Quantitative three-dimensional reconstruction of aneurysmal left ventricles. In vitro and in vivo validation

Integration of three-dimensional echocardiography into the modern-day echo laboratory

Three-dimensional echocardiography (3DE) has emerged in recent decades from a conceptual, research tool to an important, useful imaging technique that can informatively impact daily clinical practice. However, its adoption into the modern-day echo laboratory requires the acknowledgment of its value, coupled with proper leadership, education, and resources to implement and integrate its use with conventional echo techniques. 3DE integration involves important updates regarding equipment and patient selection, assimilation of 3D protocols into current clinical routine, laboratory workflow adaptation, storage, and reporting. This review will provide a practical blueprint and key points of how to integrate 3DE into today's echo laboratory, necessary resources to implement 3D workflow, logistical challenges that remain, and future directions to further improve assimilation of this relevant echo technique into the laboratory.

Three-dimensional echocardiography in various types of heart disease: a comparison study of magnetic resonance imaging and 64-slice computed tomography in a real-world population

BACKGROUND

Accurate quantification of left ventricular (LV) volumes [end-diastolic volume (EDV) and end-systolic volume (ESV)] and ejection fraction (EF) is of critical importance. The development of real-time three-dimensional echocardiography (RT3DE) has shown better correlation than two-dimensional (2D) echocardiography with magnetic resonance imaging (MRI) measurements. The aim of our study was to assess the accuracy of RT3DE and 64-slice computed tomography (CT) in the evaluation of LV volumes and function using MRI as the reference standard in a real-world population with various types of heart disease with different chamber geometry.

METHODS

The study population consisted of 66 patients referred for cardiac MRI for various pathologies. All patients underwent cardiac MRI, and RT3DE and 64 slices CT were then performed on a subsequent day. The study population was then divided into 5 clinical groups depending on the underlying heart disease.

RESULTS

RT3DE volumes correlated well with MRI values (R ² values: 0.90 for EDV and 0.94 for ESV). RT3DE measurements of EF correlated well with MRI values (R ² = 0.86). RT3DE measurements resulted in slightly underestimated values of both EDV and ESV, as reflected by biases of -9.18 and -4.50 mL, respectively. Comparison of RT3DE and MRI in various types of cardiomyopathies showed no statistical difference between different LV geometrical patterns.

CONCLUSION

These results confirm that RT3DE has good accuracy in everyday clinical practice and can be of clinical utility in all types of cardiomyopathy independently of LV geometric pattern, LV diameter or wall thickness, taking into account a slight underestimation of LV volumes and EF compared to MRI.

Role of echocardiography in clinical hypertension

Hypertension is a major and correctable cardiovascular risk factor. The correct diagnosis of hypertension and precise assessment of cardiovascular risk are essential to give proper treatment in patients with hypertension. Although echocardiography is the second-line study in the evaluation of hypertensive patients, it gives many clues suggesting bad prognosis associated with hypertension, including increased left ventricular (LV) mass, decreased LV systolic function, impaired LV diastolic function, and increased left atrial size and decreased function. Along with conventional echocardiographic methods, tissue Doppler imaging, three-dimensional echocardiography, and strain echocardiography are newer echocardiographic modalities in the evaluation of hypertensive patients in the current echocardiographic laboratories. Understanding conventional and newer echocardiographic parameters is important in the diagnosis and assessment of cardiovascular risk in hypertensive patients.

Clinical application of three-dimensional echocardiography

Echocardiography is one of the most valuable diagnostic tools in cardiology. Technological advances in ultrasound, computer and electronics enables three-dimensional (3-D) imaging to be a clinically viable modality which has significant impact on diagnosis, management and interventional procedures. Since the inception of 3D fully-sampled matrix transthoracic and transesophageal technology it has enabled easier acquisition, immediate on-line display, and availability of on-line analysis for the left ventricle, right ventricle and mitral valve. The use of 3D TTE has mainly focused on mitral valve disease, left and right ventricular volume and functional analysis. As structural heart disease procedures become more prevalent, 3D TEE has become a requirement for preparation of the procedure, intra-procedural guidance as well as monitoring for complications and device function. We anticipate that there will be further software development, improvement in image quality and workflow.

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.

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.

Rapid full volume data acquisition by real-time 3-dimensional echocardiography for assessment of left ventricular indexes in children: A validation study compared with magnetic resonance imaging

OBJECTIVE

We sought to assess the feasibility, accuracy, and reproducibility of a rapid full volume acquisition strategy using real-time (RT) 3-dimensional (3D) echocardiography (3DE) for measurement of left ventricular (LV) volumes, mass, stroke volume (SV), and ejection fraction (EF) in children.

METHODS

A total of 19 healthy children (mean 10.6 +/- 2.8 years, 11 male and 9 female) were prospectively enrolled in this study. RT 3DE was performed using an ultrasound system to acquire full volume 3D dataset from the apical window with electrocardiographic triggering in 8 s/dataset. The images were processed offline using software. The LV endocardial and epicardial borders were traced manually to derive LV end-systolic volume, end-diastolic volume, mass, SV, and EF. Magnetic resonance imaging (MRI) studies were performed on a 1.5-T scanner using a breath hold 2-dimensional cine-FIESTA (fast imaging employing steady-state acquisition) sequence.

RESULTS

All RT 3DE and MRI data were acquired successfully for analysis. Measurements of LV end-systolic volume, end-diastolic volume, mass, SV, and EF by RT 3DE correlated well by Pearson regression ( r = 0.86-0.97, P < .001) and agreed well by Bland-Altman analysis with MRI. The interobserver and intraobserver variability of RT 3DE measurements were less than 5%.

CONCLUSIONS

This prospective study demonstrated that RT 3DE measurements of LV end-systolic volume, end-diastolic volume, mass, SV, and EF in children using rapid full volume acquisition strategy are feasible, accurate, and reproducible and are comparable with MRI measurements.

Left ventricular wall motion analysis using real-time three-dimensional ultrasound

This study tested the ability of real-time 3-D (RT 3-D) echocardiography to detect and delineate regions of abnormal contraction (akinesia or dyskinesia) in a canine model of regional myocardial injury and to develop methods to simplify injury assessments. Closed chest RT 3-D scans were obtained and regional left ventricular (LV) contractile function was assessed in nine animals at baseline and after myocardial cryoinjury with a 1-cm cryoprobe. Evaluation of contractile function was based on radial shortening of LV chamber cross-sections at multiple levels. Radial length changes were analyzed using color-coded circumferential maps of the LV. Seven sets of motion maps demonstrated new areas of poorly contracting myocardium in the cryoinjured region relative to baseline. Two sets of data were excluded due to insufficient LV visualization. Motion maps derived from RT 3-D echo have the ability to detect and localize regions of abnormal LV wall motion.

