Severity Of Valvular Regurgitation Research Articles

Mismatch of Right- and Left-Sided Filling Pressures in Chronic Heart Failure

Background In patients with advanced heart failure (HF), elevated jugular venous pressure (JVP) is the most reliable sign of elevated left-sided filling pressures. However, discordance between right- and left-sided filling pressure s (R-L mismatch) could lead to inadequate or excessive therapy guided by JVP. We determined the prevalence of R-L mismatch in the current era and investigated whether mismatch might be identified from clinical information. Methods and Results Right-sided heart catheterization was performed in 537 consecutive patients hospitalized with advanced HF during complete transplantation evaluation. Patients with high filling pressures were categorized as matched (right atrial pressure (RAP) ≥10 mm Hg and pulmonary wedge pressure (PCWP) ≥22 mm Hg), high-R mismatch (RAP ≥10 but PCWP <22 mm Hg) or high-L mismatch (PCWP ≥22 but RAP <10 mm Hg). Among all of the patients, 195 (36%) were matched low and 194 (36%) were matched high, and 148 (28%) had R-L mismatch. Among patients with high filling pressures, 194 (57%) were matched high and 82 (24%) had high-L and 66 (19%) high-R mismatch. Mismatches were not associated with differences in demographic or clinical data, including pulmonary and hepatic function, or severity of valvular regurgitation and right ventricular function by echo. However, among all patients with RAP ≥10 mm Hg, pulmonary artery systolic pressure (PASP) was higher in those patients with matched high left- and right-sided pressures (59 ± 12 mm Hg) versus high-R mismatch (41 ± 13 mm Hg; P < .0001). Similarly among all patients with low RAP, PASP was lower in patients with matched low right- and left-side pressures (33 ± 11 mm Hg) versus high-L mismatch (53 ± 13 mm Hg; P < .0001). Conclusions R-L mismatch was present in >1 in 4 total patients, and >1 in 3 with elevated filling pressures. Regardless of clinical history, when empiric therapy to optimize volume status to JVP is not effective, additional measurement should be considered to establish the R-L relationship.

Color Doppler Echocardiographic Assessment of Valvular Regurgitation in Normal Infants

Despite valvular regurgitation being a common finding in children, its prevalence in infants is unclear. The aim of this study was to determine the presence and severity of valvular regurgitation in normal infants using echocardiographic screening. Two-dimensional (2D) color Doppler echocardiography was performed on 420 consecutive infants (aged 1-12 months) with structurally normal hearts. Pulsed, continuous-wave, and color Doppler imaging techniques were used to detect and evaluate regurgitant blood flow at each valve. Valvular regurgitation was present in 258 infants (61.4%). Among these, 41 (15.9%) were found to have a heart murmur. Tricuspid regurgitation was found in 237 (56.4%) infants, pulmonary regurgitation in 71 (16.9%), mitral regurgitation in 51 (12.1%), and aortic regurgitation in nine (2.1%). Regurgitation of one valve occurred in 161 (38.3%) infants, of two valves in 84 (20%), and of three valves in 13 (3.1%). Right-sided regurgitation was significantly more common than left-sided regurgitation (p < 0.05). The degree of regurgitation was trivial or mild in 97.3% of infants and the peak velocities of the regurgitant jets were < or = 2.5 m/sec in all the valves, by Doppler echocardiography. The prevalence of inaudible valvular regurgitation is high in infants with structurally normal hearts. Multiple-valve involvement with regurgitation is not uncommon. Mild severity and low velocity on color Doppler, and the structural information provided by 2D imaging strongly suggest that these regurgitant flows are physiologically normal in infancy.

