1, and systolic strain in hypertrophic cardiomyopathy (HCM) and hypertensive patients with left ventricular hypertrophy (HTN LVH) with mildly reduced or preserved ejection fraction.

MATERIALS AND METHODS

T1 mapping was performed in 45 patients with late gadolinium enhancement positive (LGE+) HCM (mean age, 53±6 years), 11 patients with LGE- (LGE-) HCM (mean age, 56±5 years), and 20 patients with HTN LVH (mean age, 55±6 years) on at 3 T magnetic resonance imaging (MRI) using the modified look-locker inversion-recovery (MOLLI) pulse sequence. Mean T1 value, ECV and circumferential strain parameters were determined for each patient.

RESULTS

Overall, the HCM patients had higher native T1 values (1242.92±68.94) and ECV (0.31±0.05) in comparison to those of the HTN LVH patients (1197±46.80, 0.27±0.04; p<0.05). In the subgroup analysis, the HCM LGE+ patients had the highest native T1 values among the three groups. The HCM LGE+ patients had higher ECV than the LGE- patients. HCM LGE- patients had higher ECV than HTN LVH patients (p<0.05). Peak systolic circumferential strain and early diastolic strain rates were reduced in the HCM LGE+ patients in comparison to the HCM LGE- and HTN LVH patients (p<0.05). Reduced peak systolic and early diastolic circumferential strain rates were associated with increased levels of ECV and native T1 values among all the patients.

CONCLUSION

HCM LGE+ patients had higher native T1 values, higher ECV, and an associated reduction in early diastolic strain rates and peak systolic circumferential strains when compared to the HCM LGE- and HTN LVH patients with mildly reduced or preserved ejection fraction.

The role of imaging in the diagnosis and management of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy, affecting approximately 1:500 people. As the yield of genetic testing is only about 35-60%, the diagnosis of HCM is still clinical and based on the demonstration of unexplained and usually asymmetric left ventricular (LV) hypertrophy by imaging modalities. In the past, echocardiography was the sole imaging modality used for the diagnosis and management of HCM. However, in recent years other imaging modalities such as cardiac magnetic resonance have played a major role in the diagnosis, management and risk stratification of HCM, particularly when the location of left ventricular hypertrophy is atypical (apex, lateral wall) and when the echocardiographic imaging is sub-optimal. However, the most unique contribution of cardiac magnetic resonance is the quantification of myocardial fibrosis. Exercise stress echocardiography is the preferred provocative test for the assessment of LV outflow tract obstruction, which is detected only on provocation in one-third of the patients.

Systolic and diastolic myocardial mechanics in hypertrophic cardiomyopathy and their link to the extent of hypertrophy, replacement fibrosis and interstitial fibrosis

Aim of the present study was to investigate the relations between myocardial mechanics and the extent of hypertrophy and fibrosis in hypertrophic cardiomyopathy (HCM). Forty-five consecutive patients with HCM and 15 subjects without structural heart disease were included. Cardiac magnetic resonance with late gadolinium enhancement (LGE) imaging was performed to evaluate biventricular function, LV mass index and presence/extent of LGE, expression of replacement fibrosis. Myocardial T1 relaxation, a surrogate of interstitial fibrosis, was measured from Look-Locker sequence. Feature-tracking analysis was applied to LV basal, mid and apical short-axis images to assess systolic and diastolic global LV circumferential strain (CS) and strain rate (CSr). Peak systolic CS and CSr were significantly higher among HCM patients as compared to control subjects (p = 0.015 and p = 0.007, respectively). The ratio of peak CSr during early filling to peak systolic CSr was significantly lower among HCM patients (p = 0.002). At multivariate linear regression analysis, LV mass index (p < 0.001) and %LV LGE (p = 0.011) were significantly and independently related to peak systolic CS; LV mass index (p < 0.001) and %LV LGE (p = 0.023) were significantly and independently related to peak systolic CSr; %LV LGE (p = 0.021) and T1 ratio (p = 0.006) were significantly and independently related to the ratio of peak CSr during early filling to peak systolic CSr. LV systolic mechanics are enhanced and LV diastolic mechanics are impaired in HCM. Extent of hypertrophy and replacement fibrosis influence the LV systolic mechanics while extent of replacement fibrosis and interstitial fibrosis influence the LV diastolic mechanics.

