Broad-beam spectral Doppler sonification of the vena contracta using matrix-array technology: A new solution for semi-automated quantification of mitral regurgitant flow volume and orifice area

OBJECTIVES: The objective of this study was to evaluate broad-beam spectral Doppler sonification of the vena contracta using a matrix-array transducer for quantification of mitral regurgitation (MR). BACKGROUND: Noninvasive assessment of the severity of valvular regurgitation remains challenging. A recent technique measures regurgitant flow directly at the vena contracta based on the product of velocity times backscattered Doppler power (proportional to orifice area). That approach, however, has been limited by relatively narrow conventional beamwidths. Matrix-array transducers, recently developed for three-dimensional imaging, can potentially provide broader beams. Therefore, we addressed the hypothesis that deliberate broadening of the Doppler beam can encompass larger regurgitant cross-sectional areas to capture a broader range of regurgitant flows. METHODS: A matrix-array transducer system was modified to provide a three-dimensionally expanded spectral Doppler sample volume. Calculations of orifice area, flow rate, and regurgitant stroke volume (RSV) from Doppler power were automated on board a routinely used echocardiographic scanner and tested in vitro. In 24 patients with isolated MR, RSV was compared with magnetic resonance imaging (MRI) mitral inflow minus aortic outflow from phase-velocity maps. RESULTS: The calculated flow rate and RSV correlated and agreed well with reference values in vitro (r = 0.98 to 0.99) and in patients (r = 0.93, mean difference 0.4 +/- 3.2 ml, p = NS vs. 0), with sufficient sonification to measure flow orifices up to 0.85 cm in diameter. Agreement with MRI was comparable in 17 patients with central and seven with eccentric jets (p = NS vs. 0). CONCLUSIONS: The broad-beam spectral Doppler technique provides accurate, largely automated quantification of regurgitant flow rate and integrated RSV directly at the lesion. The accuracy related to broader sonification is made possible by the new matrix-array transducer design.     

Effective regurgitant orifice area: A noninvasive Doppler development of an old hemodynamic concept

Objectives. The purpose of this study was to determine the feasibility, relation to other methods and significance of the effective regurgitant orifice area measurement.Background. Assessment of the severity of valvular regurgitation (effective regurgitant orifice area) has not been implemented in clinical practice but can be made by Doppler echocardiography.Methods. Effective regurgitant orifice area was calculated by Doppler echocardiography as the ratio of regurgitant volume/ regurgitant jet time-velocity integral and compared with color flow Doppler mapping, angiography, surgical classification, regurgitant fraction and variables of volume overload.Results. In 210 consecutive patients examined prospectively, feasibility improved from the early to the late experience (65% to 95%). Effective regurgitant orifice area was 28 ± 23 mm²(mean ± SD) for aortic regurgitation (32 patients), 22 ± 13 mm²for ischemic/functional mitral regurgitation (50 patients) and 41 ± 32 mm²for organic mitral regurgitation (82 patients). Significant correlations were found between effective regurgitant orifice and mitral jet area by color flow Doppler mapping (r = 0.68 and r = 0.63, p < 0.0001, respectively) and angiographic grade (r = 0.77, p = 0.0004). Effective regurgitant orifice area in surgically determined moderate and severe lesions was markedly different in mitral regurgitation (35 ± 12 and 75 ± 33 mm², respectively, p = 0.009) and in aortic regurgitation (21 ± 8 and 38 ± 5 mm², respectively, p = 0.08). Strong correlations were found between effective regurgitant orifice area and variables reflecting volume overload. A logarithmic regression was found between effective regurgitant orifice area and regurgitant fraction, underlining the complementarity of these indexes.Conclusions. Calculation of effective regurgitant orifice area is a noninvasive Doppler development of an old hemodynamic concept, allowing assessment of the lesion severity of valvular regurgitation. Feasibility is excellent with experience. Effective regurgitant orifice area is an important and clinically significant index of regurgitation severity. It brings additive information to other quantitative indexes and its measurement should be implemented in the comprehensive assessment of valvular regurgitation.     