Evaluation of the Severity of Mitral Valvular Regurgitation with Doppler Echocardiography Using Proximal Flow Convergence Method

Problem statement: Valvular regurgitation is recognized as the central cause of morbidity and mortality. Even though the clinician can detect the presence of regurgitation by mere physical examination; diagnostic methods become inevitable while estimating the severity of valvular regurgitation and in the transformation of cardiac chambers as in reaction to the volume overload condition. Lately, a promising new technology, the Echocardiography with Doppler is found to facilitate the non-invasive recognition and assessment of the severity and etiology of valvular regurgitation. Accurate measurements of regurgitant volume in patients is of utmost importance since it aids in the estimation of the progression of the disease which in turn is vital for determining the optimal time for surgical repair or replacement. Approach: Color space conversion and anisotropic diffusion segmentation techniques are utilized in this study for the pre-processing stage of the quantification of mitral regurgitation. Flow field measurements are carried out with the aid of proximal flow convergence method. Results: A calculated value of flow rate, regurgitant orifice area, regurgitant fraction and the regurgitant volume for a regurgitant orifice in the cardiovascular system are obtained from the potential Color Doppler visualization of the flow convergence region. Conclusion: The research proposed provides a significant assessment of the echocardiographic and Doppler techniques employed in the evaluation of mitral valvular regurgitation in the patients. Additionally it also proffers the estimation of mildness, severity and eccentricity of mitral valvular regurgitation on basis of the scientific literature and a consensus of a panel of experts.

Quantification of valvular regurgitation area and geometry using HPRF 3-D doppler

It is important to determine the severity of valvular regurgitation accurately because surgery is indicated only in severe regurgitations. The evaluation of, for example, mitral regurgitation is complex, and the current methods have limitations. We have developed a 3-D Doppler method to estimate the cross-sectional area and the geometry of a regurgitant jet at the vena contracta just downstream from the actual orifice. The back-scattered Doppler signal from multiple beams distributed over the area of interest was measured. The received power from these beams was then calibrated using both a priori knowledge of the lateral extent of the beams and a reference beam that was completely enclosed by the vena contracta. To isolate the Doppler signal received from the core of a regurgitant jet, a high pulse repetition frequency and a steep clutter filter are required. The method has been implemented and verified by computer simulations and by in vitro experiments using a pulsatile flow phantom and prosthetic valves with a range of holes. We were able to distinguish between mild, moderate, and severe valvular regurgitation. We were also able to quantify the regurgitational area as well as show the geometry of the regurgitation.

Effects of sedation with acepromazine on echocardiographic measurements in eight healthy thoroughbred horses

Eight normal thoroughbred horses were examined by echocardiography before and 10 minutes after they had been sedated by the intravenous administration of 0·03 mg/kg acepromazine. There were significant (P<0·025) increases...

Intravascular Hemolysis and Acute Renal Failure After Mitral and Aortic Valve Repair

Intravascular Hemolysis and Acute Renal Failure After Mitral and Aortic Valve Repair

Myocardial T1 Mapping for Detection of Left Ventricular Myocardial Fibrosis in Chronic Aortic Regurgitation: Pilot Study

The aim of this study was to identify diffuse myocardial fibrosis secondary to chronic aortic regurgitation by comparing the T1 relaxation times of left ventricular myocardium in a pilot patient group with a previously established normal range of times. Eight patients with chronic aortic regurgitation and normal coronary arteries awaiting surgical valve replacement underwent a comprehensive MRI examination that included assessment of left ventricular function, severity of valvular regurgitation, and presence of overt myocardial scar evidenced by delayed enhancement. For each patient, myocardial T1 relaxation times determined with a modified Look-Locker technique before and after contrast administration were compared with values previously established for 15 healthy volunteers. There was no statistical difference (p > 0.05) in slice-averaged myocardial T1 relaxation times either before or after gadolinium administration in the patient group compared with the normal range of times. Segmental averaged T1 relaxation times in segments with abnormal wall motion did, however, show statistically significant differences from healthy controls 10, 15, and 20 minutes after administration of gadolinium (510 vs 476 milliseconds, p = 0.001; 532 vs 501 milliseconds, p = 0.002; 560 vs 516 milliseconds, p = 0.001, respectively). Two of the aortic regurgitation patients also had focal areas of myocardial delayed enhancement. Segment-based myocardial T1 mapping has the potential for showing differences between relaxation times in aortic regurgitation and in normal hearts, suggesting the existence of a diffuse myocardial fibrotic process.

