BACKGROUND: Proximal flow convergence is a promising method to quantify mitral regurgitation but may overestimate flow when the flow field is constrained. This has not been investigated clinically, nor has a correction factor been validated. METHODS AND RESULTS: Eighty-five patients were studied intraoperatively with transesophageal echocardiography and divided into two ...

A total of 92 patients with mitral regurgitation (age 63 +/- 13 years, 51 men, 41 women), quantified by angiography, were studied using color-flow Doppler imaging of isovelocity surface areas in the flow convergence region proximal to the regurgitant orifice (PISAs) and of the regurgitant jet in the left atrium. ...

Colour flow Doppler echocardiography is a technique that is used with two-dimensional (2-D) echocardiography to study blood flow patterns in the heart and blood vessels. This method was used to define normal flow patterns and to evaluate valvular function in 40 clinically normal Thoroughbred and Thoroughbred cross horses. Flow patterns ...

Speciation applications of the flow-injection technique are discussed in relation to the hydrodynamic manifold components that are adapted for this purpose. Alterations include double halting of the propulsion system, coupling of injection valves, modifications of the transport-reaction zone, use of switching valves, and merging and splitting points. Detector remodelling, the ...

BACKGROUND: The mechanisms of blood flow during closed-chest cardiopulmonary resuscitation (CPR) in humans have been debated since the technique was first described in 1960. Two competing models, the cardiac pump theory and the thoracic pump theory, have been proposed, and some investigators have used mitral valve position during the downstroke ...

Many problems and complications associated with heart valves are related to the dynamic behavior of the valve and the resultant unsteady flow patterns. An accurate depiction of the spatial and temporal velocity and rms distributions imparts better understanding of flow related valve complications, and may be used as a guideline ...

OBJECTIVES: The aim of the present study was to investigate dynamic changes in the mitral regurgitant orifice using electromagnetic flow probes and flowmeters and the color Doppler flow convergence method. BACKGROUND: Methods for determining mitral regurgitant orifice areas have been described using flow convergence imaging with a hemispheric isovelocity surface ...

Atheroembolism from the ascending aorta is an emerging cause of noncardiac complications after open heart surgery. We designed a new arterial cannula specifically to reduce the exit force and velocity of blood flow, thereby reducing the "sandblasting" effect of the exiting blood jet. The cannula has a closed tip and ...

The relation between flow rate (Q) and transvalvular pressure-drop (DP) is of fundamental importance for a prosthetic heart valve tested in steady flow conditions. The Q-DP plot can thus be called the static characteristic of the valve. While in pulsatile flow, with time (t) as a parameter, the instantaneous Q(t)-DP(t) ...

Aortic regurgitation is most frequently assessed noninvasively by Doppler echocardiography by use of continuous wave and Doppler color flow mapping. To compare both Doppler methods, 161 patients who had undergone cardiac catheterization and complete echocardiographic studies were studied. The continuous wave parameters analyzed included the slope of the diastolic deceleration ...

Intracardiac flow patterns during heart development were studied by injection of india ink into the yolk sac circulation of chick embryos at Hamburger-Hamilton stages 10 to 17. We injected india ink into a small venule or capillary, carefully preventing application of overpressure to the vascular system, and recorded the intracardiac ...

It has been recently demonstrated that indexes obtained from the study of pulmonary venous flow by Doppler echocardiography are related to left ventricular (LV) pressures during diastole and may improve the assessment of LV filling derived from analysis of mitral flow velocities. In this study we evaluated the pattern of ...

Although left ventricular (LV) inflow and pulmonary venous (PV) flow variables estimated by transesophageal Doppler echocardiography (TEE) reflect pulmonary capillary wedge pressure (PCWP), they are also affected by changes in cardiac function. The purpose of the present study was to detect the most appropriate variable for the estimation of PCWP ...

BACKGROUND: Valvular resistance and stroke work loss have been proposed as alternative measures of stenotic valvular lesions that may be less flow dependent and, thus, superior over valve area calculations for the quantification of aortic stenosis. The present in vitro study was designed to compare the impacts of valvular resistance, ...

The purpose of the present study was to examine the relationship between variations in glottal area and vibratory patterns during phonation studied with stroboscopy and glottographic methods. Two normal speaking male and three female subjects were examined by means of simultaneous stroboscopy, flow glottography, and electroglottography. Estimations were made of ...

This paper reports some of the ways in which biomaterial considerations have influenced the design, development and construction methods for a prototype conduit valve prosthesis in which the valve body is made from alumina. This material is used principally for its ability to grow and support a thin (< 0.1 ...

