Quantification Of Valvular Regurgitation Research Articles

CMR to stratify post-TAVR paravalvular leak in patients with suboptimal echocardiography

Background Despite extensive pre-procedure evaluation, greater than mild paravalvular leak (PVL) occurs in over 10% of patients undergoing transcatheter aortic valve replacement (TAVR) and is associated with worse outcomes. Echocardiography, the standard method of imaging PVL, often has limited utility due to frequently multiple eccentric regurgitant jets. Acoustic shadowing from the valve stent and native aortic valve calcification may lead to further underestimation of PVL. Cardiovascular magnetic resonance (CMR) is considered the gold standard for quantification of valvular regurgitation. We evaluated the utility of CMR to grade PVL severity and predict outcomes in patients with suboptimal echocardiography. Methods Seventeen non-operative post-TAVR patients (NYHA class III-IV; age 84 ± 5 yrs) underwent CMR due to PVL and symptoms out of proportion to echocardiographic findings or suboptimal echocardiographic study. CMR was performed on a Siemens Avanto 1.5 T with velocity phase imaging in the ascending aorta for flow quantification. CMR PVL severity was graded by regurgitant fraction (RF; mild≤20%, moderate 21-39%, severe ≥40%). Short- and intermediate-term follow-up was conducted after CMR. Patients were followed-up for symptoms and a composite outcome of repeat invasive therapy, heart failure hospitalization, or death.

Wide limits of agreement between left ventricular stroke volume, right ventricular stroke volume and aortic and pulmonary forward flow

Objective The aim of the study was to assess the reliability of using left ventricular stroke volume (LVSV), right ventricular stroke volume (RVSV), aortic forward flow (AFF) and pulmonary forward flow (PFF) in the evaluation of valvular regurgitation by studying the extent of agreement between the different parameters in healthy subjects with only trivial valvular regurgitation. Background The quantification of valvular regurgitation by CMR is usually a second-line diagnostic tool that is used when echocardiography has proven inconclusive. According to guidelines are aortic and mitral regurgitations considered severe if the regurgitation volume > 60 ml and regurgitation fraction > 50 %. Regurgitation of a single heart valve may be calculated by comparing LVSV and RVSV derived from multislice ventricular planimetry. In isolated aortic and pulmonary regurgitation, phase contrast velocity sequences can be used as an alternative or complementary method to quantify the regurgitation volume and fraction. This method can be subject to error due to motion of the valve annulus, elastic expansion of the aortic root and inherent sequence errors. In the case of isolated mitral and tricuspid regurgitation the LVSV or RVSV can alternatively be set in relation to flow measurements in the aorta and pulmonary artery for grading the regurgitation. Methods Twenty healthy subjects (10 female and 10 male) underwent CMR imaging (Philips Achieva 1.5T) using steadystate free precession sequences to obtain short axis data sets and phase contrast velocity sequences to obtain aortic and pulmonary flow measurements. All images were analysed repeatedly (ViewForum, Philips) to acquire LVSV, RVSV, AFF and PFF. The agreement between the LVSV and AFF, PFF and RVSV was calculated using

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

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. 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. 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.

Effects of blood viscosity on proximal flow convergence calculations of regurgitant flow rate and jet dimensions as evaluated by color Doppler flow mapping: An in vitro study

There are limited data on the potential influence of blood viscosity on the quantification of valvular regurgitation by color Doppler in the clinical setting. This study was designed to evaluate the effects of blood viscosity on jet dimensions and the proximal flow convergence (proximal isovelocity surface area, PISA) method of estimating valvular insufficiency severity. We used an in vitro flow model filled with human blood at varying hematocrits (15%, 35%, and 55%) and blood viscosity (blood/water viscosity: 2.6, 4.8, 9.1) in which jets were driven through a known orifice (16 mm2) into a 110-mL compliant receiving chamber (compliance: 2.2 mL/mm Hg) by a power injection pump. Blood injections (2 and 4 mL) at flow rates of 4, 6, 8, 10, and 12 mL/s were performed. Proximal flow convergence and spatial distribution of jets were imaged by a 3.5-MHz transducer. Pressure and volume in the flow model were kept constant before each injection. Ultrasound settings were the same for all experiments. Jet area decreased significantly with increasing blood viscosity, but the difference in jet dimensions was much larger for lower than for higher flow rates and for highest blood viscosity. Estimation of flow rate by the PISA method was not significantly influenced by blood viscosity. Blood viscosity has a major influence in jet area, especially for lower flow rates, but did not change significantly the grading of regurgitation by the PISA method. Thus this factor should be considered for determining the method of choice when quantification of valvular regurgitation is performed in patients with anemia or polycythemia. (J Am Soc Echocardiogr 2001;14:569-79.)

