Relationships of global longitudinal strain with s`, long-axis systolic excursion, left ventricular length and heart rate

Background

Longitudinal left ventricular (LV) contraction can be impaired in the presence of a normal LV ejection fraction (LVEF), and abnormalities have been reported in global longitudinal strain (GLS), long-axis systolic excursion (SExc), and the peak systolic velocity (s`) of mitral annular motion using tissue Doppler imaging (TDI). However, the relationships of GLS with s` and SExc have not been systematically evaluated in subjects with a normal LVEF, and whether these relationships might be affected by variations in LV end-diastolic length (LVEDL) and heart rate is unknown.

Methods

We investigated the univariate and multivariate correlations of GLS with TDI measurements of s` and SExc (both using averages of the septal and lateral walls), LVEDL and heart rate in subjects with a normal LVEF (>50%) but a low peak early diastolic mitral annular velocity (septal e`≤ 7.0 cm/s and lateral e`≤ 9 cm/s), and thus an increased risk of a future cardiac event.

Results

84 subjects (age 66±8 years, 29 males) with a LVEF of 62±6% and GLS of -17.5±2.3% were studied. On univariate analysis the absolute value of GLS was positively correlated with s`(r = 0.28, p<0.01) and SExc (r = 0.50, p<0.001) and inversely correlated with heart rate (r = -0.36, p = 0.001), but was not correlated with LVEDL (r = -0.15). In multivariate models, SExc explained more of the variance in GLS than s`, and absolute GLS was not only positively correlated with SExc, but also inversely correlated with LVEDL. Heart rate was an independent inverse correlate of GLS in conjunction with LVEDL and either s` or SExc, but made a larger contribution in models which included s`. Interobserver correlations were close for s` and SExc (r = 0.89–0.93), but only moderate for GLS (r = 0.71).

Conclusion

In subjects with a normal LVEF but reduced e`, the absolute value of GLS is more closely related to SExc than s`, and is also independently and inversely related to LVEDL and heart rate. Measurement of SExc may provide a useful additional or alternative technique to GLS for the assessment of LV long-axis function.

Differences in the determinants of right ventricular and regional left ventricular long-axis dysfunction in Friedreich ataxia

BACKGROUND

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative condition which also has effects on the heart. In 96% of affected individuals FRDA is due to homozygosity of a GAA repeat expansion in intron 1 of the frataxin (FXN) gene. The number of GAA repeats have been shown to relate to disease severity in FRDA, this thought to be via an inverse relationship of GAA repeat number and cellular frataxin levels. We investigated the effects of FRDA on regional long axis function of the left and right ventricles, and also the relationship of long axis systolic (s`) and early diastolic (e`) peak velocities with GAA repeat number on the shorter (GAA1) and longer FXN alleles (GAA2).

METHODS

The study group of 78 adult subjects (age 32±9 years) with FRDA and normal left ventricular (LV) ejection fraction were compared to 54 healthy control subjects of similar age, sex and body size. Tissue Doppler imaging (TDI) signals were recorded at the mitral annulus for measurement of s`and e`of the septal, lateral, anterior and inferior walls and at the tricuspid annulus for measurement of right ventricular (RV) s`and e`.

RESULTS

All the regional LV s`and e`, and both RV s`and RV e`, were lower in individuals with FRDA compared to controls (p<0.001 for all). On multivariate analysis, which included LV septal wall thickness (SWT), RV s`and RV e`were both inversely correlated with GAA1 (β = -0.32 & -0.33, respectively, p = 0.01), but not with GAA2, whereas anterior and lateral s`were both inversely correlated with GAA2 (β = -0.25 and β = -0.28, p = 0.02) but not with GAA1. Increasing SWT was the most consistent LV structural correlate of lower s`and e`, whereas age was a consistent inverse correlate of e`but not of s`.

CONCLUSION

There are generalized abnormalities of both LV regional and RV long axis function in FRDA, but there are also regional differences in the association of this dysfunction with the smaller and larger GAA repeats in the FXN gene.