Usefulness of real-time three-dimensional echocardiography for reliable measurement of cardiac output in patients with ischemic or idiopathic dilated cardiomyopathy

The determination of stroke volume (SV) is a potentially important application of real-time 3-dimensional echocardiography (RT3DE). SV measurements by thermodilution were compared with values obtained using transthoracic RT3DE in a sequential cohort of patients who underwent assessment for potential cardiac transplantation. There was a strong correlation between echocardiographically derived SV and catheterization data (r = 0.95, n = 14). On average, RT3DE appeared to underestimate SV by 7.5 ml (SD = 5.8) or 17% (SD = 12%). A role for RT3DE in the measurement of SV in severe heart failure is suggested.

Effect of three-dimensional valve shape on the hemodynamics of aortic stenosis: three-dimensional echocardiographic stereolithography and patient studies

OBJECTIVES

This study tested the hypothesis that the impact of a stenotic aortic valve depends not only on the cross-sectional area of its limiting orifice but also on three-dimensional (3D) valve geometry.

BACKGROUND

Valve shape can potentially affect the hemodynamic impact of aortic stenosis by altering the ratio of effective to anatomic orifice area (the coefficient of orifice contraction [Cc]). For a given flow rate and anatomic area, a lower Cc increases velocity and pressure gradient. This effect has been recognized in mitral stenosis but assumed to be absent in aortic stenosis (constant Cc of 1 in the Gorlin equation).

METHODS

In order to study this effect with actual valve shapes in patients, 3D echocardiography was used to reconstruct a typical spectrum of stenotic aortic valve geometrics from doming to flat. Three different shapes were reproduced as actual models by stereolithography (computerized laser polymerization) with orifice areas of 0.5, 0.75, and 1.0 cm(2) (total of nine valves) and studied with physiologic flows. To determine whether valve shape actually influences hemodynamics in the clinical setting, we also related Cc (= continuity/planimeter areas) to stenotic aortic valve shape in 35 patients with high-quality echocardiograms.

RESULTS

In the patient-derived 3D models, Cc varied prominently with valve shape, and was largest for long, tapered domes that allow more gradual flow convergence compared with more steeply converging flat valves (0.85 to 0.90 vs. 0.71 to 0.76). These variations translated into differences of up to 40% in pressure drop for the same anatomic area and flow rate, with corresponding variations in Gorlin (effective) area relative to anatomic values. In patients, Cc was significantly lower for flat versus doming bicuspid valves (0.73 +/- 0.14 vs. 0.94 +/- 0.14, p < 0.0001) with 40 +/- 5% higher gradients (p < 0.0001).

CONCLUSIONS

Three-dimensional valve shape is an important determinant of pressure loss in patients with aortic stenosis, with smaller effective areas and higher pressure gradients for flatter valves. This effect can translate into clinically important differences between planimeter and effective valve areas (continuity or Gorlin). Therefore, valve shape provides additional information beyond the planimeter orifice area in determining the impact of valvular aortic stenosis on patient hemodynamics.

Quantitative analysis of aortic regurgitation: real-time 3-dimensional and 2-dimensional color Doppler echocardiographic method--a clinical and a chronic animal study

BACKGROUND

For evaluating patients with aortic regurgitation (AR), regurgitant volumes, left ventricular (LV) stroke volumes (SV), and absolute LV volumes are valuable indices.

AIM

The aim of this study was to validate the combination of real-time 3-dimensional echocardiography (3DE) and semiautomated digital color Doppler cardiac flow measurement (ACM) for quantifying absolute LV volumes, LVSV, and AR volumes using an animal model of chronic AR and to investigate its clinical applicability.

METHODS

In 8 sheep, a total of 26 hemodynamic states were obtained pharmacologically 20 weeks after the aortic valve noncoronary (n = 4) or right coronary (n = 4) leaflet was incised to produce AR. Reference standard LVSV and AR volume were determined using the electromagnetic flow method (EM). Simultaneous epicardial real-time 3DE studies were performed to obtain LV end-diastolic volumes (LVEDV), end-systolic volumes (LVESV), and LVSV by subtracting LVESV from LVEDV. Simultaneous ACM was performed to obtain LVSV and transmitral flows; AR volume was calculated by subtracting transmitral flow volume from LVSV. In a total of 19 patients with AR, real-time 3DE and ACM were used to obtain LVSVs and these were compared with each other.

RESULTS

A strong relationship was found between LVSV derived from EM and those from the real-time 3DE (r = 0.93, P <.001, mean difference (3D - EM) = -1.0 +/- 9.8 mL). A good relationship between LVSV and AR volumes derived from EM and those by ACM was found (r = 0.88, P <.001). A good relationship between LVSV derived from real-time 3DE and that from ACM was observed (r = 0.73, P <.01, mean difference = 2.5 +/- 7.9 mL). In patients, a good relationship between LVSV obtained by real-time 3DE and ACM was found (r = 0.90, P <.001, mean difference = 0.6 +/- 9.8 mL).

CONCLUSION

The combination of ACM and real-time 3DE for quantifying LV volumes, LVSV, and AR volumes was validated by the chronic animal study and was shown to be clinically applicable.

Left ventricular volume estimation for real-time three-dimensional echocardiography

The application of level set techniques to echocardiographic data is presented. This method allows semiautomatic segmentation of heart chambers, which regularizes the shapes and improves edge fidelity, especially in the presence of gaps, as is common in ultrasound data. The task of the study was to reconstruct left ventricular shape and to evaluate left ventricular volume. Data were acquired with a real-time three-dimensional (3-D) echocardiographic system. The method was applied directly in the three-dimensional domain and was based on a geometric-driven scheme. The numerical scheme for solving the proposed partial differential equation is borrowed from numerical methods for conservation law. Results refer to in vitro and human in vivo acquired 3-D + time echocardiographic data. Quantitative validation was performed on in vitro balloon phantoms. Clinical application of this segmentation technique is reported for 20 patient cases providing measures of left ventricular volumes and ejection fraction.

Three-dimensional echocardiographic measurement of left and right ventricular mass and volume: in vitro validation

INTRODUCTION

Three-dimensional (3D) echocardiography has been shown to offer highly accurate measurements of left ventricular (LV) volume and mass. The present study evaluated the accuracy of 3D surface reconstruction by the piecewise smooth subdivision method in measuring volume and mass not only in the LV but also in the more complexly shaped right ventricle (RV).

