Estimation of left ventricular cavity area with an on-line, semiautomated echocardiographic edge detection system

Intracardiac echocardiography: computerized detection of left ventricular borders

A semi-automated method for two- and three-dimensional analysis of intracardiac echocardiography (ICE) images and image sequences is reported based on detection of epicardial and endocardial borders using graph searching. The border detection method was applied to 50 ICE images acquired in vivo in five dogs and to 108 images in 16 volumetric ICE image sequences from eight cadaveric pig hearts. The ICE images from the in vivo study showed good correlation between computer-detected and observer-defined left ventricular (LV) cavity areas and epicardial areas (r = 0.99, y = 0.98x + 0.43 [cm2]; r = 0.99, y = 0.98x + 1.11 [cm2]; respectively). In the cadaveric hearts, the LV volumes were determined with the volume measurement error of 7.6 +/- 7.7% and 11.3 +/- 11.2% for the aortic valve and mitral valve image sequences, respectively. Our method facilitates an accurate and computationally efficient approach for the quantitative assessment of ICE image data in 2D and 3D.

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.

Estimation of Left Ventricular Ejection Fraction by Semiautomated Edge Detection

Left ventricular (LV) volume and ejection fraction estimation from two-dimensional echocardiograms requires off-line analysis and time-consuming manual tracing. LV volumes may be estimated on-line with a semiautomated edge detection echocardiographic system [also known as acoustic quantification (AQ)], but there are few data that compare volumes obtained from the AQ method with volumes derived from off-line manual tracing of conventional two-dimensional echocardiograms. Echocardiograms were performed in 48 patients at two medical centers. LV volumes were measured from the apical view with the method of discs and area-length formulae and from the parasternal short-axis view with the modified ellipsoid model. Based on the criterion of >/=75% endocardial visualization, 25 (52%) of the short-axis views and 14 (29%) of the apical views were analyzed by a single investigator. End-diastolic and end-systolic LV volumes derived on line with the AQ system showed a very strong linear association with off-line, manually traced volumes (r = 0.96-0.99). Correlations for ejection fraction also were strong (r = 0.90-0.96). End-diastolic and end-systolic LV volumes, measured from the apical views, were underestimated by the AQ method. However, because the error was in the same direction, ejection fractions measured with the AQ system and by manual tracing of conventional echocardiograms were similar. Estimation of ejection fraction using a semiautomated edge detection echocardiographic system is a promising method for noninvasive evaluation of systolic function in carefully selected patients.

Comparison of automatic boundary detection and manual tracing technique in echocardiographic determination of left atrial volume

Previous reports have indicated that echocardiography with automatic boundary detection (ABD) is useful for the noninvasive estimation of left ventricular volume. However, few data exist regarding the measurement of left atrial (LA) volume, which also provides pivotal information in the clinical setting. Therefore, the feasibility of LA volume measurement by ABD in comparison with the manual tracing using modified Simpson's method (SM) was evaluated. Fifty-nine patients with coronary artery-disease with sinus rhythm were examined. Using ABD, a region of interest was set around the LA border and mitral annulus from an apical four-chamber view. The maximal and minimal LA volume (Vmax and Vmin) were measured from the volume waveform. Using the SM, the maximal and minimal LA volume were measured by the manual tracing on frozen frames at the apical four-chamber view. The ABD displayed a curve of LA volume change that consisted of passive emptying, diastasis, and active emptying phases during the left ventricular diastolic period. Under these conditions, the Vmax and Vmin were 43.7 +/- 11.2 ml and 21.1 +/- 7.6 ml, respectively, yielding the volume change of 22.6 +/- 6.0 ml. By the SM, Vmax and Vmin were 43.1 +/- 9.9 ml (r = 0.94, p < 0.0001, y(ABD) = 0.91x (SM) + 3.6) and 22.0 +/- 9.0 ml (r = 0.91, p < 0.0001, y = 0.94x + 0.7), respectively, and the volume change was 22.8 +/- 6.1 ml (r = 0.82, p < 0.0001, y = 0.84x + 3.8). These results indicate that the ABD from the apical four-chamber approach could provide an accurate estimation of LA volume change, suggesting the potential value of this method in assessing LA function, although some technical difficulties need to be further overcome.

On-line analysis of echocardiographic image sequences

This paper presents a semiautomatic system for the interactive analysis of echocardiographic image sequences, able to provide useful information to cardiologists. The proposed approach combines well known techniques for the detection of left ventricular boundaries with the computation of optical flow. The initial detection of the cavity contour is based on an improved balloon model, with automatic tuning of parameters and optional model-based constraints. The computation of optical flow is performed with a fast correlation technique and the contour tracking is obtained combining motion information provided by the optical flow with model-based constraints and/or a snake-based regularization. The system is able to follow the motion of the ventricular boundaries precisely, to provide several quantitative features of the heartbeat and a dynamic representation of systolic and diastolic motion. Preliminary experimental results are presented and commented on with particular attention to their clinical relevance. Furthermore a distributed implementation of the system suitable for remote examination analysis has been realized and applied to echo images of the carotid artery.

Developments in cardiovascular ultrasound. Part 3: Cardiac applications

Echocardiography is still the principal, non-invasive method of investigation for the evaluation of cardiac disorders. Using Doppler ultrasound, indices such as coronary flow reserve and cardiac output can be determined. The severity of valvular stenosis can be determined by the area of the valve, either directly from 2D echo, from pressure half-time calculations, from continuity equations or from the proximal isovelocity surface area method. Alternatively, the severity of regurgitation can be estimated by colour or pulsed ultrasound detection of the back-projection of the high-velocity jet into the chamber. Myocardial wall abnormalities can be assessed using 2D ultrasound, M-mode or analysis from the radio-frequency-ultrasound signal. Doppler tissue imaging can be used to quantify intra-myocardial wall velocities, and 3D reconstruction of cardiac images can provide visualisation of the complete cardiac anatomy from any orientation. The development of myocardial contrast agents and associated imaging techniques to enhance visualisation of these agents within the myocardium has aided qualitative assessment of myocardial perfusion abnormalities. However, quantitative myocardial perfusion has still to be realised.

Thoracocardiography: noninvasive monitoring of left ventricular stroke volume

PURPOSE

Thoracocardiography noninvasively monitors global stroke volume by inductive plethysmographic recording of ventricular volume curves as previously validated by thermodilution. Our purpose was to investigate the potential of thoracocardiography to individually assess stroke volume of the left ventricle. We hypothesized that curves predominantly reflecting left ventricular volume could be obtained by recording waveforms from thoracocardiographic transducers placed at various levels around the chest, and by identifying their origin as the left ventricle if mean expiratory exceeded mean inspiratory stroke volumes during spontaneous breathing.

MATERIALS AND METHODS

Stroke volumes obtained by thoracocardiography in normal subjects were compared beat by beat with estimates derived from simultaneous measurements of left ventricular cavity stroke area by echocardiography with automatic boundary detection. Changes in respiratory variations of stroke volumes were analyzed during spontaneous breathing at fixed rate and tidal volume, during mechanical ventilation, and resistive loaded breathing.

