Intraventricular Flow Simulations in Singular Right Ventricles Reveal Deteriorated Washout and Low Vortex Formation

Purpose Patients with a functionally univentricular heart represent one of the most common severe cardiac lesions with a prevalence of 3 per 10,000 live births. Hemodynamics of the singular ventricle is a major research topic in cardiology and there exists a relationship between fluid dynamical features and cardiac behavior in health and disease. The aim of the present work was to compare intraventricular flow in single right ventricle (SRV) patients and subjects with healthy left hearts (LV) through patient-specific CFD simulations. Methods Three-dimensional real-time echocardiographic images were obtained for five SRV patients and two healthy subjects and CFD simulations with a moving mesh methodology were performed. Intraventricular vortex formation and vortex formation time (VFT) as well as the turbulent kinetic energy (TKE) and ventricular washout were evaluated. Results The results show significantly lower values for the VFT and the TKE in SRV patients compared with healthy LV subjects. Furthermore, vortex formation does not progress to the apex in SRV patients. These findings were confirmed by a significantly lower washout in SRV patients. Conclusions The study pinpoints the intriguing role of intraventricular flows to characterize performance of SRVs that goes beyond standard clinical metrics such as ejection fraction.

Vortex Formation Times in the Glottal Jet, Measured in a Scaled-Up Model

In this paper, the timing of vortex formation on the glottal jet is studied using previously published velocity measurements of flow through a scaled-up model of the human vocal folds. The relative timing of the pulsatile glottal jet and the instability vortices are acoustically important since they determine the harmonic and broadband content of the voice signal. Glottis exit jet velocity time series were extracted from time-resolved planar DPIV measurements. These measurements were acquired at four glottal flow speeds (uSS = 16.1–38 cm/s) and four glottis open times (To = 5.67–23.7 s), providing a Reynolds number range Re = 4100–9700 and reduced vibration frequency f* = 0.01−0.06. Exit velocity waveforms showed temporal behavior on two time scales, one that correlates to the period of vibration and another characterized by short, sharp velocity peaks (which correlate to the passage of instability vortices through the glottis exit plane). The vortex formation time, estimated by computing the time difference between subsequent peaks, was shown to be not well-correlated from one vibration cycle to the next. The principal finding is that vortex formation time depends not only on cycle phase, but varies strongly with reduced frequency of vibration. In all cases, a strong high-frequency burst of vortex motion occurs near the end of the cycle, consistent with perceptual studies using synthesized speech.

Intraventricular hemodynamics in pediatric patients with single right ventricles reveal deteriorated washout and low vortex for-mation times: An in silico study

The congenital heart disease univentricular heart (UVH) occurs with an incidence of 0.04-0.5% in newborns and is often treated with the Fontan procedure. In this intervention, the cardiac circulation is transformed into a singular circulation with only one ventricular chamber pumping. Hemodynamics the singular ventricle is a major research topic in cardiology and there exists a rela-tionship between fluid dynamical features and cardiac behavior in health and disease. By visualizing the flow using Computational Fluid Dynamics (CFD) models, an option is created to investigate the flow in patient-specific geometries. CFD simulation of the pathological single right ventricle in contrast to the healthy left ventricle is the research object of the present work. The aim is the numerical comparison of the intraventricular flow within the ventricles. Based on this, flow formation in different anatomies of the ventricles is investi-gated. Patient-specific measurements of ventricles from three-dimensional real-time echocardiographic im-ages served as the basis for the simulations with five single right ventricle (SRV) patients and two sub-jects with healthy left hearts (LV) investigated. Interpolation of these data reproduced the shape and continuous motion of the heart during a cardiac cycle. This motion was implemented into a CFD mod-el with a moving mesh methodology. For comparison of the ventricles, the vortex formation as well as the occurring turbulent kinetic energy (TKE) and washout were evaluated. Vortex formation was as-sessed using the dimensionless vortex formation time (VFT). The results show significantly lower values for the VFT and the TKE in SRV patients than for the compared LV Patients. Furthermore, vortex formation does not progress to the apex in SRV patients. These findings were confirmed by a significantly lower washout in SRV patients. Flow simulation within the moving ventricle provides the possibility of more detailed analysis of the ventricular function. Simulation results show altered vortex formation and reduced washout of SRV in comparison to healthy LV. This information could provide important information for the planning and treatment of Fontan patients.

