Three-dimensional echocardiography

Cardiac imaging: working towards fully-automated machine analysis & interpretation

INTRODUCTION

Non-invasive imaging plays a critical role in managing patients with cardiovascular disease. Although subjective visual interpretation remains the clinical mainstay, quantitative analysis facilitates objective, evidence-based management, and advances in clinical research. This has driven developments in computing and software tools aimed at achieving fully automated image processing and quantitative analysis. In parallel, machine learning techniques have been used to rapidly integrate large amounts of clinical and quantitative imaging data to provide highly personalized individual patient-based conclusions. Areas covered: This review summarizes recent advances in automated quantitative imaging in cardiology and describes the latest techniques which incorporate machine learning principles. The review focuses on the cardiac imaging techniques which are in wide clinical use. It also discusses key issues and obstacles for these tools to become utilized in mainstream clinical practice. Expert commentary: Fully-automated processing and high-level computer interpretation of cardiac imaging are becoming a reality. Application of machine learning to the vast amounts of quantitative data generated per scan and integration with clinical data also facilitates a move to more patient-specific interpretation. These developments are unlikely to replace interpreting physicians but will provide them with highly accurate tools to detect disease, risk-stratify, and optimize patient-specific treatment. However, with each technological advance, we move further from human dependence and closer to fully-automated machine interpretation.

Accuracy and reproducibility of right ventricular quantification in patients with pressure and volume overload using single-beat three-dimensional echocardiography

Background

The right ventricle is a complex structure that is challenging to quantify by two-dimensional (2D) echocardiography. Unlike disk summation three-dimensional (3D) echocardiography (3DE), single-beat 3DE can acquire large volumes at high volume rates in one cardiac cycle, avoiding stitching artifacts or long breath-holds. The aim of this study was to assess the accuracy and test-retest reproducibility of single-beat 3DE for quantifying right ventricular (RV) volumes in adult populations of acquired RV pressure or volume overload, namely, pulmonary hypertension (PH) and carcinoid heart disease, respectively. Three-dimensional and 2D echocardiographic indices were also compared for identifying RV dysfunction in PH.

Methods

A prospective cross-sectional study was performed in 100 individuals who underwent 2D echocardiography, 3DE, and cardiac magnetic resonance imaging: 49 patients with PH, 20 with carcinoid heart disease, 11 with metastatic carcinoid tumors without cardiac involvement, and 20 healthy volunteers. Two operators performed test-retest acquisition and postprocessing for inter- and intraobserver reproducibility in 20 subjects.

Results:

RV single-beat 3DE was attainable in 96% of cases, with mean volume rates of 32 to 45 volumes/sec. Bland-Altman analysis of all subjects (presented as mean bias ± 95% limits of agreement) revealed good agreement for end-diastolic volume (−2.3 ± 27.4 mL) and end-systolic volume (5.2 ± 19.0 mL) measured by 3DE and cardiac magnetic resonance imaging, with a tendency to underestimate stroke volume (−7.5 ± 23.6 mL) and ejection fraction (−4.6 ± 13.8%) by 3DE. Subgroup analysis demonstrated a greater bias for volumetric underestimation, particularly in healthy volunteers (end-diastolic volume, −11.9 ± 18.0 mL; stroke volume, −11.2 ± 20.2 mL). Receiver operating characteristic curve analysis showed that 3DE-derived ejection fraction was significantly superior to 2D echocardiographic parameters for identifying RV dysfunction in PH (sensitivity, 94%; specificity, 88%; area under the curve, 0.95; P = .031). There was significant interobserver test-retest bias for RV volume underestimation (end-diastolic volume, −12.5 ± 28.1 mL; stroke volume, −10.6 ± 23.2 mL).

Conclusions

Single-beat 3DE is feasible and clinically applicable for volumetric quantification in acquired RV pressure or volume overload. It has improved limits of agreement compared with previous disk summation 3D echocardiographic studies and has incremental value over standard 2D echocardiographic measures for identifying RV dysfunction. Despite the ability to obtain and postprocess a full-volume 3D echocardiographic RV data set, the quality of the raw data did influence the accuracy of the data obtained. The technique performs better with dilated rather than nondilated RV cavities, with a learning curve that might affect the test-retest reproducibility for serial RV studies.

