Assessment of left ventricular function by three-dimensional echocardiography

Increasing region of interest width reduces neonatal circumferential strain

OBJECTIVE

There is growing interest in speckle tracking echocardiography-derived strain as a measure of left ventricular function in neonates. However, knowledge gaps remain regarding the effect of image acquisition and processing parameters on circumferential strain measurements. The aim of this study was to evaluate the effect of using different region of interest (ROI) widths on speckle tracking derived circumferential strain in healthy neonates.

METHODS

Thirty healthy-term-born neonates were examined with speckle-tracking echocardiography in the short-axis view. Circumferential strain values were acquired and compared using two different ROI widths. Furthermore, strain values in the different vendor-defined wall layers were also compared.

RESULTS

Increasing ROI width led to a decrease in global circumferential strain (GCS) in the midwall and epicardial layers, the respective decreases in strain being -23.4 ± .6% to -22.0 ± 1.1%, p < .0001 and 18.5 ± 1.7% to -15.6 ± 2.0%, p < .0001. Segmental analyses were consistent with these results, apart from two segments in the midwall. There was no statistically significant effect on strain for the endocardial layer. A gradient was seen where strain increased from the epicardial to endocardial layers.

CONCLUSION

Increasing ROI width led to a decrease in GCS in the midwall and epicardium. There is an increase in circumferential strain when moving from the epicardial toward the endocardial layer. Clinicians wishing to implement circumferential strain into their practice should consider ROI width variation as a potential confounder in their measurements.

The feasibility of contrast echocardiography in the assessment of right ventricular size and function

BACKGROUND

Right ventricle (RV) evaluation requires dedicated imaging to achieve a comprehensive functional and anatomical assessment. Right ventricular imaging could be technically difficult which results in suboptimal visibility and inconsistent assessment between observers. The aim of this study was to assess feasibility and the additive value of contrast enhancement for right ventricular evaluation.

METHODS

Eighty patients referred for clinically indicated echocardiography studies were included. Patients with irregular rhythms were excluded. Dedicated RV-focused view was attained; RV dimensions measured, and RV segment visualization and wall motion were assessed with and without contrast enhancement. Paired sample t test was used to compare continuous variables, Wilcoxon signed-rank test to compare segments visualization on enhanced versus (vs) nonenhanced images, and Cohen kappa coefficient to assess the agreement of wall motion between two observers. Reproducibility was measured by the absolute mean difference method.

RESULTS

A total of 240 total segments of 80 patients were analyzed, and 178 (74%) were visible on unenhanced while 221 (92%) on enhanced images, P < .05. Further, RV measurements on enhanced images were consistently larger on RV focused, SAX, and RVOT. Inter- and intra-observer reproducibility showed a higher reproducibility with a lower bias on enhanced images. Absolute agreement on RV segmental wall motion between two independent observers was higher on enhanced images. Percent agreement was 78% on UE vs 89% on CE.

CONCLUSION

Contrast RV imaging is feasible and improves RV segment visualization and inter-observer agreement. Compared with unenhanced images, RV measurements on contrast images are larger and more reproducible with lower bias.

Evaluation of Left Ventricular Systolic Function and Mass in Primary Hypertensive Patients by Echocardiography

Hypertension is an independent risk factor for cardiovascular diseases. The accurate evaluation of cardiovascular risk is of paramount importance in the management of hypertensive patients. Conventional echocardiographic methods have provided the assessment of left ventricular systolic function and mass for many years. Tissue Doppler imaging, 3-dimensional echocardiography, and speckle tracking echocardiography are newer echocardiographic modalities for the left ventricular systolic function and mass quantification. The major emphasis of this review is to evaluate the left ventricular systolic function and mass by conventional and newly developed echocardiographic in hypertensive patients.

The impact of preload on 3-dimensional deformation parameters: principal strain, twist and torsion

Background

Strain analysis is feasible using three-dimensional (3D) echocardiography. This approach provides various parameters based on speckle tracking analysis from one full-volume image of the left ventricle; however, evidence for its volume independence is still lacking.

Methods

Fifty-eight subjects who were examined by transthoracic echocardiography immediately before and after hemodialysis (HD) were enrolled. Real-time full-volume 3D echocardiographic images were acquired and analyzed using dedicated software. Two-dimensional (2D) longitudinal strain (LS) was also measured for comparison with 3D strain values.

