Non-invasive left ventricular volume determination by two-dimensional echocardiography

Appropriate 3-dimensional echocardiography data acquisition interval for left ventricular volume quantification: implications for clinical application

Volume-rendered 3-dimensional echocardiography (3DE) acquired with small imaging intervals has been validated for accurate left ventricular (LV) volume measurement. However, its clinical application is often impeded by the lengthy acquisition time. The aim of this study was to examine the accuracy of LV volume measurement from 3DE data acquired at different intervals.

METHODS

Transthoracic 3DE LV data sets were acquired at intervals of 2 degrees, 6 degrees, 9 degrees, 12 degrees, 15 degrees, 18 degrees, and 20 degrees in 10 human subjects with various cardiac shapes and function. The LV end-diastolic volume and end-systolic volume were measured from each 3DE data set with the "summation of disks" method. Interobserver and intraobserver variability were also examined. Measurements obtained from data acquired at 2 degrees intervals were used as references for comparison.

RESULTS

From 10 subjects a total of 70 3DE data sets were obtained. Data acquisition time decreased from 189 +/- 143 seconds at intervals of 2 degrees to 19 +/- 6 minutes at 20 degrees. No statistically significant difference was found among the measurements derived from data obtained at various intervals. Excellent agreement was obtained between interobserver and intraobserver measurements.

CONCLUSION

Data acquired at 12 degrees and 15 degrees intervals remained accurate for LV volume measurement and saved over 80% of time in comparison with data acquired at 2 degrees intervals. A further increase in imaging intervals tended to underestimate LV volumes without significant acceleration of the procedure.

Left ventricular volume calculation with integrated backscatter from echocardiography

Integrated backscatter analysis (IB) is a new echocardiographic method for automatically differentiating tissue from blood on the basis of differences in the amplitude of reflected ultrasound. Left ventricular volume was estimated with IB by use of a modification of Pappus' theorem and a summated ellipsoid method. IB measurements correlated well with a standard biplane area-length method derived off-line from endocardial borders drawn by hand from the same echocardiographic data (y = 1.09 x - 35, r = 0.95). Integrated backscatter measurement of ventricular volume derived from six imaging planes with both the Pappus' rule and the summated ellipsoid methods correlated well with magnetic resonance imaging volume estimates (r = 0.91 and r = 0.90, respectively), whereas use of one imaging plane correlated less well (r = 0.75). Automated analysis of integrated backscatter differentiates tissue from blood sufficiently to allow accurate volume calculations compared with magnetic resonance imaging and to standard hand-drawn echo techniques. This method provides accurate measurement of left ventricular volumes that should be useful in clinical hemodynamic assessments.

Comparison of gray-scale and B-color ultrasound images in evaluating left ventricular systolic function in coronary artery disease

To confirm whether or not echocardiographic B-color images (temperature, magenta, rainbow) are superior to ordinary gray-scale images, 62 coronary artery disease (CAD) patients (42 men and 20 women) underwent gray-scale and B-color echocardiography and cineangiography within 24 hours. Left ventricular (LV) volume was derived from angiography using the single-plane area-length method and was derived from echocardiography using single-plane modified Simpson's formula. In predicting angiographic volume, the correlations between B-color images and angiography were similar to that between the gray-scale image and angiography. In evaluating LV ejection fraction, the correlation coefficients between B-color images and angiography (temperature r = 0.93, magenta r = 0.93, rainbow r = 0.92) were slightly higher than that between the gray-scale image and angiography (r = 0.85) (p less than 0.05). We conclude that B-color images yield estimates of LV volumes that are of similar accuracy to gray-scale images in patients with CAD.