RESULTS

In 170 comparisons of beat-by-beat stroke volumes, 89% of thoracocardiographic fell within +/-20% of echocardiographic estimates. Changes in tidal volume, resistive loaded breathing, and mechanical ventilation induced respiratory variations of thoracocardiographic derived stroke volumes consistent with the known effect of respiratory changes in intrapleural pressure on left ventricular stroke volumes.

CONCLUSIONS

The results suggest that thoracocardiography noninvasively tracks changes in left ventricular stroke volumes. Their absolute value may also be monitored if an initial calibration by an independent technique, such as echocardiography, is performed.

Critical appraisal of left ventricular function assessment by the automated border detection method on echocardiography. Is it good enough?

Many studies have attempted to validate the echocardiographic automated border detection (ABD) method for assessing left ventricular ejection fraction (LVEF) by comparing it with various echocardiographic and non-echocardiographic standards. The main basis of assessing its accuracy has been the coefficient of correlation. The fallacy of using coefficient of correlation for assessing agreement between two methods of measurement has been well emphasized in the literature. In the present study we used the Bland and Altman test for testing the accuracy of the ABD method. We compared the ABD method for LVEF assessment with the manual edge detection technique on echocardiography and with radionuclide ventriculography in 34 patients. The majority of patients (76%) had regional wall motion abnormality. The ABD method could be adequately performed in 25 (74%) patients. LVEF was significantly underestimated by the ABD method with very wide limits of agreement when compared with radionuclide ventriculography and the manual edge detection technique (-9.2+/-21.7 and -2.7+/-18.4 respectively, mean error+/-2 standard deviations). Stated simply, the ABD method could overestimate LVEF by 12.5 and 15.7 or underestimate by 30.9 and 21.1 when compared with radionuclide ventriculography and manual edge detection technique, respectively. This large error is by no means acceptable for clinical purposes. It is concluded that at the present stage, the ABD method cannot replace radionuclide ventriculography and manual edge detection technique for assessing LVEF.

Evaluation of left ventricular volume using automatic border detection in children: a comparison with conventional off-line echocardiographic quantification

BACKGROUND

Evaluation of the clinical usefulness of the one-line automatic border detection system for determination of left ventricular volume in children in comparison to the conventional off-line method.

METHODS

Eighty consecutive patients in whom clear images were obtained by two-dimensional echocardiography were studied. Using the Hewlett-Packard Sonos 2500 with a 3.5 or 5.5 Mhz phased array transducer, all patients were studied in the apical four-chamber imaging plane for automatic border detection and apical four-chamber and two-chamber imaging planes for manual tracing. Left ventricular end-diastolic and end-systolic volumes were measured and compared using the bi-plane Simpson method.

RESULTS

Left ventricular end-diastolic volumes obtained by automatic border detection correlated well but were slightly underestimated compared to those obtained by manual tracing (r = 0.98). Left ventricular end-systolic volumes obtained by automatic border detection also correlated well with those obtained by manual tracing (r = 0.96). Left ventricular ejection fractions compared favorably. However, left ventricular volumes obtained using the classical Pombo M-mode echocardiography showed poorer correlation with those obtained by manual tracing methods.

CONCLUSIONS

Automatic border detection is a promising method for real-time estimation of left ventricular volume. In patients with good endocardial tracking, automatic border detection can be used for routine studies of cardiovascular disease, even in children.

Color Kinesis: Principles of Operation and Technical Guidelines

Color kinesis is a new echocardiographic technique that aids in the assessment of global and regional left ventricular performance during either systole or diastole. Color kinesis uses automated border detection technology based on backscatter data to display both the magnitude and timing of endocardial motion in real time. The color kinesis display superimposes a color overlay on the two-dimensional echocardiographic image; the number of color pixels represents the magnitude of endocardial motion, while the different colors represent the timing of endocardial motion according to a predefined color scheme. Because color kinesis is an operator-dependent technique, the steps involved in performing a technically adequate study will be reviewed as well as the pitfalls and technical limitations. The potential clinical applications of color kinesis will also be discussed.

A methodology for evaluation of boundary detection algorithms on medical images

Image segmentation is the partition of an image into a set of nonoverlapping regions whose union is the entire image. The image is decomposed into meaningful parts which are uniform with respect to certain characteristics, such as gray level or texture. In this paper, we propose a methodology for evaluating medical image segmentation algorithms wherein the only information available is boundaries outlined by multiple expert observers. In this case, the results of the segmentation algorithm can be evaluated against the multiple observers' outlines. We have derived statistics to enable us to find whether the computer-generated boundaries agree with the observers' hand-outlined boundaries as much as the different observers agree with each other. We illustrate the use of this methodology by evaluating image segmentation algorithms on two different applications in ultrasound imaging. In the first application, we attempt to find the epicardial and endocardial boundaries from cardiac ultrasound images, and in the second application, our goal is to find the fetal skull and abdomen boundaries from prenatal ultrasound images.

Comparison of continuous left ventricular volumes by transthoracic two-dimensional digital echo quantification with simultaneous conductance catheter measurements in patients with cardiac diseases

Automated border detection enables real-time tracking of left ventricular (LV) volume by 2-dimensional transthoracic echocardiography. This technique has not been previously compared with simultaneously measured continuous LV volumes at rest or during transients in humans. We performed 18 studies in 16 patients (age 50 +/- 15 years, range 22 to 70; ejection fraction 63 +/- 20%, range 15% to 85%) in which continuous LV volumes acquired by digital echo quantification (DEQ) were compared with simultaneous conductance catheter volume obtained by cardiac catheterization. Both volume signals were calibrated by thermodilution-derived cardiac output and ventriculogram-derived ejection fraction. Volume traces acquired at rest were averaged to generate a comparison cycle. The averaged volume waveforms acquired by DEQ and by conductance catheter were similar during all phases of the cardiac cycle and significantly correlated (conductance catheter = slope. DEQ + intercept, slope = 0.94 +/- 0.09, intercept = 5 +/- 8 ml, r2 = 0.86 +/- 0.12, all p <0.0001). Steady-state hemodynamic parameters calculated using either averaged volume signal were significantly correlated. Transient obstruction of the inferior vena cava yielded a 45 +/- 13% decrease in end-diastolic volume. Successful recordings of DEQ volume during preload reduction were obtained in only 50% of studies. End-diastolic volumes from the 2 methods were significantly correlated (mean slope 0.88 +/- 0.31, mean intercept 14 +/- 37 ml, average r2 = 0.89 +/- 0.11, all p <0.01), as were end-systolic volumes: mean slope 0.80 +/- 0.43, intercept = -20 +/- 26 ml, r2 = 0.67 +/- 0.18, all p <0.05). We conclude that automated border detection technique by DEQ is reliable for noninvasive, transthoracic, continuous tracking of LV volumes at steady state, but has limitations in use during preload reduction maneuvers in humans.

Determination of ventricular ejection fraction: a comparison of available imaging methods. The Cardiovascular Imaging Working Group

Knowledge of left ventricular ejection fraction has been shown to provide diagnostic and prognostic information in patients with known or suspected heart disease. In clinical practice, the ejection fraction can be determined by using one of the five currently available imaging techniques: contrast angiography, echocardiography, radionuclide techniques of blood pool and first pass imaging, electron beam computed tomography, and magnetic resonance imaging. In this review, we discuss the clinical application as well as the advantages and disadvantages of each of these methods as it relates to determination of ventricular ejection fraction.