Reliability of cardiac dimensions and valvular regurgitation assessment by sonographers using hand-carried ultrasound devices

We sought to assess the reliability of some basic echocardiographic data obtained by trained sonographers using a hand-held ultrasound device. One hundred and twelve consecutive patients (mean age 61, 64 males) referred for in-hospital or ambulatory routine echocardiography were considered. All patients underwent two-dimensional and colour Doppler examination performed by a trained sonographer equipped with a hand-held ultrasound device and by a certified cardiologist equipped with a standard platform, in random order. Indexed left ventricular end-diastolic and end-systolic transverse diameters, aortic root, end-systolic left atrium transverse diameter, end-diastolic interventricular septum and posterior wall thickness were calculated by two-dimensional left parasternal long-axis view in blind conditions. Mitral and aortic valve regurgitation were investigated by colour-Doppler imaging on parasternal and apical views and compared using a 0 to 4 semi-quantitative score. Overall feasibility was high for both settings (sonographers: 93%; cardiologists: 95%; P not significant). Excellent concordance of end-diastolic diameter (kappa 0.75), left atrium (kappa 0.76) and interventricular septum thickness (kappa 0.77) results was found. Good concordance was observed for end-systolic diameter (kappa 0.66), aortic root (kappa 0.64) and posterior wall thickness (kappa 0.67) results. A high linear correlation between the couples of results was present for all parameters. A good agreement of the mitral (kappa 0.66) and aortic (kappa 0.84) regurgitation scores was also found, with a low prevalence of discordant results (mitral regurgitation: 22%, aortic regurgitation: 9%) and no > or =2-point discrepancies. In a general population referred for Doppler echocardiography, basic cardiac linear dimensions and valvular regurgitation severity assessment by trained sonographers using hand-held ultrasound devices appear accurate and reliable for routine clinical use.

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

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). 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. 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. 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). 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.

Impact of valvular regurgitation on left ventricular geometry and function in hypertensive patients with left ventricular hypertrophy: the LIFE study.

Mild-to-moderate aortic and mitral regurgitation are frequently detected by echocardiogram in asymptomatic hypertensive patients. Our goal was to assess the prevalence and impact of mild-to-moderate mitral and/or aortic regurgitation on left ventricular (LV) structure and function in patients with hypertension and LV hypertrophy (LVH). Hypertensive patients with ECG LVH enrolled in the Losartan Intervention For Endpoint reduction in hypertension (LIFE) echocardiography substudy were evaluated. Among 939 patients with needed LV measurements and Doppler data, 242 had mild (1+) valvular regurgitation, and 51 patients had moderate (2+ or 3+) regurgitation of one or both valves. In analyses adjusting for gender, patients with mild mitral and/or aortic regurgitation had larger LV internal dimensions (5.25 vs 5.33 cm, P<0.05), higher LV mass indexed for body surface area (122 vs 125 g/m(2), P<0.05) or height(2.7) (55.4 vs 57.3, P<0.05), and larger left atrial diameter. Patients with moderate regurgitation of one or both valves had larger LV chambers (5.25 vs 5.9 cm, P<0.001), greater mean LV mass (232 vs 248 g, P<0.001) and LV mass indexed for body surface area or height(2.7), and higher Doppler stroke volume. Patients with moderate valvular regurgitation also had a higher prevalence of LVH due to an increased prevalence of eccentric LVH. There were no differences among groups defined by the presence and severity of valvular regurgitation in cardiac output, total peripheral resistance, or pulse pressure/stroke volume, indicating that the observed inter-group differences in LV geometry were not due to differences in the haemodynamic severity of hypertension. Hypertensive patients with mild-to-moderate mitral or aortic valvular insufficiency have additional LV structural and functional changes that may affect prognosis.

American Society of Echocardiography: recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and Doppler echocardiography A report from the American Society of Echocardiography's Nomenclature and Standards Committee and The Task Force on Valvular Regurgitation, developed in conjunction with the American College of Cardiology Echocardiography Committee, The Cardiac Imaging Committee, Council on Clinical Cardiology, The American Heart

