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Biomedical subjects

Y B Deng

Publications and source records attributed to Y B Deng.

At least 19 recordsLinked to original sources
PubMed2001

A new noninvasive method for evaluation of coronary endothelial function in hypertensive patients based on change in diameter of the left main coronary artery induced by cold pressor test using echocardiography.

BACKGROUND: Coronary endothelial function is frequently studied by measuring the vasodilator response of coronary arteries to acetylcholine or to cold pressor test by invasive quantitative coronary angiography. Because invasive methods have substantial inherent limitations, studies should attempt to evaluate coronary endothelial function noninvasively. HYPOTHESIS: We attempted to evaluate the accuracy of measurement of the percent change in diameter of the left main trunk induced by cold pressor test with two-dimensional (2-D) echocardiography. Furthermore, we applied this method to the evaluation of coronary artery endothelial function in hypertensive patients. METHODS: We measured the left main trunk diameter in 21 subjects (51 +/- 4 years) before and after cold pressor test using quantitative coronary angiography followed immediately by 2-D echocardiography. The accuracy of measurement of the left main trunk diameter and its percent change by echocardiography was evaluated by comparing the values obtained by the two methods. In addition, using echocardiography, we compared left main trunk diameter responses to cold pressor test in 16 hypertensive patients [51 +/- 5 years (mean +/- standard deviation)] and 16 matched healthy subjects (50 +/- 4 years). RESULTS: Although there was only a weak correlation between the absolute values of the left main trunk diameter measured by the two methods (r = 0.61; p = 0.04), a strong correlation was found between the percent change in diameter measured by the two methods (r = 0.93; p = 0.0001). The percent change in diameter of the left main trunk induced by cold pressor test in hypertensive patients (-3.7 +/- 10.6%) was significantly lower than that in control subjects (13.2 +/- 6.8%, p = 0.0001). CONCLUSIONS: Percent change in diameter of the left main trunk induced by cold pressor test can be evaluated accurately using 2-D echocardiography. Our study showed reduced vasodilation or vasoconstriction of the left main trunk after cold pressor test in hypertensive patients compared with healthy subjects, indicating impaired coronary endothelial function in hypertensive patients. The present echocardiographic method is a potentially useful new noninvasive method for evaluating coronary endothelial function.

Adult↗
PubMed2001

Noninvasive detection of endothelial dysfunction in elderly with NIDDM by ultrasonography.

We compared endothelial function noninvasively in 15 elderly patients with noninsulin-dependent diabetes mellitus (NIDDM) with 12 nondiabetic elderly patients. Using high resolution ultrasound, we measured flow-mediated dilatation (FMD) of the brachial artery and sublingual nitroglycerin (NTG)-mediated dilatation. FMD was significantly impaired in subjects with NIDDM compared with control subjects. In NIDDM subjects, FMD with complications was lower than in subjects with noncomplications. However, there was no significant difference in NTG between NIDDM subjects and the control group. Hyperemic blood flow change was lower in NIDDM subjects, but not significant. These results suggest that elderly patients with NIDDM have impaired L-arginine/nitric oxide (NO) pathways and the possibility of capillary rarefaction.

Administration, Sublingual↗
PubMed1999

Evaluation of endothelial function in hypertensive elderly patients by high-resolution ultrasonography.

