Left Ventricle Hemodynamics Research Articles

Abstract 18045: Mild Coarctation of the Aorta: To Touch or Not to Touch the Patient? Looking at Left Ventricular Function and Hemodynamics

Introduction: Coarctation of the aorta (COA) is an obstruction of the aorta distal to the left subclavian artery. A peak-to-peak trans-coarctation pressure gradient (P K dP) of greater than 20 mmHg warns of severe COA and the need for interventional/surgical repair. The optimal method and timing of the intervention remain uncertain especially when the severity of COA is mild (P K dP < 20 mmHg) and it is unclear if mild COA should be treated at all. Rosenthal (2001; J Am Coll Cardiol) suggested that treatment strategies for patients with mild COA may need to be redefined as transcatheter interventions emerge, and yet the risks and benefits of such interventions in patients with mild COA are unclear. The aim of this study is to investigate the effects of transcatheter intervention on hemodynamics of the aorta and left ventricle (LV) in eleven patients with mild COA. Methods. We used specially developed computational fluid dynamics and lumped parameter modeling framework along with highly-resolved particle image velocimetry data and clinical measurements (Doppler-echocardiography, cardiac catheterization, CT and MRI) in this study. Results . COA intervention can improve aortic hemodynamics to some extent (i.e., time-averaged wall shear stress, oscillating shear index, peak jet velocity and kinetic energy [all averaged in the descending aorta] were reduced by 20%, 13.3%, 26.7% and 25%, respectively). However there is no concomitant effect on the LV hemodynamics (i.e., stroke work, normalized stroke work and peak LV pressure were reduced by only 3.8%, 3.7% and 3.2%, respectively; arterial systemic compliance was also reduced by 17%; N=11; p < 0.05). Conclusion . Our computational approach can effectively model and predict clinical conditions. Herein one must question intervention for mild COA, as it has limited utility in reducing myocardial strain. Figure 1. Catheter data and results of lumped parameter modeling in patient No. 1.

Effects of Bileaflet Mechanical Mitral Valve Rotational Orientation on Left Ventricular Flow Conditions.

We studied left ventricular flow patterns for a range of rotational orientations of a bileaflet mechanical heart valve (MHV) implanted in the mitral position of an elastic model of a beating left ventricle (LV). The valve was rotated through 3 angular positions (0, 45, and 90 degrees) about the LV long axis. Ultrasound scans of the elastic LV were obtained in four apical 2-dimensional (2D) imaging projections, each with 45 degrees of separation. Particle imaging velocimetry was performed during the diastolic period to quantify the in-plane velocity field obtained by computer tracking of diluted microbubbles in the acquired ultrasound projections. The resulting velocity field, vorticity, and shear stresses were statistically significantly altered by angular positioning of the mechanical valve, although the results did not show any specific trend with the valve angular position and were highly dependent on the orientation of the imaging plane with respect to the valve. We conclude that bileaflet MHV orientation influences hemodynamics of LV filling. However, determination of ‘optimal’ valve orientation cannot be made without measurement techniques that account for the highly 3-dimensional (3D) intraventricular flow.

Aerobic exercise training improves oxidative stress and ubiquitin proteasome system activity in heart of spontaneously hypertensive rats.

The activity of the ubiquitin proteasome system (UPS) and the level of oxidative stress contribute to the transition from compensated cardiac hypertrophy to heart failure in hypertension. Moreover, aerobic exercise training (AET) is an important therapy for the treatment of hypertension, but its effects on the UPS are not completely known. The aim of this study was to evaluate the effect of AET on UPS's activity and oxidative stress level in heart of spontaneously hypertensive rats (SHR). A total of 53 Wistar and SHR rats were randomly divided into sedentary and trained groups. The AET protocol was 5×/week in treadmill for 13weeks. Exercise tolerance test, non-invasive blood pressure measurement, echocardiographic analyses, and left ventricle hemodynamics were performed during experimental period. The expression of ubiquitinated proteins, 4-hydroxynonenal (4-HNE), Akt, phospho-Akt(ser473), GSK3β, and phospho-GSK3β(ser9) were analyzed by western blotting. The evaluation of lipid hydroperoxide concentration was performed using the xylenol orange method, and the proteasomal chymotrypsin-like activity was measured by fluorimetric assay. Sedentary hypertensive group presented cardiac hypertrophy, unaltered expression of total Akt, phospho-Akt, total GSK3β and phospho-GSK3β, UPS hyperactivity, increased lipid hydroperoxidation as well as elevated expression of 4-HNE but normal cardiac function. In contrast, AET significantly increased exercise tolerance, decreased resting systolic blood pressure and heart rate in hypertensive animals. In addition, the AET increased phospho-Akt expression, decreased phospho-GSK3β, and did not alter the expression of total Akt, total GSK3β, and ubiquitinated proteins, however, significantly attenuated 4-HNE levels, lipid hydroperoxidation, and UPS's activity toward normotensive group levels. Our results provide evidence for the main effect of AET on attenuating cardiac ubiquitin proteasome hyperactivity and oxidative stress in SHR rats.