METHODS

3D echo scans were obtained of in vitro LV's (n = 15) and RVs (n = 10). From digitized images, ventricular borders were traced and used in surface reconstructions. Mass and volume determined from the reconstructions were compared to true volume and mass determined prior to imaging. Additionally casts of two RVs were made and laser-scanned. Distances between the laser-identified points on the RV surface and the corresponding 3D echo reconstructions were measured.

RESULTS

3D LV volume agreed well with the true volume (y = 0.99x + 1.73, r = 0.99, SEE = 3.35 ml, p < 0.0001), as did 3D LV mass (y = 0.99x - 4.71, r = 0.99, SEE = 9.85 g, p < 0.0001). 3D RV volume overestimated true volume (y = 1.11x + 1.77, r = 0.99, SEE = 3.36 ml, p < 0.001) by 6.23+/-3.70 ml (p < 0.0001). 3D mass agreed well with RV mass (y = 0.78x + 17.32, r2 = 0.93, SEE = 3.54 g, p < 0.0001). 3D echo reconstructions matched the laser-scanned RV closely with residual distances of 1.1+/-0.9 and 1.4+/-1.2 mm, respectively.

CONCLUSIONS

3D echo using freehand scanning combined with surface reconstruction by the piecewise smooth subdivision surface method enables accurate determination of LV mass and volume, of RV mass and volume, and of the RV's complex shape.

Three-dimensional echocardiographic measurement of left ventricular wall thickness: In vitro and in vivo validation

INTRODUCTION

Three-dimensional (3D) echocardiography has been shown to accurately measure left ventricular (LV) volume and mass. This study evaluated the accuracy of 3D echocardiography and the CenterSurface method for measuring LV wall thickness in vitro and in vivo.

METHOD

Three-dimensional echocardiography scans, obtained from 7 LV phantoms and subjects having healthy (n = 5) or diseased (n = 8) hearts, were digitized. Endocardial and epicardial borders were outlined and used in 3D LV reconstruction. In vitro wall thickness was compared with true micrometer measurements. Three-dimensional in vivo wall thickness was compared with 2-dimensional (2D) thickness measured by the centerline method.

RESULTS

The in vitro 3D echocardiography measurements agreed closely with true wall thickness (P <.0001), as did in vivo measurements (P <.0001).

CONCLUSION

Three-dimensional echocardiography reconstruction has previously been shown to provide accurate representation of LV shape in addition to volume and mass. This study demonstrates that the CenterSurface method provides accurate quantification of wall thickness.

Three-dimensional echocardiography: in-vitro validation of a new, voxel-based method for rapid quantification of ventricular volume in normal and aneurysmal left ventricles

BACKGROUND

Previous approaches to ventricular volume calculations by 3-dimensional echocardiography (3-DE) required multiple transverse tomographic sectioning and summation of the volumes of parallel disks. These methods were time consuming and beared the risk of missing the apical volume.

METHODS

We investigated the accuracy of a new, rapid method of 3-DE volume measurements in normal (LV) and aneurysmal (aneurLV) left ventricles in fixed pig hearts. 3-D data sets of 12 LV and 8 experimentally created aneurLV were obtained using a TomTec 3-DE system. For 3-DE volume calculations, a rotational axis in the center of the left ventricle (apical-basal orientation) was defined and 3, 6 and 12 equi-angular rotational planes were created. In each plane the endocardial border was traced and the volume of the corresponding wedge was automatically calculated. The measurements were performed by 2 independent investigators blinded to the anatomic volume and were analyzed for inter- and intraobserver variability.

RESULTS

The anatomic volumes ranged from 5 to 150 ml and 9 to 40 ml in LV and aneurLV, respectively. The correlation between 3-DE and anatomic volume was excellent for LV and aneurLV traced in 3, 6 and 12 planes (r = 0.94-0.99). Ventricular volume was well predicted by 3-DE reconstruction: SEE 5.5-7.1 ml (LV), 3.0-3.2 ml (aneurLV). The correlation for interobserver measurements was good in both, LV (r = 0.99) and aneurLV (r = 0.94-0.99) even in 3 planes. The intra- and interobserver variabilities were 1.6-3.0 ml (<7%) and 7.2-7.3 ml (<15%) in LV and 1.1-1.6 (<6%) and 2.1-3.3 ml (<14%) in aneurLV respectively.

CONCLUSION

This new 3-DE method of ventricular volume measurements using a rotational approach provides rapid, accurate and reproducible volume measurements in LV and aneurLV.

Determination of left ventricular volume, ejection fraction, and myocardial mass by real-time three-dimensional echocardiography

Reconstructed three-dimensional (3-D) echocardiography is an accurate and reproducible method of assessing left ventricular (LV) functions. However, it has limitations for clinical study due to the requirement of complex computer and echocardiographic analysis systems, electrocardiographic/respiratory gating, and prolonged imaging times. Real-time 3-D echocardiography has a major advantage of conveniently visualizing the entire cardiac anatomy in three dimensions and of potentially accurately quantifying LV volumes, ejection fractions, and myocardial mass in patients even in the presence of an LV aneurysm. Although the image quality of the current real-time 3-D echocardiographic methods is not optimal, its widespread clinical application is possible because of the convenient and fast image acquisition. We review real-time 3-D echocardiographic image acquisition and quantitative analysis for the evaluation of LV function and LV mass.

Three-dimensional transesophageal echocardiography (TEE) and other future directions

As faster imaging systems enter the market, three-dimensional echocardiography is gearing up to become a useful tool in assisting the clinician to image the heart in many innovative projections. What started out as a novel idea of displaying a three-dimensional anatomic picture of the heart now provides a multitude of views of the heart and its structures. Information gained from anatomic and dynamic data has helped clinicians and surgeons in making clinical decisions. In the future, this imaging modality may become a routine imaging modality for assessing cardiac pathology and may serve to increase understanding of the dynamics of the heart.

Validation of real-time three-dimensional echocardiography for quantifying left ventricular volumes in the presence of a left ventricular aneurysm: in vitro and in vivo studies

OBJECTIVES

To validate the accuracy of real-time three-dimensional echocardiography (RT3DE) for quantifying aneurysmal left ventricular (LV) volumes.

BACKGROUND

Conventional two-dimensional echocardiography (2DE) has limitations when applied for quantification of LV volumes in patients with LV aneurysms.

METHODS

Seven aneurysmal balloons, 15 sheep (5 with chronic LV aneurysms and 10 without LV aneurysms) during 60 different hemodynamic conditions and 29 patients (13 with chronic LV aneurysms and 16 with normal LV) underwent RT3DE and 2DE. Electromagnetic flow meters and magnetic resonance imaging (MRI) served as reference standards in the animals and in the patients, respectively. Rotated apical six-plane method with multiplanar Simpson's rule and apical biplane Simpson's rule were used to determine LV volumes by RT3DE and 2DE, respectively.

