A unifying framework for understanding heart failure? Response to "Left Ventricular Torsion By Two-Dimensional Speckle Tracking Echocardiography in Patients With Diastolic Dysfunction and Normal Ejection Fraction" by Park SJ et al

Distinct Aspects of Left Ventricular Mechanical Function Are Differentially Associated With Cardiovascular Outcomes and All-Cause Mortality in the Community

Background

There are few data relating novel measures of left ventricular (LV) mechanical function to cardiovascular disease (CVD) outcomes in the community. Whether distinct components of LV mechanical function provide information regarding risk for different CVD outcomes is unclear.

Methods and Results

We used speckle tracking echocardiography to quantify distinct components of LV mechanical function (measured as LV strain in multiple planes) in 2831 Framingham Offspring Study participants (mean age, 66 years; 57% women, 97% with LV fractional shortening >0.29). Participants were followed for 6.0±1.2 years for onset of 69 coronary heart disease (CHD), 71 heart failure (HF), and 199 mortality events. Adjusting for CVD risk factors, longitudinal LV strain appeared associated with incident CHD (hazards ratio [HR] per SD increment, 1.29; 95% confidence interval [CI], 1.00–1.67; P=0.05), whereas circumferential and radial strain were not (P>0.37 for both); however, the association of longitudinal strain with CHD was nonsignificant after Bonferroni correction. By contrast, circumferential strain was a significant predictor of incident HF (HR per SD increment, 1.79; 95% CI, 1.35–2.37; P<0.0001). Decrements in circumferential, radial, and longitudinal strain measures were related to all‐cause mortality (P<0.008 for all). Results remained similar in multivariable models adjusting additionally for the conventional echocardiographic measures of LV mass and fractional shortening.

Conclusions

In our large, community‐based sample, distinct components of LV mechanical function were associated with specific CVD outcomes. Additional studies are needed to replicate these findings and investigate the prognostic and therapeutic utility of these novel measures of LV mechanical function.

Changes of ventricular and peripheral performance in patients with heart failure and normal ejection fraction: insights from ergometry stress echocardiography

AIMS

We assessed the left ventricular (LV) and peripheral performance at rest and during exercise in healthy and heart failure subjects with normal ejection fraction (HFNEF) or with reduced ejection fraction (HFREF).

METHODS

All subjects received echocardiography at rest and with bicycle Ergometer exercise. The exercise images for two-dimensional speckle tracking were acquired with submaximal heart rate of 90-100 beats/min, while images for M-mode and tissue Doppler imaging were stored with attainment of >85% of predicted heart rate.

RESULTS

A total of 80 HFNEF, 50 HFREF and 50 controls were studied. There was progressive decrease of two-dimensional global circumferential, radial and longitudinal strains (GCS, GRS and GLS), M-mode and tissue Doppler imaging long-axis parameters from controls, HFNEF to HFREF patients (all P < 0.05) at rest and on exercise. The degree of exercise-induced, long-axis augmentation (GLS and M-mode long axis excursion) decreased progressively from controls, HFNEF to HFREF subjects (all P < 0.05), while the increase in GCS and GRS was similar in all groups. The ventricular-arterial coupling ratio did not change in HFREF but reduced in HFNEF and controls during exercise (P < 0.01). All subjects had a similar resting heart rate, but patients exhibited chronotropic non-competence during exercise (P < 0.001).

CONCLUSIONS

Ventricular and peripheral dysfunction was evident in HFNEF at rest and deteriorated during exercise. The HFNEF patients had significantly impaired long-axis augmentation at stress that was intermediate between HFREF patients and controls. These findings have relevance to generation of symptoms on exercise in both HFNEF and HFREF.

Left ventricular mechanical function: clinical correlates, heritability, and association with parental heart failure

AIMS

Non-invasive measures of cardiac mechanical function may have the potential to serve as markers of risk for heart failure; however, limited data exist regarding clinical correlates and heritability of these measures in the community.