Valvular regurgitation has long been recognized as an important cause of morbidity and mortality. Although the physical examination can alert the clinician to the presence of significant regurgitation, diagnostic methods are often needed to assess the severity of valvular regurgitation and remodeling of the cardiac chambers in response to the volume overload state. Echocardiography with Doppler has recently emerged as the method of choice for the noninvasive detection and evaluation of the severity and etiology of valvular regurgitation. This article offers a critical review of echocardiographic and Doppler techniques used in the evaluation of valvular regurgitation in the adult patient, and provides recommendations for the assessment of severity of valvular regurgitation based on the scientific literature and a consensus of a panel of experts. Issues of medical management and timing of surgical intervention will not be addressed in this article, as these have been recently published[1]. Valvular regurgitation or incompetence results from various etiologies including valvular degeneration, calcification, fibrosis or infection, alteration of the valvular support apparatus or dilatation of the valve annulus. These conditions cause poor apposition of the valvular leaflets or cusps, and may lead to prolapse, flail, restricted leaflet motion or valvular perforation. With the advent of Doppler techniques that are sensitive to detection of regurgitation, trivial and physiologic valvular regurgitation, even in a structurally normal valve, is now well recognized and is noted to occur frequently in right-sided valves. The following sections describe general considerations of the role of echocardiographic and Doppler techniques in the evaluation of regurgitant lesions. ### Role of Two-dimensional echocardiography Two-dimensional (2D) echocardiography allows an evaluation of the valvular structure as well as the impact of the volume overload on the cardiac chambers. Calcifications, tethering, flail motion or vegetations can be readily assessed, which can give indirect clues as to the severity of regurgitation. While …

Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and doppler echocardiography

Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and doppler echocardiography

Comparison of Transthoracic and Intraoperative Transesophageal Color Flow Doppler Assessment of Mitral and Aortic Regurgitation

Background: We examined the agreement between transthoracic echocardiography (TTE) and intraoperative prepump transesophageal echocardiography (TEE) in the assessment of left-sided regurgitant lesions and echocardiographic variables associated with grading discrepancies. Methods: The TTE and prepump TEE studies of 54 patients undergoing aortic-valve replacement for aortic stenosis were reviewed. Agreement and correlation in assessment of aortic (AR) and mitral regurgitation (MR) severity were evaluated. Results: There was no significant difference between mean TTE and prepump TEE grading of MR (0.23 ± 0.19 vs. 0.21 ± 0.15 jet area/area of the left atrium, p = 0.49), but the correlation between the two methods was weak (r = 0.40, p = 0.003), with an exact agreement of 54%. Prepump TEE tended to grade AR as more severe (mean grade 1.43 ± 0.94 vs. 1.24 ± 0.75, p = 0.058). The correlation between the two methods in AR assessment was fair (r = 0.70, p = 0.0001) with an agreement of 59%. For MR and AR grading, no significant correlations between valvular regurgitation severity and blood pressure differences between preoperative TTE and prepump TEE were found. In 17% of cases, discrepancies in identifying severe mitral or aortic valve regurgitation could have affected patient management. Conclusions: There is modest agreement in MR and AR assessment between TTE and prepump TEE. Cardiologists, cardiac surgeons, and anesthesiologists must be aware of differences between these methods when using prepump TEE to guide intraoperative decisions.

Vena contracta width measurement: theoretic basis and usefulness in the assessment of valvular regurgitation severity.

In patients with valvular regurgitation, the regurgitation jet can be observed by Doppler color flow imaging. Vena contracta is defined as the narrowest part of the jet, just distal to the regurgitant orifice. Vena contracta dimensions reflect the severity of regurgitation. Vena contracta diameter, usually easy to measure in clinical practice, is well correlated with the effective regurgitant orifice area and the regurgitant volume. Cutoff values have been determined to identify severe regurgitation for mitral, aortic, and tricuspid valves. In clinical practice, determination of vena contracta diameter is a useful and simple method for assessment of valvular regurgitation. In the future, assessment of complex jet regurgitations will probably benefit from the contribution of three-dimensional Doppler flow imaging, which should improve the performances of the method.

