Intraventricular Flow Research Articles

Effects of the atrium on intraventricular flow patterns during mechanical circulatory support.

Simulations of the ventricular flow patterns during left ventricular assist device (LVAD) support are mainly performed with idealized cylindrical inflow, neglecting the influence of the atrial vortex. In this study, the influence of the left atrium (LA) on the intra-ventricular flow was investigated via Computational Fluid Dynamics (CFD) simulations. Ventricular flow was simulated by a combined Eulerian (carrier flow)/Lagrangian (particles) approach taking into account either the LA or a cylindrical inflow section to mimic a fully support condition. The flow deviation at the mitral valve, the blood low-velocity volume as well as the residence time and shear stress history of the particles were calculated. Inclusion of the LA deflects the flow at the mitral valve by 25°, resulting in an asymmetric flow jet entering the left ventricle. This reduced the ventricular low-velocity volume by 40% (from 6.4 to 3.9 cm3), increased (40%) the shear stress experienced by particles and correspondingly increased (27%) their residence time. Under the studied conditions, the atrial geometry plays a major role in the development of intraventricular flow patterns. A reliable prediction of blood flow dynamics and consequently thrombosis risk analysis within the ventricle requires the consideration of the LA in computational simulations.

Numerical study of the effect of LVAD inflow cannula positioning on thrombosis risk

Left ventricular assist devices (LVADs) have been increasingly used as a therapy for patients with end-stage heart failure. However, a growing number of clinical observations have shown that LVADs are associated with thromboembolic events, which are potentially related to the changes in intraventricular flow. Particularly, the flow fields around the inflow cannula (IC) of the LVAD. In this study, a fluid structure interaction (FSI) simulation was conducted to evaluate the hemodynamics of a patient specific left ventricle (LV) with varying LVAD IC orientations. The LV model was obtained from computed tomography scans and modeled to have contraction and relaxation during cardiac cycles following available experimental data of LV volume changes. The LV of the patient was assumed to have an end systolic volume of 223.7 mL and a stroke volume of 46.4 mL. Four different IC positions were considered: towards the (1) septum; (2) aortic valve (AV); (3) mitral valve (MV) and (4) inferior wall (IW). The potential thrombus growth around the IC was assumed to be caused by blood stagnation regions with low velocity (<5 mm/s) and low shear rate (<60/s) flow. Mean velocity magnitudes and low blood velocity regions around the IC were numerically obtained. To quantitatively compare the thrombosis risks of the four simulation cases, the time-averaged volumes of the low-velocity regions and the low shear rate regions were calculated. The intraventricular volumes of low velocity zones based on IC orientation are 1.42 mL toward the septum, 1.14 mL toward the AV, 0.93 mL toward the MV, and 1.24 mL toward the IW. The intraventricular volumes of low shear regions based on IC orientation are 11.54 mL toward the septum, 11.15 mL toward the AV, 9.24 mL toward the MV, and 10.7 mL toward the IW. IC orientation toward the MV results in lower volumetric regions of low flow and low shear within the ventricle, which consequently may lead to a reduced risk of thrombus formation.

Intraventricular flow visualization in different heart failure stages with blood pump support in a mock circulatory loop

The intraventricular blood flow changed by blood pump flow dynamics may correlate with thrombosis and ventricular suction. The flow velocity, distribution of streamlines, vorticity, and standard deviation of velocity inside a left ventricle failing to different extents throughout the cardiac cycle when supported by an axial blood pump were measured by particle image velocimetry (PIV) in this study. The results show slower and static flow velocities existed in the central region of the left ventricle near the mitral valve and aortic valve and that were not sensitive to left ventricular (LV) failure degree or LV pressure. Strong vorticity located near the inner LV wall around the LV apex and the blood pump inlet was not sensitive to LV failure degree or LV pressure. Higher standard deviation of the blood velocity at the blood pump inlet decreased with increasing LV failure degree, whereas the standard deviation of the velocity near the atrium increased with increasing intraventricular pressure. The experimental results demonstrated that the risk of thrombosis inside the failing left ventricle is not related to heart failure degree. The "washout" performance of the strong vorticity near the inner LV wall could reduce the thrombotic potential inside the left ventricle and was not related to heart failure degree. The vorticity near the aortic valve was sensitive to LV failure degree but not to LV pressure. We concluded that the risk of blood damage caused by adverse flow inside the left ventricle decreased with increasing LV pressure.

