PubMed Health⌕ Search

Biomedical subjects

M Merx

Publications and source records attributed to M Merx.

4 recordsLinked to original sources
PubMed2000

Rapid quantification of left ventricular function and mass using transoesophageal three-dimensional echocardiography: validation of a method that uses long-axis cutplanes.

AIMS: Despite its proven superiority compared to conventional echocardiographic techniques, three-dimensional (3D) echocardiography has not gained widespread acceptance in clinical medicine for the quantification of left ventricular volumes, function and mass. This is mainly due to the large, time-consuming process of data analysis. We sought to validate a new method that enables the accurate quantification of the left ventricle in a clinically acceptable short period of time. METHODS AND RESULTS: Left ventricular volumes, ejection fraction and mass were determined in 44 patients using 3D echocardiography. The 3D echocardiographic data sets were analysed: (i) using the conventional 'summation of slices' algorithm (slice thickness 5 and 10mm), which is based on the analysis of the 3D reconstructed left ventricle in short-axis cross-sections; and (ii) using the new method which is based on the analysis of the 3D reconstructed left ventricle in long-axis images. In each patient measurements were repeated using 3, 6, 7, 8, 9, 12 and 15 long-axis images. For all volumetric measurements there was a continuous reduction of measurement variability using increasing numbers of long-axis images. The use of more than nine long-axis images for volumes, and eight long-axis images for ejection fraction and mass, did not result in a further reduction of variability. The analysis time for volumes and masses averaged less than 5 min for the long-axis method using nine component images, compared to 20-43 min for the short-axis method. CONCLUSION: 3D echocardiography combined with a novel method based on the analysis of long-axis cross-section allows accurate quantification of left ventricular volumes, function and mass in a clinically acceptable short period of time. In the future, the combination of a real-time 3D echocardiographic acquisition technique with this analysis method should have important implications for the introduction of 3D echocardiography in clinical practice.

Echocardiography, Three-Dimensional↗
PubMed1998

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

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

Adult↗
PubMed1995

[3-dimensional reconstruction of multiplanar transesophageal echocardiography images: a methodologic report with case examples].

First experience with the dynamic three-dimensional reconstruction of transesophageal echocardiographic images in more than 100 patients with various cardiac diseases are reported. Ninety different two-dimensional image planes were acquired for each reconstruction using a conventional multiplanar transducer, connected to a stepper motor and controlled by a computer-based image acquisition system with special software. Acquisition time for one data set was 2.3 +/- 0.9 min, and calculation time to achieve three-dimensional images was 20-45 min. Several cardiac structures were reconstructed and analyzed qualitatively and quantitatively (measurements of distances and areas, volume calculation by Simpson's rule). Image sequences showing three-dimensional depth by gray scale modification were generated. After image acquisition one can select any desired cut plane to achieve perspectives that cannot be obtained by two-dimensional technique. Advantages of three-dimensional echocardiography are the display and potential quantification of pathomorphology of the left ventricle and mitral valve, atrial septal defects, intracardiac masses (i.e., myxomas, vegetations), and direct spatial imaging of complex congenital heart diseases. In principle, three-dimensional data sets have advantages for the quantitative evaluation of irregular formed cardiac structures, since the three-dimensional data set is more complete than cross-sections used in conventional two-dimensional echocardiography. Currently, however, these advantages are limited by the necessity of human interaction to segment the structures of interest.

Adolescent↗