Assessment of Mitral Regurgitation by the Measurement of Vena Contracta Using Power Doppler Echocardiography

The measurement of vena contracta is a promising method for quantification of mitral regurgitation (MR). No data exist regarding the ability of power Doppler echocardiography in the assessment of vena contracta in MR. We attempted to clarify the ability of power Doppler in the assessment of vena contracta in MR. The width of vena contracta was measured using power Doppler in 70 patients with chronic MR. Mean effective regurgitant orifice area (EROA) was calculated quantitatively by the spectral Doppler. The area of vena contracta was calculated by measuring the width of vena contracta from the following formula: Vena contracta area = * (vena contracta width/2)². The width of vena contracta ranged from 3.6 to 8.4 mm. The EROA varied from 0.10 to 0.56 cm². Good correlations were found between EROA and vena contracta area obtained by power Doppler (r = .95, p < .0001, SEE = 0.04 cm²). Strong relationships were observed between the area of vena contracta and regurgitant volume (r = 0.93, p < .0001, SEE = 8.1 ml/beat), and regurgitant fraction (r = 0.95, SEE = 6.1%). Power Doppler may provide an additional method for assessing vena contracta in MR. Abbreviations: MR = mitral regurgitation; LV = left ventricle; TVI = time-velocity integral; EROA = effective regurgitant orifice area     

Assessment of aortic regurgitation by transesophageal color Doppler imaging of the vena contracta: validation against an intraoperative aortic flow probe

OBJECTIVES: This study was performed to validate the accuracy of color flow vena contracta (VC) measurements of aortic regurgitation (AR) severity by comparing them to simultaneous intraoperative flow probe measurements of regurgitant fraction (RgF) and regurgitant volume (RgV). BACKGROUND: Color Doppler imaging of the vena contracta has emerged as a simple and reliable measure of the severity of valvular regurgitation. This study evaluated the accuracy of VC imaging of AR by transesophageal echocardiography (TEE). METHODS: A transit-time flow probe was placed on the ascending aorta during cardiac surgery in 24 patients with AR. The flow probe was used to measure RgF and RgV simultaneously during VC imaging by TEE. Flow probe and VC imaging were interpreted separately and in blinded fashion. RESULTS: A good correlation was found between VC width and RgF (r = 0.85) and RgV (r = 0.79). All six patients with VC width >6 mm had a RgF >0.50. All 18 patients with VC width <5 mm had a RgF <0.50. Vena contracta area also correlated well with both RgF (r = 0.81) and RgV (r = 0.84). All six patients with VC area >7.5 mm2 had a RgF >0.50, and all 18 patients with a VC area <7.5 mm2 had a RgF <0.50. In a subset of nine patients who underwent afterload manipulation to increase diastolic blood pressure, RgV increased significantly (34 +/- 26 ml to 41 +/- 27 ml, p = 0.042) while VC width remained unchanged (5.4 +/- 2.8 mm to 5.4 +/- 2.8 mm, p = 0.41). CONCLUSIONS: Vena contracta imaging by TEE color flow mapping is an accurate marker of AR severity. Vena contracta width and VC area correlate well with RgF and RgV obtained by intraoperative flow probe. Vena contracta width appears to be less afterload-dependent than RgV.     

Assessment of severity of mitral regurgitation by measuring regurgitant jet width at its origin with transesophageal Doppler color flow imaging.

BACKGROUND. The ability of transesophageal color Doppler echocardiography to provide high-resolution images of both cardiac structure and blood flow in real time is advantageous for many clinical purposes. This study was performed to determine the utility of the regurgitant jet width at its origin measured by transesophageal Doppler color flow imaging in the assessment of severity of mitral regurgitation. METHODS AND RESULTS. Sixty-three consecutive patients with mitral regurgitation underwent transesophageal color Doppler examination, and the diameter of regurgitant jet at its origin was measured. Both right and left cardiac catheterizations were performed within 24 hours of Doppler studies, and angiographic grading of mitral regurgitation and regurgitant stroke volume were evaluated. There was a close relation between the jet diameter at its origin measured by transesophageal Doppler color flow imaging and the angiographic grade of mitral regurgitation (r = 0.86, p less than 0.001). A jet diameter of 5.5 mm or more identified severe mitral regurgitation (grade III or IV) with a sensitivity of 92%, specificity of 92%, and positive and negative predictive values of 88% and 95%, respectively. In 31 patients with isolated mitral regurgitation, the jet diameter correlated well with the regurgitant stroke volume determined by a combined hemodynamic-angiographic method (r = 0.85, p less than 0.001). A jet diameter of 5.5 mm or more identified a regurgitant stroke volume of 60 ml or more with a sensitivity of 88%, specificity of 93%, and positive and negative predictive values of 94% and 87%, respectively. CONCLUSIONS. The regurgitant jet width at its origin measured by transesophageal Doppler color flow imaging provides a simple and useful method of measuring the severity of mitral regurgitation, and it may allow differentiation between mild and severe mitral regurgitation.     

