Strain and strain rate echocardiography

Simulating and Predicting the Mechanical Behavior of Electrospun Scaffolds for Cardiac Patches Fabrication

Fabricating helical scaffolds using electrospinning is a common approach for cardiac implantation, aiming to achieve properties similar to native tissue. However, this process requires multiple experimental attempts to select suitable electrospun properties and validate resulting mechanical responses. To overcome the time and cost constraints associated with this iterative procedure, Finite Element Analysis (FEA) can be applied using stable hyperelastic and viscoelastic models that describe the response of electrospun scaffolds under different conditions. In this study, we aim to create accurate simulations of the viscoelastic behavior of electrospun helical scaffolds. We fabricated helical fibers from Poly (3-caprolactone) (PCL) using the electrospinning process to achieve this. The electrospun samples were subjected to uniaxial deformation, and their response was modelled using existing hyperelastic and stress relaxation models. The simulations were built on experimental data for specific deformation speed and maximum strain conditions. The FEM results were evaluated by accounting for the stress-softening phenomenon, which significantly impacted the models. The electrospun scaffolds' predictions were performed in other than the initial experimental conditions to verify our simulations' accuracy and reliability.

Maternal Hypertensive Disorders of Pregnancy and Cardiac Structure and Function in the Newborn

Background

Maternal hypertensive disorders of pregnancy (HDPs) are strongly associated with offspring congenital heart defects.

Objectives

This study assessed whether infants exposed to maternal HDPs were also more likely to have subtle cardiac structural and functional abnormalities than unexposed infants.

Methods

We used regression analyses to compare: 1) left ventricular parameters from conventional echocardiography performed in infants from the Copenhagen Baby Heart Study born to mothers with preeclampsia, gestational hypertension (GH), or no HDP; and 2) advanced echocardiographic parameters for 545 term infants born to mothers with preeclampsia and 545 matched infants not exposed to HDPs.

Results

Compared with infants unexposed to HDPs (n = 17,384), infants exposed to preeclampsia (n = 754) had a thicker interventricular septum in end-diastole (adjusted mean difference [± SD] 0.05 [±0.02] mm; P = 0.004), thicker left ventricular posterior wall (0.04 [±0.02] mm; P = 0.009), larger left ventricular internal diameter (0.12 [±0.06] mm; P = 0.04), and larger left ventricular volume (0.21 [±0.10] mL; P = 0.03). Systolic function changes included increased fractional shortening (0.36% [±0.14%]; P = 0.01) and stroke volume (0.18 [±0.07] mL; P = 0.006), whereas diastolic function changes included lower transmitral early peak inflow velocity (-1.76 [±0.49] mL; P = 0.0003), lower mitral annulus lateral wall a' (-0.21 [±0.09] cm/s; P = 0.02), and smaller lateral E/e' (-1.06 [±0.38] cm/s; P = 0.005). Conversely, there was little evidence of any association between maternal GH (n = 469) and offspring left ventricular parameters.

Conclusions

Maternal preeclampsia, but not GH, was associated with subtle newborn cardiac morphological and functional alterations, including thickening of the left ventricular myocardium and altered systolic and diastolic function.

Segmental Tissue Speckle Tracking Predicts the Stenosis Severity in Patients With Coronary Artery Disease

Objective

Two-dimensional speckle tracking echocardiography (2D-STE) has been used as a diagnostic tool for coronary artery disease (CAD). However, whether vessel supplied myocardial strain and strain rate (SR) predict the severity of coronary artery stenosis in patients with CAD is unknown. This study aimed to investigate correlation of cardiac mechanical parameters in tissue speckle tracking measurements with coronary artery stenosis diagnosed by cardiac catheterization in patients with clinically diagnosed CAD.

Methods and Results

Among 59 patients analyzed, 170 vessels were evaluated by coronary angiography and the corresponding echocardiography to quantify left ventricular myocardial strain and SR. The average longitudinal strain and SR of the segmental myocardium supplied by each coronary artery were calculated to achieve vessel myocardium strain (VMS) and strain rate (VMSR). The VMS and VMSR at each of four severity levels of stenosis showed significant differences among groups (p = 0.016, and p < 0.001, respectively). The strain and SR in vessels with very severe stenosis (≥75%, group IV; n = 29), 13.9 ± 4.3, and 0.9 ± 0.3, respectively, were significantly smaller than those of vessels with mild stenosis ≤ 25%, group I; n = 88, 16.9 ± 4.9, p = 0.023, and 1.2 ± 0.3, p = 0.001, respectively. The SR in vessels with moderate stenosis (26–49%, group II; n = 37), 1.0 ± 0.2, was significantly smaller than that in vessels with mild stenosis vessels (p = 0.021). The lower VMS and VMSR, the higher possibility of severe coronary stenosis is. The VMS and VMSR lower than 13.9 ± 4.3 and 0.9 ± 0.3, respectively predicted the severe coronary stenosis. The VMS and VMSR higher than 16.9 ± 4.9 and 1.2 ± 0.3, respectively predicted mild or no coronary artery stenosis.

