Motion Of Left Ventricle Research Articles

Automated Three-Dimensional Reconstruction of the Left Ventricle From Multiple-Axis Echocardiography.

Two-dimensional echocardiography (echo) is the method of choice for noninvasive evaluation of the left ventricle (LV) function owing to its low cost, fast acquisition time, and high temporal resolution. However, it only provides the LV boundaries in discrete 2D planes, and the 3D LV geometry needs to be reconstructed from those planes to quantify LV wall motion, acceleration, and strain, or to carry out flow simulations. An automated method is developed for the reconstruction of the 3D LV endocardial surface using echo from a few standard cross sections, in contrast with the previous work that has used a series of 2D scans in a linear or rotational manner for 3D reconstruction. The concept is based on a generalized approach so that the number or type (long-axis (LA) or short-axis (SA)) of sectional data is not constrained. The location of the cross sections is optimized to minimize the difference between the reconstructed and measured cross sections, and the reconstructed LV surface is meshed in a standard format. Temporal smoothing is implemented to smooth the motion of the LV and the flow rate. This software tool can be used with existing clinical 2D echo systems to reconstruct the 3D LV geometry and motion to quantify the regional akinesis/dyskinesis, 3D strain, acceleration, and velocities, or to be used in ventricular flow simulations.

Reversible severe mitral regurgitation caused by systolic anterior motion of the mitral valve in the absence of left ventricular hypertrophy: A case report

A 67-year-old woman with exertional dyspnea was referred to our hospital. Transthoracic echocardiography revealed severe mitral regurgitation and significant left ventricular (LV) outflow tract obstruction due to prominent systolic anterior motion (SAM) of the mitral valve without LV hypertrophy. Oral bisoprolol remarkably attenuated SAM. Two- or three-dimensional echocardiographic analysis demonstrated the elongation of anterior and posterior mitral leaflets and interventricular septum (IVS) bulging due to narrow aorto-mitral angle. In the present case, elongation of mitral leaflet and hyperkinetic motion of left ventricle, and IVS bulging due to narrow aorto-mitral angle possibly play important roles in the development of SAM.<Learning objective: Mitral regurgitation due to systolic anterior motion (SAM) can be dramatically improved by beta-blocker therapy. Although the precise mechanism of SAM has not been fully elucidated, structural changes of mitral apparatus (elongation of mitral leaflet and papillary muscle displacement), and structural or functional features of left ventricle (hyperkinetic motion, small ventricle, interventricular septum bulging, narrow aorto-mitral angle) possibly play important roles in the development of SAM.>

MRI-based strain and strain rate analysis of left ventricle: a modified hierarchical transformation model

BackgroundDifferent from other indicators of cardiac function, such as ejection fraction and transmitral early diastolic velocity, myocardial strain is promising to capture subtle alterations that result from early diseases of the myocardium. In order to extract the left ventricle (LV) myocardial strain and strain rate from cardiac cine-MRI, a modified hierarchical transformation model was proposed.MethodsA hierarchical transformation model including the global and local LV deformations was employed to analyze the strain and strain rate of the left ventricle by cine-MRI image registration. The endocardial and epicardial contour information was introduced to enhance the registration accuracy by combining the original hierarchical algorithm with an Iterative Closest Points using Invariant Features algorithm. The hierarchical model was validated by a normal volunteer first and then applied to two clinical cases (i.e., the normal volunteer and a diabetic patient) to evaluate their respective function.ResultsBased on the two clinical cases, by comparing the displacement fields of two selected landmarks in the normal volunteer, the proposed method showed a better performance than the original or unmodified model. Meanwhile, the comparison of the radial strain between the volunteer and patient demonstrated their apparent functional difference.ConclusionsThe present method could be used to estimate the LV myocardial strain and strain rate during a cardiac cycle and thus to quantify the analysis of the LV motion function.

