Cardiac Ultrasound Systems Research Articles

Left atrial strain reproducibility using vendor-dependent and vendor-independent software

BackgroundTwo-dimensional speckle-tracking echocardiography (2D-STE) enables objective assessment of left atrial (LA) deformation through the analysis of myocardial strain, which can be measured by different speckle-tracking software. The aim of this study was to compare the consistency of 3 different commercially available software, which include vendor-specific software for measuring left ventricle (VSSLV), vendor-independent software packages for measuring LV strain (VISLV) and vendor-independent software packages for measuring LA strain (VISLA).MethodsSixty-four subjects (mean age: 44 ± 16 years, 50% males) underwent conventional echocardiograms using a GE Vivid 9 (GE Ultrasound, Horten, Norway) cardiac ultrasound system. Standard apical 4 and 2 chamber views of the left atrium were obtained in each subject with a frame-rate range of 40–71 frames/s. LA strain during the contraction phase (Sct), conduit phase (Scd), reservoir phase (Sr = Sct + Scd) were analyzed by 2 independent observers and 3 different software.ResultsSct, Scd, Sr were, respectively, − 11.26 ± 2.45%, − 16.77 ± 7.06%, and 28.03 ± 7.58% with VSSLV, − 14.77 ± 3.59%, − 23.17 ± 10.33%, and 38.23 ± 10.99% with VISLV, and − 14.80 ± 3.88%, − 23.94 ± 10.48%, and 38.73 ± 11.56% when VISLA was used. A comparison of strain measurements between VSSLV and VIS (VISLV and VISLA) showed VIS had significantly smaller mean differences and narrower limits of agreement. Similar results were observed in the coefficient of variation (CV) for measurements between VSSLV and VIS (VISLV and VISLA). Comparison of the intra-class correlation coefficients (ICCs) indicated that measurement reliability was weaker with VSSLV (ICC < 0.6) than with VIS (VISLV and VISLA) (ICC > 0.9). For intra-observer ICCs, VISLA > VSSLV = VISLV. For inter-observer ICCs, VSSLV > VISLA > VISLV.ConclusionsSoftware measurement results of LA strain vary considerably. We recommended not measuring LA strain across vendor platforms.

Cardiac Shear Wave Elastography Using a Clinical Ultrasound System

The propagation velocity of shear waves relates to tissue stiffness. We prove that a regular clinical cardiac ultrasound system can determine shear wave velocity with a conventional unmodified tissue Doppler imaging (TDI) application. The investigation was performed on five tissue phantoms with different stiffness using a research platform capable of inducing and tracking shear waves and a clinical cardiac system (Philips iE33, achieving frame rates of 400–700 Hz in TDI by tuning the normal system settings). We also tested the technique in vivo on a normal individual and on typical pathologies modifying the consistency of the left ventricular wall. The research platform scanner was used as reference. Shear wave velocities measured with TDI on the clinical cardiac system were very close to those measured by the research platform scanner. The mean difference between the clinical and research systems was 0.18 ± 0.22 m/s, and the limits of agreement, from −0.27 to +0.63 m/s. In vivo, the velocity of the wave induced by aortic valve closure in the interventricular septum increased in patients with expected increased wall stiffness.

Global and regional patterns of longitudinal strain in screening for chemotherapy-induced cardiotoxicity

