Acoustic Quantification Research Articles

Assessment of left ventricular diastolic filling in arterial hypertension: Comparison of pulsed doppler echocardiography and acoustic quantification

We compared acoustic quantification (AQ) to Doppler echocardiography (DE) in the evaluation of left ventricular (LV) diastolic filling in 41 hypertensives and 42 controls. In hypertensives, DE showed reduced ratios of early to late diastolic velocity, AQ revealed reduced peak to late filling rate ratios, and both techniques found prolonged acceleration times indicating abnormal filling. In 22 patients with mild hypertension and less LV hypertrophy, however, all DE filling parameters were normal. In these patients AQ indicated prolonged acceleration times and early filling times. In conclusion, AQ is useful for the identification of abnormal LV filling in arterial hypertension and might be superior to DE in detection of early diastolic dysfunction.

Acoustic quantification indexes of left ventricular size and function: Effects of signal averaging

Background: The aim of this study was to evaluate the clinical utility of using signal-averaged acoustic quantification (SAAQ) waveforms for improved assessment of left ventricular (LV) size and function. Methods and Results: Four separate protocols were performed in 47 subjects. SAAQ waveforms were used to assess alterations in LV function induced by dobutamine (15 μg/kg per minute) and esmolol (200 μg/kg per minute) in eight normal subjects. Subsequently, we analyzed SAAQ waveforms obtained in 12 patients with LV dysfunction secondary to dilated cardiomyopathy and 12 age-matched normal subjects. Finally, we developed computer software for monitoring of LV function on the basis of continuous acquisition and repeated analysis of SAAQ waveforms. We compared the interbeat variability in indexes of LV function obtained from raw AQ and SAAQ during 10 minutes of steady-state monitoring in eight patients undergoing transesophageal echocardiography. The feasibility of long-term monitoring in the intensive care setting was then studied in seven patients undergoing abdominal surgery. Our analysis tracked variations in LV function induced by dobutamine and esmolol. Significant differences in all measured indexes were found between normal subjects and patients with dilated cadiomyopathy. Signal averaging during steady-state monitoring significantly reduced the interbeat variability of all indexes (21% to 42%). In the operating room, the SAAQ monitoring system tracked hemodynamic changes in close agreement with invasive measurements. Conclusions: SAAQ allows fast and easy quantification of LV function and can track hemodynamic trends in the operating room setting. (J Am Soc Echocardiogr 1998;11:792-802.)

Evaluation of regional differences in right ventricular systolic function by acoustic quantification echocardiography and cine magnetic resonance imaging.

Accurate quantitative evaluation of right ventricular (RV) function has been limited by its complex structural geometry. Although embryological and anatomic observations suggest that the RV is composed of 2 distinct components, the RV sinus and infundibulum, most studies on RV dimensions and function viewed it as a single chamber. This study was designed to determine the volumes, relative contribution to global systolic function, and temporal course of contraction and relaxation of the RV sinus and infundibulum. Thirty-one individuals without heart disease (aged 1 month to 17 years, 16 boys and 15 girls) participated in this study. Instantaneous area over time, its derivatives, and the temporal course of contraction and relaxation were studied by acoustic quantification echocardiography and phonocardiography in 20 individuals. Global and regional RV volumes and ejection fraction were determined by cine MRI in 11 individuals. The RV sinus made up 81+/-6% of the combined RV end-diastolic volume and 87+/-4% of the combined stroke volume. The infundibulum accounted for the remaining 19+/-6% and 13+/-4%, respectively (P<0.0001). Compared with the infundibulum, the extent of RV sinus fiber shortening was significantly greater: for ejection fraction (56+/-11% versus 38+/-13%, P<0.001), fractional area change (42+/-14% versus 28+/-9%, P<0.0001), and dA/dt (27+/-17% versus 13+/-6%, P<0.0001). Analysis of temporal course of contraction and relaxation (expressed as percentage of the cardiac cycle to adjust for differences in heart rate) showed that the infundibulum follows the RV sinus: onset of contraction 53%+/-14 versus 19+/-11% of systole, time to peak systole 115+/-16% versus 97+/-19% (P< or =0.01), indicating a peristalsis-like pattern of contraction and relaxation. The results of this study demonstrate significant regional differences between the sinus and infundibulum components of the RV with regard to contribution to stroke volume, extent of fiber shortening, and sequence of mechanical activation. These data from normal individuals can be used in future research on RV function in pathological conditions.