Right ventricular wall motion abnormalities n Thalassemia Major patients

Background Movement abnormalities in the left ventricle (LV) were shown to be not really frequent in thalassemia major (TM) patients but they were associated with age, myocardial iron overload, LV dilation and dysfunction, and myocardial fibrosis. No data are available about the prevalence and the correlates of right ventricular (RV) wall motion abnormalities. This study investigated the relationship between RV and LV motion abnormalities and between RV motion and function in a large cohort of well-treated TM patients. Methods CMR was performed in 1092 TM patients (537 male; 30.6 ± 8.5 years) enrolled in the Myocardial Iron Overload in Thalassemia (MIOT) Network. Cine images were acquired to evaluate wall motion and to quantify RV volumes and ejection fraction (EF). Results

Deformation similarity measurement in quasi-conformal shape space

This paper presents a novel approach based on the shape space concept to classify deformations of 3D models. A new quasi-conformal metric is introduced which measures the curvature changes at each vertex of each pose during the deformation. The shapes with similar deformation patterns follow a similar deformation curve in shape space. Energy functional of the deformation curve is minimized to calculate the geodesic curve connecting two shapes on the shape space manifold. The geodesic distance illustrates the similarity between two shapes, which is used to compute the similarity between the deformations. We applied our method to classify the left ventricle deformations of myopathic and control subjects, and the sensitivity and specificity of our method were 88.8% and 85.7%, which are higher than other methods based on the left ventricle cavity, which shows our method can quantify the similarity and disparity of the left ventricle motion well.

A case of coronary-subclavian steal in patient with a history of coronary artery bypass grafting and carotid-subclavian bypass

Introduction: A coronary-subclavian steal phenomenon was described in patients who have undergone prior bypass surgery using the left internal mammary artery (LIMA). Case report description: A 74-year-old male with a prior 3-vessel coronary artery bypass grafting (CABG) in 2005 was admitted to the hospital with the deteriorating condition over the last four months. He had complaints of exertional chest pain which was usually gone upon taking nitroglycerin. He had a history of carotid-subclavian bypass in 1995. His prior CABG included LIMA graft to the left anterior descending artery (LAD), saphenous vein graft (SVG) to the obtuse marginal (OM), and SVG to posterior descending artery (PDA). On admission, right arm blood pressure (BP) was 130/80 mm Hg, left arm BP was 80/60 mm Hg. Initial echocardiogram showed left ventricle (LV) ejection fraction of 53%. Stress-echocardiography was positive and demonstrated wall motion abnormalities in septal, antero-septal and anterior segments of LV. Duplex ultrasound revealed bilateral carotid stenosis of 55%, left subclavian artery subocclusion and stenosis of carotid-subclavian graft with maximal linear flow velocity up to 3.5 m/sec. Nevertheless both vertebral arteries had antegrade flow. Using cardiac catheterization severe 3-vessel coronary artery disease was diagnosed but PDA and OM SVG grafts and LIMA graft were patent. Angiography showed a severe stenosis of 95% of proximal left subclavian artery, stenosis of 59% of carotid-subclavian graft. LIMA graft had retrograde flow to the left subclavian artery and the first segment of left vertebral artery. The patient underwent PTA and stent placement of the left subclavian artery. During one-year follow-up period, he was symptom free, ultrasound showed normal flow in left subclavian artery, and regional wall motion of LV appeared to be normal. Discussion: Clinical manifestation of a coronary-subclavian steal in this patient was unusual with the severe angina but without any symptoms of cerebral ischemia probably due to partly functioning carotid-subclavian graft. Percutaneous revascularization of the subclavian artery was the reasonable treatment option. That lesion was more significant than stenosis of carotid-subclavian graft, more favorable for PTA due to minimal calcification and relatively short stenosis. Conclusions: Coronary-subclavian steal syndrome is a diagnosis that should not be overlooked, especially in patients with known peripheral atherosclerosis. Percutaneous interventions due to their efficacy and low complication rates constitute the first choice treatment in patients with high surgical risk.