Keeping Donor Hearts in Completely Beating Status With Normothermic Blood Perfusion for Transplants

Previously, we reported the preservation method of donor hearts in an empty beating status with mild hypothermic perfusion. To completely avoid cardiac arrest and myocardial ischemia, we performed the beating preservation technique from procurement of hearts to transplants and assessed its efficacy for long-term preservation and feasibility for heart transplantation. Thirty-two swine donor hearts were preserved in beating status (group A, n = 8 pairs, perfused continuously with normothermic blood) or in static cold storage (group B, n = 8 pairs, stored in 4°C histidine-tryptophan-ketoglutarate solutions) for 8 hours. Then the donor hearts were implanted either in beating or static status. During transplantation, the incidence of arrhythmia, duration of anastomosis and cardiopulmonary bypass, and dosage of inotropic drugs were recorded. Hemodynamics of left ventricle and serum level of creatine kinase-MB were measured during transplantation. Myocardial ultrastructure was observed. Compared with group B, in group A the anastomotic time was significantly longer, the cardiopulmonary bypass time was significantly shorter, the cardiac output was larger, and the incidence of arrhythmia, dosage of cardiovascular-active drugs, and serum level of creatine kinase-MB were lower. After declamping for 2 hours and 3.5 hours, the left ventricular hemodynamics of group A was significantly better than that of group B. The myocardial ultrastructure of group A was superior to that of group B. Preservation of donor hearts in beating status with continuous, normothermic, blood perfusion is an effective approach for long-term preservation and is appropriate for heart transplantation.

Left Ventricular Flow Analysis: Recent Advances in Numerical Methods and Applications in Cardiac Ultrasound

The left ventricle (LV) pumps oxygenated blood from the lungs to the rest of the body through systemic circulation. The efficiency of such a pumping function is dependent on blood flow within the LV chamber. It is therefore crucial to accurately characterize LV hemodynamics. Improved understanding of LV hemodynamics is expected to provide important clinical diagnostic and prognostic information. We review the recent advances in numerical and experimental methods for characterizing LV flows and focus on analysis of intraventricular flow fields by echocardiographic particle image velocimetry (echo-PIV), due to its potential for broad and practical utility. Future research directions to advance patient-specific LV simulations include development of methods capable of resolving heart valves, higher temporal resolution, automated generation of three-dimensional (3D) geometry, and incorporating actual flow measurements into the numerical solution of the 3D cardiovascular fluid dynamics.

Assessment of the hemodynamics of left ventricle in ventricular aneurysm during the contraction phase by vector flow mapping

Objective To evaluate the systolic function of left ventricle in myocardial infarction(MI)patients with ventricular aneurysm and the changing law of blood flow in ventricle with regional abnormality of wall movement by vector flow mapping (VFM).Methods Tirty-one MI patients with ventricular aneurysm and 35 healthy participants were enrolled in this study.The characteristic of vector and streamline,and the changing of the velocity gradient in left ventricular outflow tract (LVOT), and the average flow quantity through aneurysm neck were detected in the isovolumic contraction period, the rapid ejection period and the slow ejection period by VFM.Results The distinction between aneurysm and control group was mainly the persistance of vortex in aneurysm.The size of vortex in aneurysm was highly correlated with that measured by 2-D ultrasound(P ＜0.01).The percentage of vortex duration to cardiac cycle in patients group was significantly greater than that in control group(P ＜0.01).In the early systolic contraction the velocity gradient in LVOT in patients with ventricular aneurysm was smaller than that of control group(P ＜0.05).The average flow through aneurysm neck was notablely decreased compared with control group(P ＜0.01).Conclusions VFM can reveal the hemodynamics of left ventricle with aneurysm directly as well as quantitively measure the regional velocity and flow quantity.VFM can evaluate the systolic function of left ventricle exactly. Key words: Echocardiography ; Myocardial infarction; Heart aneurysm; Hemodynamic phenomena