Relation between Doppler color flow variables and invasively determined jet variables in patients with aortic regurgitation.

OBJECTIVES. The purpose of this study was to test the hypothesis that invasively derived jet variables including regurgitant orifice area and momentum determine the characteristics of Doppler color flow jets in patients with aortic regurgitation. BACKGROUND. In vitro studies have demonstrated that the velocity distribution of a regurgitant jet is best characterized by the momentum of the jet, which incorporates orifice area and velocity of flow through the orifice. METHODS. Peak jet momentum, peak flow rate and regurgitant orifice area were determined with intraaortic Doppler catheter and cardiac catheterization techniques in 22 patients with chronic aortic regurgitation. These invasively derived variables were compared with apical and parasternal long-axis Doppler color echocardiographic variables obtained in the catheterization laboratory. RESULTS. Jet momentum increased significantly with the angiographic grade of regurgitation. The apical color jet area of aortic regurgitation increased linearly with jet momentum and regurgitant orifice area in vivo, but the correlations were only moderately good (r = 0.63 and 0.65, respectively). Color jet length also increased linearly with jet momentum and with regurgitant orifice area. There was only a trend for Doppler color jet width to increase with all invasively derived jet variables. CONCLUSIONS. Whereas jet area by Doppler color flow imaging is directly related to both orifice area and jet momentum in vivo, Doppler color variables measured in planes normal to the orifice do not correlate well enough with either jet momentum or regurgitant orifice area to predict jet flow variables in patients with aortic regurgitation. It is likely that the important influence of adjacent boundaries will limit the use of the velocity distribution of aortic regurgitant jets for determining the severity of disease.     

Three-dimensional reconstruction of the color Doppler-imaged vena contracta for quantifying aortic regurgitation: studies in a chronic animal model

BACKGROUND: The purpose of this study was to investigate the use of 3-dimensional (3D) reconstruction of color Doppler flow maps to image and extract the vena contracta cross-sectional area to determine the severity of aortic regurgitation (AR) in an animal model. Evaluation of the vena contracta with 2-dimensional imaging systems may not be sufficiently robust to fully characterize this region, which may be asymmetrically shaped. METHODS AND RESULTS: In 6 sheep with surgically induced chronic AR, 18 hemodynamically different states were studied. Instantaneous regurgitant flow rates were obtained by aortic and pulmonary electromagnetic flowmeters (EMFs) as reference standards, and aortic regurgitant effective orifice areas (EOAs) were determined from EMF regurgitant flow rates divided by continuous-wave (CW) Doppler velocities. Composite video data for color Doppler imaging of the aortic regurgitant flows were transferred into a TomTec computer after computer-controlled 180 degrees rotational acquisition. After the 3D data transverse to the flow jet were sectioned, the smallest proximal jet cross section was identified for direct measurement of the vena contracta area. Peak regurgitant flow rates and regurgitant stroke volumes were calculated as the product of these areas and the CW Doppler peak velocities and velocity-time integrals, respectively. There was an excellent correlation between the 3D-derived vena contracta areas and reference EOAs (r=0.99, SEE=0.01 cm2) and between 3D and reference peak regurgitant flow rates and regurgitant stroke volumes (r=0.99, difference=0.11 L/min; r=0.99, difference=1.5 mL/beat, respectively). CONCLUSIONS: 3D-based determination of the vena contracta cross-sectional area can provide accurate quantification of the severity of AR.     