RESULTS

Both RT3DE and 2DE correlated well with actual volumes for aneurysmal balloons. However, a significantly smaller mean difference (MD) was found between RT3DE and actual volumes (-7 ml for RT3DE vs. 22 ml for 2DE, p = 0.0002). Excellent correlation and agreement between RT3DE and electromagnetic flow meters for LV stroke volumes for animals with aneurysms were observed, while 2DE showed lesser correlation and agreement (r = 0.97, MD = -1.0 ml vs. r = 0.76, MD = 4.4 ml). In patients with LV aneurysms, better correlation and agreement between RT3DE and MRI for LV volumes were obtained (r = 0.99, MD = -28 ml) than between 2DE and MRI (r = 0.91, MD = -49 ml).

CONCLUSIONS

For geometrically asymmetric LVs associated with ventricular aneurysms, RT3DE can accurately quantify LV volumes.

Transesophageal echocardiography

Anesthesiologists are increasingly using transesophageal echocardiography in both cardiac and noncardiac cases. In cardiac anesthesia, considerable progress has been made in the evaluation of mitral valvular disease. Transesophageal echocardiography has also become more useful in the hemodynamic evaluation of patients undergoing coronary artery bypass grafting. It is particularly valuable in minimally invasive surgery and in heart surgery to correct congenital defects.

An interactive tool to visualize three-dimensional ultrasound data

Three-dimensional ultrasound can provide images that are easily understood by people who are not specialists in ultrasonography. However, current visualization methods do not perform very well on 3-D ultrasound data. Apart from some specific cases (obstetrics, cardiology), 3-D ultrasound images have not yet demonstrated major benefits from a clinical point of view. In this article, we introduce an interactive method that allows the user easily to produce 3-D images for each ultrasound examination. It is a two-step method. First, the user roughly segments the data by drawing three boundary curves in perpendicular planes. A ray-casting algorithm then automatically retrieves the details of the objects. Because it can be used routinely, this tool should help to evaluate the potential of 3-D ultrasonography.

Real-time three-dimensional echocardiography for measurement of left ventricular volumes

Left ventricular (LV) volumes are important prognostic indexes in patients with heart disease. Although several methods can evaluate LV volumes, most have important intrinsic limitations. Real-time 3-dimensional echocardiography (RT3D echo) is a novel technique capable of instantaneous acquisition of volumetric images. The purpose of this study was to validate LV volume calculations with RT3D echo and to determine their usefulness in cardiac patients. To this end, 4 normal subjects and 21 cardiac patients underwent magnetic resonance imaging (MRI) and RT3D echo on the same day. A strong correlation was found between LV volumes calculated with MRI and with RT3D echo (r = 0.91; y = 20.1 + 0.71x; SEE 28 ml). LV volumes obtained with MRI were greater than those obtained with RT3D echo (126 +/- 83 vs 110 +/- 65 ml; p = 0.002), probably due to the fact that heart rate during MRI acquisition was lower than that during RT3D echo examination (62 +/- 11 vs 79 +/- 16 beats/min; p = 0.0001). Analysis of intra- and interobserver variability showed strong indexes of agreement in the measurement of LV volumes with RT3D echo. Thus, LV volume measurements with RT3D echo are accurate and reproducible. This technique expands the use of ultrasound for the noninvasive evaluation of cardiac patients and provides a new tool for the investigational study of cardiovascular disease.

Initial clinical experience of real-time three-dimensional echocardiography in patients with ischemic and idiopathic dilated cardiomyopathy

The geometry of the left ventricle in patients with cardiomyopathy is often sub-optimal for 2-dimensional ultrasound when assessing left ventricular (LV) function and localized abnormalities such as a ventricular aneurysm. The aim of this study was to report the initial experience of real-time 3-D echocardiography for evaluating patients with cardiomyopathy. A total of 34 patients were evaluated with the real-time 3D method in the operating room (n = 15) and in the echocardiographic laboratory (n = 19). Thirteen of 28 patients with cardiomyopathy and 6 other subjects with normal LV function were evaluated by both real-time 3-D echocardiography and magnetic resonance imaging (MRI) for obtaining LV volumes and ejection fractions for comparison. There were close relations and agreements for LV volumes (r = 0.98, p <0.0001, mean difference = -15 +/- 81 ml) and ejection fractions (r = 0.97, p <0.0001, mean difference = 0.001 +/- 0.04) between the real-time 3D method and MRI when 3 cardiomyopathy cases with marked LV dilatation (LV end-diastolic volume >450 ml by MRI) were excluded. In these 3 patients, 3D echocardiography significantly underestimated the LV volumes due to difficulties with imaging the entire LV in a 60 degrees x 60 degrees pyramidal volume. The new real-time 3D echocardiography is feasible in patients with cardiomyopathy and may provide a faster and lower cost alternative to MRI for evaluating cardiac function in patients.

Effect of aneurysmectomy on left ventricular shape and function: case studies

The three dimensional (3D) conformational changes in three patients with large anterior aneurysm in the left ventricle (LV) were examined before and two years after aneurysmectomy by using 3D Cine-computerized tomography (CT). Endocardial and epicardial tracings of 6-9 short axis images encompassing the entire LV were used to reconstruct the LV in 3D. Thickness and percent thickening were calculated using our 3D-volume element approach. A regional wall stress index (stress/pressure) was calculated from regional curvature and thickness. The analysis showed that following resection of the aneurysm the end-diastolic volume was reduced from 257+/-39 to 183+/-39 ml, end-systolic volume from 172+/-39 to 92+/-46 ml and, ejection fraction increased from 34+/-7 to 51+/-13%. The endocardial aneurysm area decreased from 19.7+/-15.9 to 10.1+/-6.5 cm2, whereas the normal zone area was minimally reduced from 87.4+/-17.6 to 79.8+/-10.8 cm2. The percent thickening of the normal zone increased significantly. It is documented here for the first time by detailed 3D analysis that the resection of the LV aneurysm reduces the aneurysmal area and LV size and improves the global and regional function of the remote normal zone. Therefore, the 3D approach can help to design better surgical technique for this complex operation.