Conclusions

The actual stenosis rate in catheterization demonstrates that this technique was able to assess coronary artery condition. Thus, the application of a non-invasive method of 2D-STE to evaluate and simplify diagnosis of CAD is feasible.

Assessment of right ventricular dysfunction in patients with mitral stenosis: A speckle tracking study

PURPOSE

Although it is affected at an early stage, there is a lack of studies investigating right ventricular (RV) function in patients with mitral stenosis (MS). We aimed to investigate the correlation between conventional echocardiographic variables and tricuspid annular plane systolic excursion (TAPSE), used as an indicator of RV dysfunction.

METHODS

We enrolled 59 consecutive patients with MS and assigned them in group 1 if TAPSE ≤16, or group 2 if: TAPSE >16.

RESULTS

The mean age of the patients was 42.2 ± 8 years, and 74.6% were females. In univariate analysis, maximal mitral valve gradient, mean mitral valve gradient, systolic pulmonary arterial pressure, RV strain, and RV strain rates were associated with RV dysfunction. In multivariate analysis, both strain variables were found to be independent predictors of RV dysfunction. Kaplan Maier survival analysis showed that patients with lower RV strain had more rehospitalization rate during the one-year follow-up period.

CONCLUSIONS

RV dysfunction is common in patients with MS and is associated with higher rehospitalization rate and morbidity. Evaluation of RV strain and strain rate for early detection of RV dysfunction and prediction of rehospitalization may be an appropriate approach in mitral stenosis.

Is the child at risk? Cardiovascular remodelling in children born to diabetic mothers

OBJECTIVE

The objective of this study was to assess differences in myocardial systolic and diastolic function and vascular function in children 2-5 years of age born to diabetic as compared to non-diabetic mothers.

METHODS

This study was a retrospective cohort conducted in 2016 at The Aga Khan University Hospital, Karachi, Pakistan. It included children between 2 and 5 years of age born to mothers with and without exposure to diabetes in utero (n = 68 in each group) and who were appropriate for gestational age. Myocardial morphology and function using echocardiogram and carotid intima media thickness (cIMT) and pulse wave velocity was performed to evaluate cardiac function as well as macrovascular remodelling in these children. Multiple linear regression was used to compare the groups.

RESULTS

There was no significant difference in cardiac morphology, myocardial systolic and diastolic function, and macrovascular assessment between the exposed and unexposed groups of AGA children. Subgroup analysis demonstrated a significantly decreased mitral E/A ratio in children whose mothers were on medications as compared to those on dietary control (median [IQR] = 1.7 [1.6-1.9] and 1.56 [1.4-1.7], respectively, p = 0.02), and a higher cIMT in children whose mothers were on medication as compared to controls (0.48 [0.44-0.52] and 0.46 [0.44-0.50], respectively, p = 0.03).

CONCLUSION

In utero exposure to uncontrolled maternal diabetes has an effect on the cardiovascular structure and function in children aged 2-5 years. However, future work requires long-term follow-up from fetal to adult life to assess these changes over the life course.

Clinical application of echocardiographic-derived myocardial strain imaging in subclinical disease: a primer for cardiologists

PROPOSE OF REVIEW

To highlight the evidence to support the measurement of left ventricular (LV) global longitudinal strain (GLS) in the risk assessment and management of patients with valvular heart disease.

RECENT FINDINGS

Subclinical myocardial dysfunction that is characterized by impaired LV GLS is often present in patients with valvular disease. The addition of GLS to the LV systolic function assessment refines disease classification and improves both prognosis and management of valvular disease.

SUMMARY

The measurement of global systolic function is essential in risk assessment and management of all patients with valvular heart disease. Although LV ejection fraction remains the main parameter of systolic function, strain measurement has emerged as a promising systolic function marker. Strain describes deformation of the myocardium that occurs during the cardiac cycle in the longitudinal, circumferential, and radial planes. Of all the regional strain deformation measurements, evidence gathered over the last decade has shown that GLS improves detection of systolic dysfunction beyond LV ejection fraction and provides additional prognostic information.

In Vivo Open- and Closed-chest Measurements of Left-Ventricular Myocardial Viscoelasticity using Lamb wave Dispersion Ultrasound Vibrometry (LDUV): A Feasibility Study

Diastolic dysfunction causes close to half of congestive heart failures and is associated with increased stiffness in left-ventricular myocardium. A clinical tool capable of measuring viscoelasticity of the myocardium could be beneficial in clinical settings. We used Lamb wave Dispersion Ultrasound Vibrometry (LDUV) for assessing the feasibility of making in vivo non-invasive measurements of myocardial elasticity and viscosity in pigs. In vivo open-chest measurements of myocardial elasticity and viscosity obtained using a Fourier space based analysis of Lamb wave dispersion are reported. The approach was used to perform ECG-gated transthoracic in vivo measurements of group velocity, elasticity and viscosity throughout a single heart cycle. Group velocity, elasticity and viscosity in the frequency range 50-500 Hz increased from diastole to systole, consistent with contraction and relaxation of the myocardium. Systolic group velocity, elasticity and viscosity were 5.0 m/s, 19.1 kPa, 6.8 Pa·s, respectively. In diastole, the measured group velocity, elasticity and viscosity were 1.5 m/s, 5.1 kPa and 3.2 Pa·s, respectively.