984Left ventricular wall motion, iron, function, and iron in thalassemia major

Objectives: Movement abnormalities of the left ventricle (LV) have been reported in thalassemia major (TM) patients. Movement abnormalities can be detected through a qualitative analysis of cine CMR images. Moreover, CMR is the gold standard technique for the evaluation of myocardial iron overload (MIO), biventricular global systolic function and myocardial fibrosis. The aim of this study was to investigate the relationship between movement abnormalities and MIO, left ventricular (LV) function and myocardial fibrosis. Methods: CMR (1.5T) was performed in 1092 TM patients (537 male; 30.6 ± 8.5 years) enrolled in the Myocardial Iron Overload in Thalassemia (MIOT) Network. Cine SSFP images were used to evaluate the wall motion and to quantify LV volumes and ejection fraction (EF) by means of the MASS software. For MIO assessment, three parallel short-axis views of the LV were acquired using a T2* GRE multi-echo sequence. To detect myocardial fibrosis, late gadolinium enhanced (LGE) images were acquired. During image analysis the 17-segment LV model of the AHA/ACC was taken into account. Segmental wall motion was visually assessed by skilled observers and scored as 1 = normal, 2 = hypokinesia, 3 = akinesia and 4 = dyskinesia. The T2* value in all segments as well as the global value were calculated. Presence/absence of enhancing area was assessed for each segment. Results: Abnormal motion of LV was found in 66 (6%) patients: 60 were hypokinetic while 6 were dyskinetic. Our data demonstrated predominant involvement of wall motion abnormalities in the medium anterior, anterolateral and septal segments. The Table shows the comparison between patients with normal and abnormal motion. Patients with abnormal motion were significantly older, they had significantly lower global heart T2* value and a significantly higher number of segments with T2* < 20 ms. Left volumes and mass indexed by body surface area were significantly higher in patients with abnormal motion while the EF was significantly lower. LGE areas were detected in 196 patients (18%) and they were predominantly located in the mid-ventricular septum. There was a significant correlation between the presence of enhancement and the abnormal motion. Conclusions: Movement abnormalities in the left ventricle were not really frequent in TM patients but were associated with age, MIO, LV dilation and dysfunction, and myocardial fibrosis.2

Evaluation of interpolation methods for surface‐based motion compensated tomographic reconstruction for cardiac angiographic C‐arm data

For interventional cardiac procedures, anatomical and functional information about the cardiac chambers is of major interest. With the technology of angiographic C-arm systems it is possible to reconstruct intraprocedural three-dimensional (3D) images from 2D rotational angiographic projection data (C-arm CT). However, 3D reconstruction of a dynamic object is a fundamental problem in C-arm CT reconstruction. The 2D projections are acquired over a scan time of several seconds, thus the projection data show different states of the heart. A standard FDK reconstruction algorithm would use all acquired data for a filtered backprojection and result in a motion-blurred image. In this approach, a motion compensated reconstruction algorithm requiring knowledge of the 3D heart motion is used. The motion is estimated from a previously presented 3D dynamic surface model. This dynamic surface model results in a sparse motion vector field (MVF) defined at control points. In order to perform a motion compensated reconstruction, a dense motion vector field is required. The dense MVF is generated by interpolation of the sparse MVF. Therefore, the influence of different motion interpolation methods on the reconstructed image quality is evaluated. Four different interpolation methods, thin-plate splines (TPS), Shepard's method, a smoothed weighting function, and a simple averaging, were evaluated. The reconstruction quality was measured on phantom data, a porcine model as well as on in vivo clinical data sets. As a quality index, the 2D overlap of the forward projected motion compensated reconstructed ventricle and the segmented 2D ventricle blood pool was quantitatively measured with the Dice similarity coefficient and the mean deviation between extracted ventricle contours. For the phantom data set, the normalized root mean square error (nRMSE) and the universal quality index (UQI) were also evaluated in 3D image space. The quantitative evaluation of all experiments showed that TPS interpolation provided the best results. The quantitative results in the phantom experiments showed comparable nRMSE of ≈0.047 ± 0.004 for the TPS and Shepard's method. Only slightly inferior results for the smoothed weighting function and the linear approach were achieved. The UQI resulted in a value of ≈ 99% for all four interpolation methods. On clinical human data sets, the best results were clearly obtained with the TPS interpolation. The mean contour deviation between the TPS reconstruction and the standard FDK reconstruction improved in the three human cases by 1.52, 1.34, and 1.55 mm. The Dice coefficient showed less sensitivity with respect to variations in the ventricle boundary. In this work, the influence of different motion interpolation methods on left ventricle motion compensated tomographic reconstructions was investigated. The best quantitative reconstruction results of a phantom, a porcine, and human clinical data sets were achieved with the TPS approach. In general, the framework of motion estimation using a surface model and motion interpolation to a dense MVF provides the ability for tomographic reconstruction using a motion compensation technique.