Altered Right Ventricular Filling at Four-dimensional Flow MRI in Young Adults Born Prematurely.

To use four-dimensional (4D) flow MRI to measure intraventricular flow in young adults who were born prematurely to investigate mechanisms that may account for increased heart failure risk in this population. In this secondary analysis of a prospective study, a total of 56 young adults participated in an observational cardiac 4D flow MRI study from 2016 to 2020. There were 35 participants who had been born moderately to extremely prematurely (birth weight <1500 g or gestational age ≤32 weeks; 23 women; mean age, 26 years ± 4) and 21 term-born participants (11 women; mean age, 25 years ± 3). Participants underwent cardiac MRI, including cine cardiac structure and function assessment, as well as 4D flow MRI. In each ventricle, normalized kinetic energy (KE/end diastolic volume) and flow through the atrioventricular valve were computed and compared between term-born and preterm participants at systolic and diastolic (early diastolic filling rate [E wave] and late diastolic filling [atrial contraction] rate [A wave]) time points by using Wilcoxon rank-sum tests. Preterm-born participants had lower right ventricular (RV) E wave/A wave (E/A) KE ratios (2.4 ± 1.7 vs 3.5 ± 1.4; P <.01) and lower E/A peak filling rate ratios (computed from RV volume-time curves; 2.3 ± 1.3 vs 3.5 ± 2.5; P = .03). Additionally, viscous energy dissipation was increased during systole (5.7 µW/mL ± 3.0 vs 4.2 µW/mL ± 1.6; P = .03), increased during late diastole (3.9 µW/mL ± 4.0 vs 2.2 µW/mL ± 1.6; P = .03), and summed over the cardiac cycle (2.4 µJ/mL ± 1.0 vs 1.9 µJ/mL ± 0.6; P = .02) in preterm relative to term participants. These results suggest that RV diastolic filling is altered in young adults who were born moderately to severely prematurely.Supplemental material is available for this article. Keywords: Adults, Cardiac, Comparative Studies, MR-Imaging, Right Ventricle © RSNA, 2021.

Experimental investigation of the influence of the hydraulic performance of an axial blood pump on intraventricular blood flow.

Blood flow inside the left ventricle (LV) is a concern for blood pump use and contributes to ventricle suction and thromboembolic events. However, few studies have examined blood flow inside the LV after a blood pump was implanted. In this study, in vitro experiments were conducted to emulate the intraventricular blood flow, such as blood flow velocity, the distribution of streamlines, vorticity and the standard deviation of velocity inside the LV during axial blood pump support. A silicone LV reconstructed from computerized tomography (CT) data of a heart failure patient was incorporated into a mock circulatory loop (MCL) to simulate human systemic circulation. Then, the blood flow inside the ventricle was examined by particle image velocimetry (PIV) equipment. The results showed that the operating conditions of the axial blood pump influenced flow patterns within the LV and areas of potential blood stasis, and the intraventricular swirling flow was altered with blood pump support. The presence of vorticity in the LV from the thoracic aorta to the heart apex can provide thorough washing of the LV cavity. The gradually extending stasis region in the central LV with increasing blood pump support is necessary to reduce the thrombosis potential in the LV.