Cardiovascular Imaging Techniques in Systemic Rheumatic Diseases

The risk of cardiovascular (CV) events and mortality is significantly higher in patients with systemic rheumatic diseases than in the general population. Although CV involvement in such patients is highly heterogeneous and may affect various structures of the heart, it can now be diagnosed earlier and promptly treated. Various types of assessments are employed for the evaluation of CV risk such as transthoracic or transesophageal echocardiography, magnetic resonance imaging (MRI), and computed tomography (CT) to investigate valve abnormalities, pericardial disease, and ventricular wall motion defects. The diameter of coronary arteries can be assessed using invasive quantitative coronarography or intravascular ultrasound, and coronary flow reserve can be assessed using non-invasive transesophageal or transthoracic ultrasonography (US), MRI, CT, or positron emission tomography (PET) after endothelium-dependent vasodilation. Finally, peripheral circulation can be measured invasively using strain-gauge plethysmography in an arm after the arterial infusion of an endothelium-dependent vasodilator or non-invasively by means of US or MRI measurements of flow-mediated vasodilation of the brachial artery. All of the above are reliable methods of investigating CV involvement, but more recently, introduced use of speckle tracking echocardiography and 3-dimensional US are diagnostically more accurate.

Restrictive Cardiomyopathies: The Importance of Noninvasive Cardiac Imaging Modalities in Diagnosis and Treatment-A Systematic Review

Restrictive cardiomyopathy (RCM) is the least common among cardiomyopathies. It can be idiopathic, familial, or secondary to systematic disorders. Marked increase in left and/or right ventricular filling pressures causes symptoms and signs of congestive heart failure. Electrocardiographic findings are nonspecific and include atrioventricular conduction and QRS complex abnormalities and supraventricular and ventricular arrhythmias. Echocardiography and cardiac magnetic resonance (CMR) play a major role in diagnosis. Echocardiography reveals normal or hypertrophied ventricles, preserved systolic function, marked biatrial enlargement, and impaired diastolic function, often with restrictive filling pattern. CMR offering a higher spatial resolution than echocardiography can provide detailed information about anatomic structures, perfusion, ventricular function, and tissue characterization. CMR with late gadolinium enhancement (LGE) and novel approaches (myocardial mapping) can direct the diagnosis to specific subtypes of RCM, depending on the pattern of scar formation. When noninvasive studies have failed, endomyocardial biopsy is required. Differentiation between RCM and constrictive pericarditis (CP), nowadays by echocardiography, is important since both present as heart failure with normal-sized ventricles and preserved ejection fraction but CP can be treated by means of anti-inflammatory and surgical treatment, while the treatment options of RCM are dictated by the underlying condition. Prognosis is generally poor despite optimal medical treatment.

Echocardiographic Evaluation of Left Atrial Mechanics: Function, History, Novel Techniques, Advantages, and Pitfalls

Left atrial (LA) functional analysis has an established role in assessing left ventricular diastolic function. The current standard echocardiographic parameters used to study left ventricular diastolic function include pulsed-wave Doppler mitral inflow analysis, tissue Doppler imaging measurements, and LA dimension estimation. However, the above-mentioned parameters do not directly quantify LA performance. Deformation studies using strain and strain-rate imaging to assess LA function were validated in previous research, but this technique is not currently used in routine clinical practice. This review discusses the history, importance, and pitfalls of strain technology for the analysis of LA mechanics.

Speckle tracking and myocardial tissue imaging in infant of diabetic mother with gestational and pregestational diabetes

The aim of this study was to evaluate the myocardial changes in infants of diabetic mother either with gestational or pregestational diabetes and its relation to maternal diabetic control. The study included 45 infants of diabetic mother (IDMs) and 45 healthy newborn as a control group. IDMs were then categorized into 2 subgroups: twenty infants of mother with pregestational diabetes and twenty-five infants of mothers with gestational diabetes. The studied groups underwent measurement of the maternal and neonatal glycated Hb % (HbA1c), conventional echocardiography, tissue Doppler imaging (TDI) and two-dimensional speckle tracking imaging (STI). The weight, the rate of complications, and the rate of cesarean section were significantly higher in the IDMs group than in the control group. Significant positive correlation was present between the levels of HbA1c of IDMs and HbA1c of their mothers (P < 0.05). A significant deterioration of both systolic and diastolic functions measured by both conventional echocardiography and TDI was present in IDMs with both pre-gestational and gestational diabetes compared with the control group. Also, the septal/posterior wall ratio (SW/PW) was significantly higher in pregestational (1.86 ± 0.3) and gestational (2 ± 0.4) groups than in the control group (1 ± 0.06). Two-dimensional STI showed that the cardiac torsion was significantly impaired in pre-gestational (9.66 ± 2.5) and gestational (8.66 ± 3.9) groups when compared with the control group (5.4 ± 2.4) [P < 0.0001]. It also showed that the global strain was significantly impaired in pre-gestational (-10.4 ± 3.2) and gestational (-13.1 ± 4.7) groups when compared with the control group (-19 ± 2) [P < 0.0001]. However, no significant differences were present among the two patients' subgroups in echocardiographic data except for a significant decrease of E'/A' ratio and S wave at tricuspid annulus derived by TDI and impaired global strain derived by STI in infants of mothers with pre-gestational DM than those with gestational DM [P = 0.02]. SW/PW and cardiac torsion were significantly higher in infant of diabetic mother than the normal newborn and on the contrary systolic function and global strain were significantly lower in IDMs especially in infants of mother with pre-gestational diabetes. All the previous TDI findings did not show any significant correlation to neither maternal nor fetal HbA1c. Also, there was no significant correlation between cardiac torsion and the rest of TDI data neither in IDMs group nor in the control group. TDI and two-dimensional STI were efficient and sensitive tools able to early detect cardiac dysfunction in IDMs even in the absence of morphologic cardiac changes.