IntroductionSerial echocardiographic assessment of left ventricular ejection fraction (LVEF) is the gold standard in screening for chemotherapy-induced cardiotoxicity (CIC). Measurement of myocardial deformation using speckle tracking enables more detailed assessment of myocardial contractility. The aim of this study was to determine the relationship between global and regional longitudinal strain and CIC. MethodsThis was a prospective study of 158 breast cancer patients undergoing chemotherapy with anthracyclines with or without adjuvant trastuzumab who underwent serial monitoring by transthoracic echocardiography with assessment of myocardial deformation. CIC was defined as a decrease in LVEF to <53%. Global longitudinal strain (GLS) was estimated using EchoPAC BT12 software on a GE Vivid E9 cardiac ultrasound system. Patients were classified according to the 2015 ASE/EACVI criteria as having impaired myocardial deformation when GLS was reduced (less negative), with a cutoff of -18%. ResultsDuring a mean follow-up of 5.4 months (1-48 months), the incidence of CIC was 18.9%. A decrease in GLS was observed during follow-up for the entire cohort (baseline GLS -20.1±3.5% vs. -18.7±3.4% at last follow-up assessment, p=0.001). A total of 97 patients (61.4%) were observed to have impaired myocardial deformation (GLS ≥18%) at some point during follow-up. This decrease was more significant in patients who eventually developed CIC (GLS -17.2±2.5%, p=0.02). On analysis of regional strain, impaired contractility was observed in the septal (6 out of 6) and anterior (2 out of 3) segments. Multivariate logistic regression showed that patients who developed impaired longitudinal strain had a 4.9-fold increased risk of developing CIC (odds ratio 4.88, confidence interval 1.32-18.0, p=0.017). ConclusionsWorsening of myocardial deformation as assessed by speckle tracking is common in breast cancer patients undergoing chemotherapy, with predominantly septal and anterior wall involvement. Impaired myocardial deformation was independently associated with increased incidence of CIC.

Importância da deformação longitudinal na deteção da cardiotoxicidade induzida por quimioterapia e na identificação de padrões específicos de afetação segmentar

IntroductionSerial echocardiographic assessment of left ventricular ejection fraction (LVEF) is the gold standard in screening for chemotherapy‐induced cardiotoxicity (CIC). Measurement of myocardial deformation using speckle tracking enables more detailed assessment of myocardial contractility. The aim of this study was to determine the relationship between global and regional longitudinal strain and CIC. MethodsThis was a prospective study of 158 breast cancer patients undergoing chemotherapy with anthracyclines with or without adjuvant trastuzumab who underwent serial monitoring by transthoracic echocardiography with assessment of myocardial deformation. CIC was defined as a decrease in LVEF to <53%. Global longitudinal strain (GLS) was estimated using EchoPAC BT12 software on a GE Vivid E9 cardiac ultrasound system. Patients were classified according to the 2015 ASE/EACVI criteria as having impaired myocardial deformation when GLS was reduced (less negative), with a cutoff of ‐18%. ResultsDuring a mean follow‐up of 5.4 months (1‐48 months), the incidence of CIC was 18.9%. A decrease in GLS was observed during follow‐up for the entire cohort (baseline GLS ‐20.1±3.5% vs. ‐18.7±3.4% at last follow‐up assessment, p=0.001). A total of 97 patients (61.4%) were observed to have impaired myocardial deformation (GLS ≥18%) at some point during follow‐up. This decrease was more significant in patients who eventually developed CIC (GLS ‐17.2±2.5%, p=0.02). On analysis of regional strain, impaired contractility was observed in the septal (6 out of 6) and anterior (2 out of 3) segments. Multivariate logistic regression showed that patients who developed impaired longitudinal strain had a 4.9‐fold increased risk of developing CIC (odds ratio 4.88, confidence interval 1.32‐18.0, p=0.017). ConclusionsWorsening of myocardial deformation as assessed by speckle tracking is common in breast cancer patients undergoing chemotherapy, with predominantly septal and anterior wall involvement. Impaired myocardial deformation was independently associated with increased incidence of CIC.

Echocardiographic Parameters During Long and Short Interdialytic Intervals in Hemodialysis Patients