Noninvasive assessment of myocardial mechanics of the left ventricle in rabbits using velocity vector imaging

BACKGROUND

Our study aimed to investigate the feasibility of velocity vector imaging (VVI) to analyze left ventricular (LV) myocardial mechanics in rabbits at basal state.

MATERIAL AND METHODS

The animals used in this study were 30 New Zealand white rabbits. All rabbits underwent routine echocardiography under VVI-mode at basal state. The 2-dimensional (2-D) echocardiography images acquired included parasternal left long-axis views and short-axis views at the level of LV mitral valve, papillary muscles, and apex. Images were analyzed by VVI software.

RESULTS

At basal state, longitudinal LV velocity decreased from the basal to the apical segment (P<0.05). In the short axis direction, the highest peak myocardial velocity was found between the anterior septum and anterior wall for each segment at the same level; the peak strains and strain rates (SR) were the highest in the anterior and lateral wall compared to other segments (all P<0.05). During systole, LV base rotated in a clockwise direction and LV apex rotated in a counter-clockwise direction, while during diastole, both LV base and apex rotated in the direction opposite to systole. The rotation angle, rotation velocity and unwinding velocity in the apical segment were greater than the basal segment (P<0.05).

CONCLUSIONS

VVI is a reliable tool for evaluating LV myocardial mechanics in rabbits at basal state, and the LV long-axis short-axis and torsional motions reflect the normal regular patterns. Our study lays the foundation for future experimental approaches in rabbit models and for other applications related to the study of human myocardial mechanics.

Assessment of left ventricular longitudinal function in cats with subclinical hypertrophic cardiomyopathy using tissue Doppler imaging and speckle tracking echocardiography

Hypertrophic cardiomyopathy (HCM) in cats is characterized by concentric left ventricular (LV) hypertrophy and both diastolic and systolic dysfunction. Although impaired cardiac function detected by tissue Doppler imaging (TDI) in cats with HCM was previously reported, reference ranges of TDI in normal cats and cats with HCM have been reported as widely variable. Two-dimensional speckle tracking echocardiography (STE) was useful for assessment of cardiac function in human patients with HCM, but clinical utility was not known in cats. The aim of this study was to assess global and segmental LV myocardial function using STE in cats with HCM whose TDI variables were within the reference range. A total of 35 cats of different breeds were enrolled in this study. The HCM group (n=22) was cats diagnosed as HCM without left atrial enlargement and with normal TDI measurements. HCM cats were further divided into a segmental hypertrophy (S-HCM) group and a diffuse hypertrophy (D-HCM) group. The control group consisted of 13 clinically healthy cats. No cats in any group showed any clinical symptoms. Conventional echocardiography, TDI, and global and segmental STE indices were evaluated and compared between groups. Only the longitudinal strain rate during early diastole was significantly decreased in both HCM groups, even in all segments including those without hypertrophy in S-HCM group. This study suggests that STE parameters are the more sensitive variables compared with conventional TDI parameters to detect early myocardial diastolic dysfunction in cats with HCM.

Impact of long-axis function on cardiac surgical outcomes in patients with radiation-associated heart disease

BACKGROUND

Malignancy-associated thoracic radiation leads to radiation-associated cardiac disease (RACD) that often necessitates cardiac surgery. Myocardial dysfunction is common in patients with RACD. We sought to determine the predictive value of global left ventricular ejection fraction and long-axis function left ventricular global longitudinal strain (LV-GLS) in such patients.