Assessment of the hemodynamics of left ventricle during the isovolumic contraction phase in normal snbjects by vector flow mapping

Objective To clarify whether the phase of left ventricle(LV)isovolumic contraction is the phase of hemodynamics stasis in normal subjects by using vector flow mapping(VFM).Methods Color Doppler flow images were recorded from LV apical long-axis view in fifty healthy volunteers.The characteristics of LV intracavitary flow dynamics during isovolumic contraction were analyzed by VFM.Results A global vortex occurred in the LV chamber during the late diastole which was sustained during the whole phase of isovolumic contraction.The vortex disappeared quickly in the early and middle ejection phase.The flow in the LV was initially directed toward the apex and then briefly reversed toward the base.Conclusions Isovolumic contraction phase is not the period of hemodynamic stasis but,rather,phase with dynamic changes in intracavitary flow.The vortex during isovolumic contraction makes a dynamic contribution to flow redirection and provides efficiency for momentum transfer. Key words: Echocardiography; Ventricular function,left; Hemodynamic phemomena; Vector flow mapping

Echocardiography criteria of blood turbulence in the left ventricle during diastole in children

Objective. To study the hemodynamics in left ventricle (LV) cavity of the left ventricle by Doppler method. Design and methods. 50 children (20 female, 30 male) including 15 athletes (aged from 5 days to 18 years old) were examined. Ultrasonic scanner «SonoACE-9900» was used. Results. The wave with biphasic amplitude on peak E of transmural blood stream (named «Sh»-wave) was registered when the «control volume» was placed in LV cavity, and its velocity characteristics and duration of positive and negative phases were determined. Children with average heart rate 95,4 ± 5,2 b/min. «Sh»-wave duration was 39,4 ± 10,6 msec, and velocity characteristics of positive and negative phases were 75,4 ± 9,4 and 41,3 ± 6,5 cm/sec. respectively. Athletes with sinusal bradycardia (average heart rate 58,7 ± 2,3 b/min.) had longer «Sh»- waves (66,1 ± 15,2 msec), higher velocity characteristics of positive phase (78,8 ± 11,3 cm/sec.) and lower velocity of negative phase (32,6 ± 5,3 cm/sec.). Conclusion. The spherical turbulent blood stream in the LV can be formed during diastolic filling. It presents as an echo-signal of biphase amplitude in the middle third of LV.

Hemodynamics of normal left ventricle analyzed by vector flow mapping

Objective To investigate the hemodynamics of left ventricle(LV) in normal subjects by vector flow mapping(VFM)technique.Methods Color Doppler flow images were recorded from apical long-axis view in fifty healthy volunteers.The flow velocity vector in LV chamber during different phase of cardiac cycle was analyzed by VFM.Results During the isovolumic contraction.the LV was full of a large globe vortex.During the early ejection.the flow under the aortic valve was accelerated and ejected into the aorta.There were some brief local vortexes observed in the LV inflow at the early ejection and these vortexes disappeared during the mid and late ejection.At the instant of aortic valve closure,the intraventricular flow redirected rapidly from the base to the apex and persisted to the end of isovolumic relaxation.During the slow LV filling and left atrial contraction,a large global vortex occurred in the LV chamber again.Conclusions The distribution of flow velocity vector in the LV chamber can be detected by VFM during different phase of cardiac cycle.VFM would be a useful method for the investigation of hemodynamics in diseased heart. Key words: Echocardiography; Ventricular function; left; Hemodynamic phenomena; Vector flow mapping

Hemodynamics of the Mitral Valve Under Edge-to-Edge Repair: An In Vitro Steady Flow Study

