Simple method for estimating regurgitant volume with use of a single radius for measuring proximal isovelocity surface area: an in vitro study of simulated mitral regurgitation.

The proximal isovelocity surface area (PISA) color Doppler method with use of a hemielliptic formula is reported to be accurate for quantitating regurgitant volume (RV). However, this formula ideally requires the measurement of 2 or 3 radii and therefore is not widely used clinically. The purpose of this in vitro study was to derive a simple PISA formula for estimating RV with use of a single radius axial to the valve orifice and to compare it with the clinically used single-radius hemispherical formula (2 x pi R(2) x AV x TVI/Vp), where AV is the apparent color Doppler aliasing velocity, R is the PISA color Doppler aliasing radius, TVI is time-velocity integral of the jet by continuous wave Doppler, and Vp is the peak velocity of the jet by continuous wave Doppler. Pulsatile flow studies were performed across a convex curvilinear surface, which more closely approximates the shape of the mitral valve than does a planar surface. Pulse rates (60 to 80 bpm), peak flow velocities (4.0 to 6.0 m/s), and regurgitant orifice areas (0.2 to 1.0 cm(2)) were varied to simulate mitral regurgitation. The AVs were varied from 11 to 39 cm/s, and a single PISA aliasing radius was measured at each AV. Excellent linear correlations were obtained between the PISA radius and the actual RV measured with use of a beaker (r = 0.94 to 0.97, P <.0001). A series of simplified formulas was derived from the regression line of the PISA radius versus the RV. For example, with an AV of 21 cm/s, RV was estimated by a simplified PISA formula (where RV[mL] = 10 x R [mm] - 30) with an accuracy of 3.3 +/- 6.3 mL versus -20.3 +/- 8.7 mL for the standard single-radius PISA method (P <.0001). By using the standard single-radius hemispherical PISA formula, RV was underestimated if the radius was <20 mm. By using simplified regression equations, the PISA radius accurately estimated RV at a PISA radius <20 mm. Clinical studies are necessary to validate this concept.     

Morphological evaluation of a regurgitant orifice by 3-D echocardiography: applications in the quantification of valvular regurgitation.

The clinical evaluation of blood flow regurgitation through a heart valve or stenotic lesion is an unresolved problem. The proximal flowfield region has been the study focus in the last few years; however, investigators have failed to identify an accurate and reliable calculation scheme due to lack of geometric information about the shape and size of the regurgitating or stenotic orifice. Presented here is a superior method of calculation, by using three-dimensional (3-D) echocardiography combined with Doppler velocimetry. The geometric structure of the orifice in a regurgitating porcine prosthetic valve in vitro was formulated by 3-D image construction of sequentially obtained 2-D images. The velocity flowfield was accessed by color Doppler flow mapping (CD) and continuous-wave Doppler (CW). Two accurate methods of calculation of regurgitant variables were developed. The first method calculated peak regurgitant flow rate from CD and the second method calculated regurgitant flow volume from CW. Both methods showed excellent correlation with the corresponding true values from an electromagnetic flowmeter. The promising preliminary results in such a realistic porcine model indicate the possibility of establishing a routine procedure to be tested in the clinical setting.     

Homograft pulmonic stenosis after the Ross procedure: evaluation of the stenotic valve area by proximal isovelocity surface area (PISA).

The proximal isovelocity surface area (PISA) technique has been used to evaluate valvular regurgitant flow, regurgitant orifice area, and stenotic valve area. This report shows the usefulness of this Doppler technique in quantifying the stenotic valve area of a pulmonic valve homograft prosthesis after the Ross procedure. The patient was a 35-year-old man who had a Ross procedure 3 years earlier for aortic stenosis, which included replacement of the pulmonic valve with a cryopreserved homograft pulmonic valve. With an aliasing velocity set at 40 cm/s and a PISA radius of 1.1 cm, the pulmonic valve area was calculated as follows: Pulmonic valve peak flow rate = 2 x3.14 x1.12 x40 = 304 mL/s; Pulmonic valve area = Peak flow rate / Peak velocity = 284/350 = 0.87 cm2.     

