Reproducibility of left ventricular measurements with acoustic quantification: the influence of training.

Acoustic quantification (AQ) of two-dimensional (2-D) echocardiograms provides online estimation of left ventricular (LV) size and function. However, edge detection with AQ is influenced by gain settings and is therefore operator dependent. Our purpose was to compare AQ and conventional 2-D echo measurements of LV size and function obtained by different operators and to evaluate the influence of training on these measurements. A cardiac sonographer without previous experience with the AQ system was trained by an experienced operator. Twenty-two normal males (age, 28 +/- 4 years) participated in the study. Images were recorded with conventional 2-D and AQ echo from the short-axis and apical four-chamber views. During the initial training period, five subjects were imaged by the sonographer under the supervision of the trainer. At the initial study session, 12 subjects were imaged independently by the two operators. Following a second training period with five different subjects, the same initial 12 subjects were again imaged at a second study session. LV cavity areas were traced from the conventional 2-D echocardiograms and measured from the AQ waveforms at end-diastole and end-systole. Volumes were calculated using the single-plane area-length method. Ejection fraction (EF) was calculated from volumes. Reproducibility was determined by comparing the variability of AQ and conventional 2-D echo measurements obtained at the two sessions. A second training session reduced the operator variability only of the short-axis end-diastolic area measurement (17 +/- 11% vs 6 +/- 5%, P < 0.025). We conclude that a single training session may be adequate for the reproducible estimation of ventricular volumes with the AQ method.

Inhalation of amyl nitrite and the measurement of left ventricular outflow velocity: studies in normal, young adults.

Amyl nitrite inhalation is useful in the identification of patients with provocable left ventricular (LV) outflow tract obstruction. However, there are no prospective studies that assess the normal change in LV outflow velocity during this intervention. Eighteen normal subjects (mean age, 34+/-5 years; 9 men and 9 women) inhaled amyl nitrite during measurement of LV outflow velocity. Peak velocity increased from 109+/-16 cm/s to 144+/-24 cm/s (P<0.001). There were no significant gender differences in velocity measurements at baseline or at peak. Our study provides prospective data that may be useful when evaluating young adults for LV outflow tract obstruction with Doppler echocardiography during amyl nitrite inhalation.

Intracardiac versus transthoracic echocardiographic imaging of translation and rotation of left ventricular center of cavity area in dogs.

Motion of the left ventricular cavity center during the cardiac cycle was compared using transthoracic and intracardiac echocardiography. Rotation was comparable for the 2 methods, however, translation of the left ventricular cavity area center was greater with intracardiac echocardiography.

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.

Evaluation of diabetic patients for renal and pancreas transplantation: noninvasive screening for coronary artery disease using radionuclide methods.

Pharmacologic stress thallium scintigraphy is commonly performed in the risk assessment of diabetic patients with nephropathy before kidney and/or pancreas transplantation; however, controversy exists regarding the test's accuracy in detecting coronary artery disease. Our purpose was to compare pharmacologic stress thallium scintigraphy and also exercise radionuclide ventriculography with coronary angiography in diabetic patients undergoing evaluation for transplantation. In addition, we also determined the association of the test results with outcome after transplantation. The medical records of 47 patients (mean age, 37+/-9 years) without clinical evidence of coronary artery disease were reviewed. Forty-one patients had pharmacologic stress thallium scintigraphy performed during their evaluation. Sensitivity was 62% and specificity was 76% for detecting > or = 75% coronary artery stenosis (sensitivity was 53% and specificity was 73% for > or = 50% stenosis). Thirty-five patients had exercise radionuclide ventriculography performed. Sensitivity was 50% and specificity was 67% for detecting > or = 75% coronary artery stenosis (sensitivity was 44% and specificity was 63% for > or = 50% stenosis). Thirty patients had both pharmacologic stress thallium scintigraphy and exercise radionuclide ventriculography performed; when either test was abnormal, sensitivity in the detection of > or = 50% or > or = 75% stenosis tended to increase compared with pharmacologic stress thallium scintigraphy alone (0.05

Variability of regurgitation in Björk-Shiley mitral valves and relationship to disc occluder design: an in vitro two-dimensional color-Doppler flow mapping study.