Developmental changes in left and right ventricular function evaluated with color tissue Doppler imaging and strain echocardiography

AIMS

We evaluated the systolic and diastolic functions of both ventricles from the early neonatal period to adolescence using color tissue Doppler imaging and 2-dimensional tissue tracking echocardiography.

METHODS

We examined 100 healthy children (aged 1-5 days, n = 20; 1 month, n = 20; 1 year, n = 20; 6-7 years, n = 20; and 12-13 years, n = 20). Blood flow velocities in the mitral and tricuspid valves (E) were obtained with pulsed Doppler imaging, and longitudinal systolic (S') and early diastolic (E') peak velocities at the mid free wall segment of both ventricles were obtained with color tissue Doppler imaging. For longitudinal strain imaging, systolic peak values were obtained at the same position. In addition, peak systolic radial strain was obtained from a short-axis view of the left ventricle using the tissue tracking method. The E/E' ratio was calculated.

RESULTS

Regarding systolic indices, S' increased during development and stabilized at 6 to 7 years, and longitudinal strain reached values of the 12- to 13-year-old group at 1 year of age in both ventricles. Like longitudinal strain, radial strain in the left ventricle reached values of the 12- to 13-year-old group at the age of 1 year. Similarly, the E/E' ratio was high at 1 month or younger and decreased by 1 year.

CONCLUSIONS

Systolic and diastolic variables change markedly from birth to 1 year of age and show only small changes thereafter.

External Cardioversion of Atrial Fibrillation Causes an Early Improvement of Cardiac Performance: A Longitudinal Strain Analysis Study

Introduction:

Atrial fibrillation (AF) is often associated with heart failure. Several studies have demonstrated that resumption of sinus rhythm (SR) improves cardiac output in the long-term. Aims of this study were to evaluate the acute variations of left ventricular (LV) performance, following successful external cardioversion (ECV) of persistent AF using longitudinal strain (LSt) analysis, and the influence of inflammation.

Materials and Methods:

We enrolled 48 patients with AF (age: 73 ± 12 years, men: 83.3%). A standard transthoracic echocardiographic evaluation was performed before the procedure and 6 h later; this included the analysis of LV endocardial peak LSt, a measure of myocardial deformation. In the last 32 patients, plasma concentration of interleukin-6 (IL-6) was also determined.

Results:

Restoration of SR led to the decrease of heart rate (HR) (74 ± 21 vs 64 ± 10 bpm, P < 0.001) and LV end-systolic volume (30 ± 16 vs 27 ± 17 mL/m², P = 0.001), and to the increase of LV end-diastolic volume (LVEDV) (56 ± 20 vs 60 ± 21 mL/m², P = 0.036) and ejection fraction (EF) (48 ± 10 vs 57 ± 11%, P < 0.001). Peak LSt improved in 43 (89.6%) patients (-12.9 ± 3.3 vs -18.0 ± 4.7%, P < 0.001). Multivariate analysis (R = 0.729, P < 0.001) showed that strain changes were directly correlated with basal HR and the appearance of atrial mechanical activity and inversely correlated with corrected thyroid dysfunction, LVEDV and the presence of a permanent pacemaker. Higher levels of IL-6 negatively affected LV performance improvement.

Conclusions:

Effective ECV of AF determines a significant and fast improvement of LV performance, which is readily captured by LSt analysis. Inflammatory status may impact the response to SR restoration.

Speckle tracking derived strain in infants with severe perinatal asphyxia: a comparative case control study

BACKGROUND

Speckle tracking echocardiography is increasingly being used to assess cardiac function in neonates. The objective was to compare speckle tracking strain indices between asphyxiated infants and healthy controls and to ascertain correlations between strain and 2D Doppler derived indices and cardiac troponin (biochemical marker of myocardial injury).