Detection of diastolic dysfunction: acoustic quantification (AQ) in comparison to Doppler echocardiography

OBJECTIVES

To evaluate the potential of acoustic quantification (AQ) in detection of diastolic dysfunction in comparison to Doppler analysis, we investigated, as a model of restrictive filling pattern, nonrejecting heart transplant recipients early postoperatively.

BACKGROUND

AQ, an ultrasonic backscatter imaging system, enables instantaneous calculation of cavity areas and thus provides a new approach to diastolic function.

METHODS

Of 27 pts who have undergone heart transplantation, echocardiography has been performed at the day of biopsy. During a time course of 8 weeks echocardiographic data have been analysed at 3 different time points (early, mid and late) in 16 nonrejecting pts. Indexes of the area-change waveform and its 1. derivative (dA/dt) obtained by AQ were opposed to usual Doppler indexes.

RESULTS

In comparing data of the early and late time point of investigation, significant changes of early diastolic filling were detectable by AQ as well as by Doppler: End-diastolic areas have increased (p < 0.001), while peak filling rate (p < 0.0001), slope of area change during rapid filling (p < 0.001) and amount of relative area change during rapid filling (p < 0.001) have decreased. Complementary, Doppler derived pressure half-time (p < 0.0001) and isovolumic relaxation time (p < 0.0001) have increased while the peak early filling velocity (p < 0.0001) and its time velocity integral (p < 0.001) have decreased.

CONCLUSION

An initial restrictive filling pattern has improved 8 weeks postoperatively. Since multiple indexes, obtained from the area change waveforms, in particular the for end-diastolic area normalized peak filling rate, seem to be highly sensitive in detecting changes of diastolic function, AQ may play an important complementary role in non-invasive evaluation of restrictive filling pattern.

Two-dimensional Fourier filtration of acoustic quantification echocardiographic images: improved reproducibility and accuracy of automated measurements of left ventricular performance

To determine the accuracy of Fourier filtration in removing the high-frequency component of noise from acoustic quantification (AQ) echocardiographic images, we processed 800 parasternal short-axis images obtained from 10 study subjects. M-mode tracings were also obtained and used as gold standard for correlating the results from raw AQ and Fourier-filtered images. Left ventricular short-axis diameters measured from the raw AQ and Fourier-filtered data were compared with the M-mode diameters (r = 0.91, p < 0.001 for raw AQ; and r = 0.96, p < 0.001, for Fourier filtered images). Fractional shortening showed better correlation between Fourier-filtered images and M-mode (r = 0.79, p < 0.03) versus raw AQ and M-mode (r = 0.33, p = 0.46). Best-to-beat reproducibility was also found to be better for fractional area change (r = 0.82, p = 0.01 versus r = 0.66, p = 0.77), peak area filling rate (r = 0.87, p = 0.004 versus r = 0.62, p = 0.1), and peak are emptying rate (r = 0.99, p < 0.0001 versus r = 0.19, p < 0.7) for Fourier filtered versus raw AQ. Our results indicate that Fourier filtration of AQ data results in more accurate representation of the true endocardial borders.

Transcatheter perforation of the right ventricular outflow tract as initial therapy for pulmonary valve atresia and intact ventricular septum in the newborn

The clinical impact of transcatheter perforation and dilatation of the right ventricular outflow tract in neonates with pulmonary atresia and intact ventricular septum was reviewed. Between April 1992 and December 1994, 8 neonates underwent transcatheter perforation of the right ventricular outflow tract. Radiofrequency energy was employed in 6 patients and wire perforation in 2 patients. Mean patient age at intervention was 1.9 +/- 0.6 days and weight 3.4 +/- 0.5 kg. Median tricuspid valve annulus was 10.9 mm (range: 4.0-13.0 mm) and Z-value -0.85 (range: -4.5-1.0). The mean right ventricular systolic pressure fell from 117 +/- 16 to 55 +/- 15 mm Hg (P < 0.0001), and the right ventricular to aortic pressure ratio decreased from 1.81 +/- 0.33 to 0.82 +/- 0.28 (P < 0.0001). The arterial duct was patent in all. No acute complications occurred. Aortopulmonary shunts were performed in 7 patients at a median 6 days (range: 3-23 days) following catheterization. One patient developed sepsis and died after surgical resection of infected tissue, while a second patient died of a blocked aortopulmonary shunt 17 months following discharge. Median follow-up for the 6 surviving patients was 8 months (range: 4-32 months). One patient has achieved and a second is awaiting biventricular repair. Transcatheter perforation appears to be a promising form of therapy in selected patients with pulmonary atresia, and potentially facilitates algorithms leading to a biventricular repair.

Echocardiographic evaluation of global left ventricular function during high thoracic epidural anesthesia

OBJECTIVES

To assess the effects of high thoracic epidural anesthesia on left ventricular (LV) diastolic filling and systolic function in patients without heart disease.

DESIGN

Prospective study.

SETTING

University hospital.

PARTICIPANTS

24 ASA physical status I and II patients scheduled for elective noncardiac surgery.

INTERVENTIONS

Patients received high thoracic (HTE; n = 12) or low thoracic (LTE; n = 12) epidural anesthesia.

MEASUREMENT AND MAIN RESULTS

Left ventricular diastolic filling was noninvasively determined by precordial echocardiography using a pulsed Doppler technique and with a newly developed acoustic quantification (AQ) method that automatically detects endocardial borders and measures cavity area. All measurements were performed in awake premedicated patients. In the HTE group, the extent of sensory blockade of T1-T5, at the least, was induced with 2% lidocaine 5 ml. During HTE, systolic blood pressure (119 +/- 16 vs. 108 +/- 14 mmHg, p < 0.01), heart rate (73 +/- 9.8 vs. 63 +/- 6.8 beats/min, p < 0.01), cardiac output (CO; 4.5 +/- 1.1 vs. 3.8 +/- 1.2 L/min, p < 0.05), and fractional area change (50 +/- 11 vs. 37 +/- 11%, p < 0.01) decreased significantly, whereas end diastolic area (9.4 +/- 1.4 vs. 10.3 +/- 1.1 cm2, p < 0.01) and end systolic area (4.8 +/- 1.3 vs. 6.0 +/- 1.1 cm2, p < 0.05) showed a significant increase. As a result, stroke volume was kept constant (63 +/- 14 vs. 60 +/- 19 ml). Pulsed Doppler derived indices such as peak velocity during the early filling (E) and the atrial contraction (A) phases, peak early to atrial velocity ratio (E/A), and acceleration time remained unchanged. AQ derived peak dA/dt during the early diastolic (D1) and the atrial contraction phases (D2) and D1/D2 also remained unchanged. In contrast, in the LTE group, no significant differences were noted in all systolic and diastolic indices obtained by pulsed Doppler and AQ method.

CONCLUSIONS

High thoracic epidural anesthesia causes a decrease in CO without changing LV ejection and diastolic filling performance in healthy subjects.