BACKGROUND: Multiple investigations, both in experimental models and in middle-aged patients with essential hypertension, demonstrate impaired endothelium-dependent vasodilatation. HYPOTHESIS: We attempted to determine whether hypertension still exerts additional negative effect on endothelial function of large arteries in hypertensive elderly patients who may already be affected by endothelial dysfunction due to aging. METHODS: We compared 13 elderly patients with hypertension [69 +/- 9 years, (mean +/- standard deviation)] with 13 matched healthy elderly subjects (72 +/- 6 years) as controls. Using high-resolution vascular ultrasound, we measured brachial artery responses to reactive hyperemia (with increased flow causing endothelium-dependent dilatation) and sublingual nitroglycerin (causing endothelium-independent dilatation). RESULTS: Flow-mediated dilatation correlated inversely with age (r = -0.60, p = 0.03) in the controls. Flow-mediated dilatation was significantly impaired in hypertensive elderly patients (6.7 +/- 3.3 vs. 13.3 +/- 1.8% in controls, p < 0.0001). No significant difference could found in nitroglycerin-induced dilatation between controls (12.1 +/- 4.9%) and hypertensive elderly patients (10.2 +/- 6.8%, p = 0.5). On multivariate analysis, flow-mediated dilatation in hypertensive elderly patients was inversely related to aging (r = -0.37, p = 0.04) and mean blood pressure (r = -0.57, p = 0.03). CONCLUSIONS: Our study showed decreased flow-mediated dilatation with aging even in the healthy controls, and further decline in flow-mediated dilatation in hypertensive elderly patients compared with controls. This impairment of flow-mediated dilatation in hypertensive elderly patients was related to age and mean blood pressure, indicating that aging and hypertension may independently impair endothelial function in the brachial artery of these patients.

Aged↗
PubMed1997

[Effect of jishentang on renal lesions in diabetic rats].

OBJECTIVE: To observe the ameliorative effect of Jishentang (JST) on renal lesions in experimental diabetic rats. METHODS: The diabetic rats were randomly divided into three groups: group with out treatment, group with enalapril treatment (the dose of enalapril was 1 mg/kg.d) and group with JST treatment (the dose of JST was 22.4 g/kg.d). The treatment lasted for 8 weeks. RESULTS: (1) JST treatment attenuated the renal hypertrophy and ratio of kidney and body weight (P < 0.01). (2) JST treatment reduced the levels of SCr and BUN and the levels of Alb, beta 2-m and the activity of NAG in urine in diabetic rats significantly (P < 0.01). The levels of TG and TCh decreased and the levels of HDL-C increased in the serum of the JST treated diabetic rats (P < 0.01). (3) The glomerular basement membrane thickening and volume density of PAS positive staining in mesangial area were significantly decreased in JST treated diabetic rats. CONCLUSIONS: JST exerted obvious ameliorative effect on renal function and structure in diabetic rats.

Animals↗
PubMed1996

Determination of mitral valve area in patients with mitral stenosis by the flow-convergence-region method during changing hemodynamic conditions.

Twenty-eight patients with mitral stenosis underwent Doppler echocardiography at rest and during exercise to determine the accuracy of mitral valve area determination by the flow-convergence-region method during exercise-induced changing hemodynamic conditions. The mitral valve area calculated by using the flow-convergence-region method correlated strongly with that measured by the Gorlin formula both at rest (r = 0.85) and during exercise (r = 0.92) for all 28 patients studied. Although mitral valve area obtained by the flow-convergence-region method did not change (p = 0.1) in 16 patients with echocardiographic mitral scores > or = 12, it increased significantly during exercise (p = 0.0001) in 12 patients with echocardiographic mitral scores < 12. This study suggests that in mitral stenosis, the mitral valve area can be accurately estimated by the flow-convergence-region method both at rest and during changing hemodynamic conditions induced by supine bicycle exercise.

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↗
PubMed1996

Application of the flow convergence region method to the determination of stroke volume and cardiac output in patients with mitral stenosis.