The long interdialytic interval in thrice-weekly hemodialysis is associated with excess cardiovascular risk. However, the mechanisms behind these adverse consequences are not fully understood. This study investigated the interdialytic changes in right and left ventricular function during the 2- and 3-day intervals. Observational study with 2 random crossover sequences of recordings: 3-day followed by 2-day interval or vice versa. 41 stable patients with end-stage renal disease on standard thrice-weekly hemodialysis therapy. 3-day (long) versus 2-day (short) interdialytic interval. Interdialytic change in echocardiographic indexes of left and right ventricular function. 2-dimensional echocardiographic and tissue Doppler imaging studies were performed with a Vivid 7 cardiac ultrasound system at the start and end of the 3- and 2-day interdialytic intervals. During both intervals studied, elevations in cardiac output, stroke volume, left ventricular mass index, and peak early diastolic velocities of the left ventricle were evident. Interdialytic weight gain (3.0±1.7 vs 2.4±1.3 [SD] kg) and inferior vena cava diameter increase (0.54±0.3 vs 0.25±0.3) were higher during the 3-day versus the 2-day interval (P<0.001). Left ventricular systolic and diastolic function indexes were generally no different between interdialytic intervals. In contrast, interdialytic increases in left and right atrial volume, right ventricular systolic pressure (RVSP; 15.3±10.2 vs 4.7±5.2mmHg; P<0.001), and tricuspid regurgitation maximum velocity (0.46±0.45 vs 0.14±0.33m/s; P=0.001) were significantly greater during the 3- versus the 2-day interval. Multivariable analysis suggested that changes in interdialytic weight gain, right ventricle diastolic function, and pulmonary vascular resistance were determinants of the change in RVSP. Observational study design. Excess volume accumulation over the long interdialytic interval in hemodialysis patients results in higher left and right atrial enlargement and RVSP elevation, which clinically corresponds to pulmonary circulation overload, providing one plausible pathway for the excess mortality risk during this period.

Multi-transmit beam forming for fast cardiac imaging--experimental validation and in vivo application.

High frame rate (HFR) echocardiography may be of benefit for functional analysis of the heart. In current clinical equipment, HFR is obtained using multi-line acquisition (MLA) which typically requires broadening of transmit beams. As this may result in a significant degradation of spatial resolution and signal-to-noise ratio (SNR), the capacity of MLA to obtain high quality HFR images remains limited. As an alternative, we have demonstrated by computer simulation that simultaneously transmitting multiple focused beams into different directions [multi-line transmit (MLT)], can increase the frame rate without significantly compromising the spatial resolution or SNR. This study aimed to experimentally verify these theoretical predictions both in vitro and in vivo to demonstrate, for the first time, that cardiac MLT imaging is feasible. Hereto, the ultrasound advanced open platform, equipped with a 2.0 MHz phased array, was programmed to interleave MLT and conventional single line transmit (SLT) beam forming. Using these two beam forming methods, images of phantoms and healthy volunteers were acquired and investigated both qualitatively and quantitatively. The results confirmed our simulations that image quality of a 4MLT imaging system with a Tukey apodization scheme is very competitive to that of SLT while providing a 4 times higher frame rate. It is also demonstrated that MLT can be combined with MLA to provide images at 12- to 16-fold frame rate (about 340-450 Hz) without significantly compromising spatial resolution and SNR. This is thus the first study to demonstrate that this new ultrasound imaging paradigm is viable which could have significant impact on future cardiac ultrasound systems.

Analysis of 2-D Ultrasound Cardiac Strain Imaging Using Joint Probability Density Functions

Ultrasound frame rates play a key role for accurate cardiac deformation tracking. Insufficient frame rates lead to an increase in signal de-correlation artifacts resulting in erroneous displacement and strain estimation. Joint probability density distributions generated from estimated axial strain and its associated signal-to-noise ratio provide a useful approach to assess the minimum frame rate requirements. Previous reports have demonstrated that bi-modal distributions in the joint probability density indicate inaccurate strain estimation over a cardiac cycle. In this study, we utilize similar analysis to evaluate a 2-D multi-level displacement tracking and strain estimation algorithm for cardiac strain imaging. The effect of different frame rates, final kernel dimensions and a comparison of radio frequency and envelope based processing are evaluated using echo signals derived from a 3-D finite element cardiac model and five healthy volunteers. Cardiac simulation model analysis demonstrates that the minimum frame rates required to obtain accurate joint probability distributions for the signal-to-noise ratio and strain, for a final kernel dimension of 1 λ by 3 A-lines, was around 42 Hz for radio frequency signals. On the other hand, even a frame rate of 250 Hz with envelope signals did not replicate the ideal joint probability distribution. For the volunteer study, clinical data was acquired only at a 34 Hz frame rate, which appears to be sufficient for radio frequency analysis. We also show that an increase in the final kernel dimensions significantly affect the strain probability distribution and joint probability density function generated, with a smaller effect on the variation in the accumulated mean strain estimated over a cardiac cycle. Our results demonstrate that radio frequency frame rates currently achievable on clinical cardiac ultrasound systems are sufficient for accurate analysis of the strain probability distribution, when a multi-level 2-D algorithm and kernel dimensions on the order of 1 λ by 3 A-lines or smaller are utilized.