METHODS AND RESULTS

We used speckle-tracking echocardiography to assess LV strain and synchrony in the Framingham Offspring Study (n = 2816; mean age 67 years, 54% women). In multivariable regression analyses, male gender (vs. female, P < 0.001), higher heart rate (P < 0.0001), and presence of cardiovascular disease (P < 0.001) were associated with worse global peak strains across all planes analysed (longitudinal, transverse, circumferential, and radial). Higher diastolic blood pressure and diabetes were associated with worse longitudinal strain (P < 0.01), and greater body mass index was associated with worse radial strain (P = 0.0004). Overall, however, clinical correlates accounted for only 4-19% of the variation in measures of LV mechanical function. Select measures of LV strain were heritable: longitudinal strain (h(2)  = 16%, P = 0.002), transverse strain (h(2)  = 15%, P = 0.006), and circumferential strain (h(2)  = 30%, P < 0.0001). Furthermore, in a subset of 1437 participants with parental data available, parental heart failure was associated with worse circumferential strain in the offspring free of heart failure (P = 0.01).

CONCLUSIONS

Our investigation in a large community-based sample identified heritablity and clinical correlates of LV mechanical function, and highlighted an association of parental heart failure with worse global circumferential strain in offspring.

Reproducibility of speckle-tracking-based strain measures of left ventricular function in a community-based study

BACKGROUND

The reproducibility of echocardiographic measurements of myocardial strain, performed in a community-based setting, has not been reported previously.

METHODS

The reproducibility of left ventricular strain measurements was examined in two samples of 20 participants each from the Offspring Cohort of the Framingham Heart Study (mean age, 63 ± 9 years; 59% women). Two-dimensional speckle-tracking-based measurements of global peak left ventricular strain in systole were performed in the apical four-chamber, apical two-chamber, and midventricular parasternal short-axis views.

RESULTS

Interobserver intraclass correlation coefficients were ≥0.84 for all global strain measurements, with average coefficients of variation of ≤4% for global longitudinal and circumferential strain and <8% for global transverse and radial strain. For left ventricular strain measurements performed in each of the three views, intraobserver intraclass correlation coefficients were ≥0.91 among time points spanning a total 8-month period. The average coefficients of variation were <6% for global longitudinal and circumferential strain and <9% for global transverse and radial strain. Interobserver and intraobserver reproducibility findings were similar in analyses adjusting for frame rate.

CONCLUSIONS

Excellent reproducibility of global longitudinal and circumferential strain measurements and very good reproducibility of global transverse and radial strain measurements were observed. Taken together, these findings demonstrate the reproducibility of performing echocardiographic strain measurements in a large, epidemiologic community-based setting.

Assessment of strain and strain rate by two-dimensional speckle tracking in mice: comparison with tissue Doppler echocardiography and conductance catheter measurements

AIMS

This study was designed in order to compare the strain and strain rate deformation parameters assessed by speckle tracking imaging (STI) with those of tissue Doppler imaging (TDI) and conductance catheter measurements in chronic murine models of left ventricular (LV) dysfunction.

METHODS AND RESULTS

Twenty-four male C57BL/6J mice were assigned to wild-type (n = 8), myocardial infarction (n = 8) and transaortic constriction (n = 8) groups. Echocardiographic and conductance measurements were simultaneously performed at rest and during dobutamine infusion (5 µg/kg/min) in all animals 10 weeks post-surgery. The LV circumferential strain (Scirc) and the strain rate (SRcirc) were derived from grey scale and tissue Doppler data at frame rates of 224 and 375 Hz, respectively. Scirc and SRcirc by TDI/STI correlated well with the preload recruitable stroke work (PRSW) (r = -0.64 and -0.71 for TDI; r = -0.46 and -0.50 for STI, P < 0.05). Both modalities showed a good agreement with respect to Scirc and SRcirc (r = 0.60 and r = 0.63, P < 0.05). During stress, however, TDI-estimated Scirc and SRcirc values were predominantly higher than those measured by STI (P < 0.05). The similarity of Scirc and SRcirc measurements with respect to the STI/TDI data was examined by the Bland-Altman analysis.