Effects of balloon mitral valvuloplasty on left atrial function in mitral stenosis as assessed by pressure–area relation

Objectives. This study sought to investigate the changes induced on the pressure–area relation of the left atrium in patients with mitral stenosis after percutaneous balloon mitral valvuloplasty.Background. Left atrial (LA) function is influenced by changes in LA afterload. The latter is increased in mitral stenosis as a result of increased resistance to blood flow imposed by the stenotic mitral valve.Methods. We studied the effects of acute alterations of LA afterload induced by retrograde nontransseptal balloon mitral valvuloplasty (RNBMV) on LA function in patients with mitral stenosis. LA pressure–area relations were obtained in 15 patients with mitral stenosis (8 with sinus rhythm, 7 with atrial fibrillation) before and after valvuloplasty, as well as in 15 normal subjects. LA pressure was recorded by a catheter-tipped micromanometer introduced retrogradely into the left atrium while LA area was recorded simultaneously using acoustic quantification. The areas of the A and V loops of the pressure–area relation as well as the LA chamber stiffness constant were calculated.Results. Balloon valvuloplasty resulted in a significant increase in mitral valve area (p < 0.001) and a substantial reduction of the mean transmitral pressure gradient (p < 0.001) and mean LA pressure (p < 0.001). The area of the A loop in patients with sinus rhythm and the area of the V loop in those with atrial fibrillation increased significantly after completion of the procedure (p < 0.001). Furthermore, LA stiffness decreased in both groups.Conclusions. After RNBMV, there is a significant increase in LA pump function in patients with sinus rhythm, a significant increase in LA reservoir function in patients with atrial fibrillation and a significant reduction in LA stiffness in all patients. Marked alterations of the configuration of the LA pressure–area relation occur immediately after successful RNBMV in patients with mitral stenosis.

Assessment of left ventricular dyssynergy by color kinesis

Color kinesis is a new echocardiographic technique based on acoustic quantification. It has been developed to facilitate the ability to identify contraction abnormalities and has been incorporated into a commercialy available ultrasound imaging system. The potential of this technique to improve the qualitative and quantitative assessment of wall motion abnormalities is described. Evaluation of color-encoded images allows detection of decreased amplitude of endocardial motion in abnormally contracting segments as well as a shorter time of endocardial excursion in segments with severely decreased motion. Compared with off-line quantitative studies, color kinesis has the advantage to be used on-line, without time-consuming manual tracing of endocardial boundaries. In addition, a single end-systolic color image contains the entire picture of spatial and temporal contraction and can be digitally stored and retrieved. In patients with proven coronary artery disease, color kinesis had a sensitivity of 88%, a specificity of 77%, and an overall accuracy of 86% in identifying the presence of segmental dysfunction. The practical application of color kinesis might be to improve our ability to distinguish normal from hypokinesis, something that has always been difficult in clinical echocardiography. Segmental analysis of color kinesis images allows objective detection of dobutamine-induced regional wall motion abnormalities in agreement with conventional visual interpretation of the corresponding 2-dimensional views. A method for objective assessment of wall dynamics during dobutamine stress echocardiography would be of particular clinical value, because these images are even more difficult to interpret than conventional echocardiograms. Quantitative assessment of diastolic function may allow objective evaluation of segmental relaxation abnormalities, especially under conditions of pharmacologic stress testing. Acquisition of color kinesis images during dobutamine stress echocardiography, both transthoracic and transesophageal, may facilitate the assessment of hybernating but viable myocardium and enhance the sensitivity in the detection of coronary artery disease.

Quantitative Evaluation of Regional Left Ventriculur Function by Novel Echocardiographic Approaches

Echocardiographic methods to quantitate regional left ventricular function have been designed and validated, but currently they are tedious and time-consuming and therefore are impractical for routine clinical use. Several novel approaches have been proposed recently to improve the quantitative evaluation of regional left ventricular function. They employ new echocardiographic algorithms that facilitate the visual assessment and quantitation of both endocardial movement and myocardial contractility. The acoustic signal from endocardial borders can be detected automatically, and the temporal and spatial sequence of their movement can be tracked and color-coded. Acoustic quantification by ultrasound can also be applied to the study of myocardial function, thanks to the detection of cyclic variations of a quantitative acoustic parameter called integrated backscatter. These cyclic variations of integrated backscatter are an expression of intramyocardial contractility. Lastly, regional myocardial function can be quantified by the assessment of the velocity of myocardial contraction and relaxation using a modified Doppler algorithm. The present article presents a review oi novel modalities to quantitate regional left ventricular function by ultrasound. Technical characteristics, advantages, and limitations are presented, along with current clinical applications.