Evaluation of color kinesis, a new echocardiographic method for analyzing regional wall motion in patients with dilated left ventricles

The recently developed echocardiographic technology of color kinesis (CK) displays endocardial motion in color layers on a single end-systolic 2-dimensional echocardiographic frame. Previous work using this method is promising for quantitation of regional function, but there is limited experience in patients with severely reduced left ventricular function. Twenty patients (age 59 +/- 10 years) with dilated cardiomyopathy (left ventricular ejection fraction 22 +/- 8%) underwent CK imaging. Endocardial motion was quantitated by measuring the distance of endocardial motion during the systolic interval and also by calculating the endocardial velocity. CK measurements were compared among 4 wall motion grades (i.e., normal, hypokinetic, akinetic, and dyskinetic) assessed by qualitative wall motion scoring. There was a significant overall difference (p < 0.0001) in the mean systolic endocardial inward motion (i.e., contraction) and outward motion (i.e., expansion) among wall motion grades. The mean endocardial outward distance was significantly greater for the dyskinetic segments than for the other grades (p < 0.001). There were also differences in the mean velocity of endocardial motion among the wall motion grades. In the presence of left bundle branch block, there was no difference in the mean endocardial inward distance of the hypokinetic, akinetic, and dyskinetic septal segments. We conclude that in the absence of left bundle branch block, normal, hypokinetic, akinetic, and dyskinetic ventricular wall segments may be distinguished in patients with dilated cardiomyopathy on the basis of endocardial motion measured with CK.

Comparison of echocardiographic acoustic quantification system and radionuclide ventriculography for estimating left ventricular ejection fraction: validation in patients without regional wall motion abnormalities

Echocardiographic automated border detection of blood-endocardium interface is made on the basis of the principle of acoustic quantification. The automated border system is capable of providing on-line left ventricular (LV) cavity area and function. Recently, ABD algorithms have been devised to estimate LV volume on line from a long-axis image, calculated by established area-length method or Simpson's formula. To test the clinical validity of this newly developed echocardiographic method, LV volumes and ejection fraction measured by real-time acoustic quantification were compared with radionuclide ejection fraction in 24 subjects on the same day. Patients were included in the study if > or = 75% of their endocardium was visualized with conventional two-dimensional echocardiography. Sixteen (66%) of 24 patients had a technically adequate conventional echocardiogram with a broad range of ventricular dimensions and systolic function. None of the study patients had regional wall motion abnormalities. Echocardiographic measurements were obtained from the LV apical four-chamber, long-axis view. Ejection fraction, determined by the acoustic quantification and by radionuclide ventriculography, showed a strong linear relation (r = 0.92, standard error of the estimate = 4.4, p < 0.05). However, acoustic quantification overestimated the radionuclide ejection fraction with rather wide limits of agreement (3.8% +/- 16.4%; bias +/- 2 SD). Thus echocardiographic automated border detection technique is a reasonably accurate method for on-line assessment of LV function.

Reproducibility of left ventricular size, shape and mass with echocardiography, magnetic resonance imaging and radionuclide angiography in patients with anterior wall infarction. A plea for core laboratories

After myocardial infarction, left ventricular volume and ejection fraction can be assessed by echocardiography, magnetic resonance imaging and radionuclide angiography to guide therapy and determine prognosis. Whether a measured parameter gives the same results irrespective of the method used and the observer who performs the analysis is only partly known. Intra-observer and inter-observer variability were determined for echo and magnetic resonance imaging. Left ventricular ejection fraction measured by these techniques was related to radionuclide angiograms performed in the same period. Intra-observer variability for both echo and MRI was low and in most instances below 5%. Inter-observer variability for the echo and MRI measurements were substantially higher than intra-observer variability. Comparison of the three imaging modalities revealed systematic differences. Therefore, in clinical studies, left ventricular volume and function parameters have to be measured with the same technique and by the same observer in qualified core laboratories.

Transesophageal echocardiography: an objective tool in defining maximum ventricular response to intravenous fluid therapy

Ventricular preload is an important determinant of cardiac function, which is indirectly measured in the clinical setting by the pulmonary capillary wedge pressure (PCWP). Transesophageal echocardiography (TEE) is rapidly gaining acceptance as a monitor of cardiac function. Although it provides high-resolution images of cardiac structures, clinical assessment of ventricular preload using TEE has been subjective, since quantitative measurements have been difficult to perform in a timely fashion. Automated border detection (ABD) is a new technology used in conjunction with TEE that allows quantitative real-time, two-dimensional measurement of cavity areas. To determine whether enddiastolic area (EDA) measured by ABD can be used to determine an appropriate end point for intravenous fluid administration, nine mongrel dogs were studied. Anesthetized animals were hemorrhaged to achieve a central venous pressure of 0-5 mm Hg. Each animal was then given intravenous fluid (autologous blood followed by hetastarch) until a peak in thermodilution cardiac output (CO) was achieved. Measures of PCWP, EDA, CO, and left ventricular stroke work (LVSW) were obtained after each fluid bolus. Bivariate plots displaying administered volume versus CO, LVSW, and EDA revealed parallel curves for each of these variables with peaks evident at cumulative volumes of 50-55 mL/kg. Multiple regression with mixed model analysis of covariance was performed to determine the significance of EDA in relation to changes in CO and LVSW. Analysis was likewise performed comparing the relationship between PCWP and changes in CO or LVSW. A significant relationship was demonstrated when comparing EDA to changes in CO and LVSW (P = 0.03 and P < 0.0001, respectively). Similar analysis comparing PCWP to changes in CO and LVSW failed to demonstrate a significant relationship (P = 0.54 and P = 0.36, respectively). These data suggest that changes in EDA measured using TEE with ABD are related to trends in cardiac function and can suggest an appropriate end point for intravenous fluid administration as defined by maximum CO and LVSW. PCWP did not demonstrate a significant relationship to changes in CO and LVSW.

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.

Creation of a one-way interatrial communication in the treatment of critical pulmonary stenosis with intact ventricular septum: a case report

BACKGROUND

In biventricular repair of pulmonary outflow tract obstruction with intact ventricular septum, the right ventricle is loaded with total pulmonary blood flow acutely as the right-to-left shunt is abolished by closure of the atrial septal defect (ASD).

METHODS

We designed a one-way interatrial communication by creation of an atrial septal flap to reduce the excessive volume load of the right ventricle.

RESULTS

This procedure was successfully performed in a 3-year-old girl undergoing definitive biventricular repair for critical pulmonary stenosis associated with tricuspid stenosis and a small right ventricle.

CONCLUSIONS

We believe that creation of a one-way interatrial communication might be a good alternative to adjustable ASD and/or bidirectional Glenn shunt in biventricular repair of critical pulmonary stenosis or pulmonary atresia with intact ventricular septum.