Measurements of organ volume by ultrasonography

In a clinical context, measurements of organ volume are often performed in the diagnosis and follow-up of patients with a variety of diseases. Ultrasonography is a cheap, widely available and non-hazardous imaging modality to use for estimation of volumes, and a range of two- and three-dimensional methods have emerged to accomplish this task. This paper reviews some of the ultrasound methods available in cardiology, gastroenterology, nephrology/urology and gynaecology/obstetrics. Using two-dimensional (2D) ultrasound, the simplest method of calculating the volume of an organ is based on the multiplication of three diameters perpendicular to each other. These 2D methods are often based on geometrical assumptions which may introduce significant errors in volume estimation. Therefore, volume estimation based on three-dimensional (3D) ultrasound has been developed to increase accuracy and precision. At present, the process of making 3D images based on ultrasonography is divided into five steps: data acquisition, data digitization, data storage, data processing and data display. In conclusion, ultrasonography is a useful and reliable tool to calculate volumes of organs. In particular, 3D ultrasonography seems promising in this respect and appears to be superior to 2D ultrasonography in accuracy and precision in volume measurements.

Volumetric analysis of the right and left ventricle in a porcine heart model: comparison of three-dimensional echocardiography, magnetic resonance imaging and angiocardiography

Three-dimensional echocardiography and magnetic resonance imaging allow the volumetric analysis of ventricular volumes independent of geometric assumptions. The aim of the study was to compare these methods and the common angiocardiography in a cardiac model of known volume.

METHODS/MATERIALS

Right and left ventricular (RV, LV-) volumes were measured in a specific animal model directly ('true volume') and with different imaging techniques. Three-dimensional echocardiography (3D-Echo) and magnetic resonance imaging (MRI), both of which permit a volume estimation without necessitating geometric assumptions, and angiocardiographic volumetry which is based on the Simpson rule were used in this study.

RESULTS

The best results were achieved with MRI (RV: r(2)=0.99, mean difference: -1. 9+/-3.3%; LV: difference r(2)=0.99,: 2.9+/-5.0%). Likewise, 3D-Echo showed a very good correlation with the true volumes (RV: r(2)=0.93, difference: 9.3+/-6.3%; LV r(2)=0.96, difference: 4.8+/-9.9%). The greatest deviations were observed during angiocardiographic volumetry (LV: r(2)=0.98; difference: 14.4+/-9.2%), particularly when measuring the right ventricle (RV: r(2)=0.82, difference: 57. 9+/-40.1%). Consequently, the direct comparison between 3D-Echo and the other methods yielded the best correspondence with MRI (RV: Bias: 3.7 ml, limits of agreement: 7.7 ml; LV: Bias: 3.7 ml, limits of agreement: 4.9 ml). In contrast, the differences between 3D-Echo and angiocardiography were marked (RV: Bias: 25.5 ml, limits of agreement: 11.1 ml; LV: Bias: 8.7 ml, limits of agreement: 13.2 ml).

CONCLUSION

In a porcine cardiac model, 3D-Echo permits a relatively precise measurement of ventricular volumes with a slight under-estimation. MRI yielded the most precise volumetry, and the correlation between 3D-Echo and MRI was quite good. Particularly for the right ventricle, the angiocardiographic measurement was attached with the greatest error and thus appears ill-suited for the volumetry of geometrically more complex ventricles.

Assessment of left ventricular cardiac shape by the use of volumetric curvature analysis from 3D echocardiography

A method for three-dimensional shape analysis of left ventricle (LV) is presented in this article. The method uses three-dimensional transesophageal echocardiography (TEE) as the source to derive the 3D wire-frame model and the related shape descriptors. The shape descriptors developed in this article include regional surface changing (RSC), global surface curvature (GSC), surface distance (SD), normalized surface distance (ND), and effective radius (ER) of the endocardial surface. Based on these shape descriptors, the shape of LV could be sketched in both static and dynamic manner. The results show that the new approach provides a robust but easy method to quantify regional and global LV shape from 2D and 3D echocardiograms.

Paraplane analysis from precordial three-dimensional echocardiographic data sets for rapid and accurate quantification of left ventricular volume and function: a comparison with magnetic resonance imaging

OBJECTIVES

Three-dimensional echocardiography (3DE) calculates left ventricular volumes (LVV) and ejection fraction (EF) without geometric assumptions, but prolonged analysis time limits its routine use. This study was designed to validate a modified 3DE method for rapid and accurate LVV and EF calculation compared with magnetic resonance imaging (MRI).

METHODS

Forty subjects included 15 normal volunteers (group A) and 25 patients with segmental wall motion abnormalities and global hypokinesis caused by ischemic heart disease (group B) who underwent 3DE with precordial rotational acquisition technique (2-degree interval with electrocardiographic and respiratory gating) and MRI at 0.5 T, electrocardiogram (ECG)-triggered multislice multiphase T1-weighted fast field echo. End-diastolic and end-systolic LVV and EF were calculated from both techniques with Simpson's rule by manual endocardial tracing of equidistant parallel left ventricular short-axis slices. Slicing from the 3DE data sets were done by both 2.9-mm slice thickness (method 3DE-A) and by 8 equidistant short-axis slices (method 3DE-B); for MRI analysis, 9-mm slice thickness was used.

RESULTS

Analysis time required for manual endocardial tracing of end-diastolic and end-systolic short-axis slices was 10 minutes for the 3DE-B method compared with 40 minutes by the 3DE-A method. For all 40 subjects the mean +/- SD of end-diastolic LVV (mL) were 181 +/- 76, 179 +/- 73, and 182 +/- 76; for end-systolic LVV (mL), 120 +/- 76, 120 +/- 75, and 122 +/- 77; and for EF (%), 39 +/- 18, 38 +/- 18, and 38 +/- 18 for MRI, 3DE-A, and 3DE-B methods, respectively. The differences between 3DE-A and 3DE-B with MRI for calculating end-diastolic and end-systolic LVV and EF were not significant for the whole group of subjects as well as for the subgroups. The 3DE-B method had excellent correlation and close limits of agreement with MRI for calculating end-diastolic and end-systolic LVV and EF: r = 0.98 (-1.3 +/- 26.6), 0.99 (-1.6 +/- 21. 2), and 0.99 (0.2 +/- 5.2), respectively. The correlation between 3DE-A and MRI were r = 0.97, 0.98, and 0.98, and the limits of agreement were -1.4 +/- 36, -0.6 +/- 26, and 0.6 +/- 8 for calculating end-diastolic and end-systolic LVV and EF, respectively. In addition, excellent correlation and close limits of agreement between 3DE-A and 3DE-B with MRI for LVV and EF calculation was also found for the subgroups. Intraobserver and interobserver variability (SEE) of MRI for calculating end-diastolic and end-systolic LVV and EF were 6.3, 4.7, and 2.1; and 13.6, 11.5, and 4.7; respectively, whereas that for 3DE-B were 3.1, 4.4, and 2.2; and 6.2, 3.8, and 3. 6; respectively. Comparable observer variability was also found for the A and B subgroups.