Novel Transcatheter Mitral Prosthesis Designed to Preserve Physiological Ventricular Flow Dynamics

BackgroundCurrent mitral bioprostheses are akin to the aortic valve and therefore abolish the left ventricular (LV) physiological vortex. We evaluated the hemodynamic performance and the effects on intraventricular flow dynamics (IFD) of a novel mitral bioprosthesis that presents an innovative design mimicking the native valve. MethodsA D-shaped self-expandable stent-bovine pericardium monoleaflet valve was designed to provide physiological asymmetric intraventricular flow. Transapical implantation was consecutively performed in 12 juvenile sheep. Postimplant studies using Doppler echocardiography and IFD using echo particle imaging velocimetry were obtained immediately after the implantation and at 3 months to assess the hemodynamic performance of the prostheses. ResultsThere were 3 deaths during follow-up, 1 due to valve misplacement because of poor imaging visualization and 2 not valve related. The mean transvalvular gradient and effective orifice area were 2.2 ± 1.2 mm Hg and 4.0 ± 1.1 cm2 after implantation and 3.3 ± 1.5 mm Hg and 3.5 ± 0.5 cm2 at 3 months, respectively. LV vortex dimension, orientation, and physiological anticlockwise rotation were preserved compared with preoperative normal LV flow pattern. One animal showed a moderate paravalvular leak, others mild or none. LV outflow tract obstruction, valve thrombosis, and hemolysis were not observed. ConclusionsOur preclinical in vivo results confirm the good hemodynamic performance of this new transcatheter bioprosthesis with preservation of the physiological IFD. Clinical studies are needed to document whether these characteristics will foster LV recovery and improve the clinical outcome of patients with mitral regurgitation.

Assessment of ventricular flow dynamics by 4D-flow MRI in patients following surgical repair of d-transposition of the great arteries

ObjectivesTo use 4D-flow MRI to describe systemic and non-systemic ventricular flow organisation and energy loss in patients with repaired d-transposition of the great arteries (d-TGA) and normal subjects.MethodsPathline tracking of ventricular volumes was performed using 4D-flow MRI data from a 1.5-T GE Discovery MR450 scanner. D-TGA patients following arterial switch (n = 17, mean age 14 ± 5 years) and atrial switch (n = 15, 35 ± 6 years) procedures were examined and compared with subjects with normal cardiac anatomy and ventricular function (n = 12, 12 ± 3 years). Pathlines were classified by their passage through the ventricles as direct flow, retained inflow, delayed ejection flow, and residual volume and visually and quantitatively assessed. Additionally, viscous energy losses (ELv) were calculated.ResultsIn normal subjects, the ventricular flow paths were well ordered following similar trajectories through the ventricles with very little mixing of flow components. The flow paths in all atrial and some arterial switch patients were more irregular with high mixing. Direct flow and delayed ejection flow were decreased in atrial switch patients’ systemic ventricles with a corresponding increase in residual volume compared with normal subjects (p = 0.003 and p < 0.001 respectively) and arterial switch patients (p < 0.0001 and p < 0.001 respectively). In non-systemic ventricles, arterial switch patients had increased direct flow and decreased delayed ejection fractions compared to normal (p = 0.007 and p < 0.001 respectively) and atrial switch patients (p = 0.01 and p < 0.001 respectively). Regions of high levels of mixing of ventricular flow components showed elevated ELv.Conclusions4D-flow MRI pathline tracking reveals disordered ventricular flow patterns and associated ELv in d-TGA patients.Key Points• 4D-flow MRI can be used to assess intraventricular flow dynamics in d-TGA patients.• d-TGA arterial switch patients mostly show intraventricular flow dynamics representative of normal subjects, while atrial switch patients show increased flow disorder and different proportions of intraventricular flow volumes.• Flow disruption and disorder increase viscous energy losses.

Effect of Timings of the Lavare Cycle on the Ventricular Washout in an In Vitro Flow Visualization Setup.