Automated Left Ventricular Endocardial Border Detection Using Acoustic Quantification in Children.

OBJECTIVES: The purpose of this study was to determine the reliability and accuracy of automated border detection using acoustic quantification in children. BACKGROUND: Acoustic quantification has shown promise in adult patients as a method for on-line estimation of left ventricular size and function. However, in children, the smaller ventricular size might magnify the importance of measurement error. METHODS: We compared the cross-sectional area and fractional area change of the left ventricle as measured on line by acoustic quantification with the area and fractional area change derived by hand-digitizing the endocardial border of the left ventricle off line, both with and without the papillary muscles included in the left ventricular cavity. RESULTS: The areas and area change fractions from the two methods were highly correlated, both with inclusion and exclusion of the papillary muscles for off-line analysis. However, the regression slope was closer to unity when the papillary muscles were excluded from the left ventricular cavity during off-line digitization of the endocardial border. Analysis of agreement between the two methods showed good agreement for area measurements and fair agreement for function measurements. The magnitude of the difference between the two methods for area measurement was directly proportional to the size of the ventricle. That is, the larger the ventricle the larger the difference between the area measurements by the two methods. DISCUSSION: Automatic border detection using acoustic quantification appears to be an acceptable method for estimating the cross-sectional area and fractional area change of the left ventricle in children.

Age Dependency of Left Ventricular and Left Atrial Diastolic Variables Assessed With Acoustic Quantification

Age Dependency of Left Ventricular and Left Atrial Diastolic Variables Assessed With Acoustic Quantification

Age dependency of left ventricular and left atrial diastolic variables assessed with acoustic quantification

Age dependency of left ventricular and left atrial diastolic variables assessed with acoustic quantification

Acoustic Quantification of Left Atrial Volumes: A Promising New Method for Stratification of Patients With Diastolic Dysfunction: Correlation to Mitral Doppler Flow Pattern

Acoustic Quantification of Left Atrial Volumes: A Promising New Method for Stratification of Patients With Diastolic Dysfunction: Correlation to Mitral Doppler Flow Pattern

Impact of presence of abnormal wall motion on echocardiographic determination of left ventricular function with automated boundary detection technique: re-evaluation.

It is still unclear whether echocardiography with an automated boundary detection technique (ABD) can accurately determine the left ventricular (LV) volume and function particularly in the presence of LV wall asynergy. We intended to re-evaluate the reliability and application of the ABD, which was based on the acoustic quantification technique (Sonos 2500, Hewlett Packard) for the LV volume measurement in patients without or with LV wall asynergy. A total of 80 patients (mean age 56 years) who underwent left ventriculography (LVG) were divided into two groups. The group A consisted of 29 patients with normal LV wall motion and the group B consisted of 51 patients with generalized or regional LV wall motion abnormality. In group A patients, the LV end-diastolic volume (LVEDV) was 96 +/- 25 ml by ABD and 112 +/- 33 ml by LVG and those of LV end-systolic volume (LVESV) were 44 +/- 14 ml by ABD and 48 +/- 17 ml by LVG, thus resulting in the underestimation of LV volume by 12% in average. Under these conditions, the LV ejection fraction (LVEF) by ABD, 54 +/- 8%, correlated well with that by LVG, 58 +/- 7%. Although underestimation of LV volume by 17% in average also occurred in groups B (N.S.), LVEF was found to correlate well with that by LVG; 27 +/- 8% vs 30 +/- 11% (r = 0.87, SEE = 3.1%) for 21 patients with the generalized LV asynergy; 39 +/- 10% vs 39 +/- 12% (r = 0.86. SEE = 3.3%) for 30 patients with the regional LV asynergy. These results demonstrate the feasibility of the ABD in determining the LVEF, although underestimation can occur in measuring the absolute LV volume in patients with or without LV asynergy.

Acoustic quantification of left atrial volumes: a promising new method for stratification of patients with diastolic dysfunction: correlation to mitral Doppler flow pattern

Acoustic quantification of left atrial volumes: a promising new method for stratification of patients with diastolic dysfunction: correlation to mitral Doppler flow pattern

Detection of left ventricular systolic and diastolic abnormalities in patients with coronary artery disease by color kinesis.