Automatic backscatter analysis of regional left ventricular systolic function using color kinesis

Assessment of regional wall motion by 2-dimensional echocardiography can be performed by either semiquantitative wall motion scoring or by quantitative analysis. The former is subjective and requires expertise. Quantitative methods are too time-consuming for routine use in a busy clinical laboratory. Color kinesis is a new algorithm utilizing acoustic backscatter analysis. It provides a color encoded map of endocardial motion in real time. In each frame a new color layer is added; the thickness of the color beam represents endocardial motion during that frame. The end-systolic image has multiple color layers, representing regional and temporal heterogeneity of segmental motion. The purpose of this study was to validate the use of color kinesis for semiquantitative analysis of regional left ventricular systolic function and quantitatively in measurement of endocardial excursion. Semiquantitative wall motion scoring was performed in 18 patients using both 2-dimensional echo and color kinesis. Scoring was identical in 74% of segments; there was 84% agreement in definition of normal vs. abnormal. There was less interobserver variability in wall motion scoring using color kinesis. Endocardial excursion was quantified in 21 patients. 70% of the imaged segments were suitable for analysis. Correlation between 2-dimensional echocardiographic measurements and color kinesis was excellent, r = 0.87. The mean difference in excursion as measured by the 2 methods was -0.05 +/- 2.0 mm. In conclusion, color kinesis is a useful method for assessing regional contraction by displaying a color map of systolic endocardial excursion. This algorithm may improve the confidence and accuracy of assessment of segmental ventricular function by echocardiographic methods.

Beat-to-beat variability of left ventricular indexes measured by acoustic quantification: influence of heart rate and respiration--correlation with M-mode echocardiography

Influence of heart rate and respiration on beat-to-beat variability of left ventricular indexes measured by acoustic quantification was examined. These indexes were correlated with their counterparts measured by M-mode echocardiography. Parameters of left ventricular performance were recorded for 1 full minute in 43 children with a mean age of 5.9 +/- 3.9 years. Beat-to-beat variability was documented. The effect of respiration on such variability was examined in another 10 subjects. A wide range of heart rates and respiration did not show significant influence on the degree of variance among these parameters. The indexes measured correlated well with their counterparts measured by M-mode echocardiography. Acoustic quantification separated those with normal from those with abnormal left ventricular function with the same statistical significance as did M-mode echocardiography. A moderate degree of beat-to-beat variability occurs in acoustic quantification-derived left ventricular indexes. Heart rate variability and respiration do not influence the beat-to-beat variance of parameters of left ventricular performance measured with the acoustic quantification. Excellent correlation was documented between this technique and M-mode echocardiography.

Automatic identification of papillary muscles in left-ventricular short-axis echocardiographic images

An automatic method for identifying the location of the papillary muscles in two-dimensional (2-D) short-axis echocardiographic images is described. The technique uses both spatial and temporal information to identify the presence and track the location of the muscles in the left ventricle from end-diastole to end-systole. The three main steps of the method are spatial preprocessing, spatial processing, and temporal processing. The spatial preprocessing step includes a region of search estimation. The spatial processing step includes a papillary muscle existence test and an initial approximation of the papillary muscle points. The temporal processing includes motion-pattern evaluation and final papillary muscle location. The estimates of existence and position for the automatic method were compared with estimates made by an independent expert observer. Two hundred and ten frames, three taken from each of 70 image sequences, were evaluated. Since two regions of search were processed for each frame (one for the posterior-inferior and one for the anterior-lateral papillary muscle), a total of 420 approximations were made. Of this total, 340 automatic estimates were judged to be in close agreement with estimates made by the expert. Of the remaining 80 approximations, 54 estimates were made by the expert when the computer determined that no papillary muscle was present, 17 estimates provided poor results, and nine estimates were made by the computer when the observer concluded that no papillary muscle was present.

Mitral annular descent velocity by tissue Doppler echocardiography as an index of global left ventricular function

Mitral annular descent has been described as an index of left ventricular (LV) systolic function, which is independent of endocardial definition. Echocardiographic tissue Doppler imaging is a new technique that calculates and displays color-coded cardiac tissue velocities on-line. To evaluate mitral annular descent velocity as a rapid index of global LV function, we performed tissue Doppler imaging studies in 55 patients, aged 56 +/-15 years, within 3 hours of radionuclide ventriculographic ejection fraction. Tissue Doppler M-mode studies were obtained from each of 6 mitral annular sites, as follows: inferoseptal and lateral from apical 4-chamber views, anterior and inferior from apical 2-chamber views, and anteroseptal and posterior from apical long-axis views. Only 1 patient with severe mitral annular calcification was excluded. The group mean 6-site average peak mitral annular descent velocity was 5.5 +/- 1.9 cm/s (range 2.4 to 10.5), and the group mean ejection fraction was 49 +/- 18% (range 17 to 80%). The 6-site average peak annular descent velocity correlated linearly with LV ejection fraction (r = 0.86, SEE = 1.02 cm/s): LV ejection fraction = 8.2 (average peak mitral annular descent velocity) + 3%. The 6-site peak mitral annular descent velocity average >5.4 cm/s was 88% sensitive and 97% specific for ejection fraction >50%. The peak mitral annular descent velocity from the apical 4-chamber view (average from inferoseptal and lateral sites) correlated most closely with the LV ejection fraction (r = 0.85) as an individual view. Peak mitral annular descent velocity by tissue Doppler imaging has the potential to estimate rapidly the global LV function.

Stress echocardiography, contrast echocardiography, and tissue characterization: applications for the future

During the last three decades the application of ultrasonography has expanded rapidly. The information available to the clinician from ultrasound imaging today is vastly more significant than it was in the early years of the development of this technology. In addition to automatic information, there is an increasing potential to provide functional, dynamic perfusion and even cellular information about the heart. This article attempts to summarize briefly the advances in these areas.

Automatic border detection and three-dimensional reconstruction with echocardiography

This article reviews two important innovations in echocardiography resulting from the recent advances in the capabilities of microprocessors. The first, automatic endocardial border detection, has been implemented on computers contained entirely within echocardiograph machines and is gaining wide clinical use. The second, three-dimensional imaging, is currently under intense investigation and shows great promise for clinical application. It requires, however, further development of the specialized transducer apparatus necessary for image acquisition and the sophisticated computer-processing capability necessary for image reconstruction and display.

Assessment of left ventricular function and hemodynamics with transesophageal echocardiography

Transesophageal echocardiography (TEE) plays an important role in the evaluation of left ventricular function and hemodynamics in the critical care setting. The technique provides immediate data regarding regional myocardial ischemia, global ventricular function, volume, and the presence of cardiac tamponade. This article outlines the role of TEE in the evaluation of left ventricular function in the intensive care unit and presents practical information for the use of TEE in evaluating systolic function, diastolic function, and cardiac tamponade.

Assessment of diastolic left ventricular filling by echocardiographic automated border detection and comparison with radionuclide ventriculography

To determine whether indexes obtained from a newly developed echocardiographic automated border detection (ABD) technology provide a reliable estimate of left ventricular (LV) diastolic filling, ABD variables of LV filling were compared with volumetric measurements determined by radionuclide angiography. Forty-two patients with a variety of heart diseases (age range, 11 to 76 years) underwent ABD echocardiographic studies on the same day as the radionuclide examination. Technically adequate ABD data could be obtained in 31 patients (74%). Nineteen healthy subjects served as normal controls. Area-time and volume-time waveforms for echocardiographic measurements were obtained from LV short-axis views at the level of the papillary muscles and four-chamber apical views. Both the diastolic indexes derived from the waveform of area change (short-axis view) and volume change (four-chamber apical view) correlated with radionuclide variables. Values measured from the ABD area-time waveform showed the following correlations: peak filling rate (r = 0.86; standard error of the estimate [SEE] = 0.62), time to peak filling rate (r = 0.85; SEE = 23.11), rapid filling phase fractional change (r = 0.79; SEE = 5.51), and atrial filling phase fractional change (r = 0.71; SEE = 5.82). Correlations of indexes derived from the ABD volume-time waveform were as follows: peak filling rate (r = 0.87; SEE = 0.50), time to peak filling rate (r = 0.90; SEE = 22.03), rapid filling fractional change (r = 0.83; SEE = 5.33), and atrial filling fractional change (r = 0.77; SEE = 4.68). ABD LV filling parameters in patients with heart disease and normal control subjects were significantly different. Thus ABD data from short-axis and apical views have a strong linear relation with radionuclide ventriculographic measurements and may be used as a method to assess LV diastolic filling.

