JASE: Overcoming 3D echo's limitations in RV volumes, function
Right ventricular (RV) volumes and function measured by 3D echocardiography suffer from under- and overestimation values. These can be overcome by developing specific software for RV irregular borders and asymmetric volumes and improving spatial and temporal resolution of matrix-array transducers, according to a meta-analysis in the September issue of the Journal of the American Society of Echocardiography.
Determining accurate RV function is gaining more clinical importance, as RV dysfunction is associated with increased morbidity and mortality in patients with a variety of cardiopulmonary diseases. Two-dimensional echo is technically challenging because of the complex anatomic structure of the RV, according to the study.
When the gold standard MRI is not available or contraindicated, real-time 3D echo holds promise. However, there are still some technical challenges that need to be overcome.
Three-dimensional echo has better accuracy and reproducibility than 2D, but small studies of 3D have reported under- and overestimations of volumes and ejection fraction (EF). There have also been contradictory studies showing little bias. "This is the first study to synthesize current data on the existence, extent and factors of the bias," wrote the authors.
Yuichi J. Shimada, MD, from the Beth Israel Medical Center in New York City, and colleagues from various facilities sought to examine the data and determine what needs to be done to improve the use of 3D echo in this setting. They identified 23 studies with 488 subjects for their analysis (ages ranged from 13 to 88; average, 31). Echo measurements were compared to MRI.
Shimada and colleagues found that 3D echo significantly underestimated RV volumes and EF. Larger volumes and EFs were associated with more underestimation. Older patient age was associated with overestimation of volumes and underestimation of EF.
RV end-systolic volume (ESV) was significantly underestimated by 3D echo, with no significant trend in accuracy over time. There was more underestimation in patients under 18 years and with mean end-diastolic volume (EDV) greater than 200 mL.
Researchers said that younger patients with congenital heart disease tend to have more RV irregularity and asymmetry, leading to the underestimated volumes. Additionally, "dilated RV with larger volumes yield more distance from the transducer to the RV wall than normal-sized RVs," blurring the endocardial border and resulting in inaccurate tracking. "Inability to visualize the RV infundibulum may have accounted for the underestimation," they said.
Lower values of ESV were overestimated, which could be attributed to temporal resolution. "Time difference between true end-systole and end-diastole and the moment the images with the lowest and highest volumes were obtained creates overestimation and underestimation of RV ESV and EDV, respectively," the authors said.
The use of matrix-array transducers and semiautomated contour tracking systems were not proven to be significantly associated with the bias, although improvements to both technologies could increase the accuracy of 3D echo.
To overcome the underestimation caused by blurring of endocardial borders, research needs to focus on improving spatial resolution and semiautomated tracking systems, as well as including all volumes, especially that of the infundibulum, by matrix-array transducers, the authors concluded.
Furthermore, the bias shown in younger patients can be improved by RV-specific software, as well as more precise border tracking by semiautomated systems. Finally, enhanced temporal resolution will help improve the overestimation of smaller ESVs.
"Three-dimensional echocardiography will continue to be an attractive modality for the rapid, noninvasive, and repeatable assessment of the right ventricle, especially as it improves with innovations in technology and methods," the authors said.
Determining accurate RV function is gaining more clinical importance, as RV dysfunction is associated with increased morbidity and mortality in patients with a variety of cardiopulmonary diseases. Two-dimensional echo is technically challenging because of the complex anatomic structure of the RV, according to the study.
When the gold standard MRI is not available or contraindicated, real-time 3D echo holds promise. However, there are still some technical challenges that need to be overcome.
Three-dimensional echo has better accuracy and reproducibility than 2D, but small studies of 3D have reported under- and overestimations of volumes and ejection fraction (EF). There have also been contradictory studies showing little bias. "This is the first study to synthesize current data on the existence, extent and factors of the bias," wrote the authors.
Yuichi J. Shimada, MD, from the Beth Israel Medical Center in New York City, and colleagues from various facilities sought to examine the data and determine what needs to be done to improve the use of 3D echo in this setting. They identified 23 studies with 488 subjects for their analysis (ages ranged from 13 to 88; average, 31). Echo measurements were compared to MRI.
Shimada and colleagues found that 3D echo significantly underestimated RV volumes and EF. Larger volumes and EFs were associated with more underestimation. Older patient age was associated with overestimation of volumes and underestimation of EF.
RV end-systolic volume (ESV) was significantly underestimated by 3D echo, with no significant trend in accuracy over time. There was more underestimation in patients under 18 years and with mean end-diastolic volume (EDV) greater than 200 mL.
Researchers said that younger patients with congenital heart disease tend to have more RV irregularity and asymmetry, leading to the underestimated volumes. Additionally, "dilated RV with larger volumes yield more distance from the transducer to the RV wall than normal-sized RVs," blurring the endocardial border and resulting in inaccurate tracking. "Inability to visualize the RV infundibulum may have accounted for the underestimation," they said.
Lower values of ESV were overestimated, which could be attributed to temporal resolution. "Time difference between true end-systole and end-diastole and the moment the images with the lowest and highest volumes were obtained creates overestimation and underestimation of RV ESV and EDV, respectively," the authors said.
The use of matrix-array transducers and semiautomated contour tracking systems were not proven to be significantly associated with the bias, although improvements to both technologies could increase the accuracy of 3D echo.
To overcome the underestimation caused by blurring of endocardial borders, research needs to focus on improving spatial resolution and semiautomated tracking systems, as well as including all volumes, especially that of the infundibulum, by matrix-array transducers, the authors concluded.
Furthermore, the bias shown in younger patients can be improved by RV-specific software, as well as more precise border tracking by semiautomated systems. Finally, enhanced temporal resolution will help improve the overestimation of smaller ESVs.
"Three-dimensional echocardiography will continue to be an attractive modality for the rapid, noninvasive, and repeatable assessment of the right ventricle, especially as it improves with innovations in technology and methods," the authors said.