Postoperative left ventricular apical ballooning: Transient Takotsubo cardiomyopathy following orthotopic liver transplantation

Patient: Female, 51Final Diagnosis: Takotsubo cardiomyopathySymptoms: —Medication: —Clinical Procedure: —Specialty: Cardiology • TransplantologyObjective:Rare diseaseBackground:Left ventricular apical ballooning syndrome (LVAB), also known as Takotsubo cardiomyopathy, is a cardiac syndrome characterized by transient left ventricular dysfunction in the absence of obstructive atherosclerotic coronary artery disease. An episode of emotional stress, typically in female patients, is believed to precede and trigger the development of this syndrome.Case Report:We report a case of Takotsubo cardiomyopathy that developed after orthotopic liver transplantation in a 51-year-old woman. On D2 (day 2) the patient had severe hemodynamic compromise. Echocardiography showed systolic dysfunction of the left ventricle (LV), with ejection fraction (EF) of 20% and anteroapical akinesis and ballooning of the apical 2/3 of the LV. Troponin T was elevated but other markers of myocardial necrosis were negative, as was coronary angiography. From D7 onward, there was an improvement in the hemodynamics in conjunction with a gradual increase of LV EF. The patient was dismissed from the hospital on D30 with signs of normal cardiac function and LV motion and EF of 50%. Liver function was also excellent.Conclusions:Every major operation, including liver transplantation, is associated with emotional stress for the patient. Therefore, it is necessary to consider Takotsubo cardiomyopathy in the differential diagnosis of heart failure developing early after LT, and clinicians should subsequently use adequate diagnostic and therapeutic measures.

Fluid–structure interaction of an aortic heart valve prosthesis driven by an animated anatomic left ventricle

We develop a novel large-scale kinematic model for animating the left ventricle (LV) wall and use this model to drive the fluid–structure interaction (FSI) between the ensuing blood flow and a mechanical heart valve prosthesis implanted in the aortic position of an anatomic LV/aorta configuration. The kinematic model is of lumped type and employs a cell-based, FitzHugh–Nagumo framework to simulate the motion of the LV wall in response to an excitation wavefront propagating along the heart wall. The emerging large-scale LV wall motion exhibits complex contractile mechanisms that include contraction (twist) and expansion (untwist). The kinematic model is shown to yield global LV motion parameters that are well within the physiologic range throughout the cardiac cycle. The FSI between the leaflets of the mechanical heart valve and the blood flow driven by the dynamic LV wall motion and mitral inflow is simulated using the curvilinear immersed boundary (CURVIB) method (Ge and Sotiropoulos, 2007; Borazjani et al., 2008) [1,2] implemented in conjunction with a domain decomposition approach. The computed results show that the simulated flow patterns are in good qualitative agreement with in vivo observations. The simulations also reveal complex kinematics of the valve leaflets, thus, underscoring the need for patient-specific simulations of heart valve prosthesis and other cardiac devices.

Left ventricle wall motion quantification from echocardiographic images by non-rigid image registration

The aim of this study is to evaluate the efficiency of applying a new non-rigid image registration method on two-dimensional echocardiographic images for computing the left ventricle (LV) myocardial motion field over a cardiac cycle. The key feature of our method is to register all images in the sequence to a reference image (end-diastole image) using a hierarchical transformation model, which is a combination of an affine transformation for modeling the global LV motion and a free-form deformation (FFD) transformation based on B-splines for modeling the local LV deformation. Registration is done by minimizing a cost function associated with the image similarity based on a global pixel-based matching and the smoothness of transformation. The algorithm uses a fast and robust optimization strategy using a multiresolution approach for the estimation of parameters of the deformation model. The proposed algorithm is evaluated for calculating the displacement curves of two expert-identified anatomical landmarks in apical views of the LV for 10 healthy volunteers and 14 subjects with pathology. The proposed algorithm is also evaluated for classifying the regional LV wall motion abnormality using the calculation of the strain value at the end of systole in 288 segments as scored by two consensual experienced echocardiographers in a three-point scale: 1: normokinesia, 2: hypokinesia, and 3: akinesia. Moreover, we compared the results of the proposed registration algorithm to those previously obtained using the other image registration methods. Regarding to the reference two experienced echocardiographers, the results demonstrate the proposed algorithm more accurately estimates the displacement curve of the two anatomical landmarks in apical views than the other registration methods in all data set. Moreover, the p values of the t test for the strain value of each segment at the end of systole measured by the proposed algorithm show higher differences than the other registration method. These differences are between each pair of scores in all segments and in three segments of septum independently. The clinical results show that the proposed algorithm can improve both the calculation of the displacement curve of every point of LV during a cardiac cycle and the classification of regional LV wall motion abnormality. Therefore, this diagnostic system can be used as a useful tool for clinical evaluation of the regional LV function.

