Reliability of fetal cardiac volumetry using spatiotemporal image correlation: assessment of in-vivo and in-vitro measurements

Preliminary study on the evaluation of mitral annulus displacement in normal fetuses by automated cardiac motion quantitation

OBJECTIVES

The aim of this study was to assess the characteristics of mitral annular plane systolic excursion (MAPSE) in different longitudinal directions in normal fetuses using a new method, automatic cardiac motion quantification (aCMQ).

METHODS

A cross-sectional study was conducted in 164 fetuses with structurally normal hearts. The time-displacement curves of the septal mitral annulus (SMA) in three directions, including point A, B and C (MAPSE-SMA-A, MAPSE-SMA-B, MAPSE-SMA-C), were recorded by aCMQ. The time to peak (TTP) in three directions, including point A, B and C (TTP-SMA-A, TTP-SMA-B, TTP-SMA-C) were recorded. In the same way, various parameters of the lateral mitral annulus (LMA) were obtained including MAPSE-LMA-A, MAPSE-LMA-B, MAPSE-LMA-C, TTP-LMA-A, TTP-LMA-B and TTP-LMA-C. Free angle M-mode echocardiography (FAM) was used to obtain MAPSE of LMA (FAM-MAPSE). Finally, all the data were analyzed statistically.

RESULTS

MAPSE was positively correlated with gestational age, and the difference between the second- and third-trimester groups was statistically significant. MAPSE-LMA in point B and C were greater than those of SMA. MAPSE-LMA-C and MAPSE-SMA-A were the largest in three directions.The difference between point B and C were statistically significant (p < .05), with no significant difference at point A (p > .05). There was no significant difference found in all TTP (all p > .05). The MAPSE-LMA-C was less than the FAM-MAPSE, and the differences were found significantly (p < .05), but there was better correlation (p < .05).

CONCLUSIONS

The longitudinal movement of the fetal mitral annulus is comprehensive, with multiple directions and different displacements. Perpendicular to the mitral annulus is the maximum displacement. It is positively related to the gestational age. From the second trimester, the longitudinal contraction of the left ventricle wall has good synchronization. It possesses clinical value in selecting different methods and parameters during evaluating left ventricular function.

4D fetal echocardiography-An update

With the introduction of the electronic 4-dimensional and spatial-temporal image Correlation (e-STIC), it is now possible to obtain large volume datasets of the fetal heart that are virtually free of artifact. This allows the examiner to use a number of imaging modalities when recording the volumes that include two-dimensional real time, power and color Doppler, and B-flow images. Once the volumes are obtained, manipulation of the volume dataset allows the examiner to recreate views of the fetal heart that enable examination of cardiac anatomy. The value of this technology is that a volume of the fetal heart can be obtained, irrespective of the position of the fetus in utero, and manipulated to render images for interpretation and diagnosis. This article presents a summary of the various imaging techniques and provides clinical examples of its application used for prenatal diagnosis of congenital heart defects and abnormal cardiac function.

Three- and four-dimensional ultrasound in fetal echocardiography: an up-to-date overview

Congenital heart diseases (CHD) are the most commonly overlooked lesions in prenatal screening programs. Real-time two-dimensional ultrasound (2DUS) is the conventionally used tool for fetal echocardiography. Although continuous improvements in the hardware and post-processing software have resulted in a good image quality even in late first trimester, 2DUS still has its limitations. Four-dimensional ultrasound with spatiotemporal image correlation (STIC) is an automated volume acquisition, recording a single three-dimensional (3D) volume throughout a complete cardiac cycle, which results in a four-dimensional (4D) volume. STIC has the potential to increase the detection rate of CHD. The aim of this study is to provide a practical overview of the possibilities and (dis)advantages of STIC. A review of literature and evaluation of the current status and clinical value of 3D/4D ultrasound in prenatal screening and diagnosis of congenital heart disease are presented.

How to Acquire Cardiac Volumes for Sonographic Examination of the Fetal Heart: Part 2

The effective performance of fetal cardiac examination using spatiotemporal image correlation (STIC) technology requires 2 essential steps: volume acquisition and postprocessing. An important prerequisite is training sonologists to acquire high-quality volume data sets so that when analyzed, such volumes are informative. This article is part 2 of a series on 4-dimensional sonography with STIC. Part 1 focused on STIC technology and its features, the importance of operator training/experience and acquisition of high-quality STIC volumes, factors that affect STIC volume acquisition rates, and general recommendations on performing 4D sonography with STIC. In part 2, we discuss a detailed and practical stepwise approach for STIC volume acquisition, along with methods to determine whether such volumes are appropriate for analysis.