BACKGROUND AND AIMS OF THE STUDY: Normal prosthetic valves have regurgitation that varies according to valve type and design. The Björk-Shiley prosthetic mitral valve is a tilting disc valve that has undergone design changes since its introduction. From 1969 to 1981, Delrin, was used to make the disc occluder. After 1971, the occluder was made from Pyrolite (i.e. Conical and Radiopaque-Spherical valves). Our aim was to quantify the regurgitation of Delrin and Radiopaque-Spherical Björk-Shiley prosthetic mitral valves with color-Doppler flow mapping in an in vitro model that simulates transesophageal echocardiography imaging. MATERIALS AND METHODS: Normal unimplanted Björk-Shiley Delrin (BSD), Björk-Shiley Radiopaque-Spherical (BSS) and explanted (17 +/- 3 yrs) BSD valves (25, 27, and 29 mm) were studied in a pulse duplication system. The regurgitant leakage volume of the valves was measured with an electromagnetic flow probe at flow rates of 3.0, 5.0, and 7.0 L/min, a pulse rate of 70 beats/min, and a mean systemic pressure of 100 mmHg. Color-Doppler flow mapping was performed with a 3.7 MHz transducer positioned on the atrial chamber at an image depth of eight centimeters. The maximal regurgitant jet areas were measured offline and averaged from three beats. RESULTS: Maximal jet area, measured with color-Doppler flow mapping, correlated with regurgitant leakage volume (r = 0.82). Normal unimplanted and explanted BSD valves had greater regurgitant leakage volumes and jet areas than BSS valves for all sizes and flow rates studied. Regurgitant jet areas of normal unimplanted and explanted BSD valves were similar. CONCLUSION: Knowledge of the type of Björk-Shiley valve is important in the clinical evaluation of regurgitation severity by transesophageal echocardiography. The echocardiographic appearance of regurgitation of BSD valves does not necessarily imply valve dysfunction.

Reproducibility and variability of the amount of tricuspid regurgitation with color Doppler echocardiography.

The measurement of right atrial area was variable between different observers; however, quantitation of tricuspid regurgitation with color Doppler is a reproducible method with an acceptable error of measurement.

Acoustic lability of albumin microspheres.

The sonication of human serum albumin produces air-filled microspheres that are used in echocardiographic studies of myocardial perfusion. Recent studies suggest that the microspheres disappear when high pressures are applied, altering the relationship between the administered microsphere dose and the echocardiographic response. Because an ultrasound pulse generates a pressure wave in insonified medium, we hypothesized that with increasing acoustic pulse pressure, the microsphere concentration decreases, hence ultrasonic backscatter decreases. We measured relative integrated backscatter from albumin microspheres diluted in normal saline solution (6152 microspheres/ml) and 5% human plasma protein fraction (24,608 microspheres/ml), with increasing acoustic pulse pressures at the transducer's focus. Backscatter was also measured in normal saline solution with increasing concentrations (up to 15,380 microspheres/ml) of albumin microspheres at an acoustic pulse pressure of 0.11 MPa (1.1 atm). Backscatter and microsphere concentration were related logarithmically: y = 3.38 x 0.32; r = 0.93. Backscatter was unchanged over time at acoustic pulse (peak compression) pressures less than 0.15 MPa (1.5 atm). However, backscatter decreased readily at acoustic pulse pressures greater than 0.33 MPa (3.3 atm), which included any mixing effects. Thus, albumin microspheres are acoustically labile.

Prediction of change in mitral valve area after mitral balloon commissurotomy using cine computed tomography.

RATIONALE AND OBJECTIVES: Mitral balloon commissurotomy (MBC) can successfully increase the mitral valve area (MVA) in mitral stenosis, but the outcome is variable. In multicenter studies, qualitative echocardiographic scores obtained before MBC are only weakly predictive of the increase in MVA after MBC. METHODS: To evaluate whether the change in MVA after MBC can be predicted by evaluating mitral valve morphology using cine computed tomography (CT), we studied 12 women with mitral stenosis and 11 female control subjects. RESULTS: In the patients with mitral stenosis, MVA increased from 1.13 +/- 0.24 to 1.93 +/- 0.56 cm2 (P < .0001) after MBC. A standard echocardiographic score assessment of mitral valve morphology before MBC was not associated with the change in MVA after MBC in these patients (P > .20). However, the total mitral valve morphology score evaluated by cine computed tomography was strongly associated with the change in MVA after MBC (r = -.87; P < .0005). In addition, the individual morphologic characteristics of mitral valve mobility (P < .0025), leaflet thickness (P < .05), and subvalvular disease (P < .05) were significant predictors of the change in MVA after MBC. CONCLUSION: Cine computed tomography may be useful for predicting immediate increases in MVA in patients after MBC and may be helpful for preoperative assessment of these patients.