METHODS

Clinical and echocardiographic data from severely asphyxiated infants undergoing therapeutic hypothermia was evaluated retrospectively. This was compared with prospective data from healthy infants. Correlations between variables were assessed using Pearson's coefficient of correlation.

RESULTS

Twenty four infants with severe perinatal asphyxia were admitted during the study period of which 3 were not cooled and were excluded. The gestational age and birth weights of cases and controls were comparable. The mean left ventricular global longitudinal strain (GLS) from apical 4 chamber view was noted to be significantly impaired in the asphyxiated infants (- 11.01% ± 2.48 vs - 21.45% ± 2.74, p <0.001). Cardiac output was significantly lower in the asphyxiated infants (97 ± 26 vs 230 ± 60 ml/kg/min). In asphyxiated infants, GLS correlated positively with cardiac output (r2 = 0.86, p< 0.001) and negatively with serum troponin levels (r2 = 0.64, p< 0.001). GLS was less impaired in infants on inotropes compared to those not on inotropic support, -12.55% (1.9) vs -10.2% (1.3), p= 0.018. Infants who died had a lower global strain value compared to survivors, - 9.7% (1.6) vs - 12.8% (2.6), p = 0.02.

CONCLUSIONS

2D Speckle derived strain was impaired in asphyxiated infants. Significant correlations between GLS and cardiac output and troponin were noted.

Measurement of viscoelastic properties of in vivo swine myocardium using lamb wave dispersion ultrasound vibrometry (LDUV)

Viscoelastic properties of the myocardium are important for normal cardiac function and may be altered by disease. Thus, quantification of these properties may aid with evaluation of the health of the heart. Lamb wave dispersion ultrasound vibrometry (LDUV) is a shear wave-based method that uses wave velocity dispersion to measure the underlying viscoelastic material properties of soft tissue with plate-like geometries. We tested this method in eight pigs in an open-chest preparation. A mechanical actuator was used to create harmonic, propagating mechanical waves in the myocardial wall. The motion was tracked using a high frame rate acquisition sequence, typically 2500 Hz. The velocities of wave propagation were measured over the 50-400 Hz frequency range in 50 Hz increments. Data were acquired over several cardiac cycles. Dispersion curves were fit with a viscoelastic, anti-symmetric Lamb wave model to obtain estimates of the shear elasticity, μ(1), and viscosity, μ(2) as defined by the Kelvin-Voigt rheological model. The sensitivity of the Lamb wave model was also studied using simulated data. We demonstrated that wave velocity measurements and Lamb wave theory allow one to estimate the variation of viscoelastic moduli of the myocardial walls in vivo throughout the course of the cardiac cycle.

Assessment of left atrial function after percutaneous closure of patent foramen ovale

BACKGROUND

The influence of atrial septal occluders in left atrial (LA) function after percutaneous closure of patent foramen ovale (PFO) has not been thoroughly studied.

METHODS

Twenty-five patients (mean age 40.7 ± 12 years) undergoing percutaneous PFO closure were enrolled in this study. Transthoracic echocardiogram (TTE) was performed 3 and 6 months before the procedure. Volumetric indices (active emptying fraction: LA AEF, expansion index: LA EI, and passive emptying fraction: LA PEF), strain and strain rate (SR), were calculated during the contractile, reservoir, and conduit LA phases for the lateral, anterior, and inferior LA walls with TTE.

RESULTS

After 3 months, a decrease in the SR of the LA anterior wall was observed (from 2.12 ± 0.22 to 1.66 ± 0.26, P < 0.045), while the LA lateral wall strain was found to be increased (from 0.708 ± 0.15 to 0.783 ± 0.159, P < 0.001). Moreover, simultaneously LA AEF was greater compared with baseline (from 31.0 ± 1.6 to 34.0 ± 1.6, P < 0.004). However, all these alterations reversed at 6 months.

CONCLUSIONS

Segmental LA function is altered transiently after percutaneous PFO closure with a septal occlude. The LA anterior wall SR decreases, while the lateral wall strain increases. The impact of these alterations needs further clarification.

Diastolic dysfunction and heart failure with a preserved ejection fraction: Relevance in critical illness and anaesthesia

Epidemiological and clinical studies suggest that HF with a preserved ejection fraction will become the more common form of HF which clinicians will encounter. The spectrum of diastolic disease extends from the asymptomatic phase to fulminant cardiac failure. These patients are commonly encountered in operating rooms and critical care units. A clearer understanding of the underlying pathophysiology and clinical implications of HF with a preserved ejection fraction is fundamental to directing further research and to evaluate interventions. This review highlights the impact of diastolic dysfunction and HF with a preserved ejection fraction during the perioperative period and during critical illness.

Tissue Doppler echocardiographic markers of cardiac dysfunction in small-for-gestational age fetuses

OBJECTIVE

The objective of the study was to evaluate echocardiographic markers of cardiac dysfunction in small-for-gestational age (SGA) fetuses with normal umbilical artery Doppler.