Pitfalls in the color Doppler diagnosis of valvular regurgitation

Color Doppler flow mapping of the regurgitant jet is frequently used as a means of assessing the severity of valvular regurgitation. Although convenient, this method of assessing valvular regurgitation is subject to a number of hemodynamic and technical factors that may limit its accuracy. Variations in hemodynamic and structural factors such as orifice size, jet geometry, receiving chamber constraints, afterload, fluid viscosity, heart rate, and cardiac output may have profound effects on the measured regurgitant jet area. Variations in scanning and machine factors, such as scanning direction, Doppler angle, frame rate, color display algorithms, pulse repetition frequency (PRF), system gain, packet size, carrier frequency, wall filter, and transmit power have been shown to alter the measured regurgitant jet area significantly. Despite these limitations, color flow Doppler provides a relatively reliable noninvasive method for semiquantitative assessment of valvular regurgitation. Obviously, standardization of the design and application of the various available color mapping algorithms, as well as other machine and hemodynamic factors, would help provide more reliable and reproducible quantitative information about the degree of valvular insufficiency.     

Three-dimensional reconstruction of color doppler flow convergence regions and regurgitant jets: An in vitro quantitative study

Objectives. This study sought to investigate the applicability of a current implementation of a three-dimensional echocardiographic reconstruction method for color Doppler flow convergence and regurgitant jet imaging.Background. Evaluation of regurgitant flow events, such as flow convergences or regurgitant jets, using two-dimensional imaging ultrasound color flow Doppler systems may not be robust enough to characterize these spatially complex events.Methods. We studied two in vitro models using steady flow to optimize results. In the first constant-flow model, two different orifices were each mounted to produce flow convergences and free jets—a circular orifice and a rectangular orifice with orifice area of 0.24 cm². In another flow model, steady flows through a circular orifice were directed toward a curved surrounding wall to produce wall adherent jets. Video composite data of color Doppler flow images from both free jet and wall jet models were reconstructed and analyzed after computer-controlled 180° rotational acquisition using a TomTec computer.Results. For the free jet model there was an excellent relation between actual flow rates and three-dimensional regurgitant jet volumes for both circular and rectangular orifices (r = 0.99 and r = 0.98, respectively). However, the rectangular orifice produced larger jet volumes than the circular orifice, even at the same flow rates (p < 0.0001). Calculated flow rates by the hemispheric model using one axial measurement of the flow convergence isovelocity surface from two-dimensional color flow images under-estimated actual flow rate by 35% for the circular orifice and by 44% for the rectangular orifice, whereas a hemielliptic method implemented using three axial measurements of the flow convergence zone derived using three-dimensional reconstruction correlated well with and underestimated actual flow rate to a lesser degree (22% for the circular orifice, 32% for the rectangular orifice). In the wall jet model, the jets were flattened against and spread along the wall and had reduced regurgitant jet volumes compared with free jets (p < 0.01).Conclusions. Three-dimensional reconstruction of flow imaged by color Doppler may add quantitative spatial information to aid computation methods that have been used for evaluating valvular regurgitation, especially where they relate to complex geometric flow events.     

Colour flow imaging in severe mitral and aortic regurgitation

Several criteria have been proposed for the grading of severe aortic and mitral regurgitation by colour flow imaging. To evaluate the sensitivity of these criteria, colour flow imaging was performed in 21 patients with isolated severe mitral regurgitation and 11 patients with isolated severe aortic regurgitation prior to clinically indicated valvular surgery. In the colour flow imaging assessment of mitral regurgitation the criterion of the maximum distance of mitral regurgitant jet from mitral orifice greater than 4.5 cm was 95% sensitive (range 4.4 to 8.4 cm). Maximum ratio of mitral regurgitant jet area to left atrial area greater than 40% was 86% sensitive (range 32 to 84%) and maximum mitral regurgitant jet area greater than 6 cm2 was 100% sensitive (range 8.1 to 35.7 cm2) in the detection of severe mitral regurgitation. For aortic regurgitation, the criterion of height of regurgitant jet to height of left ventricular outflow tract greater than 65% in the parasternal long axis view was 100% sensitive (range 71 to 100%), whereas the ratio of area of regurgitant jet to area of left ventricular outflow tract greater than 60% in the short axis view was only 36% sensitive (range 8 to 74%) in the detection of severe aortic regurgitation requiring surgery. It is concluded that the most sensitive colour flow imaging criteria for severe mitral regurgitation is an absolute mitral jet area greater than 8 cm2; and for severe aortic regurgitation, ratio of height of regurgitant jet to height of left ventricular outflow tract greater than 65%.     