Three-dimensional speckle tracking echocardiography for the evaluation of segmental myocardial deformation

Background : Although the feasibility of three-dimensional (3D) speckle tracking echocardiography (STE) for the evaluation of myocardial function has been demonstrated, the poor reproducibility of strain measurements obtained with 3D STE as compared to two-dimensional (2D) STE has been controversially discussed. Aim of this study was to demonstrate the benefit of longitudinal strain analysis by 3D STE as compared to the established 2D STE techniques. Methods : 2D and 3D STE was performed in 30 volunteers with normal systolic left ventricular (LV) function using cardiac ultrasound systems from two different vendors (Vivid E9 and iE33 xMATRIX). Global and segmental longi - tudinal strain (GLS, SLS) values were analyzed for 2D STE using respective software packages (Vivid E9: EchoPAC AFI; iE33 xMATRIX: QLAB CMQ 9.0). Measurements for 3D STE were performed using specific software for Vivid E9 (EchoPAC 4DAutoLVQ) and unspecific software for iE33 xMATRIX (TomTec Imaging Systems 4D left ventricular Analysis). Intra-, interobserver and test-retest variability as well as times for acquisition and analysis were compared between 2D and 3D STE techniques. Results : The reliability of SLS measurements using 3D STE was non-inferior to the measurements obtained by 2D STE, with perpetual constant results in all tests (ICC SLS 3D 0.78 – 0.94 vs . SLS 2D 0.73 – 0.93). Agreements between SLS values were better when vendor specific 2D and 3D software was applied. GLS measurements showed inhomogeneous results for both techniques (ICC GLS 3D 0.40 – 0.93 vs . GLS 2D 0.13 – 0.91). Acquisition time was significantly shorter for 3D datasets than for 2D datasets (3D 51.0 ± 10.66 sec vs . 2D 91.0 ± 10.9 sec, p &lt; .01). Conclusion : 3D STE is a time-saving technology for the evaluation of myocardial deformation in daily clinical practice, generating results that are comparable to the conventional 2D STE techniques. SLS obtained by 3D STE seems to be a more robust parameter than GLS for the assessment of myocardial deformation, especially when vendor specific software packages are used.

Assessment of left ventricular function by different speckle-tracking software

Two-dimensional (2D) speckle echocardiography enables objective assessment of left ventricular function through the analysis of myocardial strain, which can be measured by different speckle-tracking software. The aim of this study was to compare two different commercially available cardiac ultrasound systems and their manufacturer-specific speckle-tacking software for the quantification of global myocardial strain in a healthy population. Twenty-eight healthy subjects (age: 38 +/- 12, 64% males) underwent two 2D echocardiograms within the same day using different cardiac ultrasound systems: Vivid 7 (GE Ultrasound, Horten, Norway) and Artida 4D (Toshiba Medical Systems). Standard apical and short-axis views of the left ventricle were obtained in each subject with a frame-rate range of 60 +/- 20 frames/s. Global longitudinal, radial, and circumferential strain values were analysed using their respective speckle-tracking software for Vivid (2D-strain EchoPac PC v.7.0.1, GE Healthcare, Horten, Norway) and Toshiba systems (2D Wall Motion Tracking, Toshiba Medical Systems). Global strain values were estimated from the average of regional left ventricular strain values. Agreement between the two systems and software was assessed by Bland-Altman method. Mean left ventricular ejection fraction was 59 +/- 7%. Global longitudinal, radial, and circumferential strain values were, respectively, -21.95 +/- 1.8, 46.97 +/- 5.5, and -23.18 +/- 3.3% when using 2D-strain EchoPac and -22.28 +/- 2.1, 40.74 +/- 4.3, and -27.17 +/- 4.7% when 2D Wall Motion Tracking was used (P = NS). Limits of agreement between both speckle-tracking software were narrower for global longitudinal strain (-2.25 to 3.65) than for radial and circumferential strain (-2.23 to 12.44 and -1.36 to 10.54, respectively). Two commercially available speckle-tracking software appear to be comparable when quantifying left ventricular function in a healthy population. Global longitudinal strain is a more robust parameter than radial and circumferential strain for the assessment of myocardial function when different cardiac ultrasound systems are used for analysis.