CONCLUSION

In mice, the STI- and TDI-derived strain and strain rate deformation parameters relate closely to intrinsic myocardial function. At low heart rate-to-frame rate ratios (HR/FR), both STI and TDI are equally acceptable for assessing the LV function non-invasively in these animals. At HR/FR (e.g. dobutamine challenge), however, these methods cannot be used interchangeably as STI underestimates S and SR at high values.

Comparison of velocity vector imaging echocardiography with magnetic resonance imaging in mouse models of cardiomyopathy

BACKGROUND

Myocardial strain imaging using echocardiography can be a cost-effective method to quantify ventricular wall motion objectively, but few studies have compared strain measured with echocardiography against magnetic resonance imaging (MRI) in small animals.

METHODS AND RESULTS

We compared circumferential strain (CS) and radial strain (RS) measured with echocardiography (velocity vector imaging [VVI]) to displacement encoding with stimulated-echo MRI in 2 mouse models of cardiomyopathy. In 3-month-old mice with gene targeted deficiency of cardiac myosin-binding protein-C (cMyBP-C(-/-), n=6) or muscle LIM protein (MLP(-/-), n=6), and wild-type mice (n=8), myocardial strains were measured at 3 cross-sectional levels and averaged to obtain global strains. There was modest correlation between VVI and MRI measured strains, with global CS yielding stronger correlation compared with global RS (CS R(2)=0.4452 versus RS R(2)=0.2794, both P<0.05). Overall, strain measured by VVI was more variable than MRI (P<0.05) and the limits of agreement were slightly, but not significantly (P=0.14), closer for global CS than RS. Both VVI and MRI strain measurements showed significantly lower global CS strain in the knockout groups compared with the wild type. The VVI (but not MRI) CS strain measurements were different between the 2 knockout groups (-14.5±3.8% versus -6.6±4.0%, cMyBP-C(-/-) versus MLP(-/-) respectively, P<0.05).

CONCLUSIONS

Measurements of left ventricular CS and RS are feasible in small animals using 2-dimensional echocardiography. VVI and MRI strain measurements correlated modestly and the agreement between the modalities tended to be greater for CS than RS. Although VVI and MRI strains were able to differentiate between wild-type and knockout mice, only global CS VVI differentiated between the 2 models of cardiomyopathy.

[Assessment of left ventricular twist mechanics by two-dimensional strain in severe aortic stenosis with preserved ejection fraction]

Left ventricular (LV) twist is increased in aortic stenosis (AS) and the hypothesis of a compensatory mechanism is suggested but not established. Our aim was to assess LV twist mechanics in severe AS (<1cm(2) or 0.6cm(2)/m(2)) with preserved LV ejection fraction (LVEF>50%), and to analyze its relationship with LV systolic longitudinal function, early impaired in this setting, LV diastolic function, and symptomatic status.

METHODS

Forty-five consecutive patients with severe AS and preserved LVEF (mean age 73±11 years, 47% female, LVEF 68±11%, 67% symptomatic) underwent a transthoracic echocardiography including a bidimensional strain analysis by speckle tracking method, and were compared to a control group matched for age and sex (n=15). Global longitudinal strain (GLS) was measured using the four, two, and three apical views, and LV twist mechanics from the basal and apical short axis views. LV twist was defined as the net difference between apical and basal rotation, and LV twisting and untwisting rate (in°/s) were derived from twist curves.

RESULTS

Peak apical rotation, LV twist (25±8° vs 20±6), as well as peak systolic and diastolic apical rotation rate, and peak LV twisting rate were significantly higher in patients with AS when compared to controls (all, P<0.05), whereas, the other parameters of LV twist mechanics including basal rotation, were not significantly different between groups. By contrast, the GLS was significantly lower in patients with AS when compared to controls (-17.9±4 vs -20.5±2%, P<0.01). In addition, the GLS was significantly correlated to LV torsion (r=-0.42, P<0.01). Moreover, LV twist progressively impaired with the worsening of diastolic dysfunction and with symptoms onset.

CONCLUSION

LV twist is increased in severe AS with preserved LVEF, compensating the impairment of systolic longitudinal function. However, above a certain threshold LV twist deteriorates, attesting the failure of the compensatory mechanisms, leading to advanced diastolic dysfunction and symptom onset.

