Heterogeneity of regional systolic function detected by tissue Doppler imaging is linked to impaired global left ventricular relaxation in hypertrophic cardiomyopathy

Strain Imaging Echocardiography: What Imaging Cardiologists Should Know

Despite recent advances in clinical imaging, echocardiography remains as the most accessi-ble and reliable noninvasive. Since knowledge of left ventricular systolic function remains so critically important in determining prognosis; every effort should be made to prevent subjective estimations. The advent of strain imaging echocardiography now offers a readily available and portable imaging tool that not only offers an objective characterization of myocardial dynamics; but also allows for early detection of subclinical left ventricular dysfunction. This review outlines the basic concepts of strain imaging to better understand the mechanism of myocardial function as well their applicability in the least common cardiac diagnosis among current clinical practice.

Hypertensive cardiomyopathy: A clinical approach and literature review

Hypertensive cardiomyopathy (HTN-CM) is a structural cardiac disorder generally accompanied by concentric left ventricular hypertrophy (LVH) associated with diastolic or systolic dysfunction in patients with persistent systemic hypertension. It occurs in the absence of other cardiac diseases capable of causing myocardial hypertrophy or cardiac dysfunction. Persistent systemic hypertension leads to structural and functional myocardial abnormalities resulting in myocardial ischemia, fibrosis, and hypertrophy. HTN-CM is predominantly a disease of impaired relaxation rather than impaired contractility, so patients are usually asymptomatic during resting conditions. However, their stiff left ventricles become incapable of handling increased blood volume and cannot produce appropriate cardiac output with the slight change of circulating volume that may occur during exercise. Importantly, the accompanying LVH is itself a risk factor for mortality and morbidity. Therefore, early detection of LVH development in patients with hypertension (referred to as HTN-CM) is critical for optimal treatment. In addition to pathological findings, echocardiography and cardiac magnetic resonance imaging are ideal tools for the diagnosis of HTN-CM. Timely diagnosis of this condition and utilization of appropriate treatment are required to improve morbidity and mortality in hypertensive patients. This review article presents an overview of the multidimensional impact of myocardial disorder in patients with hypertension. Relevant literature is highlighted and the effects of hypertension on cardiac hypertrophy and heart failure development are discussed, including possible therapeutic options.

Heterogeneity of regional function and relation to ventricular morphology in patients with fontan circulation

The relation between underlying ventricular morphology and regional function in patients with Fontan circulation remains unclear. The aim of this study was to compare regional function and its heterogeneity in patients with tricuspid atresia (TA), biventricular apex-forming morphology (BiV), and controls. Nineteen patients (median age 12 years) with Fontan circulation who presented consecutively were prospectively enrolled and compared with age- and heart rate-matched controls. Most patients were in New York Heart Association class I (63%). Longitudinal systolic strain (S), systolic strain rate (SRsys), and early diastolic strain rate (SRdia) peaks were obtained from 6 ventricular segments, and a coefficient of variation by segment was calculated as a measure of regional heterogeneity. Systolic S, SRsys and SRdia peaks were decreased at the right and left lateral walls in both patient groups compared with controls (p ≤0.001 for all). Patients with TA had higher systolic S and SRsys in the middle of the right lateral wall than those with BiV morphology (p = 0.009 and p = 0.001, respectively). The mean coefficients of variation assessed by S and SRsys were similar in controls and patients with TA but lower in those with BiV than in controls and patients with TA (p <0.001 and p = 0.01, respectively). The mean coefficient of variation assessed by SRdia was greater only in patients with BiV than in controls (p = 0.001). In conclusion, patients with Fontan circulation have more heterogeneous systolic and early diastolic regional function than healthy control subjects, and patients with TA have better systolic regional function in the middle of the right lateral wall and less systolic heterogeneity than patients with BiV morphology.

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, global function, and dyssynchrony in infants and children with pompe cardiomyopathy undergoing enzyme replacement therapy

BACKGROUND

Enzyme replacement therapy (ERT) for infantile-onset Pompe disease effectively reduces the left ventricular (LV) mass. This study sought to explore detailed process of LV reverse remodeling after ERT with the use of tissue Doppler and stain rate imaging.

METHODS AND RESULTS

Nine infants and children with Pompe cardiomyopathy undergoing ERT for ≥1 year, as well as 36 healthy control subjects, were studied. Global systolic and diastolic function was evaluated by peak systolic and early-diastolic velocity at mitral annulus. Temporal systolic and diastolic dyssynchrony was evaluated by the coefficient of variation of the time from the QRS complex to peak systolic and early-diastolic strain rate among 12 LV segments. All pre-ERT patients had impaired global systolic and diastolic function as well as increased regional dyssynchrony (P < .001 for each of all). During the regression of LV hypertrophy, all of these functional indices improved (P for trend <.001), with temporal diastolic dyssynchrony being a significant factor linking to LV mass index in multivariate analysis (P < .001).

CONCLUSIONS

ERT improved global LV function and dyssynchrony in Pompe patients. The relationship between LV mass and temporal diastolic dyssynchrony during reverse remodeling suggested a pathophysiologic role of dyssynchrony in Pompe cardiomyopathy.