Regurgitant jet size by transesophageal compared with transthoracic Doppler color flow imaging

Combined echocardiography and Doppler color flow mapping from transthoracic imaging windows has become the standard method for the noninvasive assessment of valvular regurgitation. This study compared regurgitant jet areas by Doppler color flow imaging derived from the newer transesophageal approach with measurements obtained from conventional transthoracic apical views. Maximal regurgitant jet area determinations and an overall visual estimate of lesion severity were obtained from 42 patients who underwent color flow examination by both techniques. Seventy-three regurgitant lesions were visualized by transesophageal flow imaging: 34 mitral, 22 aortic, and 17 tricuspid jets. Transthoracic studies in the same patients revealed fewer regurgitant lesions for each valve; 20 mitral, 16 aortic, and 12 tricuspid (p = 0.0009). A comparison of maximal jet areas determined by transesophageal and transthoracic studies showed a good overall correlation (r = 0.85, SEE = 2.8 cm2) and a systematic overestimation by the transesophageal technique (TEE = 0.96 TTX + 2.7). For the subgroup with mitral insufficiency, valve lesions visualized by both techniques were larger by the transesophageal approach (n = 18, 6.0 versus 3.6 cm2, p = 0.008). Semiquantitative visual grading of individual valve lesions by two independent observers revealed a higher grade of regurgitation with more jets classified as mild (38 versus 25), moderate (18 versus 13), and severe (17 versus 10) by esophageal imaging than by transthoracic imaging. Thus, transesophageal color flow mapping techniques yield a higher prevalence of valvular regurgitation than do transthoracic techniques in the same patients. Jet area and the overall estimate of regurgitant lesion severity were also greater by transesophageal color Doppler imaging compared with standard transthoracic imaging.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vena contracta width as a simple method of assessing mitral valve regurgitation. Comparison with Doppler quantitative methods

BACKGROUND AND AIM OF THE STUDY: Quantitative Doppler echocardiography and proximal flow convergence methods facilitate quantification of regurgitant volume (RV), regurgitant fraction (RF) and the measurement of effective regurgitant orifice (ERO) to define mitral regurgitation (MR) severity. Vena contracta width (VCW) has been proposed as a simple, accurate marker of MR, and is instrumental in predicting the angiographic severity of valvular regurgitation. The study aim was to compare VCW with quantitative Doppler methods and angiography for assessing MR. METHODS: Sixty-four patients with MR (50 males; mean age 54 +/- 8 years; range: 34-84 years) were included. The etiology of MR was coronary artery disease, infective endocarditis, rheumatic disease, dilated cardiomyopathy or mitral valve prolapse. Exclusion criteria included aortic stenosis and/or aortic insufficiency, mitral stenosis, mechanical prostheses and atrial fibrillation. RV and ERO estimated by the proximal isovelocity surface area method (PISA), and RF calculated by Doppler, were compared with VCW measured by color Doppler. The angiographic severity of MR was classified on a four-point scale, in compliance with Sellers' criteria. RESULTS: A good correlation was found between VCW and ERO (r2 = 0.70, p <0.001), RV (r2 = 0.73, p <0.001), RF (r2 = 0.71, p <0.001) and angiographic grade (r2 = 0.72, p <0.001). CONCLUSION: VCW measured by color Doppler correlates well with MR severity. In addition, VCW is a simple, reproducible quantitative measurement of MR, and is recommended for use in the non-invasive assessment of the condition.     

Quantification of mitral regurgitation with the proximal flow convergence method: a clinical study.