Contrast echo washout curves from the left ventricle: application of basic principles of indicator-dilution theory and calculation of ejection fraction

Time-intensity curves can be obtained from contrast echocardiography of the left ventricle. The purposes of this study were: 1) to verify whether these curves conform to the basic principles of indicator-dilution theory; and 2) to derive indexes of left ventricular ejection fraction from curve analysis. In seven closed chest dogs, 31 doses of the polysaccharide agent SHU-454 were injected into the left ventricular cavity during apical four chamber two-dimensional echocardiography. Data were obtained at different levels of ejection fraction, which were induced by changes in preload, afterload and contractility, and measured by single plane Simpson's rule analysis of digital subtraction left ventriculograms. In a subset of two dogs, eight incremental doses (from 1 to 8 ml) of SHU were injected in the basal state. Contrast echocardiograms were digitized off-line, the mean gray level/pixel of a region of interest inside the left ventricular cavity was measured, and the average value for three systolic frames of each beat was used to obtain time-intensity curves. A good correlation was observed between the peak of the time-intensity curve and the quantity of contrast injected (correlation coefficient r = 0.91 by a logarithmic fit). The echo intensities observed in each animal were subsequently transformed in quantity of contrast according to these functions and their natural logarithm was calculated both with and without background subtraction. All curves relating time and the natural logarithm of the corrected intensity exhibited a descending rectilinear portion (washout) in which the correlation was very good (r = 0.97 +/- 0.02 = mean +/- SD) and which was not significantly affected by background subtraction. The validity of this fit was also unaffected by heart rate (55 to 158 beats/min) and angiographic ejection fraction (22 to 74%), and only minimally influenced by duration of contrast washout (3.3 to 14.6 seconds). Ejection fraction was calculated by an algorithm derived from indicator-dilution theory: ejection fraction = [1 - e(-bd)] X 100, where b = slope of the curve and d = cardiac cycle duration. Linear regression analysis between values of ejection fraction derived by angiography and contrast echo yielded r = 0.73. A second index, based on b and d, was derived by multiple regression analysis. Linear regression analysis of this index and angiographic ejection fraction yielded a correlation of r = 0.87.(ABSTRACT TRUNCATED AT 400 WORDS)

Limitations of digital subtraction contrast echocardiography in enhancing left ventricular endocardial definition

The purpose of this study was to evaluate whether the digital subtraction technique, applied to contrast echocardiography of the left ventricle (LV), might improve endocardial edge identification by two-dimensional echocardiography. Injections of the polysaccharide agent SHU-454 were made into the LV of five closed-chest dogs. Data were obtained at different levels of ejection fraction (EF) induced by pharmacologic or mechanical interventions and were documented by left ventriculography (VGRAM) in the right anterior oblique projection. Contrast echocardiography was recorded in the apical four-chamber view. The echocardiographic images were digitized off-line into a 256 X 256 pixel matrix with 256 gray levels/pixel. Two end-diastolic frames prior to contrast appearance were averaged to obtain a mask that was subtracted from end-diastolic contrast frames corresponding to the two beats of peak intensity. The same procedure was repeated for the systolic frames. LV edges from echocardiographic images prior to contrast appearance, from digitally subtracted echo-contrast images, and from VGRAM were traced on two occasions by two different observers. LV volumes were calculated by single-plane Simpson's rule and EF was derived by the classical equation. The intra- and interobserver reproducibility in the measurement of EF was excellent for VGRAM (r = 0.95 and 0.94, respectively), it was good for two-dimensional echocardiography (r = 0.87 and 0.73), and was fair for contrast-echo (r = 0.79 and 0.68).(ABSTRACT TRUNCATED AT 250 WORDS)

Cross sectional echocardiographic assessment of cardiac chamber size and ejection fraction in children

Cross sectional echocardiography can be used to determine left ventricular size and ejection fraction in children. We used two orthogonal planes from the apical four and two chamber planes to calculate the left ventricular volume in 20 children with a variety of congenital heart lesions and compared these volumes with those calculated using angiography. Better correlations were achieved at end diastole than at end systole. Comparisons between ejection fraction calculated by angiography and echocardiography showed the correlation was closer for two-dimensional than M-mode techniques. Studies using newer two-dimensional methods suggest that an even closer correlation for volume and ejection fraction can be achieved than those reported in our initial studies. Most studies which have determined right ventricular volume have used biplane methods combining short axis and four chamber images. We used single plane area-length methods from parasternal short axis and apical four chamber planes to calculate right ventricular volume in 20 children undergoing angiocardiography for a variety of congenital heart diseases. The single plane volume method underestimated the volume calculated from angiography uniformly so that a good estimate of the angiographic ejection fraction was obtained. Adding the volumes derived from each plane provided a closer approximation of the angiographic volumes and a good estimate of the ejection fraction. High resolution ultrasound equipment and computer assisted tracing devices have made accurate noninvasive assessment of volume and function accurate and practical.