Left ventricular assist devices inherently alter the intraventricular flow field and create areas of blood stasis with potential thrombus formation. The Lavare cycle of the Medtronic HeartWare HVAD was designed to improve ventricular washout. This study aims to evaluate its effects on ventricular washout in a pulsatile in vitro setting with a focus on the timing of pump speed changes. Ventricular flow fields were obtained via particle image velocimetry in two modes: With constant left ventricular assist devices speed and with the Lavare cycle applied. The start of the Lavare cycle was shifted over an entire cardiac cycle, and ventricular washout was evaluated based on velocity fields, kinetic energy, and normalized pulsatility of flow fields. The ventricular flow fields showed dependence on the timing of the Lavare cycle and interaction between speed changes and the cardiac phase. Higher apical velocity was observed for speed decreases at the late E wave and for increases at mid systole by 29% (P = 0.002) and 61% (P < 0.001), respectively. Mean apical kinetic energy for these phases also increased by 21% (P = 0.0013) and 46% (P < 0.001). The Lavare cycle generally promotes higher apical washout and can specifically generate further improved washout if speed steps are applied at the correct timing on the cardiac cycle.

Intraventricular blood flows and myocardial contractility in impairments of coronary circulation

We examined a total of 106 patients with ischaemic heart disease (mean age - 59±7 years) and 30 apparently healthy people (mean age - 36±4 years). Myocardial revascularization was performed with the help of stenting and coronary artery bypass grafting. The patients with ischaemic heart disease were divided into 2 groups: Group 1 with postinfarction cardiosclerosis and Group 2 without Q-forming myocardial infarction. Echocardiography was performed using the Vivid E9 machine prior to operation, intraoperatively, and 10-14 after the intervention. We registered the end-systolic volume and end-diastolic volume of the left ventricle, ejection fraction, cardiac index. Alterations of velocity were assessed in relation to of the volume of the left ventricle (dVol/dt), length of the ventricle (dL/dt) in systole and diastole, as well as myocardial shift velocity in 3 endocardial regions - basal (V1), middle (V2), apical portions (V3) and interrelationship with intraventricular blood flows. It was determined that myocardial dysfunction leads to impairment of the structure of the flow, change of acceleration, which is accompanied by a decrease in the cardiac productivity. Impairment of segmental contractility of the left ventricle is manifested by a decrease of vectors of myocardial motion velocity by more than 20%. Intraventricular flows in cardiac chambers may serve as predictors of adequacy of correction of coronary pathology.

Impact of prosthetic mitral valve orientation on the ventricular flow field: Comparison using patient-specific computational fluid dynamics

Significant mitral valve regurgitation creates progressive adverse remodeling of the left ventricle (LV). Replacement of the failing valve with a prosthesis generally improves patient outcomes but leaves the patient with non-physiological intracardiac flow patterns that might contribute to their future risk of thrombus formation and embolism.It has been suggested that the angular orientation of the implanted valve might modify the postoperative distortion of the intraventricular flow field. In this study, we investigated the effect of prosthetic valve orientation on LV flow patterns by using heart geometry from a patient with LV dysfunction and a competent native mitral valve to calculate intracardiac flow fields with computational fluid dynamics (CFD). Results were validated using in vivo 4D Flow MRI. The computed flow fields were compared to calculations following virtual implantation of a mechanical heart valve oriented in four different angles to assess the effect of leaflet position. Flow patterns were visualized in long- and short-axes and quantified with flow component analysis. In comparison to a native valve, valve implantation increased the proportion of the mitral inflow remaining in the basal region and further increased the residual volume in the apical area. Only slight changes due to valve orientation were observed.Using our numerical framework, we demonstrated quantitative changes in left ventricular blood flow due to prosthetic mitral replacement. This framework may be used to improve design of prosthetic heart valves and implantation procedures to minimize the potential for apical flow stasis, and potentially assist personalized treatment planning.

Echocardiography in the Assessment of Intraventricular Flows and Pressure Gradients in Obstructive Hypertrophic Cardiomyopathy