METHODS

We studied 163 patients (age, 63 ± 14 years; 74% women) who had RACD and underwent cardiac surgery (20% had reoperations) between 2000 and 2003. In addition to standard echocardiography, LV-GLS (%) was derived from the average of 18 segments in 3 apical views of the left ventricle, using velocity vector imaging. Standard clinical and demographic parameters were recorded. All-cause mortality was recorded.

RESULTS

The mean duration between cardiac surgery and the last chest radiation was 18 ± 12 years. The median European System for Cardiac Operative Risk Evaluation (EuroSCORE) was 8, and 88 patients died over 6.6 ± 4 years. A total of 52% of patients had ≥ II+ mitral regurgitation; 23% of patients had severe aortic stenosis; and 39% of patients had ≥ II+ tricuspid regurgitation. The mean left ventricular ejection fraction was 54% ± 13%, and the mean LV-GLS was -12.9% ± 4%. In a Cox proportional survival analysis, lower LV-GLS was predictive of mortality in univariable analysis (hazard ratio, 1.07 (95% confidence interval, 1.01-1.14); P = .006); however, after adjustment for other variables, the association became nonsignificant. In patients with a EuroSCORE <median, abnormal LV-GLS (<-14.5%) was associated with significantly higher mortality (48%), compared with those with normal LV-GLS (32%).

CONCLUSIONS

In patients who have RACD and undergo cardiac surgery, LV-GLS does not sufficiently discriminate and is not independently predictive of long-term outcomes. However, in patients with a low EuroSCORE, abnormal LV-GLS was associated with higher mortality, compared with those with normal LV-GLS.

Role of multimodality cardiac imaging in the management of patients with hypertrophic cardiomyopathy: an expert consensus of the European Association of Cardiovascular Imaging Endorsed by the Saudi Heart Association

Taking into account the complexity and limitations of clinical assessment in hypertrophic cardiomyopathy (HCM), imaging techniques play an essential role in the evaluation of patients with this disease. Thus, in HCM patients, imaging provides solutions for most clinical needs, from diagnosis to prognosis and risk stratification, from anatomical and functional assessment to ischaemia detection, from metabolic evaluation to monitoring of treatment modalities, from staging and clinical profiles to follow-up, and from family screening and preclinical diagnosis to differential diagnosis. Accordingly, a multimodality imaging (MMI) approach (including echocardiography, cardiac magnetic resonance, cardiac computed tomography, and cardiac nuclear imaging) is encouraged in the assessment of these patients. The choice of which technique to use should be based on a broad perspective and expert knowledge of what each technique has to offer, including its specific advantages and disadvantages. Experts in different imaging techniques should collaborate and the different methods should be seen as complementary, not as competitors. Each test must be selected in an integrated and rational way in order to provide clear answers to specific clinical questions and problems, trying to avoid redundant and duplicated information, taking into account its availability, benefits, risks, and cost.

Association of noninvasively measured left ventricular mechanics with in vitro muscle contractile performance: a prospective study in hypertrophic cardiomyopathy patients

Background

Hypertrophic cardiomyopathy (HCM) is a primary myopathic process in which regional left ventricular dysfunction may exist without overt global left ventricular dysfunction. In obstructive HCM patients who underwent surgical myectomy (SM), we sought to determine if there is a significant association between echocardiographic longitudinal strain, histopathology, and in vitro myocardial performance (resting tension and developed tension) of the surgical specimen.

Methods and Results

HCM patients (n=122, 54±14 years, 54% men) undergoing SM were prospectively recruited. Longitudinal systolic strain and diastolic strain rates were measured at that basal septum (partially removed at SM) by using velocity vector imaging on preoperative echocardiography. Semiquantitative histopathologic grading of myocyte disarray and fibrosis and in vitro measurements of resting tension and developed tension were made in septal tissue obtained at SM. Mean basal septal systolic strain and diastolic strain rate were −8.3±5% and 0.62±0.4/s, while mild or greater degree of myocyte disarray and interstitial fibrosis were present in 85% and 87%, respectively. Mean resting tension and developed tension were 2.8±1 and 1.4±0.8 g/mm². On regression analysis, basal septal systolic strain, diastolic strain rate, disarray, and fibrosis were associated with developed tension (β=0.19, 0.20, −0.33, and −0.40, respectively, all P<0.01) and resting tension (β=0.21, 0.22, −0.25, and −0.28, respectively, all P<0.01).