Cross sectional echocardiographic assessment of left ventricular volume and ejection fraction in patients with tetralogy of Fallot. Comparison with biplane angiographic measurements

To evaluate the usefulness and accuracy of calculating left ventricular volume and ejection fraction from cross sectional echocardiograms in patients with tetralogy of Fallot, 28 patients were studied within 24 hours of cineangiography. Indexed end diastolic and end systolic volumes were calculated from three different paired echocardiographic projections: (a) the two and four chamber views from the apical impulse window, (b) the parasternal long axis view and the subxiphoid long axis view, and (c) the four chamber view and short axis precordial views at mitral and papillary muscle level. Volumes were calculated in five different ways using three different algorithms (area length, Simpson's rule, the Parisi formula). The results were compared with data obtained from biplane angiograms using Graham's formula. The correlation varied with the algorithm used: the best results were obtained with the area length method using the parasternal long axis view and the sub-xiphoid view. The correlation was less accurate for the ejection fraction. The second best correlation was obtained with the area length method using the two and four chamber apical views; the other correlations were less satisfactory. Thus these results show that left ventricular volumes can be accurately assessed by cross sectional echocardiography in children with tetralogy of Fallot and that the ejection fraction can be satisfactorily estimated. The results depend on careful gain setting and precise demonstration of the left ventricular endocardium, which is best seen in the sub-xiphoid and long axis views.

Reproducibility of left ventricular volumes by two-dimensional echocardiography

Reproducibility may be as important as absolute accuracy in assessing the utility of an echocardiographic method of left ventricular volume estimation for epidemiologic or physiologic studies. The magnitude of differences between measurements in the same subjects from day to day must be defined before any quantitative technique can be used reliably to document "real" changes in heart volume over time. Two-dimensional echocardiograms were performed serveral days apart in 30 subjects, including 20 normal subjects and 10 patients with stable coronary heart disease. Analyses of light-pen tracings provided measurements of end-diastolic volume, endsystolic volume and derived ejection fraction on both days, and differences in individual subjects between days were quantitated. Beat to beat, interobserver and intraobserver variability also were assessed. Although group values changed little from day to day, individual volume changes were substantial in some cases. Confidence limits for individual measurements were derived from analyses of intrasubject variability and were as follows: end-diastolic volume +/- 15%, end-systolic volume +/- 25%, ejection fraction +/- 10%. Confidence limits in a larger group of subjects were narrower; in a group of 30 subjects, changes of greater than 2% in end-diastolic volume, 5% in end-systolic volume and 2% in ejection fraction most likely represent real change. Intraobserver variability was minimal, but interobserver and beat to beat variability were of sufficient magnitude to suggest that serial measurements on a given subject be made ideally by a single person and that several cycles be averaged for a given measurement.

Three-dimensional echoventriculography

A method of generating a three-dimensional image of the human left ventricle by computer techniques is described. The volume of each image was estimated by a modification of Simpson's rule. The method was applied to nine suitable patients and estimations of end-diastolic and end-systolic volumes were compared to volumes determined by cineangiography. Significant linear correlation coefficients of 0.95 and 0.94 were obtained for end-diastolic and end-systolic volumes, respectively. The standard errors of estimate were 9 ml for end-diastolic volumes and 7 ml for end-systolic volumes. The value of this methodology lies in the ability to estimate left ventricular volumes with accuracy, using an imaging technique of little inconvenience and no risk to the patient and computer hardware that is readily available at most clinical institutions.