Accurate quantitation of valvular incompetence remains an important goal in clinical cardiology. It has been shown previously that when color flow Doppler mapping is used, simple measurements of apparent jet size do not correlate closely with regurgitant flow rate and regurgitant fraction. Recently the proximal flow convergence method has been proposed to quantify valvular regurgitation by analysis of the converging flow field proximal to a regurgitant lesion. Flow rate Q can be calculated as Q = 2 pi r2v(a), where v(a) is the aliasing velocity at a distance r from the orifice. In 54 patients (43 with sinus rhythm and 11 with atrial fibrillation) who had at least mild mitral regurgitation according to semiquantitative assessment, regurgitant stroke volume, regurgitant flow rate, and regurgitant fraction were calculated with the proximal flow convergence method and compared with values that were obtained by the Doppler two-dimensional echocardiographic method. Regurgitant stroke volumes (Vr) as calculated by the proximal flow convergence method correlated very closely with values that were obtained by the Doppler two-dimensional method, with r = 0.93 (y = 0.95x + 0.55) and delta Vr = -0.3 +/- 4.0 cm3. Regurgitant flow rates (Q) as calculated by both methods showed a similar correlation: r = 0.93 (y = 0.95x + 54) and delta Q = -34 +/- 284 cm3/min. The correlation for regurgitant fraction (RF) as calculated by both techniques showed r = 0.89 (y = 0.98x + 0.006) and delta RF = -0.005 +/- 0.06. All correlations were slightly better for the group of patients with sinus rhythm than for the study group of patients with atrial fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Semiquantitative grading of severity of mitral regurgitation by real-time two-dimensional Doppler flow imaging technique

An attempt was made to determine whether mitral regurgitation could be detected and its severity evaluated semiquantitatively by newly developed real-time two-dimensional Doppler flow imaging in 109 patients who underwent left ventriculography. In the Doppler flow imaging technique, Doppler signals due to blood flow in the cardiac chambers are processed using a high speed autocorrelation technique, so that the direction, velocity and turbulence of the intracardiac blood flow are displayed in the color-coded mode on the monochrome B-mode echocardiogram in real time. Mitral regurgitant flow was imaged as a jet spurting out from the mitral valve orifice into the left atrial cavity. It was noted that the regurgitant jet in the left atrial cavity had a variety of orientations and dynamic features when studied by the present technique. The sensitivity of the technique in the detection of mitral regurgitation was 86% as compared with that of left ventriculography. Mitral regurgitation in the false negative cases was mostly mild. On the basis of the farthest distance reached by the regurgitant flow signal from the mitral valve orifice, the severity of regurgitation was graded on a four point scale and these results were compared with those of angiography. A significant correlation (r = 0.87) was found between Doppler imaging and angiography in the evaluation of the severity of mitral regurgitation. A similar result was obtained for the evaluation based on the area covered by the regurgitant signals in the left atrial cavity. Thus, noninvasive semiquantitative evaluation by real-time two-dimensional Doppler flow imaging appears to be a promising clinical technique.     

Effects of changing blood viscosity and heart rate on vena contracta width as evaluated by color Doppler flow mapping. An in vitro study with a pulsatile flow model

BACKGROUND: There is only limited knowledge on how the quantification of valvular regurgitation by color Doppler is affected by changing blood viscosity. This study was designed to evaluate the effect of changing blood viscosity on the vena contracta width using an in vitro model of valvular insufficiency capable of providing ample variation in the rate and stroke volume. METHODS: We constructed a pulsatile flow model filled with human blood at varying hematocrit (15%, 35%, and 55%) and corresponding blood viscosity (blood/water viscosity: 2.6, 4.8, 9.1) levels in which jets were driven through a known orifice (7 mm2) into a 110 mL compliant receiving chamber (compliance: 2.2 mL/mmHg) by a pulsatile pump. In addition, we used variable pump stroke volumes (5, 7.5, and 10 mL) and rates (40, 60, and 80 ppm). Vena contracta region was imaged using a 3.5 MHz transducer. Pressure and volume in the flow model were kept constant during each experimental condition, as well as ultrasound settings. RESULTS: Blood viscosity variation in the experimental range did not induce significant changes in vena contracta dimensions. Also, vena contracta width did not change from normal to low hematocrit and viscosity levels. A very modest increase only in vena contracta dimension was observed at very high level of blood viscosity when hematocrit was set to 55% . Pump rate, in the evaluated range, did not influence vena contracta width. These results in controlled experimental settings suggest that the vena contracta is an accurate quantitative method for quantifying valvular regurgitation even when this condition is associated with anemia, a frequent finding in patients with valvular heart disease.     