Disease pathways and novel therapeutic targets in hypertrophic cardiomyopathy

As described in earlier reviews in this series on the molecular basis of hypertrophic cardiomyopathy (HCM), HCM is one of the archetypal monogenic cardiovascular disorders to be understood at the molecular level. Twenty years after the discovery of the first HCM disease gene, genetic studies still confirm that HCM is principally a disease of the sarcomere. At the biophysical level, myofilament mutations generally enhance Ca(2+) sensitivity, maximal force production, and ATPase activity. These defects ultimately appear to converge on energy deficiency and altered Ca(2+) handling as major common paths leading to the anatomic (hypertrophy, myofiber disarray, and fibrosis) and functional features (pathological signaling and diastolic dysfunction) characteristic of HCM. In this review, we provide an account of the consequences of HCM mutations and describe how specifically targeting these molecular features has already yielded early promise for novel therapies for HCM. Although substantial efforts are still required to understand the molecular link between HCM mutations and their clinical consequences, HCM endures as an exemplar of how novel insights derived from molecular characterization of Mendelian disorders can inform the understanding of biological processes and translate into rational therapies.

Usefulness of magnetic resonance imaging to distinguish hypertensive and hypertrophic cardiomyopathy

Different pathophysiologic pathways in the development of left ventricular (LV) hypertrophy can be reflected in phenotypical differences. A total of 119 subjects (39 with hypertension [HTN]; 43 with nonobstructive hypertrophic cardiomyopathy [HC], and 37 control subjects) underwent a standardized cardiac magnetic resonance imaging protocol for assessment of global and regional morphology and function using balanced steady-state free precession sequences and late gadolinium enhancement studies. Compared to controls, both hypertrophic groups had significantly greater maximal wall thickness and LV mass index (p <0.01). The patients with HTN had reduced ejection fraction, increased heart cavities, and increased LV wall stress (p <0.01). The HC group had supernormal ejection fraction and reduced LV wall stress (p <0.01). The HTN group had reduced anteroseptal systolic strains (p <0.02), and the HC group displayed a marked decrease in longitudinal systolic strain (p <0.01). In the HC group, an inverse relation was seen between a globally increased late gadolinium enhancement score and the ejection fraction (r = -0.5, p = 0.01), and between regional late gadolinium enhancement scores and regional systolic strain in the inferoseptal segments. Increased LV wall stress was identified as the hallmark of HTN (odds ratio 1.2, p = 0.002), while HC was best characterized by reduced total longitudinal strain (odds ratio 1.3, p = 0.002). In conclusion, our findings indicate the presence of distinctive hypertrophic phenotypes detectable by means of multiparametric magnetic resonance imaging. In HTN, impaired deformation follows the distribution of LV wall stress. On the contrary, HC is characterized by reduced global and regional deformation, in association with fibrosis.

Heterogeneity of apex-to-base dispersion in diastolic lengthening is related to impaired global left ventricular relaxation in patients with hypertrophic cardiomyopathy

BACKGROUND

The presence of apex-to-base disparity in diastolic left ventricle (LV) endocardial lengthening, based on an electromechanical activation sequence, has been recognized as an important determinant of LV diastolic properties. However, the behavior of LV apical and basal diastolic lengthening and its relationship to LV filling in hypertrophic cardiomyopathy (HCM) are unknown.

METHODS

We obtained basal and apical LV short-axis views in 27 patients with non-obstructive HCM and 25 healthy volunteers. The patients with HCM were subdivided into two groups; those with apical hypertrophy [APH(+)] or those without apical hypertrophy [APH(-)]. Eight equiangular points on the endo-myocardium at end diastole were placed in each view, and the movements of these points were automatically tracked using a two-dimensional echocardiographic tissue tracking system. Time-LV internal diameter curves were obtained and averaged. The time intervals from the aortic valve closure to the point of the first 40% of peak diastolic lengthening (T 40) were measured in each view. The standard deviation of the time to peak systolic circumferential shortening at the base and apex were calculated to assess the heterogeneity of LV contraction.

RESULTS

The time difference in the T 40 between the apex and base (dt-T 40) in the HCM-APH(+) and HCM-APH(-) groups was greater than that in the control group. The heterogeneities in LV apical systolic shortening in the HCM groups were greater than those in the control group. There were good linear correlations between the dt-T 40 and the LV early diastolic echo-parameters and the LV mass index.

CONCLUSIONS

Delayed apical relaxation and filling in patients with HCM is related to LV diastolic dysfunction and systolic dyssynchronous contraction.

Evolving anatomic, functional, and molecular imaging in the early detection and prognosis of hypertrophic cardiomyopathy

Evolving imaging modalities in hypertrophic cardiomyopathy (HCM), such as tissue Doppler, speckle tracking, measures of myocardial blood flow, and cardiac magnetic resonance with gadolinium enhancement, have advanced our understanding of the pathogenesis of myocardial dysfunction in hypertrophic cardiomyopathy. These modalities have the potential to differentiate HCM from other causes of left ventricular hypertrophy when there is uncertainty about the diagnosis and to identify affected individuals in the pre-clinical phase of the disease process. Furthermore, preliminary data suggests that functional imaging techniques may add incremental value to conventional risk stratification tools to identify individuals at high risk for sudden death or progression to congestive heart failure.