Quantification of instantaneous flow rate and dynamically changing effective orifice area using a geometry independent three-dimensional digital color Doppler method: An in vitro study mimicking mitral regurgitation

Objective: Our study was intended to test the accuracy of a 3-dimensional (3D) digital color Doppler flow convergence (FC) method for assessing the effective orifice area (EOA) in a new dynamic orifice model mimicking a variety of mitral regurgitation. Background: FC surface area methods for detecting EOA have been reported to be useful for quantifying the severity of valvular regurgitation. With our new 3D digital direct FC method, all raw velocity data are available and variable Nyquist limits can be selected for computation of direct FC surface area for computing instantaneous flow rate and temporal change of EOA. Methods: A 7.0-MHz multiplane transesophageal probe from an ultrasound system (ATL HDI 5000) was linked and controlled by a computer workstation to provide 3D images. Three differently shaped latex orifices (zigzag, arc, and straight slit, each with cutting-edge length of 1 cm) were used to mimic the dynamic orifice of mitral regurgitation. 3D FC surface computation was performed on parallel slices through the 3D data set at aliasing velocities (14-48 cm/s) selected to maximize the regularity and minimize lateral dropout of the visualized 3D FC at 5 points per cardiac cycle. Using continuous wave velocity for each, 3D-calculated EOA was compared with EOA determined by using continuous wave Doppler and the flow rate from a reference ultrasonic flow meter. Simultaneous digital video images were also recorded to define the actual orifice size for 9 stroke volumes (15-55 mL/beat with maximum flow rates 45-182 mL/s). Results: Over the 9 pulsatile flow states and 3 orifices, 3D FC EOAs (0.05-0.63 cm 2) from different phases of the cardiac cycle in each pump setting correlated well with reference EOA ( r = 0.89-0.92, SEE = 0.027-0.055cm 2) and they also correlated well with digital video images of the actual orifice peak ( r = 0.97-0.98, SEE = 0.016-0.019 cm 2), although they were consistently smaller, as expected by the contraction coefficient. Conclusion: The digital 3D FC method can accurately predict flow rate, and, thus, EOA (in conjunction with continuous wave Doppler), because it allows direct FC surface measurement despite temporal variability of FC shape. (J Am Soc Echocardiogr 2002;15:1189-96.)

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

OBJECTIVESThis 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).BACKGROUNDColor 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).METHODSA 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.RESULTSA 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 mm2had a RgF >0.50, and all 18 patients with a VC area <7.5 mm2had 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).CONCLUSIONSVena 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.

The progression of fenfluramine-associated valvular heart disease assessed by echocardiography.

An association between the dietary suppressants fenfluramine and dexfenfluramine and valvular heart disease was first described in patients from North Dakota and Minnesota in 1997. Limited data are available on the natural history of this valvulopathy after discontinuation of drug therapy. To follow the progression of fenfluramine-associated valvular heart disease after discontinuation of therapy by using serial echocardiography. Retrospective cohort study. Regional medical center in Fargo, North Dakota. 50 patients with previous exposure to fenfluramines who had at least mild mitral regurgitation or aortic regurgitation after exposure to fenfluramines on serial echocardiography between December 1994 and February 1999 (96% were female, mean body mass index was 36.6 kg/m(2), and mean duration of drug exposure was 447 days). Serial echocardiograms were reviewed by two echocardiographers who were blinded to the order of image acquisition. The severity of valvular regurgitation and presence or absence of valve leaflet restriction were assessed. As described in the initial report, significant valvular disease on initial postexposure echocardiography was common in this cohort; 38 patients (76%) had at least mild mitral regurgitation and 43 patients (86%) had at least mild aortic regurgitation. On serial echocardiograms obtained an average of 356 days apart, mitral regurgitation improved by at least one grade in 17 patients (P = 0.001) and aortic regurgitation improved by at least one grade in 19 patients (P = 0.004). Nineteen and 22 patients, respectively, experienced no change in severity of mitral and aortic regurgitation. Two patients in each group experienced worsening of regurgitation by at least one grade. Results were similar for tricuspid (P = 0.002) and pulmonic (P = 0.012) regurgitation. On serial echocardiography, fenfluramine-associated valvular regurgitation improved or remained stable in most patients after therapy ended. Worsening of valvular regurgitation was uncommon. The potential for stabilization or regression of valvular regurgitation should be taken into account when counseling patients and considering the need for and timing of valve surgery.

Detection and quantification of valvular heart disease with dynamic cardiac MR imaging.

