Effect of tissue harmonic imaging and contrast upon between observer and test-retest reproducibility of left ventricular ejection fraction measurement in patients with heart failure

Role of echocardiography in the contemporary management of chronic heart failure

Echocardiography is an excellent noninvasive tool for the assessment of ventricular size and both systolic and diastolic function, and it is routinely used in patients with heart failure. This review will discuss the role of echocardiography in heart failure diagnosis, prognostic assessment and in the management of heart failure patients.

Are measures of left ventricular systolic performance during low dose dobutamine stress echocardiograms repeatable over time?

To establish the test-retest reliability and the normal dose-response relationship of echocardiographic measures of Left Ventricular (LV) contractile function to low dose dobutamine stress in healthy individuals. Thirty healthy volunteers (23 males, 7 females) with an average age of 38 ± 13 years underwent dobutamine stress echocardiography (DSE) (at successive doses of 0, 5, 10, and 20 mcg/kg/min) on two occasions, separated by 14 days. Ejection fraction (EF) was determined from 2D echocardiographic measures of left ventricular (LV) end diastolic and end systolic volumes. Longitudinal strain (S) and strain rate (SR) were measured using 2D speckle tracking analysis from three consecutive cardiac cycles. The Intraclass Correlation Coefficient (ICC) and the Coefficient of Variation (CV) were calculated to assess reliability and variability of the study population's EF, S, and SR responses to increasing doses of dobutamine. Left ventricular S and EF gradually increased with low doses of dobutamine but reached a plateau between 10 and 20 mcg/kg/min. Strain rate, however, gradually increases with each increasing dose of dobutamine. These responses were replicated on Day 2 with a high degree of reliability as determined from the ICC and low variability as determined from the CV, which fell within acceptable limits (<10 %). Left ventricular EF, S and SR can be measured during DSE with a high degree of test-retest reliability, and may be of clinical value when serial follow up of DSE measures of LV performance is indicated over time.

Reproducibility of echocardiographic techniques for sequential assessment of left ventricular ejection fraction and volumes: application to patients undergoing cancer chemotherapy

OBJECTIVES

The aim of this study was to identify the best echocardiographic method for sequential quantification of left ventricular (LV) ejection fraction (EF) and volumes in patients undergoing cancer chemotherapy.

BACKGROUND

Decisions regarding cancer therapy are based on temporal changes of EF. However the method for EF measurement with the lowest temporal variability is unknown.

METHODS

We selected patients in whom stable function in the face of chemotherapy for breast cancer was defined by stability of global longitudinal strain (GLS) at up to 5 time points (baseline, 3, 6, 9, and 12 months). In this way, changes in EF were considered to reflect temporal variability of measurements rather than cardiotoxicity. A comprehensive echocardiogram consisting of 2-dimensional (2D) and 3-dimensional (3D) acquisitions with and without contrast administration was performed at each time point. Stable LV function was defined as normal GLS (≤-16.0%) at each examination. The EF and volumes were measured with 2D-biplane Simpson's method, 2D-triplane, and 3-dimensional echocardiography (3DE) by 2 investigators blinded to any clinical data. Inter-, intra-, and test-retest variability were assessed in a subgroup. Variability was assessed by analysis of variance and compared with Levene's or t test.

RESULTS

Among 56 patients (all female, 54 ± 13 years of age), noncontrast 3D EF, end-diastolic volume, and end-systolic volume had significantly lower temporal variability than all other methods. Contrast only decreased the temporal variability of LV end-diastolic volume measurements by the 2D biplane method. Our data suggest that a temporal variability in EF of 0.06 might occur with noncontrast 3DE due to physiological differences and measurement variability, whereas this might be >0.10 with 2D methods. Overall, 3DE also had the best intra- and inter-observer as well as test-retest variability.

CONCLUSIONS

Noncontrast 3DE was the most reproducible technique for LVEF and LV volume measurements over 1 year of follow-up.

How reliable are left ventricular ejection fraction cut offs assessed by echocardiography for clinical decision making in patients with heart failure?

We aimed to study the potential influence of the variability in the assessment of echocardiographically measured left ventricular ejection fraction (LVEF) on indications for the implantation of internal cardioverter defibrillator and/or cardiac resynchronization devices in heart failure patients. TIME-CHF was a multicenter trial comparing NT-BNP versus symptom-guided therapy in patients aged ≥60 years. Patients had their LVEF assessed at the recruiting centre using visual assessment, the area-length or biplane Simpson's method. Echocardiographic data were transferred to the study core-lab for re-assessment. Re-assessment in the core-lab was done with biplane Simpson's method, and included an appraisal of image quality. 413 patients had the LVEF analyzed at the recruiting centre and at the core lab. Image quality was optimal in 191 and suboptimal in 222. Overall, the correlation between LVEF at the recruiting centres and at the core-lab was good, independent of image quality (R² = 0.62). However, when a LVEF ≤30 % or ≥30 % was used as a cut-off, about 20 % of all patients would have been re-assigned to having either a LVEF above or below the cut-off, this proportion was not significantly influenced by image quality. We conclude that correlation between LVEF assessed by different centres based on the same ultrasound data is good, regardless of image quality. However, one fifth of patients would have been re-assigned to a different category when using the clinically important cut-off of 30 %.