OBJECTIVE: This study was undertaken to investigate the feasibility and accuracy of determination of stroke volume and cardiac output by calculating transmitral flow volume using the flow convergence region method in patients with mitral stenosis. PATIENTS AND INTERVENTIONS: Fifty-six patients with rheumatic mitral stenosis were studied using imaging and Doppler echocardiography. Aliasing velocities of 20 to 23 cm/s were used to record the flow vonvergence region proximal to the stenotic mitral orifice. The stroke volume (mL) was calculated by multiplying peak transmitral flow rate which was obtained using an angle-corrected hemispheric flow convergence equation, by transmitral velocity time integral (cm) divided by peak transmitral velocity (cm/s) recorded using continuous wave Doppler method. MAIN RESULTS: Stroke volume calculated using the flow convergence region method was not significantly different from that calculated using aortic Doppler two-dimensional echocardiographic method in 39 patients with pure mitral stenosis (75+/-19 [mean+/-1SD] versus 73+/-19 mL, P=0.12), and from that calculated using pulmonic Doppler two-dimensional echocardiographic method in nine patients with mitral stenosis with associated>2+ aortic regurgitation (77+/-12 versus 75+/-14 mL, P=0.49). No significant difference existed between the cardiac output obtained using the flow convergence region method and that obtained using Fick method in 12 patients with pure mitral stenosis. The stroke volume was overestimated by the flow convergence region method when compared with those obtained using aortic Doppler two-dimensional echocardiographic method in patients with mitral stenosis with associated >2+ mitral regurgitation (123+/-40 versus 67+/-15 mL, P=0.001). CONCLUSIONS: The present study provided an alternative way to calculate the stroke volume and cardiac output in patients with mitral stenosis.

Adult↗
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

Evaluation of ventricular septal defect by transesophageal echocardiography: intraoperative assessment.

The miniaturization of transesophageal echocardiography (TEE) probes, together with the development of the capability for biplane imaging from the esophagus, have increased the use of TEE in pediatric cardiology. The aim of this study was to evaluate the TEE findings in patients with ventricular septal defect (VSD) before and after closure primarily by means of pediatric biplane probes. This study group included 69 patients who underwent VSD closure as an isolated repair or as a part of a definitive repair of a more complicated lesion. Ages ranged from 6 days to 15.6 years (median 1 year, 4 months), with operative weights ranging from 2.9 kg to 68 kg (median 10 kg). Preoperative and follow-up transthoracic echocardiograms (TTE) were also performed. Intraoperative TEE was performed without complication in all 69 patients. Preoperative results: (1) anatomic findings: Two muscular VSDs were detected by matrix TEE but could not be observed by TTE. A patient with preoperative TTE diagnosis of an ostium primum ASD was found to have atrioventricular (AV) canal by TEE. In three of six AV canal type VSDs, both TTE and TEE demonstrated left ventricular-right atrial shunting (2) aortic regurgitation associated with VSD: Aortic regurgitation as a result of right coronary cusp prolapse was detected in one of five supracristal VSDs in which the biplane or matrix TEE was used.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Estimation of mitral valve area in patients with mitral stenosis by the flow convergence region method: selection of aliasing velocity.

OBJECTIVES: We attempted to determine the most suitable aliasing velocity for applying the hemispheric flow convergence equation to calculate the mitral valve area in mitral stenosis using a continuity equation. BACKGROUND: The flow convergence region method has been used for calculating mitral valve area in patients with mitral stenosis. However, the effect of varying aliasing velocity on the accuracy of this method has not been investigated fully. METHODS: We studied 42 patients with mitral stenosis using imaging and Doppler echocardiography. Aliasing velocities of 17, 21, 28, 34, 40 and 45 cm/s were used. The transmitral maximal flow rate (Q [ml/s]) was calculated using the hemispheric flow convergence equation Q = 2 x pi x R2 x AV x alpha/180, where R (cm) is the maximal radius of the flow convergence region, AV is the aliasing velocity, and alpha/180 is a factor accounting for the inflow angle (alpha). Mitral valve area (A [cm2]) was calculated according to the continuity equation A = Q/V, where V (cm/s) is the peak transmitral velocity by the continuous wave Doppler method. RESULTS: Mitral valve area was progressively underestimated with increasing aliasing velocity. The actual and percent differences noted between the mitral valve area by the flow convergence region method and that by two-dimensional echocardiographic planimetry were -0.06 +/- 0.23 cm2 (mean +/- SD) and 0.09 +/- 15.7% at an aliasing velocity of 21 cm/s, increasing gradually with increasing aliasing velocity, and were -1.24 +/- 0.9 cm2 and -72.56 +/- 16.4% at an aliasing velocity of 45 cm/s. Mitral valve areas estimated by the flow convergence region method at an aliasing velocity of 21 cm/s in 11 patients with associated > 2+ mitral regurgitation (2.12 +/- 1.17 cm2) and 8 with associated > 2+ aortic regurgitation (1.28 +/- 0.71 cm2) were not significantly different using planimetry (2.24 +/- 1.39 cm2, p > 0.05 and 1.27 +/- 0.74 cm2, p > 0.05, respectively) but were significantly different by the pressure half-time method (1.59 +/- 1.12 cm2, p < 0.001 and 1.63 +/- 0.93 cm2, p < 0.01, respectively). CONCLUSIONS: This study indicated the most appropriate aliasing velocity for the accurate estimation of mitral valve area in patients with mitral stenosis.