CONCLUSIONS

The 3DE-A and 3DE-B methods have excellent correlation and close limits of agreement with MRI for calculating LVV and EF in both normal subjects and cardiac patients. The 3DE-B method by paraplane analysis with 8 equidistant short-axis slices has observer variability similar to MRI and reduces the 3DE analysis time to 10 minutes, therefore offering a rapid, reproducible, and accurate method for LVV and EF calculation.

Relation between the number of image planes and the accuracy of three-dimensional echocardiography for measuring left ventricular volumes and ejection fraction

The relation between accuracy of 3-dimensional echocardiography (3DE) in determining left ventricular end-diastolic volume, end-systolic volume, and ejection fraction (compared with magnetic resonance imaging) and the number of component planes used for 3DE ventricular reconstruction was evaluated in 41 adult subjects with normal (n = 24) and abnormal (n = 17) left ventricles. Accuracy and confidence of 3DE gradually increased with use of additional component planes, so that > or = 10 planes from both parasternal and apical windows provided 3DE reconstructions that accurately predict magnetic resonance imaging-measured left ventricular volumes and ejection fraction with confidence.

Three-dimensional echocardiographic determination of left ventricular volumes and function by multiplane transesophageal transducer: dynamic in vitro validation and in vivo comparison with angiography and thermodilution

The goal of this study was to validate 3-dimensional echocardiography by multiplane transesophageal transducer for the determination of left ventricular volumes and ejection fraction in an in vitro experiment and to compare the method in vivo with biplane angiography and the continuous thermodilution method. In the dynamic in vitro experiment, we scanned rubber balloons in a water tank by using a pulsatile flow model. Twenty-nine measurements of volumes and ejection fractions were performed at increasing heart rates. Three-dimensional echocardiography showed a very high accuracy for volume measurements and ejection fraction calculation (correlation coefficient, standard error of estimate, and mean difference for end-diastolic volume 0.998, 2.3 mL, and 0.1 mL; for end-systolic volume 0.996, 2.7 mL, and 0.5 mL; and for ejection fraction 0.995, 1.0%, and -0.4%, respectively). However, with increasing heart rate there was progressive underestimation of ejection fraction calculation (percent error for heart rate below and above 100 bpm 0.59% and -8.6%, P < .001). In the in vivo study, left ventricular volumes and ejection fraction of 24 patients with symmetric and distorted left ventricular shape were compared with angiography results. There was good agreement for the subgroup of patients with normal left ventricular shape (mean difference +/-95% confidence interval for end-diastolic volume 5.2+/-6.7 mL, P < .05; for end-systolic volume -0.5+/-8.4 mL, P = not significant; for ejection fraction 2.4%+/-7.2%, P = not significant) and significantly more variability in the patients with left ventricular aneurysms (end-diastolic volume 23.1+/-56.4 mL, P < .01; end-systolic volume 5.6+/-41.0 mL, P = not significant; ejection fraction 4.9%+/-16.0%, P < .05). Additionally, in 20 critically ill, ventilated patients, stroke volume and cardiac output measurements were compared with measurement from continuous thermodilution. Stroke volume as well as cardiac output correlated well to thermodilution (r = 0.89 and 0.84, respectively, P < .001), although both parameters were significantly underestimated by 3-dimensional echocardiography (mean difference +/-95% confidence interval = -6.4+/-16.0 mL and -0.6+/-1.6 L/min, respectively, P < .005).

A simplified, practical echocardiographic approach for 3-dimensional surfacing and quantitation of the left ventricle: clinical application in patients with abnormally shaped hearts

The goal of this study was to validate the quantitative accuracy of a system for 3-dimensional (3D) echocardiographic reconstruction of the left ventricle to assess its volume and function in human beings by using 3 apical views as a simplified technique to promote practical clinical application. End-diastolic and end-systolic volumes (EDV, ESV) and ejection fraction (EF) were obtained by 3D echocardiography in 50 patients with dilated or geometrically distorted left ventricles and compared with values from magnetic resonance imaging (20 consecutive patients), angiography (22 consecutive patients), and radionuclide imaging (8 consecutive patients). Three-dimensional results were also compared with 2-dimensional (2D) echocardiographic estimates. Three-dimensional left ventricular reconstruction provided values that correlated and agreed well with pooled data from the other techniques for EDV (y = 0.93x + 9.1, r = 0.95, standard error of the estimate [SEE] = 15.2 mL, mean difference = -0.5 +/- 15.4 mL), ESV (y = 0.94x + 4.3, r = 0. 96, SEE = 11.4 mL, mean difference = 0.4 +/- 11.5 mL), and EF (y = 0. 90x + 4.1, r = 0.92, SEE = 6.2%, mean difference = -0.9 +/- 6.4%) (all mean differences not significant versus 0), with greater errors by 2D echocardiography. Intraobserver and interobserver variabilities of 3D echocardiography were less than 6% for EDV, ESV, and EF. The overall time for image acquisition and 3D reconstruction was 5 to 8 minutes. Although this 3D method uses only a small number of apical views, it accurately calculates EDV, ESV, and EF in patients with dilated and asymmetric left ventricles and is more accurate than 2D echocardiography. The flexible surface fit used to combine the 3 views provides a convenient visual output as well as quantitation. This simple and rapid 3D method has the potential to facilitate routine clinical applications that assess left ventricular function and changes that occur with remodeling.

Clinical Determinations of Volumes of Normal and Aneurysmatic Left Ventricles by Three-Dimensional Transesophageal Echocardiography