Evaluation of right ventricular volume and ejection fraction in children by two-dimensional echocardiography

We estimated right ventricular volume and ejection by two-dimensional echocardiography (2DE) and compared the measurements with those obtained by right ventricular cineangiography (ANGIO) in 20 children whose ages ranged from 1 month to 10 years and who had a variety of congenital defects. The two echocardiographic planes used for calculating volume were the apical four-chamber (A4C) and parasternal short-axis (SA) planes. End diastolic volume (EDV) and end systolic volume (ESV) were calculated from these planes by single-plane area-length methods. The EDV and ESV were uniformly underestimated, but the estimate of ejection fraction (EF) was satisfactory. For EF, r = 0.83 from the apical four-chamber view and r = 0.78 from the short-axis view. The axes of the two echocardiographic planes passed through different segments of the right ventricle (RV) and we found that the value given by adding the volumes obtained from the two single-plane segments correlated quite well with the value obtained by angiography: for EDV, 2DE = 0.62 ANGIO + 7.0, r = 0.81, standard error of the estimate (s.e.e.) = 15.4 ml; for ESV, 2DE = 0.82 ANGIO + 1.4, r = 0.85, s.e.e. = 6.5 ml; and for EF, 2DE = 0.66 ANGIO + 17.8, r = 0.82, s.e.e. = 7.4 ml. Two-dimensional echocardiography can be used to evaluate right ventricular EF derived from volume measurements or from each of the echocardiographic planes of which, in our series, the apical four-chamber EF provided the better correlation.

A longitudinal study of cardiovascular dynamic changes throughout pregnancy

Systemic blood pressure (measured with a zero-randomized sphygmomanometer), stroke volume and heart-rate (measured with a Minnesota Impedance Cardiograph), hematocrit, and their derivatives -- cardiac output and peripheral vascular resistance--have been assessed in three groups of subjects. First, a control group of 19 nonpregnant women were matched for age and weight with the subjects in the second group, which consisted of 19 patients who were seen at regular intervals on 12 to 15 occasions from 8 to 11 wk of pregnancy until 6 wk postpartum. The third group consisted of 8 patients seen from before conception, throughout pregnancy and to several months postpartum. Readings were made with the subject in each of six positions: supine, reclining, left and right lateral, left and right tilt. This paper concerns the readings obtained in the left lateral position. The data showed that pulse rate rose throughout pregnancy. Stroke volume and cardiac output rose shortly after conception, the increase over the prepregnancy level being statistically significant by 12 wk. Thereafter both values fell throughout the rest of pregnancy and were below prepregnancy levels by about term, taking some weeks to regain the prepregnancy value. There were irregular fluctuations in the level of systolic blood pressure; diastolic blood pressure fell during the first 16 wk and then rose to reach almost the prepregnancy value by term. Peripheral resistance fell during the first trimester, then increased markedly throughout the remainder of pregnancy.

Reliability of echocardiography in assessing cardiac output. A comparative study with a dye dilution technique

Because of the potential benefits froma noninvasive technique in assessing cardiac output, we compared cardiac output estimates from left ventricular echocardiograms with results obtained simultaneously by a standard technique, dye dilution in 10 healthy normal volunteers. During rest, cardiac outputs by echocardiographic and dye dilution techniques were reproducible and not significantly different. Increases in cardiac output produced by intravenous infusion of isoproterenol (15 ng/kg/min for 4 min) were accurately estimated by echocardiography in subjects whose stroke volume increased less than 40%, but were significantly underestimated when stroke volume increased more than 40%. Decreased cardiac output produced by intravenous propranolol (0.2 mg/kg) was comparable by both methods. Although echocardiography accurately estimated mean cardiac output for the group it over- or underestimated cardiac output in individual subjects. We propose that echocardiography can reliably estimate cardiac output in groups at rest and when stroke volume changes less than 40%.

Technique for evaluating left ventricular performance with apical two-dimensional echocardiography: Progress report

A technique of modelling the left ventricle for the purpose of volume determination has been devised. Two-dimensional echocardiographic data from the apical four chamber and two chamber views are used to pattern the ventricle as a stack of elliptical discs. The method has been validated for an array of regular geometric shapes commonly associated with ventricular architecture. The relative advantages of this model are discussed.