Evaluation of 3-D colour Doppler ultrasound for the measurement of proximal isovelocity surface area

Three-dimensional (3-D) colour Doppler ultrasound (US) enables flow rate estimation across a diseased valve without the need for a priori geometric assumptions. This study quantitatively evaluates the accuracy of 3-D colour Doppler US for measuring the flow rate (8. 3-75 mL/s) through a valve using the proximal flow convergence field. Flow rate measurements by this 3-D technique underestimate flow through finite circular orifices due to two major sources of error: 1. surface area slicing technique (18.3% +/- 3.8%) and 2. Doppler angle effect (41.0% +/- 1.5%). Combined total underestimation is 51% +/- 3.3%. To utilize 3-D US, the development of an improved proximal isovelocity surface area (PISA) measurement technique and a correction factor for the Doppler angle effect is required.     

二尖瓣反流对压差减半时间法测量瓣口面积的影响

目的探讨二尖瓣狭窄伴反流的患者用压差减半时间（PHT）法测量二尖瓣口面积的应用价值。方法43例风湿性心脏病二尖瓣狭窄合并轻、中度反流的患者，其中15例合并心房颤动，以PHT法、二维超声测量法分别测量二尖瓣口面积，并与心导管所得结果比较。比较三种方法测量结果的一致性。结果两种超声测量方法与心导管测量结果间的差别无显著性意义。PHT法、二维超声测量法的结果均与导管法呈正相关，相关系数分别为0．76（P〈0．05）、0．71（P〈0．05）。PHT法与导管法的相关性高于二维超声测量法。结论对二尖瓣狭窄合并轻、中度反流患者，PHT法测量瓣口面积有临床应用价值。     

A real-time 3-dimensional digital Doppler method for measurement of flow rate and volume through mitral valve in children: a validation study compared with magnetic resonance imaging.

We developed and assessed a real-time 3-dimensional (3D) digital Doppler method for measurement of flow volumes through the mitral valve in children. A total of 13 children (aged 10.46 +/- 2.5 years; 8 boys/5 girls) were enrolled. An ultrasound system (Sonos 7500, Philips, Andover, Mass) was used to acquire raw 3D velocity data for flow measurement based on Gaussian control surface theorem [flow (mL/s) = mean velocity x flow area]. Stroke volume (SV) measured by real-time 3D digital Doppler with the control surface at the mitral valve annulus or orifice was compared with the SV by phase velocity cine magnetic resonance imaging (MRI) at the ascending aorta and by left ventricular volumetric MRI measurement. The best correlation and agreement were seen at the mitral valve orifice by real-time 3D digital Doppler compared with SV by phase velocity cine MRI at the ascending aorta (r = 0.92, mean difference = -5.2 +/- 12.0 mL) and SV by left ventricular volumetric MRI measurement (r = 0.94, mean difference = -0.2 +/- 10.3 mL).     

二尖瓣返流病人收缩期左房内前向性血流的研究

本研究应用彩色多普勒超声心动图检测了31例收缩期左房内前向性血流。将脉冲多普勒取样容积置于二尖瓣口左房侧,在与负向性返流相并行的一侧出现收缩期正向性血流频谱时,定为前向性血流,彩色多普勒血流显示为红色血流。全部病人均经心血管造影及/或手术证实。结果表明,收缩期左房内前向性血流是由于大量、高速、偏心的血流在左房内折返形成漩涡而产生,此血流常发生于连枷样二尖瓣病人,阳性率为93.5％,也可以发生于非FMV严重的二尖瓣返流病人。     

Anatomical Regurgitant Orifice Detection and Quantification from 3-D Echocardiographic Images

The vena contracta and effective regurgitant orifice area (EROA) are currently used for the clinical assessment of mitral regurgitation (MR) from 2-D color Doppler imaging. In addition to being highly user dependent and having low repeatability, these methods do not represent accurately the anatomic regurgitant orifice (ARO), which affects the adequate assessment of MR patients. We propose a novel method for semi-automatic detection and quantitative assessment of the 3-D ARO shape from 3-D transesophageal echocardiographic images. The algorithm was tested on a set of 25 patients with MR, and compared with EROA for validation. Results indicate the robustness of the proposed approach, with low variability in relation to different settings of user-defined segmentation parameters. Although EROA and ARO exhibited a good correlation (r = 0.8), relatively large biases were measured, indicating that EROA probably underestimates the real shape and size of the regurgitant orifice. Along with the higher reproducibility of the proposed approach, this highlights the limitations of current clinical approaches and underlines the importance of accurate assessment of the ARO shape for diagnosis and treatment in MR patients.     