Left ventricular long axis tissue Doppler systolic velocity is independently related to heart rate and body size

Background

The physiological factors which affect left ventricular (LV) long-axis function are not fully defined. We investigated the relationships of resting heart rate and body size with the peak velocities and amplitudes of LV systolic and early diastolic long axis motion, and also with long-axis contraction duration.

Methods

Two groups of adults free of cardiac disease underwent pulsed-wave tissue Doppler imaging at the septal and lateral mitral annular borders. Group 1 (n = 77) were healthy subjects <50 years of age and Group 2 (n = 65) were subjects between 40–80 years of age referred for stress echocardiography. Systolic excursion (SExc), duration (SDur) and peak velocity (s') and early diastolic excursion (EDExc) and peak velocity (e') were measured.

Results

SExc was not correlated with heart rate, height or body surface area (BSA) for either LV wall in either group, but SDur was inversely correlated with heart rate for both walls and both groups, and after adjustment for heart rate, males in both groups had a shorter septal SDur. Septal and lateral s` were independently and positively correlated with SExc, heart rate and height in both groups, independent of sex and age. There were no correlations of heart rate, height or BSA with either e` or EDExc for either wall in either group.

Conclusion

Heart rate and height independently modify the relationship between s` and SExc, but neither are related to EDExc or e`. These findings suggest that s` and SExc cannot be used interchangeably for the assessment of LV long-axis contraction.

Possible Mechanisms Underlying Aging-Related Changes in Early Diastolic Filling and Long Axis Motion-Left Ventricular Length and Blood Pressure

Background

The transmitral E wave and the peak velocity of early diastolic mitral annular motion (e`) both decrease with age, but the mechanisms underlying these age-related changes are incompletely understood. This study investigated the possible contributions of blood pressure (BP) and left ventricular end-diastolic length (LVEDL) to age-related reductions in E and e`.

Methods

The study group were 82 healthy adult subjects <55 years of age who were not obese or hypertensive. Transmitral flow and mitral annular motion were recorded using pulsed-wave Doppler. LVEDL was measured from the mitral annular plane to the apical endocardium.

Results

Age was positively correlated with diastolic BP and septal wall thickness (SWT), inversely correlated with LVEDL (β = -0.25) after adjustment for sex and body surface area, but was not related to left ventricular end-diastolic diameter (LVEDD). Age was also inversely correlated with E (r = -0.36), septal e`(r = -0.53) and lateral e`(r = -0.53). On multivariable analysis, E was inversely correlated with diastolic BP and LVEDD, septal e`was inversely correlated with diastolic BP and positively correlated with SWT and LVEDL, after adjusting for body mass index, whilst lateral e`was inversely correlated with diastolic BP and positively correlated with LVEDL.

Conclusion

The above findings are consistent with higher BP being a contributor to age-related reductions in both E and e`and shortening of LVEDL with age being a contributor to the age-related reduction in e`. An implication of these findings is that slowing of myocyte relaxation is unlikely to be the sole, and may not be the main, mechanism underlying age-related decreases in E and e`.

A polymorphic miR-155 binding site in AGTR1 is associated with cardiac hypertrophy in Friedreich ataxia

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative condition with a heterogeneous cardiac phenotype caused primarily by an expanded GAA trinucleotide repeat in the frataxin gene (FXN). FXN is important in mitochondrial iron efflux, sensitivity to oxidative stress, and cell death. The number of GAA repeats on the smaller FXN allele (GAA1) only accounts for a portion of the observed variability in cardiac phenotype. Genetic modifying factors, such as single nucleotide polymorphisms (SNPs) in genes of the Renin-Angiotensin-Aldosterone system (RAAS), may contribute to phenotype variability. This study investigated genetic variability in the angiotensin-II type-1 receptor (AGTR1), angiotensin-converting enzyme (ACE), and ACE2 genes as cardiac phenotype modifying factors in FRDA patients. Comprehensive review of the AGTR1, ACE and ACE2 genes identified twelve haplotype tagging SNPs. Correlation of these SNPs with left ventricular internal diameter in diastole (LVIDd), interventricular septal wall thickness (SWT) and left ventricular mass (LVM) was examined in a large Australian FRDA cohort (n=79) with adjustments performed for GAA repeats, age, sex, body surface area and diastolic blood pressure. A significant inverse relationship was observed between GAA1 and LVIDd (p=0.010) but not with SWT or LVM after adjustment for covariates. The AGTR1 polymorphism rs5186 was more common in FRDA patients than in a control population (p=0.002). Using a recessive model of inheritance, the C allele of rs5186 was associated with a significant increase in SWT (p=0.003) and LVM (p=0.001). This functional polymorphism increases expression of AGTR1 by altering the binding site for miR-155, a regulatory microRNA. No significant associations with left ventricular structure were observed for the remaining RAAS polymorphisms. The AGTR1 polymorphism rs5186 appears to modify the FRDA cardiac phenotype independently of GAA1. This study supports the role of RAAS polymorphisms as modifiers of cardiac phenotype in FRDA patients.