MRI has developed very rapidly and now provides anatomic and functional information in cases of valvular heart disease. MRI has several important attributes that make it advantageous for the evaluation of valvular heart disease. First, the natural contrast between flowing blood and surrounding cardiovascular structures provides sharp delineation of endocardial ...

Attempts to quantify valvular regurgitation have recently been focused on the proximal orifice flow field. A complete description of the proximal orifice flow field is provided in this investigation. A steady state in vitro model accessible by both color Doppler ultrasound (CDU) and laser Doppler velocimetry (LDV) was utilized. Velocities ...

We studied the properties of the jet of blood entering the left ventricle from the left atrium during early diastole in 32 patients with dilated cardiomyopathy, and 24 normal subjects of similar age. The diameter of the jet was measured from the cross-sectional color Doppler image and its cross-sectional area ...

Suboptimal hemodynamic performance, tissue calcification, and limitation in long-term durability have been encountered clinically after aortic valve replacement with currently available bioprostheses. It is believed that some of these problems may be caused, directly or indirectly, by the stents of the bioprostheses. To address these deficiencies, the authors undertook the ...

To evaluate the in vivo accuracy of color Doppler flow-convergence methods for determining transmitral flow volumes and effective orifice areas in mitral stenosis, we studied two models for flow-convergence surface geometry, a hemispheric (HS) model and an oblate hemispheroid (OH) model in a chronic animal model with quantifiable mitral flows. ...

The hydrodynamic function of six size 19 mm bileaflet mechanical heart valves was investigated in a pulsatile flow simulator. The St. Jude Standard, St. Jude Haemodynamic Plus, CarboMedics, Sorin Biomedica, Duromedics and ATS valves were studied. The mean pressure drop and effective orifice area during forward flow, regurgitant volumes and ...

Recent studies have attempted to predict the severity of regurgitant lesions from color Doppler jet size, which is a function of orifice momentum for free jets. Jets of mitral and tricuspid regurgitation, however, are opposed by flows entering the atria. Despite their low velocities, these counterflows may have considerable momentum ...

Spontaneous echo contrast (SEC) is an echogenic, swirling pattern of blood flow which may be observed by transesophageal echocardiography (TEE) in the left atrium in low flow states, such as atrial fibrillation (AF). The presence of SEC has been proposed as a marker of increased thromboembolic risk. Evaluation of the ...

To obtain an optimal design of the left blood chamber of the total artificial heart (TAH), flow visualization studies were performed. Information on velocities in critical areas of the left chamber was gathered using sectional pulsed laser light. The flow patterns on the entire pumping duration were photographed frame by ...

Analysis of the flow-convergence zone proximal to a regurgitant orifice permits the noninvasive, quantitative measurement of clinically useful parameters of valvular insufficiency. However, many indexes such as flow rate reflect not only the size of the regurgitant lesion but are also highly dependent on the hemodynamic loading conditions. The effective ...

The presence of turbulence in the cardiovascular system is generally an indication of some type of abnormality. Most cardiologists agree that turbulence near a valve indicates either valvular stenosis or regurgitation, depending on the phase of its occurrence during the cardiac cycle. As no satisfying analytical solutions of the stability ...

Since the introduction of bileaflet heart valve prostheses their clinical use has continued to escalate. The first of this valve type was the Standard St. Jude Medical (SSJM) prosthetic heart valve in 1977. The Carbomedics prosthetic heart valve (CPHV), introduced in the late 1980s, was intended to improve on the ...

OBJECTIVES: This study attempted to develop and validate a simple method for calculating aortic regurgitant fraction by use of pulsed wave Doppler echocardiography. BACKGROUND: Although several investigators have been able to determine aortic regurgitant fraction by Doppler echocardiography, the methods used require accurate determination of the cross-sectional areas of intracardiac ...

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, ...

OBJECTIVES: We attempted to determine whether continuous wave Doppler backscatter power could be used to quantify mitral regurgitation. BACKGROUND: The power of a Doppler backscatter signal is proportional to the number of scatterers insonated and, hence, to the moving volume of blood. The relative power of the continuous wave Doppler ...

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" ...

The Doppler method of obtaining left ventricular Max(dP/dt) proposed recently was based on the measurement of mitral regurgitation velocity. Since Max(dP/dt) is an isovolumic phase index, its use in cases of mitral regurgitation may be open to argument. However, we had proposed a noninvasive method of estimating left ventricular Max(dP/dt) ...

To analyze the flow patterns of the left blood chamber of the Baylor total artificial heart (TAH) and to evaluate influences of the inflow valve angle to the flow patterns, flow visualization studies were performed. The inflow valve angle of the left housing was changed by 20 degrees orthogonal to ...