Automated flow quantification in valvular heart disease based on backscattered Doppler power analysis: implementation on matrix-array ultrasound imaging systems

Cardiac ultrasound imaging systems are limited in the noninvasive quantification of valvular regurgitation due to indirect measurements and inaccurate hemodynamic assumptions. We recently demonstrated that the principle of integration of backscattered acoustic Doppler power times velocity can be used for flow quantification in valvular regurgitation directly at the vena contracta of a regurgitant flow jet. We now aimed to accomplish implementation of automated Doppler power flow analysis software on a standard cardiac ultrasound system utilizing novel matrix-array transducer technology with detailed description of system requirements, components and software contributing to the system. This system based on a 3.5 MHz, matrix-array cardiac ultrasound scanner (Sonos 5500, Philips Medical Systems) was validated by means of comprehensive experimental signal generator trials, in vitro flow phantom trials and in vivo testing in 48 patients with mitral regurgitation of different severity and etiology using magnetic resonance imaging (MRI) for reference. All measurements displayed good correlation to the reference values, indicating successful implementation of automated Doppler power flow analysis on a matrix-array ultrasound imaging system. Systematic underestimation of effective regurgitant orifice areas >0.65 cm(2) and volumes >40 ml was found due to currently limited Doppler beam width that could be readily overcome by the use of new generation 2D matrix-array technology. Automated flow quantification in valvular heart disease based on backscattered Doppler power can be fully implemented on board a routinely used matrix-array ultrasound imaging systems. Such automated Doppler power flow analysis of valvular regurgitant flow directly, noninvasively, and user independent overcomes the practical limitations of current techniques.

Inside the beating heart: Toward a less-invasive approach to surgery

Intracardiac procedures are currently performed after initiation of cardio-pulmonary bypass, aortic cross-clamping, cardiac arrest, and perfusion of the heart for myocardial preservation. Although open-heart surgery provides unobstructed vision and direct access to the intracardiac regions, all these preparatory and ancillary procedures contribute to morbidity. Complications can include blood transfusion mishaps, atrial fibrillation, myocardial ischemia, and neurological dysfunction. Such adverse events are due not to the therapy itself, but to the process of approaching the target to be treated. Surgery that did not require significant interventions to access the site of disease would shorten the procedure, minimize patient trauma and side effects, and lower costs. New methods to achieve these ends are currently under development.1–3 Our approach combines readily-available 2D and 3D ultrasound (US) imaging technology with magnetic and optical tracking systems to provide a robust and accurate system for guidance inside the beating heart. A custom-built attachment device is employed to gain safe access via a mini-thoracotomy.4 Cardiac US systems are available in several forms including trans-esophogeal echocardiography (TEE), and intracardiac echocardiography (ICE). A limited number of 3D systems are also employed; however, the transducers are large and image acquisition is restricted to trans-thoracic views. We track both the US and surgical instruments using the NDI Aurora magnetic tracking system, which identifies the position and orientation of miniature six-degree-of-freedom (DOF) sensors fixed to Figure 1. (a) A cardiac phantom with a poorly-positioned and -stapled valve was positioned with ultrasound navigation alone. (b) Correct positioning and stapling was achieved with the additional use of virtual reality guidance. Arrows indicate staples in both cases.