PubMed Health⌕ Search

Biomedical subjects

Z A Li

Publications and source records attributed to Z A Li.

18 recordsLinked to original sources
PubMed1997

Evaluation of mitral valve prolapse by four-dimensional echocardiography.

To observe the stereoscopic structure and the motion of the prolapsing mitral valve and its regurgitant jet in comparison with the normal mitral valve, four-dimensional (or dynamic three-dimensional) echocardiography of mitral valve apparatus was obtained in 20 patients with mitral valve prolapse and 10 unaffected subjects by use of transthoracic and transesophageal methods. The normal mitral valve apparatus has a consistent saddle-shaped configuration, with its anterior and posterior high points located near the aortic root and posterior left ventricular wall, respectively, and its low points located medially and laterally. In mitral valve prolapse, the spatial relation of mitral leaflets and anulus can be observed in four dimensions either from the left ventricle toward the left atrium or from the left atrium toward the left ventricle; the position, size, shape, motion, and extent of functional abnormality of the prolapsing mitral valve were clearly displayed. On the long-axis view of the left ventricle and the apical four-chamber view of four-dimensional echocardiography, the part of prolapsing mitral valve that protruded into the left atrium appeared as a spoon-like depression. We also obtained four-dimensional images of regurgitant blood flow to observe the stereoscopic view of blood flow column and its cross-sectional area, spatial position, and dynamic changes. This technique is of great value in evaluating patients with mitral valve prolapse, increasing the diagnostic sensitivity and specificity, and giving assistance to the surgeons in making preoperative therapeutic decisions and assessing the intraoperative and postoperative results.

Adult↗
PubMed1996

Four-dimensional echocardiography: methods and clinical application.

4DE (i.e., dynamic three-dimensional) echocardiography is a new developing technique in recent years. In our study, a three-dimensional echo scan computer system was used to acquire and store the two-dimensional information, then to reconstruct the stereoscopic image of the heart according to its space-time continuum. It can yield a better approach, which can help identify the various structures of the heart and great arteries and facilitate understanding of spatial relations and motion. In addition, it can display physiologic information such as the direction, course, size, and shape of the blood flow. We have examined 138 patients by both transthoracic and transesophageal approaches. Our preliminary experience shows that 4DE is of great value in diagnosing congenital heart disease and valvular disease.

Adolescent↗
PubMed1995

Study on three dimensional reconstruction of transesophageal echocardiographic images.

Using biplane transesophageal echocardiography and the concept of three dimensional transthoracic echocardiography, we performed three dimensional reconstruction of transesophageal images of various clinicopathologic cases, including atrial septal defect, mitral stenosis, mitral valve prolapse and pulmonary stenosis. The hardware equipment and image processing flow chart of three dimensional reconstruction of transesophageal echocardiographic images are described. Our present study indicates that three dimensional reconstruction of transesophageal echocardiographic images could display multi-regional three dimensional structures of heart and great vessels, including superior vena cava, ascending aorta, right ventricular outflow tract, pulmonary artery and left heart, with clear, visual and stereoscopic imaging. The regional structures could be displayed at different levels of stereo-anatomic-sections and in different orientations of rotating stereo-images, which could provide accurate three dimensional anatomical information for cardiac stereo-morphological study and definition of spatial location and size of cardiac abnormalities.

Adolescent↗
PubMed1995

Left coronary artery fistula identified by color Doppler flow imaging.

Coronary artery fistula (CAF) is an abnormal communication between a coronary artery and a cardiac chamber, great vessel, or other vascular structures. The presence of the fistula is usually identified by angiography. In this paper, the diagnosis of left coronary artery-right ventricle fistula was made by color Doppler before angiography? and it was confirmed by surgery. Color Doppler flow imaging is a non-invasive method which can reveal the proximal dilatation, the course and the draining site of CAF.

Child↗
PubMed1994

Clinical application of three-dimensional transesophageal echocardiography.