Retrograde blood from the aortic cannula into the cardiopulmonary circuit may lead to aortic air emboli when nonocclusive centrifugal pumps are used. The authors tested a nonregurgitant, unidirectional valve containing a Teflon ball occluder to prevent backflow. In vitro measurements of leakage rate, forward flow pressure drop, burst strength, and ...

BACKGROUND: The proximal flow convergence method, a quantitative color Doppler flow technique, has been validated recently for calculating regurgitant flow and orifice area. We investigated the potential of the method as a tool to study different pathophysiological mechanisms of mitral valve incompetence by assessing the time course of regurgitant flow ...

The objective of this experiment was to investigate the relationship between blood damage and drive line dP/dt and valve type in the pneumatic ventricular assist device. Two mock circulatory loops were assembled using 70-ml Penn State pneumatic ventricular assist devices, one fitted with convexo-concave (CC) valves and one fitted with ...

Jet flows are consequences of many cardiac lesions. With the advent of color Doppler flow mapping, these jet flows can be visualized noninvasively. Currently, an intense effort is underway to quantify cardiac jet flows as a means to assess the severity of jet forming lesions. Two techniques, PISA and jet ...

The foramen ovale size and interatrial flow patterns were studied by combined real-time and Doppler echocardiography in 100 normal human fetuses between 20 and 38 weeks gestation. The foramen ovale, atrioventricular, and semilunar valve diameters increased linearly with gestational age. The foramen flap motion and interatrial flow patterns showed biphasic ...

Quantitation of valvular regurgitation remains an important goal in clinical cardiology. It has been described previously that with the use of color Doppler flow mapping, simple measurements of apparent jet size do not correlate closely with quantitative regurgitant indices. Recently the proximal flow convergence method has been proposed to quantify ...

Full-field measurement of instantaneous velocities in the flow field of artificial heart valves is vital as the flow is unsteady and turbulent. Particle image velocimetry (PIV) provides us the ability to do this as compared to other point measurement devices where the velocity is measured at a single point in ...

Spontaneous echo contrast has been observed in conditions of low blood flow velocity, such as rheumatic mitral stenosis and atrial fibrillation (AF). The phenomenon has been attributed to increased echogenicity due to aggregation of blood cells at low shear rates. The aim of this study was to determine whether abnormalities ...

The design of artificial heart valves has traditionally been based on the development of a prototype device which was then subjected to extensive laboratory testing in order to confirm its suitability for clinical use. In the past the in vitro assessment of a valve's performance was based principally on the ...

BACKGROUND: Valve areas derived by the Gorlin formula have been observed to vary with transvalvular volume flow rate. Continuity equation valve areas calculated from Doppler-echo data have become a widely used alternate index of stenosis severity, but it is unclear whether continuity equation valve areas also vary with volume flow ...

PURPOSE: To present a spin-echo phase-contrast (SEPC) magnetic resonance pulse sequence designed to measure the very slow flow in ventricular shunt tubing. MATERIALS AND METHODS: A flow phantom constructed of shunt tubing and incorporating no valve or a high-, medium-, or low-pressure valve was connected to a flow pump. Flow ...

Anesthetic agents may significantly alter the patient's blood pressure, and thus affect the intraoperative assessment of mitral regurgitation. This study examined the impact of an increase in afterload on a variety of parameters thought to reflect the severity of mitral regurgitation, and related them to changes in hemodynamic parameters. Twenty-four ...

High levels of turbulent stresses resulting from disturbed blood flow may cause damage to red blood cells and platelets. The purpose of this study was to evaluate the spatial distribution and temporal development of turbulent stresses downstream of three mechanical aortic valve prostheses in human subjects: the St. Jude Medical, ...

In a patient with obstructive left atrial myxoma, we analyzed by pulsed Doppler echocardiography the flow pattern through the mitral valve and in the pulmonary veins. Two mitral flow patterns were observed: the first was present near the medial commissure and along the anterior leaflet and was characterized by the ...

Eighty-six patients who had undergone aortic valve surgery were reviewed. Forty-three had received crystalloid cardioplegia, the other 43 blood cardioplegia. Spontaneous beating after cross-clamp release (blood 11; crystalloid 0; P < 0.001), number of defibrillations (blood 2.1 +/- 2.6; crystalloid 3.8 +/- 2.2; P < 0.01) and CK-MB values on ...

In this study 97 patients with mitral regurgitation (age 62 +/- 11 years, 55 men, 42 women) quantified by angiography were studied using colour flow Doppler imaging of isovelocity surface areas in the flow convergence region proximal to the regurgitant orifice. The radii of the proximal isovelocity surface areas for ...