How to Acquire Cardiac Volumes for Sonographic Examination of the Fetal Heart: Part 1

Four-dimensional sonography with spatiotemporal image correlation (STIC) technology allows acquisition of a fetal cardiac volume data set and displays a cine loop of a complete single cardiac cycle in motion. Part 1 of this 2-part article reviews STIC technology and its features, the importance of operator training/experience, and acquisition of high-quality STIC volumes, as well as factors that affect STIC volume acquisition rates. We also propose a detailed and practical stepwise approach to performing 4-dimensional sonography with STIC and begin herein by providing general recommendations. Part 2 will discuss specifics of the approach, along with how to determine whether such volumes are appropriate for analysis.

Role of 3-D ultrasound in clinical obstetric practice: evolution over 20 years

The use of 3-D ultrasound in obstetrics has undergone dramatic development over the past 20 years. Since the first publications on this application in clinical practice, several 3-D ultrasound techniques and rendering modes have been proposed and applied to the study of fetal brain, face and cardiac anatomy. In addition, 3-D ultrasound has improved calculations of the volume of fetal organs and limbs and estimations of fetal birth weight. And furthermore, angiographic patterns of fetal organs and the placenta have been assessed using 3-D power Doppler ultrasound quantification. In this review, we aim to summarize current evidence on the clinical relevance of these methodologies and their application in obstetric practice.

Diagnosis and treatment of fetal cardiac disease: a scientific statement from the American Heart Association

BACKGROUND

The goal of this statement is to review available literature and to put forth a scientific statement on the current practice of fetal cardiac medicine, including the diagnosis and management of fetal cardiovascular disease.

METHODS AND RESULTS

A writing group appointed by the American Heart Association reviewed the available literature pertaining to topics relevant to fetal cardiac medicine, including the diagnosis of congenital heart disease and arrhythmias, assessment of cardiac function and the cardiovascular system, and available treatment options. The American College of Cardiology/American Heart Association classification of recommendations and level of evidence for practice guidelines were applied to the current practice of fetal cardiac medicine. Recommendations relating to the specifics of fetal diagnosis, including the timing of referral for study, indications for referral, and experience suggested for performance and interpretation of studies, are presented. The components of a fetal echocardiogram are described in detail, including descriptions of the assessment of cardiac anatomy, cardiac function, and rhythm. Complementary modalities for fetal cardiac assessment are reviewed, including the use of advanced ultrasound techniques, fetal magnetic resonance imaging, and fetal magnetocardiography and electrocardiography for rhythm assessment. Models for parental counseling and a discussion of parental stress and depression assessments are reviewed. Available fetal therapies, including medical management for arrhythmias or heart failure and closed or open intervention for diseases affecting the cardiovascular system such as twin-twin transfusion syndrome, lung masses, and vascular tumors, are highlighted. Catheter-based intervention strategies to prevent the progression of disease in utero are also discussed. Recommendations for delivery planning strategies for fetuses with congenital heart disease including models based on classification of disease severity and delivery room treatment will be highlighted. Outcome assessment is reviewed to show the benefit of prenatal diagnosis and management as they affect outcome for babies with congenital heart disease.

CONCLUSIONS

Fetal cardiac medicine has evolved considerably over the past 2 decades, predominantly in response to advances in imaging technology and innovations in therapies. The diagnosis of cardiac disease in the fetus is mostly made with ultrasound; however, new technologies, including 3- and 4-dimensional echocardiography, magnetic resonance imaging, and fetal electrocardiography and magnetocardiography, are available. Medical and interventional treatments for select diseases and strategies for delivery room care enable stabilization of high-risk fetuses and contribute to improved outcomes. This statement highlights what is currently known and recommended on the basis of evidence and experience in the rapidly advancing and highly specialized field of fetal cardiac care.

The fetal cardiovascular response to increased placental vascular impedance to flow determined with 4-dimensional ultrasound using spatiotemporal image correlation and virtual organ computer-aided analysis

OBJECTIVE

We sought to determine if increased placental vascular impedance to flow is associated with changes in fetal cardiac function using spatiotemporal image correlation and virtual organ computer-aided analysis.

STUDY DESIGN

A cross-sectional study was performed in fetuses with umbilical artery pulsatility index >95th percentile (abnormal [ABN]). Ventricular volume (end-systole, end-diastole), stroke volume, cardiac output (CO), adjusted CO, and ejection fraction were compared to those of 184 normal fetuses.