Real Time Three‐Dimensional Stress Echocardiography Advantages and Limitations

The role of two-dimensional stress echocardiography (2D-SE) is well established for diagnosis and prognosis of patients with known or suspected coronary artery disease. 2D-SE has its limitations as multiple views of the left ventricle (LV) must be obtained within 90 seconds of peak stress from more than window to completely visualize all LV segments. 2D-SE is operator-dependent and requires advanced skills to match the same myocardial segments during stress. LV foreshortening is a frequently encountered problem in 2D-SE that may result in false negative studies. Real time three-dimensional SE (RT-3D-SE) can overcome many limitations of 2D-SE. In 3D-SE, overall wall motion of the entire LV is assessed simultaneously in different planes. 3D images can be displayed in multiplane or multislice views for ease of comparison with greater accuracy and interobserver agreement when compared to 2D. 3D-SE is quantitative, provides rapid image acquisition, requires lower level of operator skills, and avoids LV foreshortening by correct alignment of imaging planes. 3D-SE is easily applied during pharmacologic stress and is feasible during exercise-induced stress. Despite these advantages, 3D has lower temporal and spatial resolution than 2D and requires longer analysis time. With advances in transducer technology, smaller matrix footprints, and automated softwares, 3D full LV volume image acquisition can be obtained with a single beat that is less prone to artifacts. We will discuss the current application of RT-3D-SE, highlight the pros and cons of 3D-SE over conventional 2D-SE, and review major studies on 3D-SE and future implications.

The Role of Echo cardiography in Diagnosis and Follow Up of Patients with Takotsubo Cardiomyopathy or Acute Ballooning Syndrome

The transient left ventricular apical ballooning syndrome, also known as takotsubo cardiomyopathy was first described in Japan approximately 20 years ago (Satoh and coworkers, 1991). It was later described elsewhere as well and is being increasingly recognized. Takotsubo Cardiomyopathy characterized by transient apical and midventricular LV dysfunction in the absence of significant coronary artery disease that is triggered by emotional or physical stress. Its name refers to a contraption used for catching octopuses and suggests the aspect assumed by the ventricle during the systole due to the typical regional wall motion abnormalities that occur after onset. Takotsubo cardiomiopathy occurring mainly in post-menopausal women, echocardiography in the Takotsubo cardiomyopathy reveals during its acute phase a ballooning resembling the octopus trap configuration--the apex and lateral ventricular segments are hypokinetic while the base is hyperkinetic--along with reduced ejection fraction. Ventricular function will usually recover within a few days/weeks. The objective of this study is to determine the role of echocardiography in detecting and establishing the diagnosis of Takotsubo cardiomiopathy in patients with suspect acute coronary syndrome and during the follow up period. The study covered 12 adult patients the majority are women (92%) who were subjected to echocardiography evaluation as part of the clinical cardiological examination due to suspect acute coronary syndrome or Takotsubo Stress Cardiomyopathy. The patients were examined on an ultrasound machine Philips iE 33 x Matrix, ATL HDI and GE Vived 7 equipped with all cardiologic probes for adults and multi-plan TEE probes. We evaluated clinical characteristics, LV systolic function, biomarkers, and prognosis in all patients. Among all the patients referred for Echocardiographic evaluation for left ventricle motion abnormalities with suspect acute coronary syndrome, the echo exam revealed 12 patients with acute apical ballooning which involving the left ventricular apex and med-ventricle. The triggering factors were physical stress in 4 patients (33%) and emotional stress in 8 patients (67%). The initial symptom was chest pain (n = 8, 67%) rather than dyspnea (n = 4, 33%). An initial electrocardiogram (EKG) presented ST-elevation (n = 10, 83%) and T-wave inversion (n = 2, 17%), other data are shown on Table 2. Among the all patients 8 of them (66%) had normal EF by the 1st follow up (47 +/- 51 days), and the rest 4 patients (34%) had normal EF by 68 +/- 96 days. Widespread uses of echocardiography has contributed to more frequent recognition of Takotsubo stress cardiomyopathy and highlight the central role of this noninvasive method from an echocardiographers' perspective.