Conclusion

In obstructive HCM patients who underwent SM, left ventricular mechanics (echocardiographic longitudinal systolic strain and diastolic strain rates), assessed at the basal septum (myocardium removed during myectomy) and histopathologic findings characteristic for HCM (disarray and fibrosis) were significantly associated with in vitro myocardial resting and developed contractile performance.

Global cardiac alterations detected by speckle-tracking echocardiography in Fabry disease: left ventricular, right ventricular, and left atrial dysfunction are common and linked to worse symptomatic status

The aim of this study was to test the hypothesis that in patients with Fabry disease, 2D speckle-tracking echocardiography (2DSTE) could detect functional myocardial alterations such as left ventricular (LV), right ventricular (RV), and left atrial (LA) dysfunction, even when conventional cardiac measurements are normal. In addition, we hypothesized that these global cardiac alterations could be linked to worse symptomatic status in these patients. Fifty patients with Fabry disease and a control group of 118 healthy subjects of similar age and gender were included. The myocardial function and structural changes of the LV, RV, and LA were analyzed by 2DSTE and cardiac magnetic resonance imaging. Patients with Fabry disease had significantly lower functional myocardial values of the LV, RV, and LA than healthy subjects (LV, RV, and LA strain -18.1 ± 4.0, -21.4 ± 4.9, and 29.7 ± 9.9 % vs. -21.6 ± 2.2, -25.2 ± 4.0, and 44.8 ± 11.1 %, respectively, P < 0.001) and elevated rates of LV, RV, and LA myocardial dysfunction (24, 20, and 26 %, respectively), even when conventional cardiac measurements such as LVEF, TAPSE, and LAVI were normal. LV septal wall thickness ≥15 mm, RV free wall thickness ≥7 mm, and LV longitudinal dysfunction were the principal factors linked to reduced LV, RV, and LA strain, respectively. In addition, but to a lesser extent, LV and RV fibrosis were linked to reduced LV and RV strain. Patients with reduced LV, RV, and LA strain had worse functional class (dyspnea-NYHA classification) than those with normal cardiac function. In conclusion, in patients with Fabry disease, 2DSTE analyses detect LV, RV, and LA functional myocardial alterations, even when conventional cardiac measurements are normal. These functional myocardial alterations are common and significantly associated with worse symptomatic status in Fabry patients. Therefore, these findings provide important evidence to introduce global myocardial analyses using 2DSTE in the early detection of functional cardiac alterations in Fabry disease.

Physiologic or pathologic hypertrophy: how can we know?

Pathologic left ventricular hypertrophy due to hypertrophic cardiomyopathy is typically diagnosed based on compatible clinical and imaging findings. In a subset of patients however, the diagnosis is unclear, either due to the finding of concentric hypertrophy raising the possibility of physiologic hypertrophy due to athlete's heart or due to the potential of so-called hypertrophic cardiomyopathy 'phenocopies', which include Anderson-Fabry disease and cardiac amyloidosis. We review each of these diseases, highlighting important distinguishing features, the knowledge of which should permit the resolution of such diagnostic dilemmas.

