While color Doppler flow mapping has yielded a quick and relatively sensitive method for visualizing the turbulent jets generated in valvular insufficiency, quantification of the degree of valvular insufficiency has been limited by the dependence of visualization of turbulent jets on hemodynamic as well as instrument-related factors. Color Doppler flow imaging, however, does have the capability of reliably showing the spatial relations of laminar flows. An area where flow accelerates proximal to a regurgitant orifice is commonly visualized on the left ventricular side of a mitral regurgitant orifice, especially when imaging is performed with high gain and a low pulse repetition frequency. This area of flow convergence, where the flow stream narrows symmetrically, can be quantified because velocity and the flow cross-sectional area change in inverse proportion along streamlines centered at the orifice. In this study, a gravity-driven constant-flow system with five sharp-edged diaphragm orifices (ranging from 2.9 to 12 mm in diameter) was imaged both parallel and perpendicular to the direction of flow through the orifice. Color Doppler flow images were produced by zero shifting so that the abrupt change in display color occurred at different velocities. This "aliasing boundary" with a known velocity and a measurable radial distance from the center of the orifice was used to determine an isovelocity hemisphere such that flow rate through the orifice was calculated as 2 pi r2 x Vr, where r is the radial distance from the center of the orifice to the color change and Vr is the velocity at which the color change was noted. Using Vr values from 54 to 14 cm/sec obtained with a 3.75-MHz transducer and from 75 to 18 cm/sec obtained with a 2.5-MHz transducer, we calculated flow rates and found them to correlate with measured flow rates (r = 0.94-0.99). The slope of the regression line was closest to unity when the lowest Vr and the correspondingly largest r were used in the calculation. The flow rates estimated from color Doppler flow imaging could also be used in conjunction with continuous-wave Doppler measurements of the maximal velocity of flow through the orifice to calculate orifice areas (r = 0.75-0.96 correlation with measured areas).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Doppler flow velocity studies were performed in normal human fetuses between 18 and 40 weeks of gestation. Two-dimensional linear array and sector scanning techniques were used for the initial evaluation of the fetuses, which included a standard ultrasound examination to determine normal anatomy and estimated gestational age and weight. Fetal

The simplified Bernoulli relationship appears to be quite accurate for predicting gradients across discrete valvular obstructions. Controversy exists about how accurately it predicts the severity of disease in longer segment obstructions. In this study we constructed a pulsatile model of subvalvular pulmonary stensosis in vitro to study nine custom-made subvalvular tunnels 2, 4, and 7 mm in length with flow cross sections of 0.5 to 1.5 cm2 and with the stenotic segment proximal to a nonstenotic bioprosthetic valve, and a pulsatile model in vitro of a 16 mm long tunnel-like ventricular septal defect (VSD) of varying cross-sectional area (0.20 to 0.64 cm2). We also compared the observations in vitro with those in an open-chest dog preparation with a tunnel-like interventricular communication. In the subpulmonic stenosis model, for each individual tunnel, 10 instantaneous peak gradients between 15 to 105 mm Hg were available. The pressure gradients across the tunnel alone, measured in the subvalvular area, were consistently higher than the measured gradients across the tunnel plus valve, suggesting some relaminarization of flow (i.e., a decrease in velocity) and pressure recovery (i.e., an increase in pressure) distal to the obstruction. Continuous-wave Doppler velocities across the 4 and 7 mm tunnels for the highest gradients were slightly lower than for the 2 mm tunnel at the same gradients, and it was only for the 0.5 cm2 cross section, 4 and 7 mm tunnels that there was a suggestion of minor viscous energy loss. For all the subvalvular tunnels studied, the Bernoulli relationship accurately predicted the results of the pressure drop across the tunnel only, while the gradient across tunnel plus valve was consistently lower. For the VSD tunnel model in vitro, the Doppler-derived gradients were approximately 40% higher than the measured gradients. The findings for the subvalvular and VSD tunnels in vitro and similar findings in the open-chest dogs with VSD suggest that relaminarization of flow and recovery of pressure occurred distal to the tunnel orifice, whereas continous-wave Doppler findings correlate with the highest instantaneous gradients measured in the lowest pressure areas at the vena contracta of the tunnel.

Qualitative and quantitative changes in left ventricular shapes were analyzed in 14 normal fetuses, 29 normal newborns, and 12 normal infants. Qualitative observations demonstrated that most fetuses and newboms with dominant right ventricles had flattened or even indented interventricular septae, which changed left ventricular shape into an ellipse. In contrast, left ventricular shapes in infants were round, similar to shapes described in older children and adults. When changes in shape or septal distortions were gross, interobserver agreement was 100%; when changes were less altered from a circular shape, interobserver agreement was 78%. To

Our efforts indicate that transvascular passage of small phased-array probes can be easily accomplished and is a promising technique for detailed visualization of cardiac structures. This approach may provide an alternative to transesophageal echocardiography, particularly for guiding interventional procedures such as placement of transcatheter closure devices in pediatric patients.