Adolescent↗
PubMed1994

Estimation of regurgitant flow volume based on centerline velocity/distance profiles using digital color M-Q Doppler: application to orifices of different shapes.

OBJECTIVES: In this study we investigated the centerline velocity profile method for flow computation as applied to noncircular, as well as circular, orifices using digital color flow data. BACKGROUND: Recently it has been suggested that flow volume through an orifice can be estimated more accurately by computing the axial "centerline" flow velocity/distance profile proximal to the orifice. METHODS: A total of seven different orifices were mounted in a constant-flow model: four circular orifices, two rectangular orifices with a major/minor axis ratio of 4:1 and 8:1 and an ovoid orifice having a major/minor axis ratio of 2:1. Three different flow rates were examined (1.68, 3.48 and 6.48 liters/min). Digital measurements of flow velocity at discrete positions along the centerline progressing toward the orifice were analyzed to yield complete flow velocity profiles for each orifice at each flow rate. RESULTS: A clear separation of the flow profiles for the three different flow rates was observed independent of orifice size for all of the circular orifices. The velocity/distance acceleration curves showed highly significant correlations using multiplicative regression fits (y = ax-b, r = 0.94 to 0.99, all p < 0.0001). An equation for quantitatively correlating the a and b coefficients from the multiplicative regression fits with flow rates was derived from stepwise regression analysis: Flow rate = 23a + 3.3b - 1.5 (r = 0.97, p < 0.0001, SEE 0.46 liter/min). CONCLUSIONS: In view of the various sizes and shapes encountered clinically for regurgitant orifices, the simplicity of this method for the estimation of the severity of regurgitant lesions might be of importance for clinical applications of this method.

Blood Flow Velocity↗
PubMed1993

Effects of adjacent surfaces of different shapes on regurgitant jet sizes: an in vitro study using color Doppler imaging and laser-illuminated dye visualization.