Differences in global and regional left ventricular myocardial mechanics in various morphologic subtypes of patients with obstructive hypertrophic cardiomyopathy referred for ventricular septal myotomy/myectomy

Patients with obstructive hypertrophic cardiomyopathy (HC) have various left ventricular (LV) shapes: reverse septal curvature (RSC, commonly familial), sigmoid septum (SS, common in hypertensives), and concentric hypertrophy (CH). Longitudinal (systolic and early diastolic) strain rate (SR) is sensitive in detecting regional myocardial dysfunction. We sought to determine differences in longitudinal SR of patients with obstructive HC, based on LV shapes. We studied 199 consecutive patients with HC (50% men) referred for surgical myectomy. Clinical and echocardiographic parameters were recorded. LV shapes were classified on echocardiography, using basal septal 1/3 to posterior wall ratio: RSC = ratio >1.3 (extending to mid and distal septum), SS = ratio >1.3 (extending only to basal 1/3), and concentric = ratio ≤1.3. Longitudinal systolic and early diastolic SRs were measured from apical 4- and 2-chamber views (VVI 2.0; Siemens, Erlangen). Distribution of RSC, SS, and CH was 50%, 28%, and 22%, respectively. Patients with RSC were significantly younger (47 ± 12 vs 64 ± 10 and 57 ± 11, respectively) with lower hypertension (40% vs 71% and 67%, respectively) than patients with SS or CH (both p <0.001). Patients with RSC had lower global systolic (-0.99 ± 0.3 vs -1.05 ± 0.3 and -1.17 ± 0.3) and early diastolic SR (0.95 ± 0.4 vs 0.98 ± 0.3 and 1.16 ± 0.4) versus patients with SS and CH (in 1/s, both p <0.01), despite being much younger and less hypertensive. RSC was associated with abnormal global LV systolic (beta 0.16) and early diastolic (beta -0.17) SR (both p <0.01). In conclusion, patients with HC with RCS have significantly abnormal LV mechanics, despite being younger and less hypertensive. A combination of LV mechanics and shapes could help differentiate between genetically mediated and other causes of obstructive HC.

Determining the role of fibrosis in hypertrophic cardiomyopathy

Fibroblast activity within the heart may be considered a basically constructive process. Hyperactivity of fibroblasts, however, may result in the accumulation of extracellular matrix proteins with adverse effects on cardiac structure and function including electrical instability and increased risk of arrhythmogenic cardiac death. The detection of cardiac fibrosis by dedicated imaging techniques, mainly gadolinium-enhanced MRI, holds promise to refine patient management in a variety of cardiac conditions. This review aims to summarize the current knowledge regarding fibrosis in hypertrophic cardiomyopathy.

Systolic function reserve using two-dimensional strain imaging in hypertrophic cardiomyopathy: comparison with essential hypertension

BACKGROUND

Although patients with hypertrophic cardiomyopathy (HCM) have normal ejection fractions at rest, the investigators hypothesized that these patients have differentially abnormal systolic function reserves, limiting their exercise capacity compared with patients with hypertension (HTN).

METHODS

Forty patients with HCM (mean age, 39.1 ± 12 years), 20 patients with HTN with LVH, and 33 healthy individuals underwent resting and peak exercise echocardiography using two-dimensional strain imaging. Peak longitudinal systolic strain (εsys) and strain rate were measured in apical views. Circumferential εsys and left ventricular (LV) twist were analyzed from short-axis views. LV systolic dyssynchrony was measured from regional longitudinal strain curves as the standard deviation of time to peak strain (time from the beginning of the Q wave on electrocardiography to peak εsys) between 12 segments. The differences between resting and peak exercise values were analyzed, and functional reserve was calculated as the difference divided by the resting value.

RESULTS

In patients with HCM, resting values for longitudinal εsys, systolic strain rate, early diastolic strain rate, and atrial diastolic strain rate were significantly lower, while circumferential εsys and twist were higher, compared with patients with HTN and controls (P < .0001). Functional systolic reserve increased during exercise in controls (17 ± 6%), increased to a lesser extent in patients with HTN (10 ± 16%), and was markedly attenuated in patients with HCM (-23 ± 28%) (P < .001). At peak exercise, even with augmented circumferential εsys and twist in patients with HCM (P < .01) compared with those with HTN, both remained lower than in controls (P < .001). LV dyssynchrony was amplified during exercise in patients with HCM compared with those with HTN (P < .001). Within the entire population, exercise capacity was clearly correlated with systolic functional reserve. However when taken separately, it was mainly related to resting LV dyssynchrony and diastolic function in patients with HCM, whereas it was linked to age and LV wall thickness in those with HTN.