Left ventricular pressure-volume relations with transesophageal echocardiographic automated border detection: comparison with conductance-catheter technique

Pressure-volume relations are important means used to assess left ventricular (LV) contractility; however, on-line volume acquisition has been limited to the invasive conductance catheter. The objective was to compare simultaneous measures of LV volume by transesophageal echocardiographic automated border detection (ABD) and conductance catheter and their respective pressure-volume relations during steady state and alterations in preload and contractility. Seven dogs had placement of high-fidelity pressure and conductance catheters, a vena caval balloon occluder, and a transesophageal probe. An automated Simpson's rule volume algorithm was used from the transverse four-chamber view. Inotropic modulation was induced with dobutamine in four dogs and propranolol in three. Relative changes in ABD volume were linearly related to conductance volume at steady state with group mean r = 0.93 +/- 0.03, standard error of estimate (SEE) = 10 +/- 2%. Changes in end-diastolic volume, end-systolic volume, and stroke work with caval occlusion were also significantly correlated:r = 0.93 =/- 0.04, SEE = 3.6 ml; r = 0.89 +/- 0.04, SEE = 3.8 +/- 1.9 ml; and r = 0.86 +/- 0.05, SEE = 40 +/- 21 mJ, respectively. The overall bias was for absolute ABD volume to be less. End-systolic and maximal elastance values by ABD were significantly higher than by the conductance method; baseline group average 4.97 +/- 0.92 mm Hg/ml versus 2.70 +/- 1.15 mm Hg/ml and 6.63 +/- 1.66 mm Hg/ml versus 3.20 +/- 1.37 mm Hg/ml (p<0.05), respectively. However, the direction and relative magnitude of changes in elastance with inotropic modulation were similar.

Quantitative three-dimensional reconstruction of left ventricular volume with complete borders detected by acoustic quantification underestimates volume

Recently a new acoustic-quantification (AQ) technique has been developed to provide on-line automated border detection with an integrated backscatter analysis. Prior studies have largely correlated AQ areas with volumes without direct comparison of volumes for agreement. By using complete AQ-detected borders as the input to a validated method for three-dimensional echocardiographic (3DE) reconstruction, we can compare an entire cavity volume measured with the aid of AQ against a directly measured volume. This would also explore the possibility of applying AQ to 3DE reconstruction to reduce tracing time and enhance routine applicability. To compare reconstructed volumes with actual values in a stable standard allowing direct volume measurement, the left ventricles of 13 excised animal hearts were studied with a 3DE system that automatically combines two-dimensional (2D) images and their locations. Intersecting 2D views were obtained with conventional scanning and AQ imaging, with gains optimized to permit 3D reconstruction by detecting the most continuous AQ borders for each view, with maximal cavity size. Reconstruction was performed with manually traced central endocardial reflections and AQ-detected borders visually reproduced the left ventricular shapes; the AQ reconstructions, however, were consistently smaller. The reconstructed left ventricular (LV) volumes correlated well with actual values by both manual and AQ techniques (r = 0.93 and 0.88, with standard errors of 2.3 cc and 2.0 cc, p = not significant [NS]). Agreement with actual values was relatively close for the manually traced borders (y = 0.93x + 0.68, mean difference = -0.8 +/-2.2 cc). AQ-derived reconstructions consistently underestimated LV volume by 39 +/- 10% (y = 0.62x-0.09, mean difference = -7.8 +/- 3.0 cc, different from manually traced and actual volumes by analysis of variance [ANOVA], F = 69, p<0.00001). The AQ-detected threshold signal was displaced into the cavity, and volume between walls and false tendons was excluded, leading to underestimation, which increased with increasing cavity volume (r = 0.76). The AQ technique can therefore be applied to 3DE reconstruction, providing volumes that correlate well with directly measured values in a stable in vitro standard, minimizing observer decisions regarding manual border placement after image acquisition. However, when the complete borders needed for 3D reconstruction are used, absolute volumes are underestimated with current algorithms that integrate backscatter and displace the detected threshold into the ventricular cavity.

Automatic Border Detection to Assess Right Ventricular Function Following Surgical Treatment of Thromboembolic Pulmonary Hypertension

Automatic border detection (ABD) has been developed as a potentially useful means for evaluating ventricular function on line in an automatic fashion. Its success with tracking left ventricular function is established, but little is known about its ability to assess right ventricular (RV) function. Accordingly, 20 patients with severe pulmonary hypertension due to chronic thromboembolic disease underwent standard two-dimensional echocardiography and imaging with ABD before and after pulmonary thromboendarterectomy to correct pulmonary hypertension. ABD-derived results were compared to manually planimetered RV areas calculated from the apical four-chamber view. Doppler tricuspid regurgitant velocity fell significantly with surgery from 4.4 +/- 0.6 to 2.9 +/- 0.7 m/sec (P < 0.001). The mean values for RV areas derived by manual planimetry and ABD were similar, as was fractional area shortening, which improved significantly with surgery (manual 0.24 +/- 0.01 preoperative vs 0.31 +/- 0.11 postoperative, P < 0.05; and ABD 0.19 +/- 0.05 preoperative vs 0.32 +/- 0.15 postoperative, P < 0.001). There was, however, very little correlation between the individual values for ABD versus manually derived RV areas and fractional area shortening, with the best correlation being the RV end-diastolic areas after surgery (y = 0.684x + 7.9, r = 0.564, P = 0.01). These results demonstrate that both manually planimetered RV areas and those determined by ABD can adequately follow changes in ventricular function over time. However, variability within each technique may prevent direct comparison of the absolute values of the two techniques. (ECHOCARDIOGRAPHY, Volume 13, March 1996)

A multiple active contour model for cardiac boundary detection on echocardiographic sequences

Tracing of left-ventricular epicardial and endocardial borders on echocardiographic sequences is essential for quantification of cardiac function. The authors designed a method based on an extension of active contour models to detect both epicardial and endocardial borders on short-axis cardiac sequences spanning the entire cardiac cycle. They validated the results by comparing the computer-generated boundaries to the boundaries manually outlined by four expert observers on 44 clinical data sets. The mean boundary distance between the computer-generated boundaries and the manually outlined boundaries was 2.80 mm (sigma=1.28 mm) for the epicardium and 3.61 (sigma=1.68 mm) for the endocardium. These distances were comparable to interobserver distances, which had a mean of 3.79 mm (sigma=1.53 mm) for epicardial borders and 2.67 mm (sigma=0.88 mm) for endocardial borders. The correlation coefficient between the areas enclosed by the computer-generated boundaries and the average manually outlined boundaries was 0.95 for epicardium and 0.91 for endocardium. The algorithm is fairly insensitive to the choice of the initial curve. Thus, the authors have developed an effective and robust algorithm to extract left-ventricular boundaries from echocardiographic sequences.