Early changes in left ventricular long-axis function in Friedreich ataxia: relation with the FXN gene mutation and cardiac structural change

OBJECTIVE

Friedreich ataxia (FRDA) is an autosomal recessive condition due to a GAA triplet expansion in the FXN gene that causes increased left ventricular (LV) wall thickness and can progress to LV systolic dysfunction. However, the changes in myocardial function that occur before a reduction in LV ejection fraction are incompletely understood.

METHODS

LV long-axis function was assessed by measurement of tissue Doppler imaging (TDI) peak systolic (S`), early diastolic (E`), and atrial velocities (A`) at the septal and lateral borders of the mitral annulus in 60 subjects homozygous for a GAA expansion in the FXN gene who had preserved LV ejection fraction. Comparison was made with 60 sex- and age-matched controls. TDI velocities at 5 years were compared with baseline values in 17 FRDA subjects with follow-up studies who still had preserved ejection fraction.

RESULTS

S` and E` were reduced in FRDA subjects at both the septal and the lateral mitral annular borders. Lateral E` was independently and inversely related to age, blood pressure, septal wall thickness, and the number of GAA repeats in the smaller allele of the FXN gene, whereas septal E` was not correlated with GAA repeat number. At 5 years, there was a reduction in lateral S` and E` but no change in septal TDI velocities.

CONCLUSION

Subjects with FRDA have impairment of septal and lateral long-axis LV function, but there also seem to be regional differences in the effects of this condition that are at least partly related to the degree of genetic abnormality.

Point of care ultrasound for basic haemodynamic assessment: novice compared with an expert operator

Miniaturization of ultrasound equipment has led to the development of hand-held echocardiography devices suitable for bedside evaluation of cardiac function. Basic assessment of the haemodynamic state can be performed using a limited transthoracic echocardiography examination. This study evaluated a third generation device (SonoSite Titan) used by novice and expert operators. Limited transthoracic examination was performed on 30 healthy volunteers by an expert and a novice operator. The novice had performed 10 studies prior to data accrual. Agreement analysis was performed using weighted least products regression and Bland-Altman analysis. Acceptable results for the novice were achieved following 20 studies (including practice sessions) for basic haemodynamic assessment and following 40 studies for all measured parameters. The SonoSite Titan is acceptable for basic transthoracic measurements to determine the basic haemodynamic state and cardiac output measurements. We recommend a minimum of 20 training studies for novice operators prior to clinical use.

Factors associated with mitral annular systolic and diastolic velocities in healthy adults

BACKGROUND

Measurements of systolic mitral annular velocity (S'), early diastolic mitral annular velocity (E'), and late diastolic mitral annular velocity (A') are used to assess left ventricular (LV) function.

OBJECTIVE

We sought to investigate the relationship between septal and lateral annular velocities and determine whether these velocities are related to body size (including body mass index [BMI]), heart rate (HR), blood pressure, or LV mass.

METHODS

A total of 60 healthy participants who were normotensive, between age 20 and 52 years, underwent standard echocardiography and measurement of septal and lateral S', E', and A'.

RESULTS

The lateral velocity exceeded the septal velocity for S', E', and A'. There was only weak to moderate correlation between the velocities at the two sites (r = 0.43-0.60). Septal S' was positively correlated with height and HR, and lateral S' was correlated with HR. Septal E' was negatively correlated with age, BMI, LV mass, and diastolic blood pressure, but lateral E' was only negatively correlated with age and BMI. Septal A' was positively correlated with age, HR, and BMI, whereas lateral A' was only positively associated with age.