P1503Decrement of vortex formation time during dobutamine stress echo

Background Vortex Formation Time (VFT) is a novel index of systolic and diastolic function which may be also affected by left ventricular geometry, but has never been evaluated during dobutamine stress echocardiography (DSE) protocols. We sought to investigate the changes in VFT during DSE protocol. Methods DSE was performed in 50 consecutive patients. Patients with poor acoustic window, atrial fibrillation, cardiac valve disease or pacemaker were excluded. Apical four and apical two chamber views were acquired and the following parameters were calculated off- line without knowledge of DSE result both at rest and at peak: left ventricular end-diastolic and end-systolic volume, stroke volume, ejection fraction, stroke work, e and a wave peak velocity and VTI, TDI-derived mitral annular early diastolic velocity at the lateral wall and mitral valve diameter. VFT calculated according to the following equation: VFT = [4 *(1 − β) * α3 * EF]/π, where α = (LVEDV/α3)(1/3) and is affected by ventricular geometry and β = VTIa-wave/(VTIe wave + VTIa-wave) reflecting the atrial filling fraction. Results Median age of the study population was 61 [53–72], 38 men (76%) and 13 (26%) had an old myocardial infarction. Fifteen patients (30%) were positive for myocardial ischemia during DSE. At rest, median LVEDV was 121.5ml (101.8–148.0), median EF (%): 59.9 [54.4–64.1], median atrial filling fraction: 0.43 [0.40–0.48], median mitral valve diameter (cm): 2.8 [2.6–3.0] and median VFT: 2.44 [1.74–3.10]. At peak, median LVEDV was 102.0ml [86.4–122.3] median EF (%) 65.7 [58.8–69.8], median atrial filling fraction: 0.67 [0.59–0.73], median mitral valve diameter (cm): 2.7 [2.5–2.9] and median VFT: 1.45 [1.05–1.88]. VFT decreased in the whole population (Wilcoxon rank test, p<0.001) (figure 1A) and when patients were stratified according to test result. Median VFT decrease was significantly higher in patients with a positive DSE (50%) than in patients with negative DSE (39%) (Mann- Whitney U test, p=0.048) (figure 1B). Figure 1 Conclusion The VFT decreased significantly during DSE and most prominently in patients with ischemic response. This may indicate the deterioration of left ventricular diastolic or systolic function as well as change in left ventricular geometry during DSE protocol.

Left ventricular vortex formation time in elite athletes: novel predictor of myocardial performance

BackgroundEfficient transportation of blood through the left ventricle (LV) during diastole depends on vortex formation. Vortex formation time (VFT) can be measured by echocardiography as a dimensionless index. As elite athletes have supranormal diastolic LV function, we aim to assess resting and post-exercise VFT in these athletes and hypothesised that VFT may predict myocardial performance immediately post-exercise.MethodSubjects were world class speedskaters training for the Winter Olympic Games. Echocardiographic measurements were obtained before and immediately after 3000 m of racing. VFT was computed as 4×(1−β)/π×α³×left ventricle ejection fraction where β is the fraction of diastolic stroke volume contributed by atrial contraction, α is the biplane end diastolic volume (EDV)1/3 divided by mitral annular diameter during early diastole.ResultsBaseline VFT was 2.6±0.7 (n=24, age 22±3 years, 67% males). Post-exercise, heart rates increased (64±10 vs 89±12 beats/min, p<0.01); however, VFT was unchanged (2.9±1.0, p>0.05). VFT at rest correlated modestly with post-exertion early diastolic mitral in-flow velocity (E; r=0.59, p=0.01), tissue Doppler-derived early mitral annular velocity (E′; septal and lateral, both r=0.59, p=0.01) and systolic annular velocity (S′; septal: r=0.46, p=0.02 and lateral: r=0.48, p=0.02) but not late diastolic mitral in-flow velocity (A; r=0.06, p>0.05) or annular velocity (A′; septal: r=0.34, p=NS and lateral: r=0.35, p>0.05).ConclusionThere was no significant difference between VFT at rest and immediately post-exercise. However, VFT at rest correlated with immediate post-exercise augmented systolic and early diastolic tissue Doppler indicators of myocardial performance in elite athletes.