Color kinesis (CK) is a recently developed echocardiographic technique based on acoustic quantification that automatically tracks and displays endocardial motion in real time and has been used in initial studies to improve the evaluation of global and regional wall motion. For further validation of the use of CK for analysis of segmental ventricular dysfunction, we assessed its sensitivity and specificity for detection of regional systolic and diastolic wall motion abnormalities in patients with coronary artery disease (CAD). Two-dimensional (2-D) echocardiography and CK were used to study 15 normal subjects and 63 patients with technically good quality echocardiographic tracings, who underwent coronary arteriography within 1 month of echocardiography. Significant (> 70% luminal diameter stenosis) CAD was present in 50 patients (79%). Color kinesis tracked endocardial motion accurately in 93% of left ventricular segments. Wall motion score, systolic segmental endocardial motion (SEM), and the time of systolic SEM (tSEM) and diastolic (tDEM) segmental endocardial motion were calculated. Intra- and interobserver variability were within narrow limits. SEM and tSEM were significantly lower and tDEM was significantly higher in the patient population than in the control group (p < 0.001). Comparison between CK and 2-D echocardiography showed a correlation coefficient of 0.81 between the two techniques. The score was identically graded in 74% of segments, with concordance of 82% in diagnosing segments as abnormal. Interobserver concordance was 86% for CK (r = 0.85) and 81% for 2-D echocardiography (r = 0.80). The sensitivity and specificity of systolic and diastolic CK parameters for the detection of CAD were 88 and 92% and 77 and 85%, respectively. The positive predictive values were 93 and 96%, respectively, the negative predictive values were 63 and 73%, respectively, and the overall accuracy was 86 and 91%, respectively. Our data suggest that CK is a feasible and sensitive technique for identifying regional systolic as well as diastolic wall motion abnormalities in patients with CAD.

Objective echocardiographic evaluation of the cardiovascular system: state of the art.

For over a quarter of a century, echocardiography has made an unparalleled contribution to clinical cardiology as a major tool for real-time imaging of cardiac dynamics. Echocardiography is widely used to assess cardiac function and provides noninvasive information, which is invaluable for the diagnosis of various disease states. However, despite its numerous advantages echocardiography has remained mostly qualitative and subjective. The continued progress in our understanding of the interaction between ultrasound and tissue has brought about several new developments, which allow quantitative analysis of ultrasound data. Among these new developments are endocardial boundary detection (frequently referred to as acoustic quantification) and color kinesis, which provide a more objective, robust, and convenient evaluation of cardiac and vascular dynamics that embraces multiple clinical applications. This review describes these two techniques, focusing on their current status and the evolving clinical applications.

Validity of acoustic quantification colour kinesis for detection of left ventricular regional wall motion abnormalities: a transoesophageal echocardiographic study

Transoesophageal echocardiography is a sensitive monitor for intraoperative myocardial ischaemia. Colour kinesis is a new technology for echocardiographic assessment of regional wall motion based on acoustic quantification. We have examined the feasibility and accuracy of quantitative segmental analysis of colour kinesis images to provide objective evaluation of systolic regional wall motion during the perioperative period using transoesophageal echocardiography (TOE). Two-dimensional echocardiograms were obtained in the transgastric short-axis and long-axis views in 60 patients with coronary artery disease undergoing noncardiac surgery. End-systolic colour overlays superimposed on the grey scale images were obtained with colour kinesis to colour encode left ventricular endocardial motion throughout systole. These colour-encoded images were divided into segments and compared with corresponding conventional two-dimensional images. Six hundred of a potential 720 left ventricular wall segments were of sufficient resolution for grading by experts; they diagnosed wall motion abnormalities in 61 of these segments by a conventional method. In comparing the conventional TOE method with colour kinesis, there were 60 true positives, 482 true negatives, 57 false positives and 1 false negative result. This yielded a sensitivity of 98%, specificity of 89%, positive predictive value of 51% and negative predictive value of 100%. Translational and rotational movement of the heart and papillary muscle interference were common problems accounting for false positive diagnoses. We conclude that colour kinesis provides a basis for objective and on-line evaluation of left ventricular regional wall motion which is a sensitive but non-specific method. It may be a useful aid for the less experienced because it can potentially direct the anaesthetist's attention towards specific segments.