Optimization of 3-D Divergence-Free Flow Field Reconstruction Using 2-D Ultrasound Vector Flow Imaging

3-D blood vector flow imaging is of great value in understanding and detecting cardiovascular diseases. Currently, 3-D ultrasound vector flow imaging requires 2-D matrix probes, which are expensive and suffer from suboptimal image quality. Our recent study proposed an interpolation algorithm to obtain a divergence-free reconstruction of the 3-D flow field from 2-D velocities obtained by high-frame-rate ultrasound particle imaging velocimetry (High Frame Rate echo-Particle Imaging Velocimetry, also known as HFR Ultrasound Imaging Velocimetry (UIV)), using a 1-D array transducer. The aim of this work was to significantly improve the accuracy and reduce the time-to-solution of our previous approach, thereby paving the way for clinical translation. More specifically, accuracy was improved by optimising the divergence-free basis to reduce Runge phenomena near domain boundaries, and time-to-solution was reduced by demonstrating that under certain conditions, the resulting system could be solved using widely available and highly optimised generalised minimum residual algorithms. To initially illustrate the utility of the approach, coarse 2-D subsamplings of an analytical unsteady Womersely flow solution and a steady helical flow solution obtained using computational fluid dynamics were used successfully to reconstruct full flow solutions, with 0.82% and 4.8% average relative errors in the velocity field, respectively. Subsequently, multiplane 2-D velocity fields were obtained through HFR UIV for a straight-tube phantom and a carotid bifurcation phantom, from which full 3-D flow fields were reconstructed. These were then compared with flow fields obtained via computational fluid dynamics in each of the two configurations, and average relative errors of 6.01% and 12.8% in the velocity field were obtained. These results reflect 15%–75% improvements in accuracy and 53- to 874-fold acceleration of reconstruction speeds for the four cases, compared with the previous divergence-free flow reconstruction method. In conclusion, the proposed method provides an effective and fast method to reconstruct 3-D flow in arteries using a 1-D array transducer.     

Evaluation of hypertrophic cardiomyopathy by Doppler color flow imaging: initial observations

We evaluated hypertrophic cardiomyopathy in 12 patients by Doppler color flow imaging and continuous-wave Doppler echocardiography. Mitral regurgitation was detected by continuous-wave Doppler echocardiography in eight patients and was related to the degree of systolic anterior motion of the mitral valve. Adequate color flow images were obtained in 10 of the 12 patients, and mitral regurgitation was demonstrated in 6. A qualitative and quantitative analysis of the color flow imaging revealed a temporal pattern in the left ventricular outflow tract that consisted of normal-velocity laminar flow during early systole followed by turbulent flow in midsystole. The maximal amount of mitral regurgitation on color flow imaging occurred late in systole, after the appearance of turbulent flow in the left ventricular outflow tract. Of the 12 patients, 10 had late-peaking continuous-wave Doppler velocity profiles in the left ventricular outflow tract. The peak velocity detected in the left ventricular outflow tract was positively correlated with the degree of systolic anterior motion of the mitral valve. Patients with higher peak velocities in the left ventricular outflow tract had prolonged ejection times. These findings on Doppler echocardiography support the concept of left ventricular outflow obstruction in some patients with hypertrophic cardiomyopathy.     

应用三维彩色多普勒超声对扩张型心肌病与二尖瓣脱垂患者二尖瓣反流的评价

目的：应用三维彩色多普勒超声（3D-CDE）直视下描绘二尖瓣反流（MR）的反流口面积（ROA）,探讨3D-CDE对评价不同发病机制MR方面的临床应用.方法：选取不同程度MR的二尖瓣脱垂（MVP）和扩张型心肌病（DCM）患者各30例,观察两个病例组反流口的形状及PISA的三维空间形态.用ASE推荐的二维综合方法对这60例患者的MR程度进行划分,分别用3D-ROA法和2D-PISA法测量每位患者的ROA,并对两种方法进行相关性分析.结果：两个病例组反流口的形状及PISA的三维空间形态有不同.两个病例组3D-ROA法和2D-PISA法所测结果均具有相关性.DCM组两种方法相关性较好（r=0.783,Y=0.661x-0.45,P＜0.001）,MVP组两种方法相关性良好,大于DCM组（r=0.924,Y=1.172x-0.057,P＜0.001）.DCM组2D-PISA法比3D-ROA法低估了大约26％.结论：3D-ROA法与传统二维方法相比可以更直观、更准确的评价功能性MR.     