Three-dimensional transesophageal echocardiography is a new and evolving cardiac imaging technique. We reported our experiences of its clinical applications in 59 patients. A series of special temporal longitudinal views were selected by the frame grabber. Then the computer connected each digitized endocardial surface of the longitudinal views according to their spatial position and reconstructed the three-dimensional, cardiac shaded picture with gray scale. The three-dimensional transesophageal echocardiographic images were divided into three areas. The right area was right anterior to the esophagus and included such structures as the superior vena cava, right atrium, interatrial septum, and left atrium; the size, shape, and location of an atrial septal defect could be clearly shown. In the middle area the origin and the course of the two great arteries could be visualized, thus facilitating the diagnosis of transposition of the great arteries; in patients with obstruction of the right ventricular outflow tract, the circular ridgelike narrowing in the right ventricle was clearly visualized. In the left area the contour and size of the left ventricle and left atrium and the shape and point of coaptation of the mitral valve could be demonstrated; in patients with mitral valve prolapse, part of either leaflet protruded into the left atrium and appeared as a spoonlike depression in the mitral valve. Other entities subjected to three-dimensional transesophageal echocardiographic reconstruction included cor triatriatum, left atrial myxoma, aneurysm of sinus of Valsalva, dissecting aortic aneurysm, mitral stenosis, mitral regurgitation, and mitral valve prolapse.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Three-dimensional transesophageal echocardiography in the diagnosis of mitral valve prolapse.

Because the anulus of the mitral valve is nonplanar in systole, false-positive diagnosis of mitral valve prolapse may result from two-dimensional transthoracic echocardiography. Because of the superior image quality of TEE, we used the three-dimensional TEE technique to evaluate the mitral valve in both normal subjects and patients with mitral valve prolapse and with ruptured chordae tendineae. After a conventional TEE examination, sequential images of longitudinal views were obtained by probe rotation. The images at 5-degree intervals were stored in machine cine memory loop; the special temporal images were selected with ECG gating and videorecorded. During the examination, 6 to 8 images of the left heart were recorded for later off-line, three-dimensional reconstruction. A total of 42 subjects were studied: 32 normal, 9 with mitral valve prolapse, and 1 with ruptured chordae tendineae. In normal subjects, three-dimensional TEE showed nonplanarity of the entire mitral valve, which assumes a saddle shape. In mitral valve prolapse, either the anterior or posterior leaflet protruded into the left atrium like a spoon; when both leaflets are involved, they prolapse like two spoons. The anterior and posterior leaflets coapted poorly, and there was a seam between them. In ruptured chordae tendineae the tip of the mitral leaflet protruded during systole into the left atrium far from the coaptation point and was perpendicular to the body of the mitral valve and parallel to the anterior and posterior walls of the left atrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Determination of most appropriate Nyquist velocity for applying hemispherical flow convergence equation to calculate flow rate using the transorifice pressure gradient: digital computer analysis of Doppler color flow convergence region.

Nyquist velocity and transorifice pressure gradient dramatically influence color aliasing shape and accuracy of simple hemispherical flow convergence equation for calculation of flow rate. The present in vitro study was performed to determine whether the value of Nyquist velocity, at which the shape of proximal isovelocity surface is best fit for a given shape assumption in different orifice size, and the flow rate may be a determinable and orifice size independent function of clinically measurable peak velocity or transorifice pressure gradient. Steady flow was driven through circular discrete orifices with diameter of 3.8 mm, 5.5 mm and 10 mm and flow rate ranging from 2.88 L/min to 8.28 L/min. For every flow rate, Doppler color encoded M-mode images through the center of flow convergence region were transferred into the microcomputer in their original digital format. The continuous wave Doppler traces of maximal velocity through the orifice were performed for the calculation of pressure gradient. Direct numerical spatial velocity measure using color pixel intensity was obtained from the transferred color encoded M-mode images with computer software. The shape of isovelocity surface was determined by the ratio of calculated flow rate with hemispherical flow convergence equation to the actual flow rate. Both the flow rate and orifice size influence the position of the velocity profile curve. The shape of isovelocity surface is not constant and changes with the velocities used for the calculation of flow rates for a given flow rate and orifice size or pressure gradient and also changes with the flow rate or transorifice pressure gradients for a constant Nyquist velocity and orifice size.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1993

Visualization of patent foramen ovale by biplanar transesophageal echocardiography.