Aim To evaluate results of myomectomy by intraventricular pressure gradients (IVPG) and blood flows in patients with obstructive hypertrophic cardiomyopathy (OHCMP).Material and methods The study included a total of 76 subjects, 42 patients with OHCMP (mean age, 39±7 years) and 34 healthy volunteers (mean age, 41±3 years). Prior to and after myomectomy, transthoracic echocardiography was performed and followed by digital image processing and calculation of IVPG and left ventricular (LV) vortex flows. Vector analysis was used to estimate the myocardial displacement rate (V), vortex flows, and LV apex-to-base pressure gradients.Results The study showed a dynamic decrease in the LV apex-to-outflow IVPG by more than 50% and recovery of myocardial contraction velocity in the septal area (р&lt;0.001). The decrease in LV cavity pressure gradient serves as an index for evaluating the effectiveness of OHCMP correction. Myomectomy reduces the load on the myocardium and abolishes mitral valve regurgitation with improvement of LV blood flows as also evidenced by the dynamics of long axis velocity change during the cardiac cycle (dL / dt) and the myocardial contraction velocity (V).Conclusion Effectiveness of the surgical correction of OHCMP is based on the dynamics of myocardial contraction velocities, vortex blood flows, and a decrease in LV apex-to-base IVPG.

Colour-Doppler echocardiography flow field velocity reconstruction using a streamfunction-vorticity formulation.

We introduce a new method (Doppler Velocity Reconstruction or DoVeR), for reconstructing two-component velocity fields from colour Doppler scans. DoVeR employs the streamfunction-vorticity equation, which satisfies mass conservation while accurately approximating the flow rate of rotation. We validated DoVeR using artificial colour Doppler images generated from computational fluid dynamics models of left ventricle (LV) flow. We compare DoVeR against the conventional intraventricular vector flow mapping (iVFM1D) and reformulated iVFM (iVFM2D). LV model error analysis showed that DoVeR is more robust to noise and probe placement, with noise RMS errors (nRMSE) between 3.81% and 6.67%, while the iVFM methods delivered 4.16-24.17% for iVFM1D and 4.06-400.21% for iVFM2D. We test the DoVeR and iVFM methods using in vivo mouse LV ultrasound scans. DoVeR yielded more haemodynamically accurate reconstructions, suggesting that it can provide a more reliable approach for robust quantification of cardiac flow.

Evaluation of patients with a HeartMate 3 left ventricular assist device using echocardiographic particle image velocimetry

PurposePoor left ventricular (LV) function may affect the physiological intraventricular blood flow and physiological vortex formation. The aim of this study was to investigate the pattern of intraventricular blood flow dynamics in patients with LV assist devices (LVADs) using echocardiographic particle image velocimetry.Materials and methodsThis prospective study included 17 patients (mean age 57 ± 11 years, 82% male) who had received an LVAD (HeartMate 3, Abbott Laboratories, Chicago, Illinois, USA) because of end-stage heart failure and poor LV function. Eleven (64%) patients had ischemic cardiomyopathy, and six patients (36%) had nonischemic cardiomyopathy. All patients underwent echocardiography, including intravenous administration of an ultrasound-enhancing agent (SonoVue, Bracco, Milan, Italy). Echocardiographic particle image velocimetry was used to quantify LV blood flow dynamics, including vortex formation (Hyperflow software, Tomtec imaging systems Gmbh, Unterschleissheim, Germany).ResultsContrast-enhanced ultrasound was well tolerated in all patients and was performed without adverse reactions or side effects. The LVAD function parameters did not change during or after the ultrasound examination. The LVAD flow was on average 4.3 ± 0.3 L/min, and the speed was 5247 ± 109 rotations/min. The quantification of LV intraventricular flow demonstrated substantial impairment of vortex parameters. The energy dissipation, vorticity, and kinetic energy fluctuation indices were severely impaired.ConclusionsEcho particle velocimetry is safe and feasible for the quantitative assessment of intraventricular flow in patients with an LVAD. The intraventricular LV flow and vortex parameters are severely impaired in these patients.

Improved Efficiency of Intraventricular Blood Flow Transit Under Cardiac Stress: A 4D Flow Dobutamine CMR Study.