Biplane methods of determining left ventricular volumes are inaccurate in the presence of aneurysmal distortions. Multiplane transesophageal echocardiography, which provides multiple, unobstructed cross-sectional views of the heart from a single, stable position, has the potential for more accurate determinations of volumes of irregular cavity forms than the biplane methods. The aim of the study was to determine the feasibility of three-dimensional measurements of ventricular volumes in patients with normal and aneurysmatic left ventricles by using multiplane transesophageal echocardiography. With the echotransducer in the mid-esophageal (transesophageal) position, nine echo cross-sectional images of the left ventricle in approximately 20 degrees angular increments were obtained from each of 29 patients with coronary artery disease who had undergone biplane ventriculography during diagnostic cardiac catheterization. In 17 of these 29 patients, echo cross-sectional images of the left ventricle with the echotransducer in transgastric position were also obtained. End-diastolic volume, end-systolic volume, and ejection fraction were determined from multiplane transesophageal echocardiographic images and biplane ventriculographic images by the disc-summation method and compared with each other. In another ten patients with indwelling pulmonary artery catheters, stroke volumes calculated from multiplane transesophageal echocardiographic images were compared with those derived from thermodilution cardiac output measurements. Correlations between biplane ventriculographic and multiplane transesophageal echocardiographic measurements were higher in the ten patients with normal ventricular shape [for end-diastolic volumes, r = 0.91, SEE = 19 ml; for end-systolic volumes, r = 0.98, SEE = 9.3 ml; for ejection fractions (EFs), r = 0.91, SEE = 5.4%] than in the 19 patients with ventricular aneurysms (for end-diastolic volumes, r = 0.61, SEE = 31.5 ml; for end-systolic volumes, r = 0.66, SEE = 32.5 ml; for EFs, r = 0.79, SEE = 8%). Correlations between echocardiographic volumes from the transesophageal and transgastric transducer positions were high independent of left ventricular geometry (for end-diastolic volumes, r = 0.84, SEE = 13.1 ml; for end-systolic volumes, r = 0.98, SEE = 9.6 ml; for EFs, r = 0.97, SEE = 3.4%). In 12 observations (4 normal and 8 aneurysmal) from the ten patients with indwelling pulmonary artery catheters, correlation between stroke volumes determined from thermodilution cardiac output measurements and those derived from multiplane transesophageal echocardiographic images was high (r = 0.91, SEE = 6 ml). The results indicate that three-dimensional measurements of volumes of irregular and distorted left ventricles are feasible with multiplane transesophageal echocardiography. This method may be more accurate than biplane methods, especially in the presence of left ventricular aneurysms.

Three-dimensional echocardiographic measurement of right ventricular volume in children with congenital heart disease validated by magnetic resonance imaging

Measurement of right ventricular volume and function by two-dimensional echocardiography is unreliable because of the asymmetric shape of the right ventricle. The purpose of this study was to validate the accuracy of transthoracic three-dimensional echocardiography in assessing right ventricular volumes in children with congenital heart disease after surgical repair of the defects, by comparison with those measured by magnetic resonance imaging. We examined 13 children after repair of tetralogy of Fallot (10), hypoplastic left heart syndrome (2), or atrial septal defect (1). Each underwent magnetic resonance imaging followed by three-dimensional echocardiography done with a transthoracic 5 MHz, prototype internally rotating omniplane transducer. In both methods, endocardial borders were manually traced and volumetric slices were summated. Close correlation was observed between the two methods (R2 0.91 for end-systolic volumes, 0.90 for end-diastolic volumes, 0.64 for ejection fraction, and 0.92 for interobserver variability). A limits-of-agreement analysis showed no adverse trend between the two methods under values of 100 ml and low variation around the mean values. We conclude that three-dimensional echocardiography measurement of right ventricular volumes correlates closely with magnetic resonance imaging in children with operated congenital heart disease and may allow accurate serial evaluation in these patients.

Left ventricular ejection fraction in patients with normal and distorted left ventricular shape by three-dimensional echocardiographic methods: a comparison with radionuclide angiography

BACKGROUND

Serial evaluation of left ventricular (LV) ejection fraction (EF) is important for the management and follow-up of cardiac patients. Our aim was to compare LVEF calculated from two three-dimensional echocardiographic (3DE) methods with multigated radionuclide angiography (RNA), in patients with normal and abnormally shaped ventricles.

METHODS AND RESULTS

Forty-one consecutive patients referred for RNA underwent precordial rotational 3DE acquisition of 90 cut-planes. From the volumetric data set, LVEF was calculated by (a) Simpson's rule (3DS) through manual endocardial tracing of LV short-axis series at 3 mm slice distance and (b) apical biplane modified Simpson's method ( MS) in 29 patients by manual endocardial tracing of the apical four-chamber view and its computer-derived orthogonal view. Patients included three groups: A, 17 patients with LV segmental wall motion abnormalities; B, 13 patients with LV global hypokinesis; and C, 11 patients with normal LV wall motion. For all the 41 patients, there was excellent correlation, close limits of agreement, and nonsignificant difference between 3DS and RNA for LVEF calculation (r = 0.99, [-6.7, +6.9] and p = 0.9), respectively. For the 29 patients, excellent correlation and nonsignificant differences between LVEF calculated by both 3DS and BMS and values obtained by RNA were found (r = 0.99 and 0.97, p = 0.7 and p = 0.5, respectively). In addition, no significant difference existed between values of LVEF obtained from RNA, 3DS, and BMS by the analysis of variance (p = 0.6). The limits of agreement tended to be closer between 3DS and RNA (-6.8, +7.2) than between BMS and RNA (-8.3, +9.7). The intraobserver and inter-observer variability of RNA, 3DS, and BMS for calculating LVEF(%) were (0.8, 1.5), (1.3, 1.8), and (1.6, 2.6), respectively. There were closer limits of agreement between 3DS and RNA for LVEF calculation in A, B, and C patient subgroups [(-3.5, +5), (-8.4, +5.6), and (-7.8, +8.6)] than that between BMS and RNA [(-8.1, +10.7), (-11.9, +9.3), and (-9.1, +11.3)], respectively.

CONCLUSIONS

No significant difference existed between RNA, 3DS, and BMS for LVEF calculation. 3DS has better correlation and closer limits of agreement than BMS with RNA for LVEF calculation, particularly in patients with segmental wall motion abnormalities and global hypokinesis. 3DS has a comparable observer variability with RNA. Therefore the use of 3DS for serial accurate LVEF calculation in cardiac patients is recommended.

System for quantitative three-dimensional echocardiography of the left ventricle based on a magnetic-field position and orientation sensing system

Accurate measurement of left-ventricular (LV) volume and function are important to monitor disease progression and assess prognosis in patients with heart disease. Existing methods of three-dimensional (3-D) imaging of the heart using ultrasound have shown the potential of this modality, but each suffers from inherent restrictions which limit its applicability to the full range of clinical situations. We have developed a technique for image acquisition using a magnetic-field system to track the 3-D echocardiographic imaging planes and 3-D image analysis software including the piecewise smooth subdivision method for surface reconstruction. The technique offers several advantages over existing methods of 3-D echocardiography. The results of validation using in vitro LV's show that the technique allows accurate measurement of LV volume and anatomically accurate 3-D reconstruction of LV shape and is, therefore, suitable for analysis of regional as well as global function.

Infarct size and location determine development of mitral regurgitation in the sheep model

OBJECTIVE

This study tests the hypothesis that neither small nor large myocardial infarctions that include the anterior papillary muscle produce mitral regurgitation in sheep.

METHODS

Coronary arterial anatomy to the anterior left ventricle and papillary muscle was determined by dye injection in 41 sheep hearts and by triphenyl tetrazolium chloride in 13. Development of acute or chronic mitral regurgitation and changes in left ventricular dimensions were studied by use of transdiaphragmatic echocardiography in 21 sheep after infarction of 24% and 33% of the anterior left ventricular mass. These data were compared with previous data from large and small posterior left ventricular infarctions.