CONCLUSIONS

Patients with HCM have significantly limited systolic function reserve and more dynamic dyssynchrony with exercise compared with those with HTN. Two-dimensional strain imaging during stress may provide a new and reliable method to identify patients at higher cardiovascular risk.

Association between septal strain rate and histopathology in symptomatic hypertrophic cardiomyopathy patients undergoing septal myectomy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is histopathologically characterized by myocyte hypertrophy, disarray, interstitial fibrosis, and small intramural coronary arteriole dysplasia, which contribute to disease progression. Longitudinal systolic and early diastolic strain rate (SR) measurements by speckle tracking echocardiography are sensitive markers of regional myocardial function. We sought to determine the association between septal SR and histopathologic findings in symptomatic HCM patients who underwent surgical myectomy.

METHODS

We studied 171 HCM patients (documented on histopathology) who underwent surgical myectomy to relieve left ventricular outflow tract obstruction. Various clinical and echocardiographic parameters were recorded. Segmental longitudinal systolic and early diastolic SRs (of the septal segment removed at myectomy) were measured from apical 4- and 2-chamber views (VVI 2.0; Siemens, Erlangen, Germany). Histopathologic myocyte hypertrophy, disarray, small intramural coronary arteriole dysplasia, and interstitial fibrosis were classified as none, mild (1%-25%), moderate (26%-50%), and severe (>50%).

RESULTS

The mean age was 53 ± 14 years (52% men, ejection fraction 62% ± 5%, mean left ventricular outflow tract gradient 102 ± 39 mm Hg, and basal septal thickness of 2.2 ± 0.5 cm). Mean longitudinal systolic and early diastolic SRs were -0.91 ± 0.5 and 0.82 ± 0.5 (1/s), respectively. There was an inverse association between systolic and early diastolic septal SR and degree of myocyte hypertrophy, disarray, and interstitial fibrosis (all P < .05). There was no association between histopathologic characteristics and other echocardiography parameters. On multivariable regression analysis, myocyte disarray and echocardiographic septal hypertrophy were associated with systolic and early diastolic septal SR (P < .05).

CONCLUSION

In HCM patients, there is inverse association between various histopathologic findings and septal SR. Strain rate might potentially provide further insight into HCM pathophysiology.

Effects of subacute dietary salt intake and acute volume expansion on diastolic function in young normotensive individuals

AIMS

Chronic excess salt intake may have blood pressure-independent adverse effects on the heart such as myocardial hypertrophy and fibrosis. Effects of subacute sodium loading with excess dietary salt on diastolic function in normotensive individuals have been conflicting and the mechanisms are poorly understood.

METHODS AND RESULTS

Thirteen healthy normotensive subjects (age 24 ± 4 years) entered a 2-week crossover study with 1 week of a low-salt diet <10 mEq/day and 1 week of a high-salt diet >200 mEq/day. At the end of each study week, left ventricular dimensions, systolic, and diastolic function were assessed with echocardiography before and after 2 L of normal saline infusion. One week of high-salt and low-salt diets did not lead to differences in echocardiographic parameters of systolic or diastolic function, even after rapid volume expansion with saline infusion. The peak early diastolic strain rate (SR) increased after volume loading both after completion of low-salt (1.62 ± 0.23/s vs. 1.82 ± 0.14/s, P < 0.05) and high-salt diets (1.67 ± 0.16/s vs. 1.86 ± 0.22/s, P < 0.05). There was a positive correlation between the peak early diastolic SR and the cardiac index (r = 0.52, P = 0.017).