Introduction: The effects of heart rate, inotropy, and lusitropy on multidimensional flow patterns and energetics within the human heart remain undefined. Recently, reduced volume and end-diastolic kinetic energy (KE) of the portion of left ventricular (LV) inflow passing directly to outflow, Direct flow (DF), have been shown to reflect inefficient LV pumping and to be a marker of LV dysfunction in heart failure patients. In this study, we hypothesized that increasing heart rate, inotropy, and lusitropy would result in an increased efficiency of intraventricular blood flow transit. Therefore, we sought to investigate LV 4D blood flow patterns and energetics with dobutamine infusion.Methods: 4D flow and morphological cardiovascular magnetic resonance (CMR) data were acquired in twelve healthy subjects: at rest and with dobutamine infusion to achieve a target heart rate ~60% higher than the resting heart rate. A previously validated method was used for flow analysis: pathlines were emitted from the end-diastolic (ED) LV blood volume and traced forward and backward in time to separate four functional LV flow components. For each flow component, KE/mL blood volume at ED was calculated.Results: With dobutamine infusion there was an increase in heart rate (64%, p < 0.001), systolic blood pressure (p = 0.02) and stroke volume (p = 0.01). Of the 4D flow parameters, the most efficient flow component (DF), increased its proportion of EDV (p < 0.001). The EDV proportion of Residual volume, the blood residing in the ventricle over at least two cardiac cycles, decreased (p < 0.001). The KE/mL at ED for all flow components increased (p < 0.001). DF had the largest absolute and relative increase while Residual volume had the smallest absolute and relative increase.Conclusions: This study demonstrates that it is feasible to compare 4D flow patterns within the normal human heart at rest and with stress. At higher heart rate, inotropy and lusitropy, elicited by dobutamine infusion, the efficiency of intraventricular blood flow transit improves, as quantified by an increased relative volume and pre-systolic KE of the most efficient DF component of the LV volume. The change in these markers may allow a novel assessment of LV function and LV dysfunction over a range of stress.

In Vitro Investigation of the Effect of Left Ventricular Assist Device Speed and Pulsatility Mode on Intraventricular Hemodynamics

Stroke has become the main cause of mortality and morbidity in patients treated with Left Ventricular Assist Devices (LVADs). The hemodynamics of the left ventricle are altered by the implantation of an LVAD, with the increase of thrombogenic flow patterns, such as stagnation regions. Time-resolved stereo particle image velocimetry (Stereo-PIV) measurements of the flow inside a patient-specific model of the left ventricle (LV) implanted with an LVAD were performed. The effects of LVAD speed, peripheral resistance and afterload were investigated. The impact of activating the LVAD pulsatility mode (periodic speed modulation) was also evaluated. Analysis of the velocity measurements in two orthogonal planes revealed stagnation zones which may be favorable to thrombus formation. Increasing LVAD speed, despite increasing the flow rate through the inflow cannula, does not automatically result in smaller stagnation regions. These results demonstrated the strong interdependence of peripheral resistance, afterload and flow through the LVAD. As a consequence, the pulsatility mode showed very limited effect on overall flow rate. However, it did reduce the size of high stagnation areas. This study showed how LVAD speed, peripheral resistance and afterload impact the complex intraventricular flow patterns in a ventricle implanted with an LVAD and quantify their thrombogenic risk.

Intraventricular vector flow mapping 3-D by triplane Doppler echocardiography

Heart failure affects the heart’s ability to meet the oxygen needs of the organs. It concerns more than one million people in France. It can be defined by the reduced capacity of the heart to be fi...

A 3-dimensional-printed left ventricle model incorporated into a mock circulatory loop to investigate hemodynamics inside a severely failing ventricle supported by a blood pump.

Intraventricular blood stasis is a design consideration for continuous flow blood pumps and might contribute to adverse events such as thrombosis and ventricular suction. However, the blood flow inside left ventricles (LVs) supported by blood pumps is still unclear. In vitro experiments were conducted to imitate how the hydraulic performance of an axial blood pump affects the intraventricular blood flow of a severe heart failure patient, such as velocity distribution, vorticity, and standard deviation of velocity. In this study, a silicone model of the LV was constructed from the computed tomography data of one patient with heart failure and was 3D printed. Then, intraventricular flow was visualized by particle image velocimetry equipment within a mock circulation loop. The results showed that the axial blood pump suctions most of the blood in a severely failing LV, there was an altered flow status within the LV, and blood stasis appeared in the central region of the LV. Some blood may be suctioned from the aortic valve to the blood pump because the patient's native heart was severely failing. Blood stasis at the LV center may cause thrombosis in the LV. The vortex flow near the inner wall of the LV can thoroughly wash the left ventricular cavity.