Fast simulation of second harmonic ultrasound field using a quasi-linear method

Nonlinear propagation of sound has been exploited in the last 15 years in medical ultrasound imaging through tissue harmonic imaging (THI). THI creates an image by filtering the received ultrasound echo around the second harmonic frequency band. This technique produces images of enhanced quality due to reduced body wall reverberation, lower perturbations from off-axis echoes, and multiple scattering of reduced amplitude. In order to optimize the image quality it is essential to be able to predict the amplitude level and spatial distribution of the propagating ultrasound pulse. A method based on the quasi-linear approximation has been developed to quickly provide an estimate of the ultrasound pulse. This method does not need to propagate the pulse stepwise from the source plane to the desired depth; it directly computes a transverse profile at any depth from the definitions of the transducer and the pulse. The computation handles three spatial dimensions which allows for any transducer geometry. A comparison of pulse forms, transverse profiles, as well as axial profiles obtained by this method and state-of-the-art simulators, the KZKTexas code, and Abersim, shows a satisfactory match. The computation time for the quasi-linear method is also smaller than the time required by the other methods.

Myocardial perfusion scintigraphy in asymptomatic diabetic patients: a critical review

The increasing prevalence of diabetes mellitus and the associated high cardiovascular risk has made the non-invasive identification of silent coronary heart disease in diabetic individuals an important issue. This strategy could identify higher risk asymptomatic patients with diabetes mellitus in whom coronary revascularization may improve the outcome beyond that achieved by currently recommended medical management. Stress myocardial perfusion imaging has been shown to be effective in detecting coronary heart disease and predicting adverse cardiac events in asymptomatic diabetic patients. However, the clinical utility of myocardial perfusion scintigraphy is debated intensively due to the paucity of prospective and outcome based evidence. The controversy stems from several observational studies, epidemiologic data and cost-effectiveness analyses. Thus, although several authors and professional organizations advocate the use of stress imaging for screening higher risk asymptomatic diabetic patients, others are cautious in recommending any kind of stress testing in that population. This review is based on a broad survey of the literature and discusses the potential role of stress myocardial perfusion scintigraphy in screening asymptomatic diabetic subjects for coronary heart disease in the current era and in relation with other non-invasive screening tools.

Comparison of Different Methods for Detection of Diastolic Filling Abnormalities

OBJECTIVE

Heart failure is associated with poor prognosis and the differentiation of patients on the basis of diastolic filling patterns helps to identify several groups of patients with incrementally higher risk. However, this is reliant on accurate definition of filling patterns. The aim of this study was to compare preload reduction with contrast-enhanced pulmonary venous Doppler recordings for the correct assessment of diastolic filling pattern.

METHODS

In all, 20 patients with heart failure and 25 healthy volunteers were studied on 2 separate days. Preload reduction was achieved with the Valsalva maneuver (nonstandardized and standardized) and sublingual nitroglycerin. Responses were compared among the 3 methods and the filling patterns obtained on each day with the various methods compared.

RESULTS

Although pulmonary venous Doppler improved the diastolic classification over mitral Doppler, preload reduction resulted in better classification and improved sensitivity, specificity, and positive and negative predictive values. No advantage was observed for either the standardized Valsalva or pharmacologic preload reduction.

CONCLUSION

Preload reduction is an essential part of the assessment of diastolic filling grade in patients with heart failure as it can identify pseudonormal filling (mildly increased filling pressures), reversible restrictive filling (high filling pressures), and nonreversible restrictive filling pattern (very high filling pressures).

Time domain simulation of nonlinear acoustic beams generated by rectangular pistons with application to harmonic imaging

A time-domain numerical code (the so-called Texas code) that solves the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation has been extended from an axis-symmetric coordinate system to a three-dimensional (3D) Cartesian coordinate system. The code accounts for diffraction (in the parabolic approximation), nonlinearity and absorption and dispersion associated with thermoviscous and relaxation processes. The 3D time domain code was shown to be in agreement with benchmark solutions for circular and rectangular sources, focused and unfocused beams, and linear and nonlinear propagation. The 3D code was used to model the nonlinear propagation of diagnostic ultrasound pulses through tissue. The prediction of the second-harmonic field was sensitive to the choice of frequency-dependent absorption: a frequency squared f2 dependence produced a second-harmonic field which peaked closer to the transducer and had a lower amplitude than that computed for an f1.1 dependence. In comparing spatial maps of the harmonics we found that the second harmonic had dramatically reduced amplitude in the near field and also lower amplitude side lobes in the focal region than the fundamental. These findings were consistent for both uniform and apodized sources and could be contributing factors in the improved imaging reported with clinical scanners using tissue harmonic imaging.