It is difficult for conventional transthoracic echocardiography (TTE), by which precise and accurate images of interatrial septum (IAS) can not be acquired, to diagnose patent foramen ovale (PFO) clearly. To evaluate the diagnostic value of biplanar transesophageal echocardiography (TEE) for PFO, TTE and biplanar TEE were performed simultaneously in 270 patients. It was found that in 7 patients patent foramen ovale was detected only through longitudinal planes of biplanar TEE. IAS, which consists of primitive septum and membrane of fossa ovalis, can be directly visualized by two-dimensional images of TEE; in patients with PFO, a dull color flow, which shunts from the right atria to the left atria through the gap between primitive septum and fossa ovalis, can be detected by color Doppler flow images. Furthermore, some right-to-left shunting microbubbles through the valve of patent fossa ovalis can be discovered by cardiac acoustic contrast echocardiography. In conclusion, biplanar TEE combined with color Doppler image and cardiac acoustic contrast facilitates a definite diagnosis of patent foramen ovale as the excellent anatomic images of IAS can be obtained from multiple views under this kind of performance.

Adult↗
PubMed1992

Biplane transesophageal echocardiography: an anatomic-ultrasonic-clinical correlative study.

In 427 subjects TEE was performed with either a uniplane or biplane transducer; in seven cadavers the cardiac anatomic segments were observed in several levels and directions. Nine transverse and six longitudinal views were compared with the corresponding cardiac anatomic segments. Based on this correlative study, the levels of segments, insertion depth, anatomic structure identification, image characteristics, clinical applications, and the advantages as well as the limitations of biplane TEE are discussed.

Adolescent↗
PubMed1992

The relationship between intracardiovascular smoke-like echo and erythrocyte rouleaux formation.

Intravascular smoke-like echo always appears in regions of stasis, but the exact mechanism of its production is unclear. We investigated its appearance in relation to erythrocyte rouleaux formation. To study this relationship we performed a series of in vitro and animal experiments. In the in vitro study, we observed an erythrocyte suspension by ultrasonography and found it to be echo-free. Under the microscope, red blood cells were observed in a dispersed state. If an equal amount of lymphocyte separation solution was added to the suspension, smoke-like echo appeared, and red blood cells were seen in a rouleaux pattern. In animal (mongrel dogs) experiments, under physiologic conditions with normal blood flow velocity, all cardiac cavities and the inferior vena cava were echo-free. When stasis was induced experimentally in the inferior vena cava, red blood cells aggregated to form rouleaux and smoke-like echo appeared. On resumption of normal blood flow, the rouleaux dispersed to form erythrocytes again. The mechanism of production of intracardiovascular smoke-like echo is closely related to the formation of erythrocyte rouleaux. When rouleaux are formed, they become larger and appear nearer or larger than the ultrasonic wavelength. Thus reflections are produced and smoke-like echo appears.

Animals↗
PubMed1991

Biplane transesophageal echocardiography: imaging sections and anatomic segments.

In order to recognize correctly the images of transesophageal echocardiography (TEE), in 410 subjects TEE was performed with uniplane or biplane transducer, and in 7 corpses the cardiac anatomic segments were observed, at various levels and in different directions, 9 transverse and 6 longitudinal views were compared with the corresponding cardiac anatomic segments. Based on this study, the authors reported the levels of segments, insertion depth, anatomic structure identification, image characteristics and clinical application of TEE, and the advantages of biplane TEE are discussed.

Adolescent↗
PubMed1991

Potential antitumor agents. 61. Structure-activity relationships for in vivo colon 38 activity among disubstituted 9-oxo-9H-xanthene-4-acetic acids.

Analogues of 9-oxo-9H-xanthene-4-acetic acid (XAA) bearing small, lipophilic 5-substituents are among the most dose-potent compounds yet reported with the capability of causing hemorrhagic necrosis of implanted colon 38 tumors in mice. To further extend structure-activity relationships among this class of compound, a series of XAA derivatives bearing two small lipophilic groups at various positions have been prepared and evaluated. The 5,6-disubstituted compounds in particular show consistently high levels of both dose potency and activity, suggesting this is the optimal configuration among substituted 9-oxo-9H-xanthene-4-acetic acids. The 5,6- dimethyl and 5-methyl-6-methoxy are the most effective analogues, showing in vivo colon 38 activity comparable to that of FAA at 10-15-fold lower doses and superior activity to FAA at the respective optimal doses, and the former has been selected for detailed evaluation.

Animals↗