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.

Digital storage and analysis of color Doppler echocardiograms.

Color Doppler flow mapping has played an important role in clinical echocardiography. Most of the clinical work, however, has been primarily qualitative. Although qualitative information is very valuable, there is considerable quantitative information stored within the velocity map that has not been extensively exploited so far. Recently, many researchers have shown interest in using the encoded velocities to address the clinical problems such as quantification of valvular regurgitation, calculation of cardiac output, and characterization of ventricular filling. In this article, we review some basic physics and engineering aspects of color Doppler echocardiography, as well as drawbacks of trying to retrieve velocities from video tape data. Digital storage, which plays a critical role in performing quantitative analysis, is discussed in some detail with special attention to velocity encoding in DICOM 3.0 (medical image storage standard) and the use of digital compression. Lossy compression can considerably reduce file size with minimal loss of information (mostly redundant); this is critical for digital storage because of the enormous amount of data generated (a 10 minute study could require 18 Gigabytes of storage capacity). Lossy JPEG compression and its impact on quantitative analysis has been studied, showing that images compressed at 27:1 using the JPEG algorithm compares favorably with directly digitized video images, the current goldstandard. Some potential applications of these velocities in analyzing the proximal convergence zones, mitral inflow, and some areas of future development are also discussed in the article.

Limitations of color flow doppler imaging in the quantification of valvular regurgitation: Velocity of regurgitant jet, rather than volume, determines size of color doppler image

The objective of this study was to determine the validity of estimation of regurgitant volume by visual assessment of color flow Doppler display. An experimental apparatus was designed that is capable of ejecting precise volumes of echogenic material from one chamber to another under continuous color flow Doppler monitoring. The velocity of flow was altered independently by changing either the size of the orifice through which flow occurred or the ejection rate. In this manner the differential effects of volume and velocity on the color flow Doppler image could be examined. The maximum area encompassed by the color flow Doppler pattern for each ejection was planimetered by using commercially available on-line software. In addition the reviewer in each case applied a subjective grade to the appearance of the color flow jet (1+ to 4+). Comparison was then made of the color flow Doppler appearance of equal volumes flowing at different velocities and of different volumes flowing at different velocities. In the initial series a solution of agitated hetasarch was used. When equal volumes were imaged at different velocities the higher-velocity jet appeared larger, both subjectively (3+ vs 1+) and by measuring the area encompassed in the Doppler flow profile (40.3 +/- 1.8 vs 22.0 +/- 1.4 cm2, p = 0.0001). Furthermore, when different volumes were imaged at different velocities, the smaller volume (3 ml vs 6 ml) appeared larger when it was flowing at higher velocity (3+ vs 2+, 40.3 +/- 1.8 vs 32.4 +/- 1.3 cm2, p = 0.0006). These experiments were repeated with blood, confirming the results of the initial study.(ABSTRACT TRUNCATED AT 250 WORDS)

Cine MR imaging of valvular heart disease: display and imaging parameters affect the size of the signal void caused by valvular regurgitation.

The effects of display and imaging parameters on the measured size of the signal void representing valvular regurgitation on cine MR imaging were examined. Sixteen patients with valvular regurgitation were studied. Six cine acquisition modes were evaluated in five patients. Echo times (TEs) (8, 12, and 17 msec) and flip angles (30 degrees and 50 degrees) were varied. The variable display parameters were [Z x (blood pool signal intensity - lung signal intensity)] at window width (Z = 0.75, 1.00, 1.25) and (Y x window width + lung signal intensity) at window level (Y = 0.00, 0.25, 0.50). The area of the signal void was significantly (p less than .01) affected by the window level (2.7 +/- 0.8 cm2 at Y = 0.00, 4.4 +/- 1.1 cm2 at Y = 0.25, and 5.6 +/- 1.4 cm2 at Y = 0.50) and window width (3.6 +/- 0.9 cm2 at Z = 0.75 and 4.9 +/- 1.1 cm2 at Z = 1.25). With standardized display parameters, TE influenced the area (3.3 +/- 1.1 cm2 at 8 msec and 7.8 +/- 1.5 cm2 at 12 msec; p less than .01). Variations in the value of TE and display settings cause differences in the measured area of the regurgitant signal void. Quantification of valvular regurgitation by cine MR imaging requires strict standardization of display and imaging parameters.

Conclusions: role of various techniques in the quantification of valvular regurgitation

Conclusions: role of various techniques in the quantification of valvular regurgitation

Quantification of valvular regurgitation before and after medical and surgical therapy by radionuclide angiography

Quantification of valvular regurgitation before and after medical and surgical therapy by radionuclide angiography