Results

Longitudinal (pre-HD: −24.57 ± 2.51, post-HD: −21.42 ± 2.15, P < 0.001); circumferential (pre-HD: −33.35 ± 3.50, post-HD: −30.90 ± 3.22, P < 0.001); and radial strain (pre-HD: 46.47 ± 4.27, post-HD: 42.90 ± 3.61, P < 0.001) values were significantly decreased after HD. The values of 3D principal strain (PS), a unique parameter of 3D images, were affected by acute preload changes (pre-HD: −38.10 ± 3.71, post-HD: −35.33 ± 3.22, P < 0.001). Twist and torsion values were decreased after HD (pre-HD: 17.69 ± 7.80, post-HD: 13.34 ± 6.92, P < 0.001; and pre-HD: 2.04 ± 0.86, post-HD:1.59 ± 0.80, respectively, P < 0.001). The 2D LS values correlated with the 3D LS and PS values.

Conclusion

Various parameters representing left ventricular mechanics were easily acquired from 3D echocardiographic images; however, like conventional parameters, they were affected by acute preload changes. Therefore, strain values from 3D echocardiography should be interpreted with caution while considering the preload conditions of the patients.

The Role of Automated 3D Echocardiography for Left Ventricular Ejection Fraction Assessment

Ejection fraction is one of the most powerful determinants of prognosis and is a crucial parameter for the determination of cardiovascular therapies in conditions such as heart failure, valvular conditions and ischaemic heart disease. Among echocardiographic methods, 3D echocardiography has been attributed as the preferred one for its assessment, given an increased accuracy and reproducibility. Full-volume multi-beat acquisitions are prone to stitching artefacts due to arrhythmias and require prolonged breath holds. Single-beat acquisitions exhibit a lower temporal resolution, but address the limitations of multi-beat acquisitions. If not fully automated, 3D echocardiography remains time-consuming and resource-intensive, with suboptimal observer variability, preventing its implementation in routine practice. Further developments in hardware and software, including fully automated knowledge-based algorithms for left ventricular quantification, may bring 3D echocardiography to a definite turning point.

High-frame rate four dimensional optoacoustic tomography enables visualization of cardiovascular dynamics and mouse heart perfusion

Functional imaging of mouse models of cardiac health and disease provides a major contribution to our fundamental understanding of the mammalian heart. However, imaging murine hearts presents significant challenges due to their small size and rapid heart rate. Here we demonstrate the feasibility of high-frame-rate, noninvasive optoacoustic imaging of the murine heart. The temporal resolution of 50 three-dimensional frames per second provides functional information at important phases of the cardiac cycle without the use of gating or other motion-reduction methods. Differentiation of the blood oxygenation state in the heart chambers was enabled by exploiting the wavelength dependence of optoacoustic signals. Real-time volumetric tracking of blood perfusion in the cardiac chambers was also evaluated using indocyanine green. Taken together, the newly-discovered capacities offer a unique tool set for in-vivo structural and functional imaging of the whole heart with high spatio-temporal resolution in all three dimensions.

Quantitative assessment of left ventricular function by 3-dimensional speckle-tracking echocardiography in patients with chronic heart failure: a meta-analysis

OBJECTIVES

To provide a comprehensive analysis of the clinical utility of 3-dimensional (3D) speckle-tracking echocardiography for left ventricular (LV) function in patients with chronic heart failure (CHF).

METHODS

Literature searches were conducted in the PubMed, Embase, Web of Science, and China BioMedicine databases on relevant articles published before October 1, 2012. Crude standardized mean differences with 95% confidence intervals (CIs) were calculated.