Assessment of cardiac volumes and left ventricular mass by cine computed tomography before and after mitral balloon commissurotomy.

We used cine computed tomography (CT) to determine whether decreased mitral valve gradients and pulmonary artery pressures resulted in decreased right ventricular and atrial volumes after percutaneous mitral balloon commissurotomy (MBC). In patients treated for severe mitral stenosis, previous studies have shown that after the mitral valve gradient decreases, the left atrial volume is reduced and left ventricular stroke volume is increased. The effects of commissurotomy on right heart chamber sizes have been difficult to assess with angiography and echocardiography. Moreover, in follow-up studies performed after surgery, changes in cardiac chamber volumes occurring after the mitral valve gradient and pulmonary pressure are reduced are confounded by the effects of thoracotomy. Our group has previously demonstrated that cine CT can accurately measure both left and right cardiac chamber volumes. We studied 11 female patients before, immediately after, and at 1 year after MBC, and 9 female control subjects of comparable age. To assess cardiac chamber volumes, we used cine CT. To assess the effects of MBC, we used cardiac catheterization and Doppler echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of left ventricular function with an automated border detection system and comparison with radionuclide ventriculography.

Quantification of 2-dimensional echocardiograms with a recently developed automated border detection (ABD) system provides on-line estimation of left ventricular (LV) function. Previous studies showed that short-axis cavity area measurements with the ABD system approximate manually traced cavity areas obtained with conventional 2-dimensional echocardiography. Further clinical validation needs a comparison of LV function between the ABD system and established methods. Fractional area change and ejection fraction measured by the ABD system were compared with ejection fraction measured by radionuclide ventriculography. Echocardiographic measurements were obtained from LV short-axis views at the level of the papillary muscles. Calculation of ejection fraction by the ABD system was based on an algorithm using a modified ellipsoid model. Forty-six patients underwent echocardiography on the same day as radionuclide ventriculography. Patients were included in the study if > or = 75% of the endocardium was visualized with conventional 2-dimensional echocardiography. Twenty-seven of 46 patients (59%) had a technically adequate, conventional echocardiogram. Fractional area change with the ABD system was highly correlated with ejection fraction from radionuclide ventriculography (r = 0.92; SEE 8.4%). Ejection fraction determined by the ABD system and radionuclide ventriculography also showed a strong linear relation in the 23 patients without severe wall motion abnormality (r = 0.90; SEE 9.5%). It is concluded that LV function measurements by the ABD system and radionuclide ventriculography have a strong linear relation.

Cardiac ultrasound. Progress and prospects.

Echocardiography is unique in its role as both a routine, mature technology and an expanding, innovative field. For the foreseeable future, ultrasound will remain one of the most important methods of diagnostic cardiac imaging.

Impact of transesophageal echocardiography on the anticoagulation management of patients admitted with focal cerebral ischemia.

Transesophageal echocardiography (TEE) improves the diagnostic accuracy of transthoracic echocardiography in the identification of potential cardiac sources of embolus. However, there are few studies of the impact of TEE on the medical management of patients with focal cerebral ischemia. The records of 52 consecutive, hospitalized patients undergoing both TEE and transthoracic echocardiography for suspected cardiac source of embolus were reviewed to determine the influence of TEE on the decision to anticoagulate patients. Of 52 patients, 39 had focal cerebral ischemia (transient ischemic attack, n = 9; acute cerebral infarction, n = 30). In 4 of these 39 patients (10%), the TEE results changed the management of anticoagulation. In 19 of 39 patients (49%), the TEE results helped confirm anticoagulation decisions, and in 16 (41%), the results had no effect on anticoagulation decisions, because of overriding clinical information. Ten of the latter 16 patients had TEE evidence for a possible source of an embolus, but were not anticoagulated; 5 of these were poor candidates for long-term anticoagulation, and the others had right-to-left shunting across a patent foramen ovale or an interatrial septal aneurysm. Clinical variables (atrial fibrillation, TEE findings and pre-TEE anticoagulation status) were considered as possible predictors of post-TEE anticoagulation status using logistic regression analysis; the strongest predictor of post-TEE anticoagulation status was pre-TEE anticoagulation status (p < 0.0005). Despite the selection of patients presumed to receive maximal benefit from TEE, this study suggests that TEE findings are not predictive of subsequent anticoagulation management. However, TEE is at least confirmatory of anticoagulation decisions in most cases.