Edge-to-edge repair (ETER) is a mitral valve repair technique that restores valvular competence by suturing together the free edges of two leaflets. This repair technique alters mitral valve inflow and thus left ventricle hemodynamics during diastole. Our objective was to investigate fluid mechanics immediately downstream of the mitral valve under ETER during diastole. Fresh porcine mitral valves of the annulus size M32 with chordae removed were installed into a steady flow loop simulating a peak diastolic inflow through the mitral valve. Digital particle image velocimetry was used to measure the velocity field immediately downstream of the mitral valve under normal and ETER conditions. First, to study the suture length effect, suture was applied in the central position of the leaflet edge with suture lengths of 3 mm, 6 mm, and 9 mm, respectively. Then, 3 mm suture was set in the central, lateral, and commissural positions of the leaflet edge to study the suture position effect. Flow rate was 15 l/min. Velocity, Reynolds shear stress (RSS), and effective orifice area were assessed. A total of five mitral valves were tested. The normal mitral valve without the ETER had one jet downstream of the valve, but the mitral valve with the central or lateral sutures under the ETER had two jets downstream of the valve with a recirculation region downstream of the suture. The maximum velocity, the maximum RSS in the jets, the pressure drop across the mitral valve, and the jet deflection angle increased with the increase in suture length in the central position. When the suture position effect was investigated with the 3 mm suture, the maximum velocity, the maximum RSS, and the pressure drop across the valve in the central suture position were greater than those of the lateral and the commissural suture positions. The lateral suture demonstrated major and minor jets with the greater maximum velocity and maximum RSS in the major jet. When the suture was in the commissural position, the flow field downstream of the mitral valve was similar to that of the normal mitral valve without the ETER. The effective orifice area was smallest when the suture was applied in the central position as compared with other suture positions. Both suture length and position have an important impact on fluid mechanics downstream of the mitral valve under the ETER in terms of flow pattern, maximum velocity, and RSS distribution. The altered hemodynamics of the mitral valve and thus of the left ventricle by the ETER may change mitral valve and left ventricle function.

Valvular Heart Disease

Aortic regurgitation (AR) is characterized by diastolic reflux of blood from the aorta into the left ventricle (LV). Acute AR typically causes severe pulmonary edema and hypotension and is a surgical emergency. Chronic severe AR causes combined LV volume and pressure overload. It is accompanied by systolic hypertension and wide pulse pressure, which account for peripheral physical findings, such as bounding pulses. The afterload excess caused by systolic hypertension leads to progressive LV dilation and systolic dysfunction. The most important diagnostic test for AR is echocardiography. It provides the ability to determine the cause of AR and to assess the severity of AR and its effect on LV size, function, and hemodynamics. Many patients with chronic severe AR may remain clinically compensated for years with normal LV function and no symptoms. These patients do not require surgery but can be followed carefully for the onset of symptoms or LV dilation/dysfunction. Surgery should be considered before the LV ejection fraction falls below 55% or the LV end-systolic [corrected] dimension reaches 55 mm. Symptomatic patients should undergo surgery unless there are excessive comorbidities or other contraindications. The primary role of medical therapy with vasodilators is to delay the need for surgery in asymptomatic patients with normal LV function or to treat patients in whom surgery is not an option. The goal of vasodilator therapy is to achieve a significant decrease in systolic arterial pressure. Future therapies may focus on molecular mechanisms to prevent adverse LV remodeling and fibrosis.

Molecular normalization of dystrophin in the failing left and right ventricle of patients treated with either pulsatile or continuous flow-type ventricular assist devices