RESULTS

Ligation of two diagonal arteries infarcts 24% of the left ventricular mass and 82% of the anterior papillary muscle. Ligation of both diagonals and the first circumflex branch infarcts 33% of the left ventricle and all of the anterior papillary muscle. Neither infarction causes mitral regurgitation, although left ventricular cavity dimensions increase significantly at end systole. After the smaller infarction, the left ventricular cavity enlarges 150% over 8 weeks without mitral regurgitation.

CONCLUSIONS

In sheep small and large infarctions of the anterior wall that include the anterior papillary muscle do not produce either acute or chronic mitral regurgitation despite left ventricular dilatation. In contrast large posterior infarctions produce immediate mitral regurgitation owing to asymmetric annular dilatation and discoordination of papillary muscle relationships to the valve. After small posterior infarctions that include the posterior papillary muscle, mitral regurgitation develops because of annular and ventricular dilatation during remodeling.

Distortions of the mitral valve in acute ischemic mitral regurgitation

BACKGROUND

In the absence of papillary muscle rupture, the precise deformations that cause acute postinfarction mitral valve regurgitation are not understood and impair reparative efforts.

METHODS

In 6 Dorsett hybrid sheep, sonomicrometry transducers were placed around the mitral annulus (n = 6) and at the tips and bases of both papillary muscles (n = 4). Later, specific circumflex coronary arteries were occluded to infarct approximately 32% of the posterior left ventricle and produce acute 2 to 3+ mitral regurgitation. Before and after infarction, distance measurements between sonomicrometry transducers produced three-dimensional coordinates of each transducer every 5 ms.

RESULTS

After infarction, the annulus dilated asymmetrically orthogonal to the line of leaflet coaptation, but the annular area increased only 9.2% +/- 6.3% (p = 0.02). At end-systole, posterior papillary muscle length increased 2.3 +/- 0.9 mm (p = 0.005); the posterior papillary muscle tip moved closer to the annular plane and centroid, and the anterior papillary muscle tip moved away.

CONCLUSIONS

Small deformations in mitral valvular spatial geometry after large posterior infarctions are sufficient to produce moderate to severe mitral regurgitation. The most important changes are asymmetric annular dilatation, prolapse of leaflet tissue tethered by the posterior papillary muscle, and restriction of leaflet tissue attached to the anterior papillary muscle.

Reference Techniques for Left Ventricular Volume Measurement by Three-Dimensional Echocardiography: Determination of Precision, Accuracy, and Feasibility

The use of multiple in vitro reference methods to validate three-dimensional (3-D) echocardiographic techniques makes comparison difficult. In an attempt to establish a reference standard, we studied precision, accuracy, and feasibility of a true left ventricular (LV) volume measurement in six dog heart specimens using three techniques, called fluid, sheath, and cast. LV volumes ranged from 30 to 105 mL. Intraobserver variability was minimal in all combinations (1.26% to 2.8%) with a statistically insignificant tendency to higher values in the cast method. The cast method, however, exhibited significantly higher interobserver variability (5.78%) as compared to that ranging from 1.47% to 1.59% in the remaining two techniques. Regression analysis demonstrated high correlations among the three techniques assessed by 95% confidence limits and correlation coefficient (R(2) > 0.98, P < 0.01). Mean differences among the techniques (0.12 to 1.08 mL) were not significant. The fluid technique was easy to perform. The sheath technique required some practice. The cast method was sensitive to accurate preparation of a gelatin mixture. We conclude that the fluid and sheath techniques are precise, accurate, and feasible. We recommend their use as reference standards in laboratory LV volume measurement. Validation 3-D echocardiographic studies using either of these two techniques will be comparable. Although the accuracy of the cast technique is excellent, its lower precision makes it a second choice. It could be used in cases where an LV cavity cast is required and higher interobserver variability is acceptable.

Determination of left ventricular mass and circumferential wall thickness by three-dimensional reconstruction: in vitro validation of a new method that uses a multiplane transesophageal transducer

Elevated left ventricular mass and increased wall thickness have important prognostic implications in clinical medicine. However, these parameters have been incompletely characterized by one- and two-dimensional echocardiography. Therefore this study was performed to validate in vitro measurement of left ventricular mass and circumferential wall thickness with a multiplane transesophageal transducer and three-dimensional reconstruction. Results for mass measurements were also compared with a standard method for the determination of left ventricular mass, the Penn convention. Fourteen necropsied left ventricles were scanned in a water bath by a volume-rendering, three-dimensional reconstruction system. There was an excellent correlation and high agreement for determination of three-dimensional left ventricular mass (r = 0.98; standard error of the estimate [SEE] = 9.6 gm; y = 1.02x + 0.46) and wall thickness (r = 0.93; SEE = 1.4 mm; y = 0.95x + 1.64) compared with anatomic measurements. Left ventricular mass by a simulated Penn convention revealed a lower correlation and larger error compared with three-dimensional measurements (r = 0.72; SEE = 42.8 gm; y = 1.01x + 9.61). Therefore determination of left ventricular mass by three-dimensional reconstruction was validated in vitro and was superior to one-dimensional echocardiographic methods.

Performance of a miniature magnetic position sensor for three-dimensional ultrasound imaging

A miniature magnetic position sensor used for three-dimensional ultrasound imaging was tested for precision and accuracy in vitro. The sensor alone was able to locate points with root-mean-square (rms) uncertainty of 1.7 mm and accuracy of 0.05 +/- 0.62 mm over its specified operating range of 50 cm. With an ultrasound imaging system, a point was located from arbitrary viewing windows with 2.4-mm rms uncertainty and 0.06 +/- 0.68 mm accuracy. If viewing windows were limited to those representative of a typical ultrasound examination, the system could achieve rms uncertainty in point location of < 1 mm. Performance was not affected by operation of the imaging system when the sensor was mounted on an ultrasound scanhead. Sensitivity to metals in the operating environment was also measured.

Transesophageal echocardiography

This article presents an overview of the benefits and efficacy of transesophageal echocardiography (TEE) in the critically ill patient. The echocardiographic evaluation of ventricular function both regional and global, is discussed with special emphasis on ischemic heart disease; assessment of preload, interrogation of valvular heart disease (prosthetic and native) and its complications; endocarditis and its complications; intracardiac and extracardiac masses, including pulmonary embolism; aortic diseases (e.g., aneurysan, dissection, and traumatic tears); evaluation of patent foramen ovale and its association with central and peripheral embolic events; advancements in computer technology; and finally, the effect of TEE on critical care.