Usefulness of the multiplanar reformatting mode of three-dimensional echocardiography in evaluating valvular and structural heart disease: An experience from Saudi Arabia

OBJECTIVE

The aim of this study is to compare the feasibility and capacity of multiplanar reformatting (MPR) mode of three-dimensional echocardiography (3DE-MPR technique) with two-dimensional echocardiography (2DE) for visualizing morphological details during evaluation of congenital heart disease (CHD). The study also seeks to validate the accuracy of 3DE MPR in determining cardiac valvular lesions and the application of the 3DE-MPR technique in daily clinical practice.

METHODS

A cross-sectional study was carried out at Madinah Cardiac Centre, Saudi Arabia from May to December 2012. Various forms of CHD were diagnosed in 43 patients by conventional 2DE, and the patients were then examined with the 3DE-MPR technique using dedicated software and a standard protocol.

RESULTS

Of the 43 patients, 23 (53.5%) were males and 20 (46.5%) females. Their age varied from 30 days to 146 months (mean age, 70.2 months and SD = 42.5 months) and their weight from 4 to 42 kg (mean weight, 20.2 kg and SD = 9.7 kg). The 2DE showed left heart lesions in nine patients (20.9%), right heart lesions in 23 (53.5%), atrial septal defects in five (11.6%) and complex CHD in six patients (14%). The 3DE MPR technique application and analysis was possible in all patients. The study demonstrated the fields where 3DE MPR was of additive value to conventional 2DE for the vena contracta area in valvular regurgitation severity and the planimetry for the valvular stenosis precise estimation, enface views of atrial septal defects with direct visualisation of shape and size of the defect, and segmental analysis of complex CHD using one window. The clinician and surgeon were then able to determine the mechanism and severity of the lesions and thus decide on appropriate treatment and management.

CONCLUSION

The study demonstrated the usefulness of 3DE-MPR as a complement to conventional 2DE. The technique is a significant technological breakthrough that allows instant visualization of morphological details and precise determination of cardiac valvular lesions, which were less clearly delineated by 2DE alone.

Feasibility and effectiveness of three-dimensional echocardiography in diagnosing congenital heart diseases

Three-dimensional echocardiography (3DE), a novel approach employed in detecting congenital heart disease (CHD), has gained popularity since it was made commercially available in 2002. This modality is now accepted as an important diagnostic tool for diagnosing CHD. Advancement in transducer technologies and digital data processing allows the use of 3DE in daily clinical practice. In this review, modes of 3DE data acquisition and storage methods in the echocardiogram's machine's hard disk (data processing) are examined. Analysis of the acquired data (cropping or slicing the data set) and methods of illustrating the cropped data set for cardiologists and pediatric cardiovascular surgeons are also discussed. Published literature was searched in PubMed using the keywords "three-dimensional echocardiography", "congenital heart disease", "cropping", and "echoangiogram". This search produced 100 articles, which were further short-listed to 30 articles. Based on this algorithm, the final selected 30 articles were extensively examined in the current review. The clinical applications of real-time transthoracic 3DE, as well as novel transesophageal 3DE and color flow 3DE data set analyses (echoangiogram) in the routine practice of CHD assessment, are also reviewed. Finally, the limitations 3DE, together with the potential future developments required to improve various techniques of 3DE to make it more readily applicable, are examined.

The changing paradigm of stress echocardiography: risk stratification, prognosis, and future directions

The use of stress echocardiography has undergone considerable evolution in the past 3 decades. Although stress echocardiography was first introduced as a noninvasive diagnostic tool for determining the presence or absence of coronary artery disease (CAD), it later served a prognostic role as well. The importance of stress echocardiography in risk stratification and prognosis is substantially undervalued by clinicians. The identification of patients at risk for future cardiac events has become a primary objective in noninvasive evaluation of patients with suspected or known CAD. In particular, the ability of stress echocardiography to identify patients at low (< 1%), intermediate (1%-5%), or high (> 5%) risk for future cardiac events is essential to decision making in patient management. Moreover, previous studies have conclusively demonstrated the incremental prognostic value of stress echocardiography over clinical and treadmill exercise data in predicting future cardiac events. This article presents a primarily single-center experience of retrospective and observational studies that address the current role of stress echocardiography and summarize its use for risk stratification, prognosis, and determining clinical outcomes, as well as cost-effective integration of such information in patient management decision making.