CONCLUSION

In healthy normotensive individuals, subacute excess dietary sodium intake does not affect diastolic function. The peak early diastolic SR, similar to other mitral Doppler and tissue Doppler parameters of diastolic function, appears to be strongly dependent on pre-load.

An initial study on left ventricular diastolic function in patients with hypertrophy cardiomyopathy using single-beat, real-time, three-dimensional echocardiography

Objectives

To assess the regional diastolic function in patients with hypertrophic cardiomyopathy (HCM) by using single-beat, real-time, three-dimensional echocardiography (RT-3DE).

Methods

Sixty-five patients with HCM in sinus rhythm together with fifty age- and gender-matched normal controls were studied by two dimensional echocardiography (2DE) and RT-3DE. The parameters analyzed by RT-3DE included: left ventricular (LV) volumes, left ventricular ejection fraction (LVEF), end diastolic sphericity index (EDSI), diastolic dyssynchrony index (DDI), dispersion end diastole (DISPED), and normalized 17 segmental volume-time curves.

Results

Evaluated by RT-3DE, LVEF was slightly lower compared with 2DE (63.2 ± 6.8% vs. 59.1 ± 6.4%, P < 0.0001). Normal subjects had relatively uniform volumetric curves for all LV segments. In HCM patients, the segmental volumetric curves were dyssynchronous. Increased DDI and DISPED in end diastole were observed in patients with HCM (9.95 ± 3.75, 41.76 ± 17.19, P < 0.0001), and not all abnormal volumetric segments occurred in the hypertrophic regions.

Conclusions

Patients with HCM have presented regional diastolic dyssynchrony in the diastole phase, and this preclinical lesion can be recognized by single-beat RT-3DE.

Left ventricular geometry and diastolic function in the hypertensive heart: impact of age

BACKGROUND AND AIM

The impact of aging on the relationship between left ventricular (LV) mass/geometry and diastolic function as assessed by updated echocardiographic methods, such as tissue Doppler, is poorly defined. We investigated this issue in a cohort of hypertensive patients.

METHODS

A total of 660 hypertensives (mean age 65 ± 13 years, 48% men) with preserved LV systolic function underwent a comprehensive echo-Doppler examination for routine clinical indications. For the present analysis, the subjects have been divided in two age groups (<65 or ≥65 years).

RESULTS

Overall, 61% of subjects fulfilled the criteria for LVH, 18% for left atrial (LA) enlargement and 11% for altered LV filling index. Concentric LV geometry was 1.4-fold higher in older hypertensives than in younger counterparts; also the prevalence of LA enlargement and altered LV filling was 2.0- and 1.9-fold higher in the former group, respectively. In older hypertensives, at variance from younger ones, neither LV mass nor relative wall thickness (RWT), a continuous index of LV geometry, were independently correlated to conventional as well as tissue Doppler LV diastolic indexes.

CONCLUSIONS

Our findings suggest the relationship between cardiac hypertrophy and diastolic function in hypertensive subjects is affected by aging-associated factors unrelated to the amount of LV mass as assessed by standard echocardiography.

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.

Energy transfer from systole to diastole: a novel device-based approach for the treatment of diastolic heart failure

We hypothesized that attachment of elastic coil to the left ventricular (LV) wall, capable of exerting outward forces may allow the transfer of energy from systole to diastole and improve diastolic function.

METHODS AND RESULTS

An extra-ventricular-device, composed of a series of elastic elements interposed between spiral screws attached to the epimyocardium of the LV free-wall was developed. The hemodynamic and mechanical effects of the device were tested using a computerized model, an in vitro model utilizing a computerized-controlled fluid pump, eight healthy sheep and 10 mini-pigs induced with diastolic dysfunction by renal wrapping. The computerized and in vitro models predicted a reduction of the LV diastolic pressure curve and partial normalization of the pressure-volume loop. The sheep study demonstrated preservation of animal's wellbeing including maintaining cardiac mechanical function with stable energy transfer from systole to diastole throughout the 6 months follow-up. The mini-pigs study showed an increase in the early diastolic to systolic strain-rate ratio in the mid-endocardial level (23 ± 10%, P = 0.008) and an increase in early apical reverse rotation rate of 50% (P = 0.016 compared to control).