STUDY DESIGN

Cardiac function was evaluated in 58 SGA (mean gestational age, 38 weeks) and 58 gestational-age matched normally grown fetuses by conventional echocardiography (peak early [E] and late [A] ratios and myocardial performance index [MPI]), and tissue Doppler imaging (TDI) (annular peak velocities and MPI').

RESULTS

With conventional echocardiography, SGA fetuses had a nonsignificant trend to increased E/A ratios and left MPI compared with controls. TDI demonstrated that SGA fetuses had significantly lower right E' and A' peak velocities and higher MPI' values.

CONCLUSION

These findings further support that a proportion of SGA fetuses have true late-onset intrauterine growth restriction, which is associated with subclinical cardiac dysfunction, as previously described for early-onset intrauterine growth restriction.

Left atrial function: physiology, assessment, and clinical implications

The interest in the left atrium (LA) has resurged over the recent years. In the early 1980s, multiple studies were conducted to determine the normal values of LA size. Over the past decade, LA size as an imaging biomarker has been consistently shown to be a powerful predictor of outcomes, including major public health problems such as atrial fibrillation, heart failure, stroke, and death. More recently, functional assessment of the LA has been shown to be, at least as, if not more robust, a marker of cardiovascular outcomes. Current available data suggest that the combined evaluation of LA size and LA function will augment prognostication. The aim of this review is to provide a critical appraisal of current echocardiographic techniques for the assessment of LA function and the implications of such assessment for prediction and disease prevention.

Case report: transesophageal echocardiography detected severe regional wall motion abnormalities signifying failed reimplantation of an anomalous left main coronary artery

PURPOSE

Anomalous coronary arteries comprise a spectrum ranging from benign to fatal. The most ominous lesion that occurs is the left main coronary artery (LMCA) originating from the opposite aortic sinus. This defect usually presents as sudden death in a healthy young adult immediately after exercise. We report a case of reimplantation of an anomalous LMCA, discovered in a 15-yr-old girl during investigations for atypical chest pain.

CLINICAL FEATURES

The intraoperative transesophageal echocardiography (TEE) confirmed that the anomalous LMCA originated from the right aortic sinus. The anomalous LMCA was reimplanted to the left aortic sinus, but the patient could not be weaned from cardiopulmonary bypass because of severe hypotension. The TEE demonstrated severe regional wall motion abnormalities (RWMA) in the territory of the LMCA with akinesis of the septal, antero-septal, anterior, and lateral walls. Using TEE, flow could not be seen in the reimplanted LMCA, hence, the differential diagnosis was established as failed reimplantation of the LMCA, coronary air embolism, or poor myocardial preservation, but the latter two causes were extremely unlikely. Surgical inspection of the reimplanted LMCA did not reveal a correctable problem. A left internal mammary artery to proximal left anterior descending (LAD) artery graft was completed with resolution of the previous RWMA. Recovery of function in the lateral wall confirmed retrograde flow from the LAD into the circumflex artery.

CONCLUSIONS

Transesophageal echocardiography was critical in rapidly determining the cause of hemodynamic instability following this uncommon operation. Despite the availability of newer techniques to detect and quantify RWMA, the assessment of wall motion and contractility remains subjective.

A dual-chamber, thick-walled cardiac phantom for use in cardiac motion and deformation imaging by ultrasound

Determination of the mechanical properties of the myocardium is crucial for cardiac diagnosis. Cardiac strain and strain rate imaging may enable such quantification. To further develop these methodologies, an experimental setup allowing the recording of ultrasonic deformation data in a reproducible manner is necessary. Such setup with biventricular polyvinyl alcohol heart phantoms has been built. To test this setup, segmental longitudinal, radial and circumferential displacement, velocity, strain and strain rate in the phantoms were measured using a clinical ultrasound scanner and commercially available deformation imaging algorithms (based on both tissue velocity imaging and speckle tracking). The model deformation was close to that observed in the human left ventricular wall and was highly reproducible (e.g., the average peak longitudinal strain for the mid- and apical phantom segments equals -15.32 +/- 0.53% and -19 +/- 6% for the ventricle wall). The experimental setup is a valuable source of data for the development of algorithms for deformation estimation.

Ex Vivo measurements of myocardial viscoelasticity using Shearwave Dispersion Ultrasound Vibrometry (SDUV)

Stiffening of the left ventricle can compromise the ability of the heart to pump sufficient amounts of blood into the systemic circulation and could lead to heart failure. Quantifying mechanical properties of the left ventricular (LV) myocardium using a noninvasive technique would be of great benefit in clinical settings. We investigated the feasibility of using Shearwave Dispersion Ultrasound Vibrometry (SDUV) to measure viscoelasticity of the myocardium. A mechanical actuator was used to induce shear waves at multiple frequencies (40-500 Hz) in excised LV myocardium and urethane rubber samples, and a pulse echo ultrasound transducer was used to detect the motion at each frequency. An anti-symmetric Lamb wave model was fit to the shear wave dispersion curves in four orthogonal directions to obtain elastic and viscous moduli.