Quantitative echocardiographic assessment of native mitral regurgitation: two- and three-dimensional techniques

Chronic mitral regurgitation (MR) is a common valvular lesion. During recent years, it has become increasingly evident that moderate to severe MR, even in the absence of left ventricular dilatation and dysfunction, may have adverse prognostic consequences. Thus, the accurate quantification of MR, using echocardiography, is vitally important in clinical medicine. Because of the mitral valve's structural complexity, MR is often difficult to define, especially with two-dimensional (2D) imaging methods. Both qualitative and quantitative approaches to the quantification of MR are widely used. Color Doppler imaging allows measurement of the regurgitant jet area and vena contracta (VC) width; these two qualitative methods are simple to apply in daily practice but often are inaccurate, especially in patients with eccentric MR. 2D quantitative methods include the calculation of regurgitant fraction, regurgitant volume, and proximal isovelocity surface area. While these parameters are well-established indicators of MR severity, they require tailored image acquisition and additional calculations; moreover, their accuracy may be compromised in the setting of eccentric MR or aortic insufficiency. With three-dimensional (3D) echocardiography, many of the geometric assumptions necessary with 2D imaging are obviated. A realistic depiction of the VC, which often is non-circular, and of the anatomic regurgitant orifice area, which usually is non-planar, becomes possible with 3D zoom-mode imaging. Ongoing efforts to characterize MR in asymptomatic or minimally symptomatic patients include investigations into stress echocardiography and strain rate imaging. The distinct geometry of the mitral valve, and the various mechanisms of MR, will continue to challenge cardiac research teams during the coming years.     

Assessment of severity of aortic regurgitation by M-mode colour Doppler flow imaging

To assess the value of measuring the aortic regurgitant jet diameter at its origin by M-mode colour Doppler imaging, 82 patients with aortic regurgitation underwent, within 72 h of each other, colour Doppler examination and angiography. After excluding one patient without colour Doppler aortic regurgitation and five with a highly eccentric regurgitant jet, we found a close relationship between the jet diameter at its origin measured by M-mode colour Doppler and the angiographic grade of aortic regurgitation (r = 0.88). A jet diameter greater than or equal to 12 mm identified severe aortic regurgitation (grade III or IV) with a sensitivity of 86.4% and a specificity of 94.4%. In 38 patients, the jet diameter correlated well with the regurgitant fraction measured by a combined haemodynamic-angiographic method (r = 0.88). A jet diameter greater than or equal to 12 mm identified a regurgitant fraction greater than or equal to 40% with a sensitivity of 88.2% and a specificity of 95.2%. This study indicates that the size of the regurgitant jet diameter at its origin measured by M-mode colour Doppler provides a simple and useful measure of the severity of aortic regurgitation. It may allow differentiation between mild or moderate and severe aortic regurgitation and evaluation of regurgitant fraction.     

Three-Dimensional Echocardiography in Valvular Heart Disease

Two-dimensional echocardiography (2DE) with color Doppler has been the standard tool for assessing valvular heart disease. However, this requires conceptualizing three-dimensional (3D) valvular anatomy from individual 2D slices, which is inadequate for complex valvular abnormalities. Similarly, Doppler-based methods are inherently limited by several assumptions and are influenced by hemodynamics and concomitant valvular disease. 3DE has improved both morphological and functional assessment of valvular heart disease. It provides additional morphological information, which leads to better understanding of the mechanism of valvular dysfunction and surgical planning. 3D planimetry has proven to be accurate in the evaluation of valvular stenosis. This direct assessment eliminates measurement errors and could potentially serve as new gold standard. The continuity equation for aortic stenosis can be simplified by directly measuring left ventricular outflow tract area and stroke volume. In patients with valvular regurgitation, vena contracta area can be directly measured by using 3D color Doppler which is more accurate than the standard 2D methods. By applying hemi-elliptical formula or directly measuring isovelocity surface area, 3DE has significantly improved the accuracy in regurgitant severity assessment. This is particularly useful in patients with eccentric jets. 3DE has an advantage over 2DE in assessment of tricuspid valve due to its complex geometry. Direct planimetry of orifice area in tricuspid stenosis, or vena contracta area in tricuspid regurgitation are promising although validation studies are needed before they can be applied for clinical decision making. 3DE has not been widely studied in pulmonic valve disease but preliminary data indicate that it is feasible. (Echocardiography 2012;29:88-97)     

Can signal intensity of the continuous wave Doppler regurgitant jet estimate severity of mitral regurgitation?