Rapid resolution of hyperkinesis after exercise. Two-dimensional echocardiographic studies in normal subjects.

Abnormal wall motion detected with exercise echocardiography identifies ischemic myocardium, while normal myocardium exhibits hyperkinetic motion. The normal, hyperkinetic response to exercise is transient and is predictive of an excellent prognosis. However, there are few data on the duration of the hyperkinesis after peak exercise. Our purpose was to determine the time course of wall thickening after exercise in eight normal subjects with two-dimensional echocardiography. Percentage of wall thickening increased from 53 +/- 24 percent at baseline to 82 +/- 24 percent at 0 to 2 min postexercise (p < 0.001 vs baseline) and then decreased to 64 +/- 27 percent at 2 to 4 min, and 54 +/- 20 percent at 5 to 7 min (both NS vs baseline). We conclude that (1) systolic wall thickening is maximal within the initial 2 min following peak exercise, and (2) accurate identification of hyperkinetic, normal myocardium with exercise echocardiography requires immediate postexercise imaging.

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

BACKGROUND: Automated edge detection of endocardial borders in echocardiograms provides objective, reproducible estimation of cavity area; however, most methods have required off-line analysis. A recently developed prototype echocardiographic imaging system permits real-time automated edge detection during imaging and thus, the potential for measurement of cyclic changes in cavity area and the assessment of left ventricular function on-line. Our purpose was to compare measurements of endocardial area manually traced from conventional echocardiograms with those obtained with the real-time automated edge detection system in normal subjects. METHODS AND RESULTS: Two training sets of images were used to establish optimal methods of gain setting; the settings were then evaluated in a test set of images. In the high-gain training group (n = 8 subjects, 119 images), gain settings were adjusted sufficiently high to display at least 90% of the endocardial border. Manually drawn and real-time area measurements correlated at r = 0.92, but manually drawn areas were underestimated by computer. In the low-gain training group (n = 7 subjects, 104 images), gain settings were adjusted sufficiently low to avoid cavity clutter despite the presence of dropout of endocardial edges. Manually drawn and real-time areas again correlated (r = 0.79), but manually drawn areas were overestimated by computer. In the intermediate-gain test group (n = 7 subjects, 105 images), gain settings were balanced between maximal endocardial definition (greater than or equal to 90%) and minimal cavity clutter (less than or equal to 1 cm2). Manually drawn and real-time areas correlated at r = 0.91 for the group, and r ranged from 0.94 to 0.99 in individual subjects. Interobserver variability was 9.5% for manually traced areas and 10.6% for real-time area measurements. CONCLUSIONS: Real-time on-line automated edge detection provides accurate estimation of manually drawn cavity areas. Although the method is gain dependent, measurements are reproducible. The system should have clinical application in settings in which measurements of left ventricular function are important.

Reproducibility of quantitative backscatter echocardiographic imaging in normal subjects.

Cyclic backscatter variation is useful in differentiating normal from ischemic and myopathic myocardium; however, there are few data on the reproducibility of clinical cyclic variation measurements. Therefore, a study using 2-dimensional and M-mode backscatter imaging was performed in 20 normal male subjects by 2 observers at an initial session and by 1 of the observers after 1 week. Cyclic variation on M-mode was calculated as the difference between the end-diastolic backscatter and the backscatter at the nadir. Two-dimensional determinations of backscatter were made using a single frame at end-diastole and one at end-systole. The cyclic change was the difference between backscatter measured in the end-diastolic and end-systolic frames. There were no statistically significant differences in analysis of variance among the grouped repeated measurements in either the interventricular septum or the posterior left ventricular wall. At the initial session, cyclic backscatter variation in the posterior wall using M-mode techniques was 5.9 +/- 1.8 dB (SD). The cyclic change in backscatter in the septal wall, using the 2-dimensional technique, was 4.3 +/- 2.4 dB. In the posterior wall, the cyclic change in backscatter was 5.7 +/- 1.7 dB. Pairwise observer correlations between repeated measurements ranged from -0.48 to 0.45. Thus, although there were no significant differences in group means on repeat measurements, repeated measurements in individual subjects were not reliably reproduced because of limited independent sampling of backscatter measurements at only 2 points in the heart cycle. Increased independent sampling and measurement from a backscatter waveform throughout the cardiac cycle may improve reproducibility of measurements.