Transnasal transesophageal echocardiography

Transesophageal echocardiography has been used as a diagnostic tool in the critical care unit. However, long-term serial evaluation of ventricular function with transesophageal echocardiography is difficult because of the current probe sizes and intolerance to prolonged oral intubation. We performed 139 intubations (64 oral and 75 transnasal) with a new prototype probe in 128 patients referred for transesophageal echocardiography. Transnasal intubation with the prototype probe was possible in 63/75 attempts. Oral intubation was successful in all 64 attempts. Patients tolerated transnasal intubation well when mildly sedated or awake. Two-dimensional echocardiographic views obtained with the nasal probe were similar to those obtained with a standard monoplane probe. Image quality was rated as good or acceptable in nearly all cases. Transgastric short-axis imaging of the left ventricle combined with acoustic quantification provided stable left ventricular area waveforms. Using custom developed software we showed the feasibility of monitoring left ventricular performance with minimal probe adjustment while graphically displaying and updating left ventricular area and fractional area change. Thus, transesophageal echocardiography with a prototype miniaturized monoplane probe passed transnasally is feasible, safe, and well tolerated by patients. This probe provides excellent two-dimensional echocardiographic images and may allow long-term echocardiographic monitoring of ventricular performance. (J Am Soc Echocardiogr 1997;10:728-37.)

On-line automated border detection for echocardiographic quantification of right ventricular size and function in children.

Rapid, accurate assessment of right ventricular (RV) size is important for the management of children with congenital heart disease. The usefulness of the Acoustic Quantification system of automated border detection (ABD) and on-line quantification (AQ) for assessment of RV size was tested in 36 children. AQ data were compared to "corrected AQ" measurements (after correction for cavity areas erroneously included in the region of interest) required for AQ. Furthermore, the influence of necessary changes to gain settings was tested in "lateral gain control" (LGC) images obtained by removal of ABD overlays. All results were compared to conventional echocardiography (echo), and agreement with magnetic resonance imaging (MRI) RV areas was assessed. Systematic differences (+/-) limits of agreement with MRI (transverse plane) for conventional echo and AQ (apical four-chamber view) were as follows: end-diastolic -0.8 +/- 3.8 (conventional echo) versus -1.7 +/- 4.6 (AQ) cm2/m2 (p < 0.001); end-systolic -1.3 +/- 3.2 versus -4.9 +/- 5.8 (AQ) cm2/m2 (p < 0.001); fractional area change 7.8 +/- 17.0% versus 26.9 +/- 31.4% (AQ) (p < 0.001). Differences between conventional echo, LGC, and corrected AQ areas were not statistically significant. The best agreement between MRI and echocardiography was with conventional echo. We conclude that automated border detection of the RV can be performed successfully with the AQ system at a fixed point in the cardiac cycle. For adequate assessment of RV function manual corrections of online AQ results are still required, which results in an important reduction of the time gain of on-line quantification.

Stress echocardiography: new techniques.

Stress echocardiography is frequently used to evaluate coronary artery disease, and also in quantitative assessment of right and left ventricular function or cardiac valve integrity in patients with cardiomyopathy or during chemotherapy. Various new ultrasound techniques in stress echocardiography are now playing a significant role in this important area of cardiological diagnostics. New methods of echocardiographic signal processing have been developed to provide more quantitative and reproducible information on cardiac function during stress. The most important are: (1) raw data analysis techniques for endocardial border detection (acoustic quantification, CK = colour kinesis), (2) tissue Doppler imaging for myocardial velocity analysis and (3) transpulmonary contrast agents (Albunex, Laevovist, BY 963) for improving endocardial border delineation and for future analysis of myocardial perfusion. Like all new techniques, they must first be subjected to comprehensive scientific assessment, and appropriate training should be given, taking into account physical and physiological limits. These limits will constantly be redefined as echocardiographic techniques continue to change presenting new challenges for the further development of ultrasound technology. In this review, the improved new techniques will be discussed in detail.

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). Beat-to-beat reproducibility was also found to be better for fractional area change ( r = 0.82, p = 0.01 versus r = 0.66, p = 0.07), peak area filling rate ( r = 0.87, p = 0.004 versus r = 0.62, p = 0.1), and peak area 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. (J Am Soc Echocardiogr 1997;10:310-9.)

G45 Left ventricular diastolic filling in hypertensives with normal transmitral flow velocity: A study by real time acoustic quantification

G45 Left ventricular diastolic filling in hypertensives with normal transmitral flow velocity: A study by real time acoustic quantification