RESULTS

Seven case-control studies were included with a total of 375 patients with CHF and 181 healthy control participants. Meta-analysis results showed that the LV ejection fraction in the patients was significantly lower than in the controls (standardized mean difference, -4.62; 95% CI, -6.19 to -3.04), whereas the LV end-diastolic volume (LVEDV) and LV end-systolic volume (LVESV) in the patients were higher than in the controls (LVEDV: standardized mean difference, 1.76; 95% CI, 1.09 to 2.44; LVESV: standardized mean difference, 2.04, 95% CI, 1.30 to 2.78). The results also indicated that the patients had a greater delay in the standard deviation of the time to peak area tracking and the maximum difference in the time to peak area tracking in the 16 LV segments than the controls (standard deviation of the time to peak area tracking: standardized mean difference, 3.01; 95% CI, 1.73 to 4.29; maximum difference in the time to peak area tracking: standardized mean difference, 3.26; 95% CI, 1.58 to 4.93). Furthermore, global longitudinal, circumferential, and radial strain were also significantly impaired in the patients compared to the controls (longitudinal strain: standardized mean difference, 2.75; 95% CI, 1.11 to 4.39; circumferential strain: standardized mean difference, 2.71; 95% CI, 1.15 to 4.27; radial strain: standardized mean difference, 1.80; 95% CI, 0.45 to 3.14).

CONCLUSIONS

This meta-analysis suggests that LV function in patients with CHF can be noninvasively and objectively measured by 3D speckle-tracking echocardiography.

Functional assessment of the left atrium by real-time three-dimensional echocardiography using a novel dedicated analysis tool: initial validation studies in comparison with computed tomography

AIMS

A novel real-time three-dimensional echocardiography (RT3DE) analysis tool specifically designed for evaluation of the left atrium enables comprehensive evaluation of left atrial (LA) size, global, and regional function using a dynamic 16-segment model. The aim of this study was the initial validation of this method using computed tomography (CT) as the method of reference.

METHODS AND RESULTS

The study population consisted of 34 prospectively enrolled patients with clinical indication for pulmonary vein isolation. A dynamic polyhedron model of the left atrium was generated using RT3DE. LA maximum and minimum volumes (LA(max)/LA(min)) and emptying fraction (LAEF) were determined and compared with the results obtained by CT. High correlations between RT3DE and CT were found for LA(max) (r = 0.92, P < 0.001), LA(min) (r = 0.95, P < 0.001), and LAEF (r = 0.82, P < 0.001). LA(max) and LA(min) were lower by RT3DE than by CT (95.0 ± 44.7 vs. 119.8 ± 50.5 mL, P < 0.001 and 58.1 ± 41.3 vs. 83.3 ± 52.6 mL, P < 0.001, respectively), whereas LAEF was measured higher by RT3DE (42.8 ± 15.2 vs. 34.2 ± 15.4%, P < 0.001, respectively). RT3DE measurements closely correlated in terms of intra-observer (intra-class correlation r = 0.99, r = 0.99, r = 0.96, respectively) and inter-observer variability (r = 0.97, r = 0.98, r = 0.88, respectively).

CONCLUSIONS

LA volumes and EF as assessed by RT3DE correlate highly with CT measurements, albeit there is some bias between the imaging modalities. Most importantly, RT3DE measurements using the novel dedicated LA analysis tool are robust in terms of observer variability and thus suitable for follow-up analyses.

Use of ultrasound in the ICU

Echography has developed as an indispensable tool in diagnosis and subsequent therapy in the critically ill. Although pulmonary and abdominal ultrasounds play a major role in their management, this article will discuss the advantages and indications of echocardiography in the intensive care unit (ICU). The assessment of morphological abnormalities, left or right ventricular malfunction, pulmonary arterial hypertension and valvular dysfunctions is a routine indication of echocardiography. Actually, besides contractility, several preload and even afterload indicators can also be assessed. In short, this bedside tool rapidly provides insight in the haemodynamics without invasive pressure estimations.

Online 3-D reconstruction of the right atrium from echocardiography data via a topographic cellular contour extraction algorithm

A computational method providing online, automated 3-D reconstruction of the right atrium of the human heart is presented in this paper. Endocardial boundaries were extracted from transesophageal ultrasound data by a topographic cellular contour extraction (TCCE) algorithm. The TCCE method was implemented on a continuous-time, analog, massively parallel processor, and on a digital serial processor. Processing speeds were 500 or 40 frames per second, depending on the hardware used. Extracted boundary point sets were rendered into a 3-D mesh and the volume of the cavity was quantified. Accuracy of volume quantification was validated on 60 in vitro static phantoms and 12 clinical subjects. For the clinical recordings, reference volumes were estimated from manually delineated endocardial boundaries. The average error of volume quantification by the TCCE method was 8% +/-5% ( n = 12), the average of the interobserver variability between two independent human experts was 5% +/-2% ( n = 6). Interactive planning of atrial septal defect closure in pediatric cardiology is presented as an example that demonstrates a potential clinical application of the method.