Left ventricular volume and ejection fraction determination by cross-sectional echocardiography in patients with coronary artery disease: a prospective study

In a prospective study the accuracy of cross-sectional echocardiography for determination of left ventricular (LV) volume and ejection fraction (EF) was analyzed in 53 patients with coronary artery disease and compared to that of cineangiocardiography (angio). From the apex of the heart phased-array wide-angle (84 degrees) electronic echocardiograms were received in the RAO-equivalent view. Angios were obtained in a 30 degree RAO view. Using Simpson's rule, end-diastolic (EDV) and end-systolic (ESV) LV volumes were calculated and the EF derived. Left ventricular long axis was transected in eight segments, yielding seven diameters. In 50 of the 53 patients cross-sectional echocardiograms could be recorded. The correlation between cineangiocardiography and cross-sectional echocardiography for EDV was highly significant: r = 0.936, y = 0.667x + 27.1, standard error of estimate (syx) +/- 22.2 ml; for ESV: r = 0.970, y = 0.699x + 14.7, syx +/- 14.5 ml; for stroke volume: r = 0.721, y = 0.503x + 11.3, syx +/- 15.3 ml; for EF: r = 0.909, y = 0.740x + 11.3, syx +/- 6.0%. Angio mean long axis was 10.2 +/- 1.2 cm, cross-sectional echocardiographic long axis 8.7 +/- 1.3 cm. Mean LV diameter determined by cineangiocardiography was longer than when determined by cross-sectional echocardiography. The mean difference reached 2.0 cm in the middle of the LV. Our prospective comparative study revealed that LV volumes and EF were underestimated by cross-sectional echocardiography compared to cineangiocardiography because of a methodological systematic error caused by a tangential cut of the heart. In the RAO-equivalent view the "true" long axis was missed. The high corrleation coefficients, however, indicate that the "true" LV volume and EF can be calculated from the given regression equation. Serial measurements should be legitimated.

Cross-sectional echocardiography. II. Analysis of mathematic models for quantifying volume of the formalin-fixed left ventricle

Cross-sectional echocardiography was used to quantify volume in 21 canine left ventricles that were fixed in formalin and immersed in mineral oil. Area, length and diameter measurements were obtained from short- and long-axis cross-sectional images of the left ventricle and volume was calculated by seven mathematic models. Calculated volume was then compared, by linear regression and percent error analyses, with fluid volume of the left ventricle, obtained by filling the chamber with a known amount of fluid. Volumes ranged from 13-146 ml. Mathematic models using short-axis area and long-axis length gave higher correlation coefficients (r = 0.982 and r = 0.969) and lower mean errors (10-20%) than standard formulas previously used for M-mode echo and angiography. Thus, short-axis area analysis with cross-sectional echocardiography is well-suited for quantifying left ventricular volumes in dogs.

Cross-sectional echocardiography. I. Analysis of mathematic models for quantifying mass of the left ventricle in dogs

Cross-sectional echocardiography was used to quantify left ventricular mass noninvasively in 21 dogs. Short- and long-axis cross-sectional images of the left ventricle were reproducibly traced at endocardial and epicardial borders during stop-motion video-tape replay. We used area, length and diameter measurements to calculate left ventricular mass by seven mathematic models, including the standard formulas used with M-mode echocardiography and cineangiography. Calculated mass was compared with excised weight of the left ventricle by regression and percent error analyses. Formulas using short-axis areas and long-axis length resulted in higher correlation coefficients (0.94--0.95) and lower mean errors (6--7%) than for standard formulas. Since short-axis areas account for regional left ventricular irregularities, noninvasive quantification of left ventricular mass by cross-sectional echocardiography in dogs is most accurate with formulas using short-axis areas.

Left ventricular volume from paired biplane two-dimensional echocardiography

To evaluate the applicability of two-dimensional echocardiography to left ventricular volume determination, 30 consecutive patients undergoing biplane left ventricular cineangiography were studied with a wide-angle (84 degrees), phased-array, two-dimensional echocardiographic system. Two echographic projections were used to obtain paired, biplane, tomographic images of the left ventricle. We used the short-axis view (from the precordial window) as an anolog of the left anterior oblique angiogram, and the long-axis, two-chamber view (from the apex impulse window) as a right anterior oblique angiographic equivalent. A modified Simpson's rule formula was used to calculate systolic and diastolic left ventricular volumes from the biplane echogram and the biplane angiogram. These methods correlated well for ejection fraction (r = 0.87) and systolic volume (r = 0.90), but only modestly for diastolic volume (r = 0.80). These correlations are noteworthy because 65% of the patients had significant segmental wall motion abnormalities. The volumes determined from the minor-axis dimensions of M-mode echograms in 23 of the same patients correlated poorly with angiography.