Echocardiographic speckle-tracking based strain imaging for rapid cardiovascular phenotyping in mice

RATIONALE

High-sensitivity in vivo phenotyping of cardiac function is essential for evaluating genes of interest and novel therapies in small animal models of cardiovascular disease. Transthoracic echocardiography is the principal method currently used for assessing cardiac structure and function; however, standard echocardiographic techniques are relatively insensitive to early or subtle changes in cardiac performance, particularly in mice.

OBJECTIVE

To develop and validate an echocardiographic strain imaging methodology for sensitive and rapid cardiac phenotyping in small animal models.

METHODS AND RESULTS

Herein, we describe a modified echocardiographic technique that uses speckle-tracking based strain analysis for the noninvasive evaluation of cardiac performance in adult mice. This method is found to be rapid, reproducible, and highly sensitive in assessing both regional and global left ventricular (LV) function. Compared with conventional echocardiographic measures of LV structure and function, peak longitudinal strain and strain rate were able to detect changes in adult mouse hearts at an earlier time point following myocardial infarction and predicted the later development of adverse LV remodeling. Moreover, speckle-tracking based strain analysis was able to clearly identify subtle improvement in LV function that occurred early in response to standard post-myocardial infarction cardiac therapy.

CONCLUSIONS

Our results highlight the utility of speckle-tracking based strain imaging for detecting discrete functional alterations in mouse models of cardiovascular disease in an efficient and comprehensive manner. Echocardiography speckle-tracking based strain analysis represents a method for relatively high-throughput and sensitive cardiac phenotyping, particularly in evaluating emerging cardiac agents and therapies in mice.

Racial and ethnic differences in subclinical myocardial function: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Racial/ethnic differences in the incidence and severity of heart failure (HF) are not well understood, but may be related to pre-existing variations in myocardial function.

OBJECTIVE

To examine racial/ethnic differences in regional myocardial function among asymptomatic individuals free of known cardiovascular disease.

DESIGN, SETTING AND PATIENTS

The Multi-Ethnic Study of Atherosclerosis is a prospective, observational study of individuals without baseline cardiovascular disease, representing four major racial/ethnic groups. A total of 1099 study participants underwent cardiac MRI with tissue tagging; for each study, peak systolic strain (Ecc) and strain rate (SRs) were determined in four left ventricular (LV) regions.

MAIN OUTCOME MEASURES

Multiple linear regression was used to analyse the relationship between race/ethnicity and regional strain (Ecc and SRs) while adjusting for cardiovascular risk factors.

RESULTS

Compared with other racial/ethnic groups, Chinese-Americans had the greatest magnitude of Ecc in a majority of LV regions (-19.60±3.78, p<0.05); Chinese-Americans also had the greatest absolute values for SRs in all regions, reflecting higher rate of systolic contraction (-2.01±0.76, p<0.05). Conversely, African-Americans had the lowest Ecc values (-17.50±4.00, p<0.05) in the majority of wall regions while Hispanics demonstrated the lowest rate of contractility in all wall regions (-1.44±0.50, p≤0.001) in comparison with the other racial/ethnic groups. These race-based differences remained significant in the majority of LV wall regions after adjusting for multiple variables, including hypertension and LV mass.

CONCLUSIONS

Important race-based differences in regional LV systolic function in a large cohort of asymptomatic individuals have been demonstrated. Further research is needed to investigate the possible mechanisms related to the race/ethnicity-based variations found in this study.

Current controversies in heart failure with a preserved ejection fraction

Heart failure with a preserved ejection fraction is a fascinating and multifaceted condition that has provoked enormous debate and a wealth of mechanistic studies. Controversies exist with regard to its nomenclature. If its nomenclature is questioned, one can be certain the pathogenesis is ill understood. If the pathogenesis is disputed, the diagnosis becomes difficult and inconsistent. These diagnostic challenges result in inappropriate recruitment to clinical trials. Therefore, the trials may be underpowered and difficult to interpret. This paper examines contemporary theories of heart failure with a preserved ejection fraction, clarifies the controversies and attempts to resolve the divergences of opinion.