CONCLUSIONS

S', E', and A' are not only of different magnitudes at the septal and lateral sites, but are not closely correlated. There are relationships between annular velocities and body size, HR, blood pressure, and LV mass that differ between the septal and lateral annulus, providing a possible explanation for the lack of close correlation in these velocities and suggesting that these variables may need to be considered when interpreting annular velocities.

Effect of preload reduction by haemodialysis on new indices of diastolic function

Assessment of mitral annular motion diastolic velocities by M-mode or tissue Doppler imaging and the propagation velocity of early diastolic filling (Vp) by colour M-mode have been proposed as preload-independent indices of diastolic function. The aim of the present study was to determine the effects of preload reduction by haemodialysis on these new echocardiographic indices and to assess the relationship between these indices. The study group comprised 17 patients with chronic renal failure in sinus rhythm with normal left ventricular systolic function who underwent echocardiography 30 min prior to and 30 min following haemodialysis. Following dialysis there were significant reductions in weight (P<0.001), left atrial diameter (P=0.001), the peak Doppler velocity of early diastolic transmitral flow (P=0.005) and the ratio of Doppler velocities of early to late diastolic transmitral flow (P=0.02), consistent with a reduction in intravascular volume. There was no change after dialysis in early diastolic mitral annular velocity using M-mode (P=0.19) or tissue Doppler imaging from either the septal or lateral walls (P=0.88 and P=0.15 respectively), but there was a reduction in Vp after dialysis (55 to 49 cm/s; P=0.04). There were only weak correlations between Vp and the early diastolic mitral annular velocities (r<0.6 for all). We conclude that the assessment of diastolic function by the mitral annular early diastolic velocity appears to be preload-independent, that Vp may be affected by preload and that there is only a weak relationship between Vp and the early diastolic mitral annular velocity.

An assessment of tissue harmonic versus fundamental imaging modes for echocardiographic measurements

The study aimed to evaluate whether a significant difference exists between tissue harmonic imaging (THI) and fundamental imaging (FI) in routine quantitative echocardiographic assessment. We also examined the effects of THI on endocardial definition (ED). Fifty-eight unselected patients (29 men, 29 women; mean age 53 years) referred for transthoracic echocardiography were studied with use of both FI and THI modes. Two independent observers made M-mode measurements of the following: left atrium, aortic root, and left ventricular internal dimensions and wall thickness; they also measured left ventricular outflow tract diameter and left atrial area from 2-dimensional images. Endocardial definition was assessed with use of an arbitrary scoring system (0 = endocardium not visualized, 1 = endocardium visualized but suboptimally, 2 = endocardium well defined) and the American Society of Echocardiography 16-segment model. No significant difference existed between cardiac measurements derived from FI and THI. However, a highly significant improvement in ED occurred with THI (ED index 1.83 versus 1.70, P <.0001). This study suggests that no systematic differences exist in standard echocardiographic measurements between THI and FI, even in the setting of improved ED.

Blood testosterone values in patients with congenital virilizing adrenal hyperplasia

To evaluate the usefulness of blood testosterone (T) in monitoring the effects of therapy in congenital virilizing adrenal hyperplasia due to 21- or 11- hydroxylation defect (CVAH), T levels were measured on 45 occasions in 13 patients with CVAH; 32 urinary 17-ketosteroid levels and 31 preganetriol values were available for comparison. Bone age levels, growth data, and medication are listed to help assess the clinical state of the patient at the time of each T determination. Blood T values were above normal for age and sex in untreated patients with CVAH and declined with glucocorticoid suppression. A blood T value of 20 ng/100 ml appeared to distinguish between well-controlled cases and those with inadequate steroid suppression. Serial measurement of blood T in girls and in prepubertal boys with CVAH provides assistance in evaluating chemical control of the disease, particularly when accurate 24-h urine collections cannot be obtained for 17-ketosteroid and pregnanetriol assessments.