CONCLUSIONS

This study presents a novel concept of using a mechanical device to transfer energy from systole to diastole, potentially enhancing diastolic function.

Left ventricular twist mechanics in hypertrophic cardiomyopathy assessed by three-dimensional speckle tracking echocardiography

Left ventricular (LV) twist represents a phenomenon that links systolic contraction with diastolic relaxation and plays a major role in cardiac physiology; thus, the study of twist mechanics is of particular interest in hypertrophic cardiomyopathy (HC). Three-dimensional speckle tracking echocardiography (3D-STE) has the potential to overcome the limitations of 2-dimensional imaging and provide a greater understanding of LV twist in HC. We aimed to examine LV twist mechanics in HC using 3D-STE. Echocardiograms from subjects with a diagnosis of HC were examined for 3D-STE analysis. Age- and gender-matched healthy subjects were tested as a control group. Forty patients with HC (age 37 ± 16 years; 42.5% women) and 40 control subjects (age 35 ± 10 years; 42.5% women) were examined. Compared with the controls, the patients with HC showed increased peak LV twist (16.5 ± 4.7° vs 12.0 ± 3.9°, p <0.001) mainly because of increased apical rotation of those with LV outflow tract obstruction (obstruction, 12.7 ± 4.4° vs nonobstruction, 9.7 ± 2.8°, p = 0.02). In addition, the patients with HC displayed onset of torsion recoil occurring closer to the aortic valve closure (94 ± 6% vs 85 ± 6%, p <0.001; time normalized by the length of systole), limited completion of untwist during early diastole (31 ± 12% vs 62 ± 15%, p <0.001), and delayed peak untwist velocity (22 ± 7% vs 13 ± 9%, p <0.001; time normalized by the length of diastole). In conclusion, the evaluation of twist mechanics using 3D-STE provides novel insight regarding alterations in LV mechanics in patients with HC. Elucidating the characteristics of the wringing motion of the heart might help to broaden the understanding of the hyperdynamic contraction and impaired relaxation observed in these patients.

Cardiac myosin binding protein C insufficiency leads to early onset of mechanical dysfunction

BACKGROUND

Decreased expression of cardiac myosin binding protein C (cMyBPC) as a result of genetic mutations may contribute to the development of hypertrophic cardiomyopathy (HCM); however, the mechanisms that link cMyBPC expression and HCM development, especially contractile dysfunction, remain unclear.

METHODS AND RESULTS

We evaluated cardiac mechanical function in vitro and in vivo in young mice (8-10 weeks of age) carrying no functional cMyBPC alleles (cMyBPC(-/-)) or 1 functional cMyBPC allele (cMyBPC(±)). Skinned myocardium isolated from cMyBPC(-/-) hearts displayed significant accelerations in stretch activation cross-bridge kinetics. Cardiac MRI studies revealed severely depressed in vivo left ventricular (LV) magnitude and rates of LV wall strain and torsion compared with wild-type (WT) mice. Heterozygous cMyBPC(±) hearts expressed 23±5% less cMyBPC than WT hearts but did not display overt hypertrophy. Skinned myocardium isolated from cMyBPC(±) hearts displayed small accelerations in the rate of stretch induced cross-bridge recruitment. MRI measurements revealed reductions in LV torsion and circumferential strain, as well reduced circumferential strain rates in early systole and diastole.

CONCLUSIONS

Modest decreases in cMyBPC expression in the mouse heart result in early-onset subtle changes in cross-bridge kinetics and in vivo LV mechanical function, which could contribute to the development of HCM later in life.