Shearwave dispersion ultrasound vibrometry applied to in vivo myocardium

Diastolic properties of the myocardium are important for normal cardiac function and may contribute to the condition of heart failure. Measuring the viscoelastic properties of the left ventricular myocardium is difficult in vivo using noninvasive methods. In this study, we used a mechanical actuator to create harmonic, propagating mechanical waves in the myocardial tissue in vivo. The motion was measured using ultrasound imaging techniques. The wave propagation velocities were measured over the 50-350 Hz frequency range. The dispersion curves were fit with an asymmetrical Lamb wave model to obtain estimates of the shear elasticity and viscosity of the myocardial tissue. The method was applied to estimate viscoelastic properties of the myocardium during diastole and systole.

Speckle tracking echocardiography: A new approach to myocardial function

Echocardiography is the most common diagnostic method for assessing cardiac function but some limitations affect this technique. Until now, visual assessment of wall motion and thickening has allowed only a subjective evaluation of myocardial function and requires long-term training. Recently, new echocardiographic techniques have been introduced to evaluate myocardial mechanics. Tissue Doppler imaging (TDI) technique is limited by angle-dependency such that only deformation along the ultrasound beam can be derived from velocities, while myocardium deforms simultaneously in three dimensions. Speckle tracking echocardiography (STE) is a more recent technique that provides a global approach to left ventricular myocardial mechanics, giving information about the three spatial dimensions of cardiac deformation. In this editorial, we describe the physical and pathophysiological concepts of STE, discussing the differences compared to TDI and underlining the pitfalls of this new technique.

Cardiac functional evaluation using vector velocity imaging after chemotherapy including anthracyclines in children with cancer

BACKGROUND AND OBJECTIVES

Anthracyclines are effective drugs that are widely used in pediatric cancer treatment. Previous studies have demonstrated that exposure to low-dose anthracyclines (<300 mg/m(2)) induces a progressive decrease in cardiac function during long-term follow-up. The goal of this study was to assess left ventricular function using vector velocity imaging (VVI) in children undergoing low-dose anthracycline therapy.

SUBJECTS AND METHODS

We examined 14 asymptomatic patients who had been treated with anthracyclines and had normal fractional shortening (FS) and ejection fraction (EF). In all of the patients, standard two-dimensional (2D) pulsed and tissue Doppler echocardiographic measurements were taken from an apical 4-chamber view. The peak myocardial velocity, peak strain rate (SR), peak strain, and displacement were obtained from VVI. Data were compared with 14 age-matched healthy controls.

RESULTS

From the regional wall motion analysis using VVI in the left ventricle, the peak myocardial velocity and displacement of the lateral wall were increased significantly more than the septum, and there were no significant differences between the patients and the controls. Although systolic strain, and the systolic and diastolic SRs showed no significant differences between the septum and lateral wall in the controls, those of septum, in the patients, were decreased significantly more than those of lateral wall (p<0.05). In comparison with the controls, these changes in septal strain and SRs of patients were significant (p<0.05).

CONCLUSION

Anthracycline therapy, even low-dose, can induce changes in regional wall function before global dysfunction. Also, the strain and SR obtained from VVI may be useful for early detection of these changes.

Atrial and ventricular function in thalassemic patients with supra-ventricular arrhythmias

The aims of this study were to evaluate through Color Doppler Myocardial Imaging (CDMI) echocardiography if atrial or ventricular myocardial alterations could be detectable in patients with thalassemia major (THAL) and if these alterations could be considered as predictive elements for supra-ventricular arrhythmic events. Twenty-three patients with THAL underwent clinical and electrocardiographic evaluation; patients were grouped in THAL1 (9 with supra-ventricular arrhythmias) and THAL2 (14 without arrhythmias); 12 healthy subjects were considered as control group (C). We examined through conventional 2D Color Doppler echocardiography some morphological and functional parameters regarding left ventricular (LV) systolic and diastolic function, and through CDMI the velocities at mitral annulus level, the regional LV and left atrial (LA) strain and strain rate. All THAL patients had LV dimension (p<0.05), LA area (p<0.01) and E/Em ratio (p<0.001) to be significantly higher than controls. The mitral annulus longitudinal velocities were significantly lower in THAL1 than in THAL2 (p<0.001); the E/Em ratio was higher in THAL1 than THAL2 (p<0.001). The THAL1 showed a lower systolic strain rate of atrial wall than THAL2 and C (p<0.05). The multiple regression highlighted a significantly inverse correlation among E/Em and atrial strain (p<0.02). CDMI showed both THAL subgroups had subtle systolic and diastolic left ventricular myocardial alterations, which could represent the onset of developing "iron cardiomyopathy" and are related to supra-ventricular arrhythmia. Monitoring these parameters in the THAL patients could contribute to decisions about follow-up and therapy.