OBJECTIVES: The present study was designed to estimate the influence of different-shaped adjacent surfaces on regurgitant jets as assessed by color Doppler imaging and laser-illuminated dye optical visualization. BACKGROUND: Because color Doppler techniques provide real-time two-dimensional imaging of flow, the evaluation of valvular regurgitation by analysis of variance-encoded regurgitant jets by this method has been widely used in clinical studies. However, recent studies have demonstrated that color Doppler jet sizes are affected not only by several hemodynamic factors and instrument settings but also by the interaction between jets and adjacent wall surfaces. In clinical conditions, jets may interact with adjacent walls of variable shapes that might have different effects on the jet size. METHODS: An in vitro model was constructed consisting of a rigid, optically clear receiving chamber that had no outlet resistance and had a pulsatile pump ejecting through 1.5, 2.3 and 3.1 mm2 inflow orifices into the chamber. The surfaces were flat or smoothly and equally curved, convex and concave aluminum positioned at 0, 2 and 4 mm from and to the side of the inflow orifices. The pump was run with stroke volumes from 0.5 to 3.0 ml and with a pulse frequency of 70 beats/min. The echocardiographic and laser beams were aimed at the inflow orifice imaging jets perpendicular to the surfaces (vertical view) through the central plane of the jet flows. Maximal jet areas were measured by both color Doppler techniques and laser-illuminated dye visualization. RESULTS: Color Doppler study showed fair correlation between the jet areas and the stroke volumes (r = 0.83 to 0.99), but the jet sizes under different surface conditions were variable. All the surface jet areas at a jet-surface distance of 0 and 2 mm were smaller than free jet areas at the same stroke volume for both flat and convex surfaces (p < 0.001). Flow constraint by the concave surface resulted in the smallest jet areas (p < 0.001). The color Doppler jet areas on the curved surfaces were significantly smaller than the laser-illuminated dye visualization jet areas (p < 0.01 to 0.0001). However, at intermediate jet-surface distances (4 mm and sometimes 2 mm with higher velocity flows), jet interaction with the flat and especially with the convex surface resulted in larger jets. This effect was most pronounced on dye fluorescence studies because flow around these jets consisted mainly of low velocity vortical events with only partial surface adherence and these low velocity swirling flows were not well imaged by color Doppler technique. CONCLUSIONS: Our study suggests that the different-shaped adjacent surfaces with different degrees of flow alterations resulted in variable decreases in jet size and that color Doppler imaging could not encode and image the angled and low velocity swirling events well when jets flowed along the curved surfaces. These effects need to be taken into account when interpreting color Doppler images.

Analysis of Variance↗
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↗
PubMed1993

Determination of the most appropriate velocity threshold for applying hemispheric flow convergence equations to calculate flow rate: selected according to the transorifice pressure gradient. Digital computer analysis of the Doppler color flow convergence region.

BACKGROUND: While flow convergence methods have been promising for calculating volume flows from color Doppler images, it appears that the velocity threshold used and the transorifice pressure gradient dramatically influence the accuracy of application of the simple hemispheric flow convergence equation for calculation of flow rate. The present in vitro study was performed to determine whether the value of velocity threshold at which the shape of proximal isovelocity surface best fits given shape assumptions with different orifice sizes and flow rates is predictable as a function independent of orifice size from clinically measurable peak velocity or transorifice pressure gradient information. METHODS AND RESULTS: In an in vitro model built to facilitate ultrasound imaging, steady flow was driven through circular discrete orifices with diameters of 3.8, 5.5, and 10 mm. Flow rates ranged from 2.88 to 8.28 L/min with corresponding driving pressure gradients from 14 to 263 mm Hg. At each flow rate, Doppler color-encoded M-mode images through the center of the flow convergence region were obtained and transferred into the microcomputer (Macintosh IIci) in their original digital format. Then, the continuous wave Doppler traces of maximal velocity through the orifice were derived for the calculation of driving pressure gradient. Direct numerical spatial velocity measurements were obtained from the digital color encoded M-mode velocities with computer software. For each flow rate, we could calculate flow volume from any number of velocity distance combinations with a number of assumptions and use the results to assess expected flow convergence shape based on a priori knowledge of the progression from oblate hemispheroid to hemisphere to prolate hemispheroid changes observed previously. Our results showed that for a given ratio of calculated flow rate to actual flow rate (0.7 and 1), the velocity threshold that could be used for the calculation of flow rate with a hemispheric flow convergence equation correlated well with the pressure gradient for a given orifice size, and the differences in velocity threshold that could be used this way among different orifice sizes once they were adjusted for the covariate pressure gradients were not statistically significant (P = .79 for ratio = 0.7, and P = .81 for ratio = 1). CONCLUSIONS: Our present study provides an orifice size-independent quantitative method that can be used to select the most suitable velocity threshold for applying a simple hemispheric flow convergence equation based on clinically predictable pressure gradients ranging from 40 to 200 mm Hg, and it offers a correction factor that can be applied to the hemispheric flow convergence equation when the pressure gradient is less than 40 mm Hg.

Blood Flow Velocity↗