Magnetic resonance (MR) imaging is rapidly gaining acceptance as an accurate, reproducible, noninvasive method for optimal assessment of structural and functional parameters in patients with valvular heart disease. The severity of valvular regurgitation can be evaluated with cine gradient-echo MR imaging, which allows measurement of the area of the signal void corresponding to the abnormal flow jet. Alternatively, this modality can be used to obtain ventricular volumetric measurements and calculate the regurgitant fraction, or velocity-encoded cine (VEC) MR imaging can be used to quantify regurgitant blood flow. The severity of valvular stenosis can be determined by evaluating the flow jet and associated findings with either modality or by using VEC MR imaging to calculate the transvalvular pressure gradient and valve area. Dynamic MR imaging allows accurate assessment of ventricular function and comprehensive evaluation of pathophysiologic changes. In addition, good interstudy reproducibility suggests a role for VEC MR imaging in assessing the effects of therapeutic intervention and monitoring regurgitant fraction, thereby helping in surgical planning and the prevention of ventricular dysfunction. With greater cost-effectiveness and the increasing availability of new hardware and more advanced techniques, MR imaging will become a routine procedure in valvular heart disease.

Flow Convergence Flow Rates from 3-Dimensional Reconstruction of Color Doppler Flow Maps for Computing Transvalvular Regurgitant Flows Without Geometric Assumptions: An In Vitro Quantitative Flow Study

Objective: This study was designed to develop and test a 3-dimensional method for direct measurement of flow convergence (FC) region surface area and for quantitating regurgitant flows with an in vitro flow system. Background: Quantitative methods for characterizing regurgitant flow events such as flow convergence with 2-dimensional color flow Doppler imaging systems have yielded variable results and may not be accurate enough to characterize those more complex spatial events. Method: Four differently shaped regurgitant orifices were studied: 3 flat orifices (circular, rectangular, triangular) and a nonflat one mimicking mitral valve prolapse (all 4 orifice areas = 0.24 cm 2) in a pulsatile flow model at 8 to 9 different regurgitant flow rates (10 to 50 mL/beat). An ultrasonic flow probe and meter were connected to the flow model to provide reference flow data. Video composite data from the color Doppler flow images of the FC were reconstructed after computer-controlled 180° rotational acquisition was performed. FC surface area (S cm 2) was calculated directly without any geometric assumptions by measuring parallel sliced flow convergence arc lengths through the FC volume and multiplying each by the slice thickness (2.5 to 3.2 mm) over 5 to 8 slices and then adding them together. Peak regurgitant flow rate (milliliters per second) was calculated as the product of 3-dimensional determined S (cm 2) multiplied by the aliasing velocity (centimeters per second) used for color Doppler imaging. Results: For all of the 4 shaped orifices, there was an excellent relationship between actual peak flow rates and 3-dimensional FC-calculated flow rates with the direct measurement of the surface area of FC ( r = 0.99, mean difference = –7.2 to –0.81 mL/s, % difference = –5% to 0%), whereas a hemielliptic method implemented with 3 axial measurements of the flow convergence zone from 2-dimensional planes underestimated actual flow rate by mean difference = –39.8 to –18.2 mL/s, % difference = –32% to –17% for any given orifice. Conclusions: Three-dimensional reconstruction of flow based on 2-dimensional color Doppler may add quantitative spatial information, especially for complex flow events. Direct measurement of 3-dimensional flow convergence surface areas may improve accuracy for estimation of the severity of valvular regurgitation. (J Am Soc Echocardiogr 1999;12:1035-44.)

Estimation of turbulent shear stress in free jets: application to valvular regurgitation.

In an attempt to better assess the severity of valvular regurgitation, an in-vitro experiment has been conducted to estimate turbulent shear stress levels within free jets issuing from different orifice shapes and sizes by means of hot-wire anemometry. On the basis of the measured mean velocities and the jet profiles, the distributions of the normalized kinematic turbulent shear stress (uv/Um2) were estimated for different jets by using an equation available for self-preserving circular jet. The results indicate that the equation can estimate the distributions of uv/Um2 independent of the orifice shape and Reynolds number of the jet. For the range of Reynolds numbers considered, the estimation of maximum turbulent shear stress inferred from these distributions suggests that the critical shear stress level of approximately 200 N/m2, corresponding to destruction of blood cells, is exceeded for typical blood flow velocity of 5 m/s at the valvular lesion.