How accurately, reproducibly, and efficiently can we measure left ventricular indices using M-mode, 2-dimensional, and 3-dimensional echocardiography in children?

BACKGROUND

Measurements of left ventricular (LV) size, mass, and function are the most common and important tasks for echocardiography in clinical practice and research in children with congenital and acquired heart diseases. There are little data to compare the utility of M-mode (MM), 2-dimensional (2D), and 3-dimensional (3D) echocardiographic techniques for quantification of LV indices. The objective of the study was to assess the accuracy, reproducibility, and efficiency of these echocardiographic methods for measurement of LV indices in children.

METHODS

A prospective study was conducted in 20 consecutive children (mean 10.6 +/- 2.8 years, 11 male and 9 female subjects) using conventional MM, 2D, and real-time 3D echocardiography (RT3DE). A Sonos 7500 system (Philips Medical Systems, Andover, MA) was used. M-mode and 2DE measurements were made according to the American Society of echocardiography recommendations. To include the entire LV for volumetric measurement, full-volume 3D data sets were acquired from 4 electrocardiogram gated subvolumes. The 3DE measurements were made off-line manually using 4-plane and 8-plane algorithms by 4D Echo-View (TomTec Imaging Systems, Munich, Germany) and a semiautomated algorithm by QLAB (Philips Medical Systems). Magnetic resonance imaging studies were also performed to determine the LV indices by a disk summation method based on the Simpson principle.

RESULTS

The correlation and agreement between MM, 2D, and RT3D echocardiography and magnetic resonance imaging measurements are good (r = 0.81-0.97) for the 3 methods. The correlation was superior for RT3DE compared with 2DE and MM. The correlation and agreement were similar for the three 3DE methods. The intra- and interobserver variabilities ranged from MM (4.3%-4.8% and 7.0%-8.7%), 2DE (3.3%-4.5% and 5.5%-7.3%), and 3DE (0.4%-2.3%, and 0.2%-4.8%). The total time (acquisition and analysis) used for MM measurements was the least compared with 2DE and 3DE. The total time for 3DE using the semiautomated algorithms was not significantly different compared with that for 2DE.

CONCLUSIONS

Our study showed that MM provides the most efficient assessment of LV indices but is the least accurate and reproducible technique compared with 2DE and 3DE. Three-dimensional echocardiography using both automated and manual analysis algorithm is superior to MM and 2DE for measurements of LV indices, and the automated 3DE algorithm is as efficient as 2DE. Therefore, 3DE using the automated algorithm is the method of choice for quantification of LV indices.

Comparison of contrast agent-enhanced versus non-contrast agent-enhanced real-time three-dimensional echocardiography for analysis of left ventricular systolic function

Ultrasound contrast has shown to improve endocardial border definition. The purpose of this study was to evaluate the value of contrast agent-enhanced versus non-contrast agent-enhanced real-time 3-dimensional echocardiography (RT3DE) for the assessment of left ventricular (LV) volumes and ejection fraction. Thirty-nine unselected patients underwent RT3DE with and without SonoVue contrast agent enhancement and magnetic resonance imaging (MRI) on the same day. An image quality index was calculated by grading all 16 individual LV segments on a scale of 0 to 4: 0, not visible; 1, poor; 2, moderate; 3, good; and 4, excellent. The 3-dimensional data sets were analyzed offline using dedicated TomTec analysis software. By manual tracing, LV end-systolic volume, LV end-diastolic volume, and LV ejection fraction were calculated. After contrast agent enhancement, mean image quality index improved from 2.4 +/- 1.0 to 3.0 +/- 0.9 (p <0.001). Contrast agent-enhanced RT3DE measurements showed better correlation with MRI (LV end-diastolic volume, r = 0.97 vs 0.86; LV end-systolic volume, r = 0.96 vs 0.94; LV ejection fraction, r = 0.94 vs 0.81). The limits of agreement (Bland-Altman analysis) showed a similar bias for RT3DE images with and without contrast agent but with smaller limits of agreement for contrast agent-enhanced RT3DE. Also, inter- and intraobserver variabilities decreased. In a subgroup, patients with poor to moderate image quality showed an improvement in agreement after administration of contrast agent (+/-24.4% to +/-12.7%) to the same level as patients with moderate to good image quality without contrast agent (+/-10.4%). In conclusion, contrast agent-enhanced RT3DE is more accurate in assessment of LV function as evidenced by better correlation and narrower limits of agreement compared with MRI, as well as lower intra- and interobserver variabilities.

