A new method for quantitation of mitral regurgitation based on color flow Doppler imaging of flow convergence proximal to regurgitant orifice.

BACKGROUND: Imaging of the flow convergence region (FCR) proximal to a regurgitant orifice has been shown to provide a method for quantifying the regurgitant flow rate. According to the continuity principle, the FCR is constituted by concentric hemispheric isovelocity surfaces centered at the orifice. The flow rate is constant across all isovelocity surfaces and equals the flow rate through the orifice. For any isovelocity surface the flow rate (Q) is given by: Q = 2 pi r2 Vr, where 2 pi r2 is the area of the hemisphere and Vr is the velocity at the radial distance (r) from the orifice. METHODS AND RESULTS: We studied 52 consecutive patients with mitral regurgitation (mean age, 49 years; age range, 21-66 years) verified by left ventricular angiography using color flow mapping. The FCR r was measured as the distance between the first aliasing limit--at a Nyquist limit obtained by zero-shifting the velocity cutoff to 38 cm/sec--and the regurgitant orifice. Seven patients without evidence of an FCR had only grade 1+ mitral regurgitation angiographically. There was a significant relation between the Doppler-derived maximal instantaneous regurgitant flow rate and the angiographic degree of mitral regurgitation in the other patients (rs = 0.91, p less than 0.001). The regurgitant flow rate by Doppler also correlated with the angiographic regurgitant volume (r = 0.93, SEE = 123 ml/sec) in the 15 patients in normal sinus rhythm and without other regurgitant lesions in whom it could be measured. The correlation between regurgitant jet area within the left atrium and the angiographic grade was only fair (rs = 0.75, p less than 0.001). CONCLUSIONS: Color flow Doppler provides new velocity information about the proximal FCR in patients with mitral regurgitation. According to the continuity principle, the maximal instantaneous regurgitant flow rate, obtained with the FCR method, may provide a quantitative estimate of the severity of mitral regurgitation, which is relatively independent of technical factors.

[Doppler estimation of the stenotic mitral valve area. Direct application of the continuity equation to the flow convergence region]. / Stima mediante Doppler dell'area mitralica stenotica. Applicazione diretta dell'equazione di continuità alla regione di convergenza del flusso.

The continuity equation, applied to the flow convergence region (FCR), fournishes a simple alternative to calculate stenotic valve area. The flow rate in the FCR can be calculated by multiplying the hemispheric isovelocity surface area by the velocity of the isovelocity surface. Since according to the continuity principle the flow rate through any isovelocity surface equals the flow rate through the stenotic orifice, the stenotic orifice area can be calculated as: 2 pi r2Vr/Vm, where 2 pi r2 is the hemispheric isovelocity area, Vr is the velocity at the radial distance r from the orifice and Vm is the peak jet velocity. This study was designed to analyze the validity of application of the continuity equation to the FCR for estimating mitral orifice area by Dopler ultrasound. We studied 35 consecutive patients with rheumatic mitral stenosis. Three patients were excluded; the final study population consisted of 32 patients (8 men and 24 women; mean age 56 years). Nine patients were in normal sinus rhythm and 23 in atrial fibrillation. Doppler examination was performed from the apical approach within 24 hours of cardiac catheterization. On color Doppler image Vr was defined as the first aliasing limit (lowered to 38 cm/s to increase FCR r); r represented the maximal early diastolic distance between the first alias and the stenotic orifice in a direction parallel to that of the transducer; Vm was the early diastolic peak jet velocity by continuous wave Doppler.(ABSTRACT TRUNCATED AT 250 WORDS)

A new method for quantification of regurgitant flow rate using color Doppler flow imaging of the flow convergence region proximal to a discrete orifice. An in vitro study.

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)

Color Doppler diagnosis of mechanical prosthetic mitral regurgitation: usefulness of the flow convergence region proximal to the regurgitant orifice.

In prosthetic or paravalvular prosthetic mitral regurgitation, transthoracic color Doppler flow mapping can sometimes fail to detect the regurgitant jet within the left atrium because of the shadowing by the prosthetic valve. To overcome this limitation, we assessed the utility of color Doppler visualization of the flow convergence region (FCR) proximal to the regurgitant orifice in 20 consecutive patients with mechanical prosthetic mitral regurgitation documented by surgery and cardiac catheterization (13 of 20 patients). In addition, we studied 33 patients with normally functioning mitral prostheses. Doppler studies were performed in the apical, subcostal, and parasternal long-axis views. An FCR was detected in 95% (19 of 20) of patients with prosthetic mitral regurgitation. A jet area in the left atrium was detected in 60% (12 of 20) of patients. In 18 of 19 patients with Doppler-detected FCR, the site of the leak was correctly identified by observing the location of the FCR. A trivial jet area was detected in eight patients with a normally functioning mitral prosthesis; in none was an FCR identified. Thus color Doppler visualization of the FCR proximal to the regurgitant orifice is superior to the jet area in the diagnosis of mechanical prosthetic mitral regurgitation. Moreover, FCR permits localization of the site of the leak with good accuracy.

A new method for estimating left ventricular dP/dt by continuous wave Doppler-echocardiography. Validation studies at cardiac catheterization.

In this study, we explored the use of continuous wave Doppler-echocardiography guided by color Doppler flow-mapping as a method for noninvasively calculating the rate of pressure rise (RPR) in the left ventricle. Continuous wave Doppler determination of the velocities in mitral regurgitant jets allows calculation of instantaneous pressure gradients between the left ventricle and the left atrium. Left atrial pressure variations in early systole can be considered negligible; therefore, the rising segment of the mitral regurgitation velocity curve should reflect left ventricular pressure increase. We studied 50 patients (mean age, 51 years; range, 25-66 years) in normal sinus rhythm with color Doppler-proven mitral regurgitation and compared the Doppler-derived left ventricular RPR with peak dP/dt obtained at cardiac catheterization. Doppler studies were performed simultaneously with cardiac catheterization in 11 patients and immediately before in the remaining cases. Two points were arbitrarily selected on the steepest rising segment of the continuous wave mitral regurgitation velocity curve (point A, 1 m/sec, point B, 3 m/sec), and the time interval (t) between them was measured. Following the Bernoulli relation, the pressure rise between points A and B is 32 mm Hg (4vB2-4vA2) and the RPR is 32 mm Hg/t. Results showed a linear correlation between the Doppler RPR and peak dP/dt (r = 0.87, SEE = 316 mm Hg/sec). The RPR in the left ventricle can be derived from the continuous wave Doppler mitral regurgitation velocity curve.

[The role of echocardiography and pulsed Doppler in the congenital absence of the pericardium. Description of 2 cases]. / Il ruolo dell'ecocardiografia e del Doppler pulsato nell'assenza congenita del pericardio. Descrizione di due casi.

Congenital absence of the left pericardium, partial or complete, is an uncommon cardiac defect. Most patients affected by this abnormality are asymptomatic. Usually it is suspected on the basis of a chest X-ray showing a normal sized cardiac shadow projecting entirely to the left of the spine. Computed axial tomography confirmed the absence of the left pericardium detecting the interposition of the left lung between the ascending aorta and main pulmonary artery. The M-mode, two-dimensional, and Doppler-cardiographic findings of complete congenital absence of the left pericardium are described in two cases. Imaging seems to be not specific for this abnormality; however in both cases pulsed Doppler detected mild tricuspid and pulmonic valve regurgitation.