Visual estimates of the intensity of the continuous wave (CW) Doppler regurgitant jet signal have been used to estimate the severity of valvular regurgitation. Theoretically, the strength of the reflected Doppler signal is a function of the number of scatterers. To test this approach quantitatively, free jets were produced in 27 experiments using a power injector and cornstarch suspension varying in concentration from 1% to 3%. Flow volume was varied from 5 to 15 ml, and orifice diameter varied from 2.5 to 10 mm. Machine settings were kept constant. Also, 22 patients with mitral regurgitation (MR)--5 mild, 11 moderate, and 6 severe by angiography--were studied. Average signal intensity under the CW Doppler flow curve was calculated using a computer image processor. In MR patients, average regurgitant flow (RF) intensity was compared with average mitral forward flow (FF) signal intensity. (1) The intensity under the CW flow signal in the free jet experiments correlated well with injection volume (r greater than 0.98). (2) RF average signal intensity did not correlate with angiographic MR severity (r = 0.21), but the ratio of RF to FF average signal intensity did correlate with MR severity (r = 0.73). (3) The sensitivity and the specificity of an RF/FF ratio greater than 0.65 for angiographically severe mitral regurgitation were both 83%. (4) The sensitivity and specificity of an RF/FF ratio less than 0.50 for angiographic mild mitral regurgitation were both 80%. The ratio of regurgitant to forward mitral flow CW Doppler signal intensity appears to be an accurate and clinically applicable method for estimating the severity of mitral regurgitation.     

Echocardiography flow quantification for determining the severity of heart valve insufficiency

BACKGROUND: Beyond conventional echocardiographic Doppler methods allowing only semiquantitative estimation of the severity of valvular regurgitation, new approaches are attempting to quantify regurgitant flow as a measure of left ventricular volume overload. Different concepts are leading to significant differences in accuracy and feasibility in clinical routine between the methods. We are reviewing the existing methods with their advantages and limitations as well as the underlying hemodynamic concepts. ECHOCARDIOGRAPHIC METHODS FOR ESTIMATION OF SEVERITY: Semiquantitative methods are jet area/jet length method, proximal jet width as well as the pressure half-time method. Determination of regurgitant flow is permitted by means of the continuity method, PISA ("Proximal Isovelocity Surface Area") method, ACOM ("Automated Cardiac Output Measurement") technique, and the PVI ("Power-Velocity Integral") method. Grading of severity is usually based on a scale from 1 to 3 or 1 to 4 where semiquantitative methods are limited by a significant overlap of the individual degrees and therefore only provide rough estimates of severity. Compared to this, quantitative methods allow quantitative determination of regurgitant flow, regurgitant volume, regurgitant fraction, and effective regurgitant orifice area based on different Doppler flow measurements, that are again affected by specific limitations: (1) the continuity method is considerably limited because it is measuring the flow through two different valves; (2) the PISA method is dependent on the geometry of the proximal flow convergence zone and requires highly skilled observers; (3) the ACOM method is also dependent on the geometry of the proximal flow convergence zone und ideally requires three-dimensional color Doppler datasets; (4) the PVI method provides direct measurement of regurgitant flow from a pulsed Doppler signal of sufficient high quality, however, this method is not widely available, yet. For the decision which method to apply the following should be taken into account: (1) interpretation of semiquantitative findings depends on the extent by which the methods' estimation of flow deviates from a measurement of flow; (2) accuracy of the quantitative methods depends on the underlying hemodynamic concept and the simplifying assumptions. CONCLUSION: Current echocardiography provides a broad spectrum of semiquantitative und quantitative Doppler methods for the estimation of regurgitant flow. Since semiquantitative methods only allow rough estimates of severity, quantitative measurement of regurgitant volume/fraction or effective regurgitant orifice area should be attempted in any case with uncertainty whether regurgitation is mild, moderate, or severe.