Registration of multiview real-time 3-D echocardiographic sequences

Real-time 3-D echocardiography opens up the possibility of interactive, fast 3-D analysis of cardiac anatomy and function. However, at the present time its quantitative power cannot be fully exploited due to the limited quality of the images. In this paper, we present an algorithm to register apical and parasternal echocardiographic datasets that uses a new similarity measure, based on local orientation and phase differences. By using phase and orientation to guide registration, the effect of artifacts intrinsic to ultrasound images is minimized. The presented method is fully automatic except for initialization. The accuracy of the method was validated qualitatively, resulting in 85% of the cardiac segments estimated having a registration error smaller than 2 mm, and no segments with an error larger than 5 mm. Robustness with respect to landmark initialization was validated quantitatively, with average errors smaller than 0.2 mm and 0.5 degrees for initialization landmarks rotations of up to 15 degrees and translations of up to 10 mm.

Volume stitching in three-dimensional echocardiography: distortion analysis and extension to real time

Three-dimensional (3D) echocardiography is challenging due to limitation of the data acquisition rate caused by the speed of sound. ECG-gated stitching of data from several cardiac cycles is a possible technique to achieve higher resolution. The aim of this work is two-fold: it is, firstly, to provide a method for real-time presentation of stitched echocardiographic images acquired over several cardiac cycles and, secondly, to demonstrate that the geometrical distortion of the images is decreased when stitching is applied to 3D ultrasonic data of the left ventricle (LV). We present a volume stitching algorithm that merges data from N consecutive heart cycles into an assembled data volume. The assembly is performed in real time, making immediate volume rendering of the full volume possible. In-vivo images acquired with this technique are presented. Through simulations with a kinematic model of the LV wall, geometrical distortion and volume estimation errors due to long image capture time was quantified for 3D recordings of the LV. Curves showing the variation throughout the cardiac cycle of the maximal geometrical distortion in the LV walls are presented, as well as curves showing the volume estimates compared with the true LV volume of the model. We conclude that real-time display of stitched 3D ultrasound data is feasible and that it is an adequate technique for increasing the volume acquisition rate at a given spatial resolution. Furthermore, the geometrical distortion decreases substantially for data with higher volume rate and, for a full scan of the LV, stitching over at least four cycles is recommended.

Harmonic 3-D echocardiography with a fast-rotating ultrasound transducer

Although the advantages of three-dimensional (3-D) echocardiography have been acknowledged, its application for routine diagnosis is still very limited. This is mainly due to the relatively long acquisition time. Only recently has this problem been addressed with the introduction of new real-time 3-D echo systems. This paper describes the design, characteristics, and capabilities of an alternative concept for rapid 3-D echocardiographic recordings. The presented fast-rotating ultrasound (FRU)-transducer is based on a 64-element phased array that rotates with a maximum speed of 8 Hz (480 rpm). The large bandwidth of the FRU-transducer makes it highly suitable for tissue and contrast harmonic imaging. The transducer presents itself as a conventional phased-array transducer; therefore, it is easily implemented on existing 2-D echo systems, without additional interfacing. The capabilities of the FRU-transducer are illustrated with in-vitro volume measurements, harmonic imaging in combination with a contrast agent, and a preliminary clinical study.