Effects of percutaneous mitral commissurotomy on longitudinal left ventricular dynamics in mitral stenosis: quantitative assessment by tissue velocity imaging.

OBJECTIVE: We hypothesized that mitral annular velocities would improve immediately after relief of mitral stenosis and that serial assessment could be used as an index for quantifying functional changes after percutaneous mitral commissurotomy (PMC). METHODS: Longitudinal left ventricular annular velocities were quantified by spectral pulsed wave Doppler tissue velocity imaging in 25 patients (16 women; mean age [+/-SD], 29.2 +/- 8.6 years) who had isolated mitral stenosis and were in sinus rhythm, and were compared with 30 age- and sex-matched control subjects. Echocardiography was performed 1 to 24 hours before PMC and 48 to 72 hours after, and changes in velocities from the lateral and septal corners of the mitral annulus in early diastole, late diastole, isovolumic contraction, and ejection were recorded. RESULTS: Systolic and diastolic mitral annular velocities were significantly less in patients with mitral stenosis than in control subjects. After PMC, peak annular velocity of systolic excursion in ejection and peak annular velocity in early diastole showed significant improvement. The change in peak annular velocity in early diastole in the lateral wall correlated well with improvement in the mitral valve orifice area by planimetry (ratio of mitral valve orifice area, 1.92 +/- 0.42; ratio of peak annular velocity in early diastole, 1.36 +/- 0.22; r = 0.65; P <.001). CONCLUSION: Serial evaluation of changes in mitral annular velocities by Doppler tissue imaging aids clinical assessment of immediate improvement in left ventricular function after PMC.     

Quantitative assessment of in vitro jets based on three-dimensional color Doppler reconstruction

Three-dimensional (3-D) color Doppler imaging of flow jets was performed to investigate the effects of flow rate and orifice size on jet volumes. Flow jets were generated using a flow model to simulate mitral regurgitation. This flow model consisted of a ventricular chamber, a valvular plate and an atrial chamber. Steady flow was driven through circular orifices having diameters of 2.5, 3.5, 4.5, and 6 mm, respectively, with flow rates of 5, 10, 15, 20, and 25 mL/s to form free jets in the atrial chamber. An ATL Ultramark 9 HDI system was used to perform 3-D color Doppler imaging of the flow jets. A transesophageal probe was rotated by a stepper motor to create 3-D color Doppler images of the jets. The color jet volumes for different hemodynamic conditions were measured and then compared with the theoretical predictions. Results showed that the jet volume estimated from the 3-D color Doppler was directly proportional to the flow rate and inversely proportional to the orifice size. The estimated jet volumes correlated well (r > 0.95) with theoretical predictions. This study supports the use of color jet volume as a parameter to quantify mitral regurgitation.     

Acquisition of 3-D Arterial Geometries and Integration with Computational Fluid Dynamics

A system for acquisition of 3-D arterial ultrasound geometries and integration with computational fluid dynamics (CFD) is described. The 3-D ultrasound is based on freehand B-mode imaging with positional information obtained using an optical tracking system. A processing chain was established, allowing acquisition of cardiac-gated 3-D data and segmentation of arterial geometries using a manual method and a semi-automated method, 3D meshing and CFD. The use of CFD allowed visualization of flow streamlines, 2-D velocity contours and 3-D wall shear stress. Three-dimensional positional accuracy was 0.17–1.8 mm, precision was 0.06–0.47 mm and volume accuracy was 4.4–15%. Patients with disease and volunteers were scanned, with data collection from one or more of the carotid bifurcation, femoral bifurcation and abdominal aorta. An initial comparison between a manual segmentation method and a semi-automated method suggested some advantages to the semi-automated method, including reduced operator time and the production of smooth surfaces suitable for CFD, but at the expense of over-smoothing in the diseased region. There were considerable difficulties with artefacts and poor image quality, resulting in 3-D geometry data that was unsuitable for CFD. These artefacts were exacerbated in disease, which may mean that future effort, in the integration of 3-D arterial geometry and CFD for clinical use, may best be served using alternative 3-D imaging modalities such as magnetic resonance imaging and computed tomography. (E-mail: P.Hoskins@ed.ac.uk)     

Quantitative assessment of regurgitant flow with total digital three-dimensional reconstruction of color Doppler flow in the convergent region: in vitro validation.