RESULTS

A total of 34 fetuses were evaluated at a median gestational age of 28.3 (range, 20.6-36.9) weeks. Mean ventricular volumes were lower for ABN than normal cases (end-systole, end-diastole) with a proportionally greater decrease for left ventricular volume (vs right). Mean left and right stroke volume, CO, and adjusted CO were lower for ABN (vs normal) cases. Right ventricular volume, stroke volume, CO, and adjusted CO exceeded the left in ABN fetuses. Mean ejection fraction was greater for ABN than normal cases. Median left ejection fraction was greater (vs right) in ABN fetuses.

CONCLUSION

Increased placental vascular impedance to flow is associated with changes in fetal cardiac function.

Accuracy, agreement, and reliability of fetal cardiac measurements using 4-dimensional spatiotemporal image correlation

OBJECTIVES

The purpose of this study was to evaluate the accuracy, agreement, and reliability of 4-dimensional sonography using spatiotemporal image correlation (STIC) in fetal cardiac measurements during the second and third trimesters.

METHODS

Four-dimensional cardiac STIC volumes were acquired from 150 low-risk singleton pregnancies at gestational ages of 18 to 38 weeks. A total of 11 dimensions of the fetal heart and great vessels were analyzed by two different observers. Accuracy was assessed by comparing the measurements acquired by 4-dimensional STIC with those determined by 2-dimensional echocardiography by calculating the mean error and mean percent error and depicted by Bland-Altman plots. Absolute agreement and reliability of STIC-based measurements were evaluated on the basis of an intraclass correlation coefficient (ICC).

RESULTS

For STIC-based measurements of cardiac dimensions, good accuracy was achieved by the two experienced observers (mean percent error, -3.10% to 0.87% for observer A; -2.49% to -0.33% for observer B), and absolute agreement was almost perfect (ICC, 95% confidence interval, 0.916-0.993 for observer A; 0.957-0.990 for observer B). Interobserver ICCs among the two observers were between 0.909 and 0.990 (95% confidence interval), whereas intraobserver ICCs for observer A were between 0.894 and 0.989, and those for observer B were between 0.893 and 0.985, showing no significant differences in the reliability of SITC with regard to observers.

CONCLUSIONS

Four-dimensional sonography with STIC is a feasible and accurate method for fetal cardiac dimension measurements in the second and third trimesters. It is in good agreement with 2-dimensional echocardiography and can be performed by different observers.

Reproducibility of echocardiographic measurements of human fetal left ventricular volumes and ejection fractions using four-dimensional ultrasound with the spatio-temporal image correlation modality

OBJECTIVES

To determine the reproducibility, both reliability and agreement, of measurements of fetal left ventricular parameters from volumes obtained by spatio-temporal image correlation (STIC) acquisition applying virtual organ computer-aided analysis (VOCAL) and Simpson's rule (method of discs). Furthermore the success rate of STIC acquisition was determined.

STUDY DESIGN

In 84 pregnancies between 20 and 34 weeks of gestation the fetal heart was scanned using the STIC modality. An optimal four-chamber view in end-diastole and end-systole was obtained. Left ventricular end-diastolic volume, left ventricular end-systolic volume, stroke volume and ejection fraction were determined. For calculations based on Simpson's rule only one plane was traced, whereas for VOCAL six planes were traced. To quantify the reliability intraclass correlation coefficients were calculated for both intra- and inter-observer measurements. Agreement of measurements was evaluated by Bland-Altman plots.

RESULTS

The STIC volumes of 54 women (64%) were excluded from the study because of poor quality, leaving 30 volumes for further analysis. Intraclass correlation coefficients for intra-observer reliability for VOCAL and Simpson were 0.99 and 0.99 for left ventricular end-diastolic volume, 0.95 and 0.92 for left ventricular end-systolic volume, 0.98 and 0.97 for stroke volume, 0.76 and 0.77 for ejection fraction, respectively. Intraclass correlation coefficients for inter-observer reliability for VOCAL and Simpson were 0.97 and 0.86 for left ventricular end-diastolic volume, 0.97 and 0.86 for left ventricular end-systolic volume, 0.95 and 0.81 for stroke volume, 0.68 and 0.63 for ejection fraction, respectively. According to Bland-Altman plots, the mean percentage difference and 95% limits of intra- and inter-observer agreement for left ventricular stroke volume measurements using VOCAL were -0.2 (-25.1, 24.7)% and 2.8 (-34.2, 39.8)%, respectively. For left ventricular stroke volume measured with Simpson versus VOCAL the mean percentage difference and 95% limits of agreement were -1.8 (-22.1, 18.5)%.

CONCLUSIONS

4D STIC enables reproducible measurements of left ventricular volumes. Reliability of the VOCAL mode is not essentially different from the single-plane method used in Simpson's rule. The large percentage of poor quality STIC volumes and the wide limits of inter-observer agreement would create obstacles for the clinical applicability of this technique.