Hemodynamic effects of pyruvate infusion in dogs

PURPOSE

Although pyruvate supplementation enhances endurance in humans and increases cardiac output in dogs, its effects on cardiac and peripheral vascular function are not known. Thus, we assessed the cardiovascular effects of pyruvate infusion.

MATERIALS AND METHODS

Aortic, left ventricular (LV), and pulmonary (Ppa) pressures and LV stroke volume (Svlv; derived from aortic flow probe) were measured after thoracotomy in eight anesthetized dogs. LV area or volume changes were measured using either an epicardial echocardiography (n = 6) or a conductance catheter (n = 2). LV end-systolic elastance (Eeslv) and preload recruitable stroke force (PRSFlv) relations, as estimates of contractility, were generated by transient inferior vena cava occlusion. Simultaneous stroke volume to arterial pressure relations during the occlusions were used to measure arterial elastance (Ea), and steady-state systemic and pulmonary vascular resistances were used as measures of arterial tone. Graded doses of pyruvate (8, 16, and 32 mg/kg/min), dobutamine (positive control) and propranolol (negative control) and placebo (volume control) were sequentially given.

RESULTS

Dobutamine increased Eeslv, PRSFlv, whereas propranolol had the opposite effect on Eeslv and PRSFlv. Pyruvate at 32 mg/kg/min increased heart rate, Ppa, and SVlv and decreased LV end-diastolic area, and systemic vascular resistance without changing arterial pressure, Eeslv, PRSFlv, or Ea.

CONCLUSIONS

We conclude that pyruvate infusion in normal dogs induces venodilation but does not alter either cardiac contractility or arterial tone.

Left atrial size and function: assessment using echocardiographic automatic boundary detection

OBJECTIVE

To evaluate the waveforms of left atrial area changes obtained by automated boundary detection with newly developed acoustic quantification technology.

DESIGN

All subjects had measurements of left atrial areas taken in the apical four chamber, parasternal long axis, and parasternal short axis views using both conventional echocardiographic methods and automatic boundary detection on two occasions separated by at least a week. On the second visit measurements were also repeated in healthy volunteers after acute intravenous volume loading with 1 litre of saline over 2-5 minutes.

SETTING

A university medical school echocardiographic laboratory.

SUBJECTS

12 healthy male volunteers and 8 patients with cardiac disease (5 with congestive heart failure, 1 with mitral stenosis, and 2 with hypertensive left ventricular hypertrophy, and dilated left atria).

RESULTS

There was close correlation between conventionally derived left atrial areas and those obtained by automatic boundary detection, particularly in the apical four chamber view (r = 0.98). Both inter and intra observer variabilities (coefficient of variation) for left atrial areas measured by automatic boundary detection were good (4.7-14.2% and 8.1-18.6% respectively). The reproducibility (coefficient of variation) for derived indices of left atrial function, however, was much poorer (10.4-104.8% and 12.5-88% respectively). After acute volume loading significant increases in left atrial area were observed at all stages in the cardiac cycle.

CONCLUSIONS

These data demonstrate that although the reproducibility of left atrial functional indices is poor, instantaneous left atrial cavity measurements with automatic boundary detection are reproducible. This suggests that automatic boundary detection may assist in serial non-invasive measurement of left atrial size to assess disease states and treatments.

The clinical utility of automatic boundary detection for the determination of left ventricular volume: a comparison with conventional off-line echocardiographic quantification

The aim of this study was to compare measurements of echocardiographic volume with an on-line automatic boundary detection imaging system with those of a conventional off-line method for routine clinical studies. Automatic boundary detection imaging shows promise as a rapid, on-line method for quantitating left ventricular volumes by echocardiography. However, there is little information about the role of automatic boundary detection for routine clinical studies. Ninety-seven patients with a variety of clinical diseases who were referred for clinical transthoracic echocardiographic evaluation were studied in apical four-chamber and two-chamber imaging planes. End-diastolic volume, end-systolic volume, and ejection fraction obtained with automatic boundary detection images were compared with those of conventional off-line analysis. Segmental endocardial definition and border tracking were evaluated on all automatic boundary detection images. Left ventricular end-diastolic volumes obtained by automatic boundary detection correlated well but were systematically under-estimated compared with off-line analysis for the apical two-chamber (r = 0.83; underestimation = 42 +/- 33 ml; p < 0.05) and four-chamber views (r = 0.83; underestimation = 43 +/- 31 ml; p < 0.05). Left ventricular end-systolic volumes also correlated well but were underestimated by automatic boundary detection for the apical two-chamber (r = 0.83; underestimation = 14 +/- 26 ml; p < 0.05) and four-chamber views (r = 0.83; underestimation = 18 +/- 24 ml; p < 0.05). Ejection fraction was not predicted accurately for the entire study population (n = 97). However, for patients with complete endocardial definition (n = 32), automatic boundary detection accurately predicted ejection fraction with no systematic error compared with manually traced images for both the apical two-chamber (r = 0.86; p < 0.05) and four-chamber (r = 0.82; p < 0.05) views. Segmental analysis of endocardial tracking revealed significantly better tracking of the septal and lateral walls compared with other regions (p < 0.05). End-diastolic and end-systolic volumes determined by automatic boundary detection correlate well but underestimate volume compared with conventional off-line analysis. However, ejection fraction compares favorably for the two methods when there is complete endocardial definition.

The assessment of left ventricular filling dynamics using an online automatic border detection algorithm: comparison with cineventriculography

An echocardiographic system has been developed that performs automatic endocardial border detection and instantaneously calculates and displays a waveform of left ventricular cavity area versus time. The purpose of this study was to compare measurements of left ventricular filling dynamics from automatic border detection echocardiography with similar measurements from cineventriculography. Thirty-three patients undergoing cardiac catheterization had automatic border detection echocardiography performed within 45 minutes of cineventriculography. Ten patients had normal catheterization findings and 23 had cardiac disease. The automatic border detection waveforms generated from two echocardiographic views were measured to determine the fraction of filling occurring during the early diastolic rapid filling phase and during the filling phase resulting from atrial contraction. Similar fractions were derived from curves generated from frame-by-frame measurements of cineangiographic volumes. Results were analyzed by correlating echocardiographic and cineventriculographic results, and by a limits of agreement analysis (limits of agreement were +/- 2 standard deviations of the mean difference between echocardiography and cineventriculography). There were significant correlations between echocardiography and cineventriculography for each of the parameters studied. The best results were obtained for the apical four-chamber view (rapid filling fraction r = 0.72, P < 0.0001, atrial filling fraction r = 0.56, P < 0.001). Differences in filling patterns between normal and abnormal patient groups detected by cineventriculography were also detected by automatic border detection echocardiography. However, broad limits of agreement were observed, that may limit the ability of the automatic border detection system to reliably predict cineventriculographic results in an individual patient. Automatic border detection echocardiography can provide information about left ventricular filling dynamics that is similar to that obtained from frame-by-frame analysis of cineventriculograms. However, the variability in the results may limit the application of the technique in individual patients.