BACKGROUND: This study was designed to develop and test a total digital 3-dimensional (3D) color flow map reconstruction for proximal isovelocity surface area (PISA) measurement in the convergent region. METHODS: Asymmetric flow convergent velocity field was created in an in vitro pulsatile model of mitral regurgitation. Image files stored in the echocardiographic scanner memory were digitally transferred to a computer workstation, and custom software decoded the file format, extracted velocity information, and generated 3D flow images automatically. PISA and volume flow rate were calculated without geometric assumption. For comparison, regurgitant volume was also calculated, using continuous wave Doppler, 2-dimensional (2D), and M-mode color flow Doppler with the hemispheric approach. RESULTS: Flows from 3D digital velocity profiles showed a closed, excellent relation with actual flow rates, especially for instantaneous flow rate. Regurgitant volume calculated with the 3D method underestimated the actual flow rate by 2.6%, whereas 2D and the M-mode method show greater underestimation (44.2% and 32.1%, respectively). CONCLUSION: Our 3D reconstruction of color flow Doppler images gives more exact information of the flow convergent zone, especially in complex geometric flow fields. Its total digital velocity process allows accurate measurement of convergent surface area and improves quantitation of valvular regurgitation.     

Flow velocity acceleration in the left ventricle: a useful Doppler echocardiographic sign of hemodynamically significant mitral regurgitation

Doppler echocardiography is a sensitive method to detect mitral regurgitation in patients with both native and prosthetic valves. However, estimates of the amount of mitral regurgitation remain semiquantitative, and even severe mitral regurgitation may be underestimated in the presence of markedly eccentric regurgitant jets or acoustic shadowing of the left atrium by mitral or aortic prostheses. This report describes the Doppler findings in 10 patients with severe native valve mitral regurgitation (angiographic grade III or IV) and in 15 patients with severe bioprosthetic mitral regurgitation that required valve replacement. An increase in peak mitral flow velocity above normal values was seen in eight of 10 patients with severe native valve mitral regurgitation (greater than or equal to 130 cm per second) and 11 of 15 patients with severe prosthetic valve mitral regurgitation (greater than or equal to 210 cm per second). One of 10 patients with a native valve and four of 15 patients with a bioprosthetic valve appeared to have only a localized left atrial systolic flow disturbance, incorrectly suggesting that the mitral regurgitation was mild. However, in all patients with severe mitral regurgitation, a low velocity (less than 100 cm per second) flow signal could be recorded in the left ventricle that was directed toward the mitral valve in systole. This flow signal showed a gradual increase in velocity as the sample volume was moved toward the mitral valve, with an abrupt further increase on entry into the left atrium. This signal was continuous with antegrade mitral flow and had the same orientation as mitral regurgitation recorded by continuous wave technique from the apex. A similar flow signal was not recorded in the left ventricle of any individual in a control group of 30 patients who had no mitral regurgitation or who had angiographic grade I or II mitral regurgitation. These findings suggest that acceleration of left ventricle flow toward the mitral valve in systole is only recorded when there is hemodynamically significant mitral regurgitation that is approximately equal to angiographic grade III or IV. Recognition of this Doppler finding may help in the estimation of mitral regurgitation severity, especially in difficult diagnostic situations.     