Assessment of radial movement of left ventricle with velocity vector imaging in patients with dilated cardiomyopathy

Objective To assess the radial systolic function of left ventricle(LV) in patients with dilated cardiomyopathy(DCM) by velocity vector imaging(VVI).Methods Sixteen patients with DCM and twenty control subjects were detected by VVI.VVI data were collected from the six basal segments and six mid segments in parastenal LV short axis views.The radial systolic velocity(V) ,strain(e) ,strain rate(SR),the time to peak systolic velocity(PTV) and the time to maximum strain(PTe) were measured with special software.The differene of the earliest and the latest time to peak velocity(T-max) and the standard deviation of time to peak velocity(T-SD) of 12 segments were calculated.Results Compared to the controlled group,patients with DCM had significantly lower radial V,e and SR (P ＜0.01) in all the 12 segments,significantly longer PTV and PTe (P ＜ 0.05) in most segments, and significantly larger T-max and T-SD (P ＜0.05).Conclusions VVI is useful to assess the abnormalities in LV radial movement in patients with DCM and could provide more information about regional cardiac function. Key words: Echocardiography; Cardiomyopathy, dilated; Ventricular function, left; Velocity vector imaging

Tracking Endocardial Motion Via Multiple Model Filtering

Tracking heart motion plays an essential role in the diagnosis of cardiovascular diseases. As such, accurate characterization of dynamic behavior of the left ventricle (LV) is essential in order to enhance the performance of motion estimation. However, a single Markovian model is not sufficient due to the substantial variability in typical heart motion. Moreover, dynamics of an abnormal heart could be very different from that of a normal heart. This study introduces a tracking approach based on multiple models, each matched to a different phase of the LV motion. First, the algorithm adopts a graph cut distribution matching method to tackle the problem of segmenting LV cavity from cardiac MR images, which is acknowledged as a difficult problem because of low contrast and photometric similarities between the heart wall and papillary muscles within the LV cavity. Second, interacting multiple model (IMM), an effective estimation algorithm for Markovian switching system, is devised subsequent to the segmentations to yield state estimates of the endocardial boundary points. The IMM also yields the model probability indicating the model that most closely matches the LV motion. The proposed method is evaluated quantitatively by comparison with independent manual segmentations over 2280 images acquired from 20 subjects, which demonstrated competitive results in comparisons with related recent methods.

MR Harmonic Phase surface for tracking cardiac motion

Purpose Quantitative analysis of left ventricle motion can be performed by tracking the tag surfaces motion, where the intersection of orthogonal tag surfaces resolves the 3D motion of the heart tissue. Although, previous work was done to construct tag surfaces between image slices, it was restricted to the specific tag lines and not between them. The reconstruction of the tag surfaces, based on their harmonic phase value, enables an accurate tracking of 3D motion of the cardiac tissue, which will enable an objective and accurate assessment of cardiac function.

Determination of Three-Dimensional Left Ventricle Motion to Analyze Ventricular Dyssyncrony in SPECT Images

A method to compute three-dimension (3D) left ventricle (LV) motion and its color coded visualization scheme for the qualitative analysis in SPECT images is proposed. It is used to investigate some aspects of Cardiac Resynchronization Therapy (CRT). The method was applied to 3D gated-SPECT images sets from normal subjects and patients with severe Idiopathic Heart Failure, before and after CRT. Color coded visualization maps representing the LV regional motion showed significant difference between patients and normal subjects. Moreover, they indicated a difference between the two groups. Numerical results of regional mean values representing the intensity and direction of movement in radial direction are presented. A difference of one order of magnitude in the intensity of the movement on patients in relation to the normal subjects was observed. Quantitative and qualitative parameters gave good indications of potential application of the technique to diagnosis and follow up of patients submitted to CRT.