ObjectivesWe investigated the integrity of dystrophin in left ventricle (LV) and right ventricle (RV) of patients with end-stage heart failure due to ischemic cardiomyopathy (IHD) or dilated cardiomyopathy (DCM), and compared the efficacy of pulsatile or continuous flow assist devices on dystrophin reverse remodeling. BackgroundRecently we demonstrated that the amino (N)-terminus of dystrophin is preferentially disrupted in failing LV myocardium irrespective the underlying etiology, and that this defect is reversed by mechanical unloading using left ventricular assist device (LVAD) therapy. MethodsMyocardial samples were obtained from seven normal controls, seven failing hearts (either DCM or IHD), and 14 failing-heart patients who underwent placement of either pulsatile (7 patients) or continuous flow (7 patients) LVADs for progressive refractory HF. The expression and integrity of dystrophin in these samples were determined by immunohistochemistry using antibodies against the N-terminal and carboxyl (C)-terminal domains. ResultsImmunohistochemical staining identified disruption of the N-terminal dystrophin in both LVs and RVs of all seven failing-heart patients, whereas the C-terminus was normal. Furthermore, this disruption was reversed in 12 of the 14 patients after LVAD therapy using either pulsatile or continuous devices; the degree of the reverse remodeling was similar in both ventricles, although greater recovery was noted in patients treated with pulsatile flow devices. ConclusionsIntegrity of the N-terminus of dystrophin is a useful indicator of both LV and RV function. In addition to improving LV hemodynamics, LVAD therapy results in amelioration of the myocardial structure of the right cardiac chamber.

Computational Modeling of Left Ventricle Dynamics and Flow Based on Ultrasonographic Data

A computational model combined ultrasonographic data and computational fluid dynamics (CFD) was developed and applied to an anatomically realistic model of the human left ventricle. The proposed methodology employs but not limited to ultrasonographic scans of a human left ventricle to obtain a set of time-varying images of morphology and dynamics of the left ventricle, which are utilized in generating a dynamic geometrical model for blood flow simulation. A so-called Two-Chamber-View modeling method has been proposed to obtain digitized anatomical images on two mutually orthogonal planes that cut through the left ventricle chamber along the long axis from base to apex, and from which two endocardial borderlines in the two planes are extracted for each time frame. Endocardial contours in the short-axis plane is approximated as an ellipse with two radii determined from the extracted endocardial borderlines in the two long-axis planes and stacked up from base to apex to generate a fully three-dimensional geometric model. Physiological conditions of inflow/outflow at orifices notionally representing the mitral and aortic vales are obtained also based on the ultrasonographic images by deriving flow rates at the orifices directly through calculating time-variation-rate of the left ventricle volume. Computational modeling of left ventricle hemodynamics is accomplished by using an in-house NS solver with specific modification for blood flow in heart chamber. The reconstructed CFD model well captures the three-dimensional dynamics of endocardial wall in terms of contraction and expansion phases in the left ventricle; and the dominant fluid dynamics involving vortices and swirls are simulated reasonably. Our computed results indicate that realistic modeling of both geometry and physiological conditions of left ventricle is of great importance in correctly predicting the behavior of the dominant vortex flow and their influence on the heart function.

Left ventricular function and remodeling after myocardial infarction in aging rats.

Adaptations of the aging left ventricle (LV) to hemodynamic overload are functionally and structurally distinct from those of the young organism. This study describes the influence of aging on LV hemodynamics and remodeling late after myocardial infarction (MI) in Fischer 344 Brown Norway rats. In sham rats at 23 mo, LV weight, myocyte cross-sectional area (CSA), and myocardial fibrosis were increased, whereas LV dP/dt, LV relaxation, and maximal LV systolic function declined with respect to younger rats (7, 12, and 18 mo of age). Isometric myocardial function was evaluated in papillary muscles of 12- and 23-mo-old sham rats. Myocardial systolic function was decreased in older rats. To determine how aging affects LV function and remodeling after MI, rats were infarcted at 7 and 18 mo of age and were studied 5 mo later. Infarct size was similar in each group. Right ventricular weight, LV end-diastolic pressure, and volume index were increased, whereas LV dP/dt, peak cardiac index, and peak developed LV pressure declined after MI. However, there were no significant differences between young and older rats in any variable of LV systolic function or remodeling after MI. Myocyte CSA increased in younger rats after MI but was unchanged in 23-mo-old rats. After MI, myocardial fibrosis was significantly increased from baseline only in younger rats. The negative interaction of aging and MI on myocyte hypertrophy and fibrosis was highly significant. The findings indicate that baseline LV and myocradial function decline with age. In the aging rat after MI, despite limited compensatory hypertrophy and more advanced baseline myocardial fibrosis, the long-term functional and structural adaptations to MI are similar to those of the mature adult heart.

Software to characterize hemodynamics in left ventricle, aorta, and coronary arteries

Software to characterize hemodynamics in left ventricle, aorta, and coronary arteries