Intraventricular flow features and cardiac mechano-energetics after mitral valve interventions – feasibility of an isolated heart model

Abstract The aim of this work was the development of an isolated heart setup to delineate the interactions between intraventricular flow features, hemodynamic parameters and mechano-energetics after certain mitral valve therapies. Five porcine hearts were explanted and prepared for (i) edge-to-edge mitral valve repair, (ii) implantation of a rotatable biscupid mechanical valve prosthesis. Flow structures were visualized using echocardiography while hemodynamics was recorded in terms of pressures, flow rates and ventricular volume. Hemodynamic and cardiac mechano-energetics implied a marginal effect (&lt;5%) of alternating leaflet orientation on ventricular pre-load and stroke work. After edge-to-edge repair, substantial variations in flow structures were observed. Beside promoting profound insights into fundamental physiologic mechanisms, the setup may be used for validation of computer aided therapy planning tools.

Analysis of inter-system variability of systolic and diastolic intraventricular pressure gradients derived from color Doppler M-mode echocardiography

Assessment of intraventricular pressure gradients (IVPG) using color Doppler M-mode echocardiography has gained increasing interest in the evaluation of cardiac function. However, standardized analysis tools for IVPG quantification are missing. We aimed to evaluate the feasibility, the test-retest observer reproducibility, and the inter-system variability of a semi-automated IVPG quantification algorithm. The study included forty healthy volunteers (50% were men). All volunteers were examined using two ultrasound systems, the Philips Epiq 7 and the General Electric Vivid 6. Left ventricular diastolic (DIVPG) and systolic (SIVPG) intraventricular pressure gradients were measured from the spatiotemporal distribution of intraventricular propagation flow velocities using color Doppler M-mode in standard apical views. There was good feasibility for both systolic and diastolic IVPG measurements (82.5% and 85%, respectively). Intra and inter-observer test-retest variability measured with the intraclass correlation coefficient were 0.98 and 0.93 for DIVPG respectively, and 0.95 and 0.89 for SIVPG respectively. The inter-system concordance was weak to moderate with Lin’s concordance correlation coefficient of 0.59 for DIVPG and 0.25 for SIVPG. In conclusion, it is feasible and reproducible to assess systolic and diastolic IVPG using color Doppler M-mode in healthy volunteers. However, the inter-system variability in IVPG analysis needs to be taken into account, especially when using displayed data.

Intraventricular Flow Patterns in Patients Treated with Left Ventricular Assist Devices.

The success of left ventricular assist device (LVAD) therapy is hampered by complications such as thrombosis and bleeding. Understanding blood flow interactions between the heart and the LVAD might help optimize treatment and decrease complication rates. We hypothesized that LVADs modify shear stresses and blood transit in the left ventricle (LV) by changing flow patterns and that these changes can be characterized using 2D echo color Doppler velocimetry (echo-CDV). We used echo-CDV and custom postprocessing methods to map blood flow inside the LV in patients with ongoing LVAD support (Heartmate II, N = 7). We compared it to healthy controls (N = 20) and patients with dilated cardiomyopathy (DCM, N = 20). We also analyzed intraventricular flow changes during LVAD ramp tests (baseline ± 400 rpm). LVAD support reversed the increase in blood stasis associated with DCM, but it did not reduce intraventricular shear exposure. Within the narrow range studied, the ventricular flow was mostly insensitive to changes in pump speed. Patients with significant aortic insufficiency showed abnormalities in blood stasis and shear indices. Overall, this study suggests that noninvasive flow imaging could potentially be used in combination with standard clinical methods for adjusting LVAD settings to optimize flow transport and minimize stasis on an individual basis.