Effects of flow vortex on a chorded mitral valve in the left ventricle

AbstractAn Immersed Boundary fluid–structure interaction model is developed to investigate the dynamic behaviour of a prosthetic chorded mitral valve (MV) inside the left ventricle (LV). In order to simulate more realistic physiological flow conditions, in vivo magnetic resonance images of the LV are used to determine the anatomical structure and the motion of the LV. The LV geometry and its motion are incorporated into the dynamic MV model. This model allows us to investigate the influences of the flow vortex generated by the LV motion on the MV dynamics, as well as the impact of the motion of the chordae attachment points (CAPs). Results are compared with two other cases: (i) an LV model with no prescribed motion of the CAPs, (ii) a Tube model in which the LV is replaced by a tube, although the motion of the chordae is incorporated. These special cases enable the influence of the chordae motion and the vortex on the behaviour of the MV to be analysed independently. It is found that when the MV is placed inside a dynamic LV, the chordae and the valve stretch are significantly increased in the commissural region, and the flow field is strongly asymmetric, with a clockwise single vortex appearing after the early rapid filling phase of the diastole. Given that we impose a flow rate boundary condition, the reverse pressure gradient cannot be established and, hence, the valve does not close properly. Clearly, the presence of the flow vortex alone is not strong enough to aid the valve closure. Copyright © 2009 John Wiley &amp; Sons, Ltd.

A Computational Fluid Dynamic (CFD) Tool for Optimization and Guided Implantation of Biomedical Devices

We are developing computational tools to perform virtual surgeries under physiological conditions with patient-specific anatomies. Virtual surgery can revolutionize the biomedical device (BMD) design and implantation by: enabling the optimization of BMD on the specific patient's anatomy and flow conditions, which has already been shown to significantly affect the hemodynamics; and facilitating surgical planning to select the best location/orientation for BMD implantation. As shown by past research the difference in the implantation, for example, of a bileaflet mechanical heart valve (BMHV) can affect the performance and hemodynamics of the valve. We have developed a powerful CFD tool that can simulate the blood flow through biomedical devices with moving boundaries and the fluid-structure interaction (FSI) under physiologic conditions. This tool has been tested in different applications with complex anatomic configurations, such as aneurysm hemodynamics, Fontan surgeries, and BMHV flows. The FSI simulations of a BMHV flow was validated against in vitro experiments and could capture all the flow features with great accuracy. We have recently carried out FSI simulations of a BMHV implanted in a anatomically realistic aorta in which the left ventricle (LV) was replaced by a pulsatile inflow waveform. In this work, we propose to extend our method to simulate the flow through a BMHV driven by the actual LV motion. The anatomy of the heart is obtained from MRI scan of unhealthy volunteer (St. Jude Hospital) and the left ventricle and the aorta geometry are extracted. The first step is to simulate the flow through a stationary LV with an implanted BMHV to test the capabilities of FSI-CFD tool in real anatomical setting. The second step is to impose theoretical kinematics for LV motion and test the interaction of the BMHV with the flow. The last step is to extract the real patient-specific LV wall motions from MRI data and specify it into the simulation. The shear stress and other parameters will be calculated in the flow field and the cardiovascular walls to identify the locations with high chance of blood cell damage. This work is supported by NIH Grant RO1-HL-07262 and the Minnesota Supercomputing Institute.

Speckle Tracking for Assessment of Cardiac Motion and Dyssynchrony

Dyssynchrony estimation using echocardiography is increasingly used as a quantitative tool to qualify candidates for cardiac resynchronization therapy (CRT) and evaluate its effect post procedure. Conventionally, tissue Doppler imaging (TDI) has been used for this application, but its utility and accuracy are limited by the angle of incidence-dependent nature of Doppler velocity measurement. Recently, speckle tracking technology applied to B-mode images has been developed for wall motion analysis including dyssynchrony estimation. Regional motion is tracked by observing the movement of two-dimensional (2D) speckle patterns in ultrasound images. Three-dimensional (3D) speckle tracking is also possible and can be used to evaluate 3D cardiac motion of the entire left ventricle. Speckle tracking can provide assessment of regional strain and dyssynchrony in cardiac motion for more objective diagnosis.