Assessment of mitral regurgitation by 3-dimensional proximal flow convergence using magnetic resonance imaging: comparison with echo-Doppler

To test the feasibility of assessing mitral regurgitation (MR) severity using cardiac magnetic resonance (CMR) 4D velocity vectors to quantify regurgitant volume (RVol) by analysis of the proximal flow convergence, compared to Doppler based proximal isovelocity surface area (PISA) and CMR volume-based methods. In a prospectively designed study, 27 patients with various grades of MR underwent CMR and echo-Doppler on the same day. By CMR, multiple slices were obtained parallel to the mitral valve by phase-contrast imaging, using 3D velocity vectors, as well as short-axis cine images for left and right ventricular volume measurements. Using dedicated software developed in our laboratory, the perimeter of the proximal flow convergence region was semi-automatically measured for each temporal phase, and for each short-axis slice. The CMR-PISA RVol was calculated as the sum of PISA perimeters throughout systole, multiplied by slice width. For comparison, CMR-volumetric RVol was calculated by 2 methods: Volumetric (difference between left and right ventricular stroke volumes) and Flow-based (stroke volume -aortic flow). Echo-PISA RVol was calculated by echo-Doppler based PISA method. RVol by CMR-PISA correlated highly with echo-PISA (r?=?0.87) and with CMR-volumetric (r?=?0.86) and CMR-flow (r?=?0.72). For comparison Doppler-RVol and CMR-volume-based RVol had r?=?0.83. On average CMR-PISA was 16?±?25 ml less than echo-PISA, but 12?±?22 ml larger than CMR-volumetric RVol. The observed 3D shape of the PISA envelope by 4D-CMR resembled a hemiellipsoid rather than a hemisphere. This feasibility study suggests that CMR-based 4D-PISA may be able to assess MR severity quantitatively without any geometric assumptions.     

Value of pulmonary venous flow characteristics in the assessment of severity of native mitral valve regurgitation: an angiographic correlated study.

To evaluate the relation between left ventricular angiography and pulmonary venous flow velocity in native mitral valve regurgitation, 28 patients with sinus rhythm and valvular and/or coronary artery disease underwent transesophageal echocardiography within 24 hours after cardiac catheterization. Group I consisted of 17 patients, seven patients without (grade 0) and 10 patients with angiographically mild to moderate mitral regurgitation (grades 1 and 2). Group II consisted of 11 patients with angiographically severe mitral regurgitation (grades 3 and 4). Mitral regurgitation by transesophageal echocardiography was evaluated by measuring the regurgitant jet sizes and color-guided pulsed Doppler pulmonary venous flow velocities. Multivariate analysis revealed that the most powerful predictor (p less than 0.001) of angiographically severe (grades 3 and 4) mitral regurgitation was reversed systolic flow into the left upper pulmonary vein (sensitivity 82%, specificity 100%, positive predictive value 100%). If this variable was excluded from analysis, jet area and jet length (p less than 0.001) were the next best predictors for angiographically severe mitral regurgitation. Mean values of systolic peak pulmonary venous flow velocities were significantly lower in patients from group II, 13.0 +/- 11.1 cm/s versus 43.4 +/- 20.6 cm/s (group I) with p less than 0.005. This finding was also true for systolic time velocity integral, 1.3 +/- 1.3 cm (group II) versus 7.8 +/- 5.3 cm (group I) with p less than 0.005.(ABSTRACT TRUNCATED AT 250 WORDS)     

Early ovarian cancer: 3-D power Doppler

Transvaginal sonography plays an important role in the assessment of the morphology of ovarian lesions. However, the accuracy of the technique is limited due to the significant number of false-positive results. Color Doppler imaging and pulsed Doppler spectral analysis enable evaluation of ovarian tumor blood flow, analysis of the distribution of blood vessels, and quantitative measurement of blood flow velocity waveforms. These parameters increase the sensitivity and specificity of ultrasound evaluation of ovarian tumors. Unfortunately, there is no consensus as to which Doppler parameters and cutoff values are the most predictive of malignancy. Three-dimensional (3-D) power Doppler ultrasound provides a new tool to evaluate features of tumor vascularity. Three-dimensional ultrasound and 3-D power Doppler imaging in patients with “positive” findings on standard ultrasound tests, which encompass annual gray-scale transvaginal sonography followed by transvaginal color Doppler ultrasound in selected cases, represent a novel approach for early and accurate detection of ovarian cancer through screening. Combined evaluations of morphology and neovascularity by 3-D power Doppler ultrasound may improve early detection of ovarian carcinoma. Contrast-enhanced 3-D power Doppler sonography facilitates visualization of adnexal tumor vessels, which may aid in differentiating benign from malignant adnexal lesions.