The use of echocardiography for quantitative evaluation of left ventricular function

Echocardiography is a valuable technique for the diagnosis and serial follow-up of patients with impaired cardiac function. It is subject to certain limitations due to the assumptions inherent in deriving ventricular volume from a one-dimensional measurement and must be interpreted with caution in cases of suspected regional abnormalities of contraction. Given these caveats, echocardiography is valuable in the quantitative assessment of cardiac size and the level of compensation in patients with primary myocardial disease, valvular heart disease, and left ventricular hypertrophy. It can detect abnormal contraction in some patients with ischemic heart disease and provides an accurate method to serially follow changes produced as a result of drug or surgical therapy. Finally, two-dimensional techniques promise to provide a new perspective on the evaluation of patients with regional wall motion abnormalities.

A new, noninvasive technique for inducing post-extrasystolic potentiation during echocardiography

Left ventricular function was evaluated in 34 patients with the echocardiogram, and an external mechanical cardiac stimulator was used to induce a ventricular premature contraction (VPC) noninvasively. Extent of post-extrasystolic potentiation (PESP) was determined by comparing systolic dimensional shortening and ejection fraction of the sinus beat preceding the VPC to that of the potentiated beat which followed it. Using this technique, a VPC could be introduced into the cardiac cycle of 30 of the 34 patients, six of whom were free of obvious cardiac disease and 24 of whom had valvular, coronary or myopathic heart disease. The only complication observed was mild breast ecchymosis in a female patient. Systolic dimensional shortening and ejection fraction increased from control values by an average of 21% and 17% respectively, with a range of 0-100%. The degree of PESP was very reproducible in repeat studies and when the same patients were subsequently evaluated during a spontaneously occurring or catheter-induced VPC. The technique can safely and reliably induce post-extrasystolic potentiation during echocardiography and is a potentially important adjunct to the noninvasive evaluation of left ventricular function.

The anatomy of the heart in the sonogram. A comparison between anatomic and ultrasonic cross-section

Cardiac sonography has only recently been introduced as a diagnostic procedure. In order to facilitate the interpretation and evaluation of the ultrasonic cardiac cross-section displayed by this two-dimensional technique, we performed anatomic cross-sections corresponding to ultrasonic cross-sections. The ultrasonic cross-sectional images were taken from children with a real-time-motion scanner. The anatomic cross-sections were taken from adult hearts. Two ultrasonic transverse cross-sections are compared with the two corresponding anatomic cross-sections and three ultrasonic longitudinal cross-sections with one corresponding anatomic cross-section. The direct comparison between anatomic and ultrasonic cross-sections best promotes the understanding of the latter: such a comparison shows certain gaps of information in the ultrasonic display, mostly due to the physical prerequisites of the technique. Morphological details, therefore, should be interpreted with great care. In spite of these disadvantages, sonography is the only non-invasive method that provides an exact analysis of the heart's structure. In addition to this, the real-time-motion technique allows observation of the movements of cardiac structures.

The effect of left ventricular pressure or volume overload on ventricular dimension in children. Left ventricular volume determination from one or two ventricular dimensions

The effect of pressure or volume overload on the geometry of the left ventricle (LV) was determined in order to examine the feasibility and accuracy of LV volume determinations from one minor axis or two dimensions (one minor axis and the longest length). The longest length (LL) and minor axis (MA) in both the anteroposterior (AP) view and lateral (LAT) view were determined from the LV cine silhouette in patients with normal LV volume and pressure (group 1), LV pressure (LVP) overload group (LVP greater than 140 mm Hg, group 2), and LV volume overload group (LV end-diastolic volume greater than 124% of normal, group 3). The ratio of the MA to the LL, which represents the spherical configuration of the LV, was less than "normal" in group 2, and higher than "normal" in group 3. In all groups the LV was less spherical at end-systole than at end-diastole. Additionally, the (MA)3 had a different relationship to true LV volume (biplane LV volume) in the three groups and from diastole to systole in each group. Left ventricular volume calculation from one minor axis was associated with a large error. In contrast, left ventricular volume can be accurately determined from two ventricular dimensions using either the anteroposterior or lateral ventricular image (r larger than or equal to 0.97).