Ultrasound frame rate requirements for cardiac elastography: experimental and in vivo results

Cardiac elastography using radiofrequency echo signals can provide improved 2D strain information compared to B-mode image data, provided data are acquired at sufficient frame rates. In this paper, we evaluate ultrasound frame rate requirements for unbiased and robust estimation of tissue displacements and strain. Both tissue-mimicking phantoms under cyclic compressions at rates that mimic the contractions of the heart and in vivo results are presented. Sinusoidal compressions were applied to the phantom at frequencies ranging from 0.5 to 3.5 cycles/sec, with a maximum deformation of 5% of the phantom height. Local displacements and strains were estimated using both a two-step one-dimensional and hybrid two-dimensional cross-correlation method. Accuracy and repeatability of local strains were assessed as a function of the ultrasound frame rate based on signal-to-noise ratio values. The maximum signal-to-noise ratio obtained in a uniformly elastic phantom is 20 dB for both a 1.26 Hz and a 2 Hz compression frequency when the radiofrequency echo acquisition is at least 12 Hz and 20 Hz respectively. However, for compression frequencies of 2.8 Hz and 4 Hz the maximum signal-to-noise ratio obtained is around 16 dB even for a 40 Hz frame rate. Our results indicate that unbiased estimation of displacements and strain require ultrasound frame rates greater than ten times the compression frequency, although a frame rate of about two times the compression frequency is sufficient to estimate the compression frequency imparted to the tissue-mimicking phantom. In vivo results derived from short-axis views of the heart acquired from normal human volunteers also demonstrate this frame rate requirement for elastography.

Echocardiographic examination in rats and mice

Rats and mice are the predominant experimental species in cardiovascular research due to the widespread availability of genetic and transgenic rodent models of heart disease. Phenotyping of these models requires reliable and reproducible methods to noninvasively and serially assess cardiovascular structure and function. However, the small size of rodents has presented a challenge. Many of these challenges have been overcome in recent years due to significant technological advances in echocardiographic capabilities. For example, improved spatial resolution and increased frame rates have allowed more precise and accurate quantification of diminutive structures, myocardial function, and blood flow in mice. Consequently, transthoracic echocardiography (TTE) has emerged as a popular and powerful tool for cardiac phenotypic characterization in rodents. This chapter will focus on the use of TTE in rodents for evaluating (1) left ventricular (LV) chamber dimensions and wall thickness, (2) LV mass, (3) global LV systolic and diastolic function, (4) regional LV systolic function by newly developed tissue Doppler imaging (TDI), and (5) hemodynamic parameters. Reliability of these measurements depends on various factors such as the skill and experience of the sonographer and the image analyzer, the type, depth, and duration of anesthesia, and animal characteristics. These topics will also be discussed.

Is albuminuria an indicator of myocardial dysfunction in diabetic patients without overt heart disease? A study with Doppler strain and strain rate imaging

The aim of this study was to address whether albuminuria could predict myocardial dysfunction in diabetic patients without overt heart disease. We studied 67 patients with normal left ventricular (LV) ejection fraction and no evidence of LV hypertrophy or coronary artery disease (47 patients with type 2 diabetes mellitus and hypertension and 20 patients with hypertension only). Diabetes patients were divided into 3 groups based on albuminuria status: group II = no albuminuria (n = 20, <30 mg/d), group III = microalbuminuria (n = 13, 30-300 mg/d), and group IV = macroalbuminuria (n = 14, >300 mg/d). Twenty patients with hypertension only served as a control group (group I). Conventional 2-dimensional and Doppler echocardiography was done. Peak strain, peak systolic strain rate (SR), and peak diastolic SR of 6 LV segments in the apical views were measured and averaged in each patient. Conventional 2-dimensional parameters such as LV ejection fraction; left atrium volume index; LV mass; deceleration time; and mitral early peak, mitral late peak, myocardial early peak diastolic, and myocardial peak systolic velocities were not different among the 4 groups. However, peak strains were significantly lower in group III (P = .002) and group IV (P < .001) than in group I; and the absolute value of peak systolic SR was lower in group III (P = .033) and group IV (P < .001) than in group I. Furthermore, the value of peak diastolic SR was lower in group IV than in group I (P = .014). In diabetic patients with albuminuria, Doppler strain and SR imaging detected subclinical LV systolic and diastolic dysfunction; and albuminuria was associated with myocardial dysfunction in diabetic patients without overt heart disease.

In vivo validation of a novel method for regional myocardial wall motion analysis based on echocardiographic tissue tracking

The objective of this study was to validate a recently developed tissue tracking (TT) method for cardiac motion, by comparing it with precise invasive measurements of motion and to prove its capability to reflect moderate hemodynamic changes induced by asynchronous activation. In four open-chest sheep, sono-crystals measured the left ventricle(LV) equator's diameters simultaneously with 2D ultrasound acquisition. The LV was paced either from the posterior or from the lateral wall, just prior to the normal LV activation. Global functional indices were calculated based on the regional motions extracted by the TT method. The correlation coefficient between the shortening of the diameters and the global circumferential strain (GCS) was 0.99 +/- 0.004. The peak GCS differentiated between the pacing modes (paired t test, P < 0.05). The GCS, a measurement closely based on the TT method, followed the precise sono-crystals measurements and reflected moderate hemodynamic changes, thus providing a substantial proof of the TT method's accuracy and clinical value.