Changes in electrocardiographic morphology reflect instantaneous changes in left ventricular volume and output in cardiac surgery patients

We examined the relation between changes in R-to-T wave amplitude ratios (R:T) and left ventricular (LV) performance as cardiac output was rapidly varied by inferior vena caval occlusion in 6 subjects prior to cardiopulmonary bypass. To assess the influence of contractility, paired studies before and after bypass were performed in 4 subjects. Stroke volume and cardiac output were assessed by aortic flow probe, and transesophageal echocardiographic LV area measures using the automated border-detection method were used to give LV stroke area, stroke force, maximal LV area, fractional area change, end-systolic elastance, and preload recruitable stroke force. Data were collected on computer and analyzed by linear regression. Significant changes in R:T and measured LV variables during the inferior vena caval occlusion were stroke volume (r = 0.81), LV stroke area (r = 0.77), LV stroke force (r = 0.81), maximal LV area (r = 0.78), and cardiac output (r = 0.80). However, R:T varied inconsistently in relation to fractional area change. After cardiopulmonary bypass, the linear relation between R:T with LV stroke force, LV stroke volume, and maximal LV area persisted, but at a lesser slope. Although absolute pre-inferior vena caval occlusion R:T did not correlate with end-systolic elastance or preload recruitable stroke force, the change in the slope of these linear relations correlated well with the change in end-systolic elastance after surgery (r = 0.92). Instantaneous changes in electrocardiographic morphology reflect changes in LV preload-dependent variables, whereas long-term changes in electrocardiographic morphology may also reflect changes in contractile state.

Pitfalls in creation of left atrial pressure-area relationships with automated border detection

Creation of pressure-area relationships (loops) with automated border detection (ABD) involves correction for the variable inherent delay in the ABD signal relative to the pressure recording. This article summarizes (1) the results of in vitro experiments performed to define the range of, and factors that might influence, the ABD delay; (2) the difficulties encountered in evaluating a thin-walled structure like the left atrium in the dog model; and (3) the solutions to some of the difficulties found. The in vitro experiments showed that the ABD delay relative to high-fidelity pressure recordings ranges from 20 to 34 msec and 35 to 57 msec at echocardiographic frame rates of 60/sec and 33/sec, respectively. The delay was not influenced significantly by the type of transducer used, distance from the target area, or size of the target area. The delay in the ABD signal, relative to the echocardiographic image, ranges from nil to less than one frame duration, whereas it is delayed one to two frame durations relative to the electrocardiogram processed by the imaging system. In the dog model, inclusion of even small areas outside the left atrium rendered curves with apparent physiologic contour but inappropriately long delays of 90 to 130 msec. To exclude areas outside the left atrial cavity, time-gain compensation and lateral gain compensation were used much more extensively than during left ventricular ABD recording. By changing the type of sonomicrometers used in our experiments, we were able to record simultaneously ABD and ultrasonic crystal data. However, both spontaneous contrast originating from a right-sided heart bypass pump and electronic noise from the eletrocautery severely interferred with ABD recording.

Reproducibility of quantitative pediatric transesophageal echocardiography

Transesophageal echocardiography (TEE) is commonly used to monitor cardiac function and to assess cavitary size. For the interpretation of quantitative echocardiographic data, the degree of their reproducibility should be considered. The variability of quantitative TEE was evaluated in this study. To assess intraobserver, beat-to-beat, interobserver, and repositioning variability, TEE examinations of 46 patients with congenital heart defects were analyzed. The mean beat-to-beat variability of 8.5% (range 4.2% to 12.3%) exceeded the mean intraobserver variability of 4.9% (1.9% to 8.1%). The mean interobserver difference between two observers was 3.4% (0.2% to 11.9%). Differences in image acquisition caused by repositioning of the transesophageal probe contributed the most (6.4% to 13.3%; mean 10.5%) to the variability of two-dimensional TEE. Changes seen on TEE studies should be interpreted as abnormal only when they exceed the total variability of this method.

Structural and left ventricular histologic changes after implantable LVAD insertion

Long-term support on the implantable left ventricular assist device (LVAD) produces structural changes in the recipient's heart. To assess the possibility of heart "recovery" we reviewed the records of 19 HeartMate LVAD recipients to determine structural and left ventricular histologic changes during LVAD support. Intraoperative transesophageal echocardiographic studies were performed in the operating room before LVAD insertion, immediately after LVAD insertion, and at explantation and heart transplantation (mean duration of support, 76 +/- 34 days). The initiation of LVAD pumping led to an immediate decrease (p < 0.001) in left ventricular dimensions, which were not significantly different by the time of device explantation. Left ventricular fractional shortening did not significantly improve during LVAD support (0.07 +/- 0.03 before LVAD; 0.11 +/- 0.10 immediately after LVAD; 0.11 +/- 0.11 before explantation). Histologic specimens showed a significant reduction in the number of wavy fibers, and contraction band necrosis (p < 0.01), both markers of acute myocyte damage. However, myocardial fibrosis increased (p < 0.05). Myocyte diameter increased slightly (p = 0.07). We conclude that implantable LVAD support is associated with immediate changes in ventricular structure. Histologic markers of acute myocyte damage improve, but fibrosis increases. Because the structural changes occur immediately, they do not indicate "recovery" of left ventricular function, but merely changes in loading conditions.

Echocardiographic automatic boundary detection to measure left atrial function after the maze procedure

Automatic boundary detection (ABD) is a new echocardiographic modality providing continuous on-line measurements of cavitary area throughout the cardiac cycle. The maze procedure is a new surgical intervention designed to restore sinus rhythm and mechanical atrial contraction as a definitive treatment for patients with atrial fibrillations for whom medical therapy has failed. To evaluate whether ABD may define left atrial function in patients after the maze procedure, we obtained pulsed Doppler recordings of mitral inflow velocity and echocardiographic ABD in 25 patients, 6 +/- 2 months after the maze procedure. We measured the left atrial end-systolic cavitary area, mid-diastolic area before atrial contraction, and end-diastolic area (in square centimeters). Left atrial contraction by Doppler was compared with that derived by ABD in patients who underwent the maze procedure and control subjects (n = 13), both qualitatively and quantitatively (atrial filling fraction vs active atrial contraction [ABD] where atrial contraction (in percent) = (mid-diastolic area - end-diastolic area) x 100/(end-systolic area - end-diastolic area in percent]). Restoration of atrial contraction after the maze procedure was detected by Doppler in 19 patients (76%) and by ABD in 21 patients (84%). The atrial filling fraction was 19 +/- 4% in patients compared with values of 34% +/- 8% in control subjects (p < 0.001). By ABD atrial contraction was 20% +/- 6% in patients whereas control subjects exhibited values of 41% +/- 14% p < 0.001). The Doppler-derived atrial filling fraction and ABD-derived atrial contraction were closely correlated (r = 0.91; p < 0.001; y = 0.59x + 8.6). Thus Doppler techniques complemented by ABD provide direct quantitative indexes of left atrial function throughout the cardiac cycle. Although left atrial contraction and filling are reduced after the maze procedure, left atrial function is restored in most patients with a history of atrial fibrillation, and echocardiographic ABD is a sensitive technique for its detection.