Rapid and Accurate Measurement of Left Ventricular Function with a New Second-Harmonic Fast-Rotating Transducer and Semi-Automated Border Detection

Measurement of left ventricular (LV) volume and function are the most common clinical referral questions to the echocardiography laboratory. A fast, practical, and accurate method would offer important advantages to obtain this important information. To validate a new practical method for rapid measurement of LV volume and function. We developed a continuous fast-rotating transducer, with second-harmonic capabilities, for three-dimensional echocardiography (3DE). Fifteen cardiac patients underwent both 3DE and magnetic resonance imaging (reference method) on the same day. 3DE image acquisition was performed during a 10-second breath-hold with a frame rate of 100 frames/sec and a rotational speed of 6 rotations/sec. The individual images were postprocessed with Matlab software using multibeat data fusion. Subsequently, with these images, 12 datasets per cardiac cycle were reconstructed, each comprising seven equidistant cross-sectional images for analysis in the new TomTec 4DLV analysis software, which uses a semi-automated border detection (ABD) algorithm. The ABD requires an average analysis time of 15 minutes per patient. A strong correlation was found between LV end-diastolic volume (r = 0.99; y = 0.95x - 1.14 ml; SEE = 6.5 ml), LV end-systolic volume (r = 0.96; y = 0.89x + 7.91 ml; SEE = 7.0 ml), and LV ejection fraction (r = 0.93; y = 0.69x + 13.36; SEE = 2.4%). Inter- and intraobserver agreement for all measurements was good. The fast-rotating transducer with new ABD software is a dedicated tool for rapid and accurate analysis of LV volume and function.

Evaluation of cardiac function in primates using real-time three-dimensional echocardiography as applications to safety assessment

INTRODUCTION

A timed non-invasive determination of cardiac function is potentially important for safety pharmacology and toxicity studies. The objectives of this study were to evaluate the accuracy of real-time three-dimensional (RT3D) echocardiography measurements of the left ventricular (LV) volume and LV function and to investigate the effects of some drugs on LV function in cynomolgus monkeys.

METHODS

RT3D echocardiography was performed (SONOS 7500, Philips Med Sys) under isoflurane inhalation. RT3D echocardiography measurements and reconstructions were obtained using Tom-Tec (4DLV analysis). We determined end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), stroke volume (SV), cardiac output (CO) and heart rate as assessments of LV function. EDV, calculated from two-dimensional (2D) echocardiography and RT3D echocardiography, and the actual LV volume were evaluated and compared. Furthermore, each parameter was determined before and after intravenous infusion (5 or 10 min) of propranolol, verapamil and dobutamine.

RESULTS

A strong correlation was found between the actual LV volume and that calculated from RT3D echocardiography (r=0.96, p<0.001). Propranolol (0.1 mg/kg/10 min, n=5) caused an increase in ESV, but not EDV, resulting in a decrease in EF and SV, while verapamil produced increases in both EDV and ESV. Dobutamine (0.01 mg/kg/5 min, n=5) produced decreases in both EDV and ESV and thereby the increased CO resulted from the increased SV.

DISCUSSION

These results demonstrate that RT3D echocardiography provides a feasible and accurate estimation of LV volume and EF for safety pharmacology and toxicity studies.

Feasibility of 3D harmonic contrast imaging

Improved endocardial border delineation with the application of contrast agents should allow for less complex and faster tracing algorithms for left ventricular volume analysis. We developed a fast rotating phased array transducer for 3D imaging of the heart with harmonic capabilities making it suitable for contrast imaging. In this study the feasibility of 3D harmonic contrast imaging is evaluated in vitro. A commercially available tissue mimicking flow phantom was used in combination with Sonovue. Backscatter power spectra from a tissue and contrast region of interest were calculated from recorded radio frequency data. The spectra and the extracted contrast to tissue ratio from these spectra were used to optimize the excitation frequency, the pulse length and the receive filter settings of the transducer. Frequencies ranging from 1.66 to 2.35 MHz and pulse lengths of 1.5, 2 and 2.5 cycles were explored. An increase of more than 15 dB in the contrast to tissue ratio was found around the second harmonic compared with the fundamental level at an optimal excitation frequency of 1.74 MHz and a pulse length of 2.5 cycles. Using the optimal settings for 3D harmonic contrast recordings volume measurements of a left ventricular shaped agar phantom were performed. Without contrast the extracted volume data resulted in a volume error of 1.5%, with contrast an accuracy of 3.8% was achieved. The results show the feasibility of accurate volume measurements from 3D harmonic contrast images. Further investigations will include the clinical evaluation of the presented technique for improved assessment of the heart.