scholarly journals The total cavopulmonary connection resistance: a significant impact on single ventricle hemodynamics at rest and exercise

2008 ◽  
Vol 295 (6) ◽  
pp. H2427-H2435 ◽  
Author(s):  
Kartik S. Sundareswaran ◽  
Kerem Pekkan ◽  
Lakshmi P. Dasi ◽  
Kevin Whitehead ◽  
Shiva Sharma ◽  
...  
Keyword(s):  
Heart Rate ◽  
Single Ventricle ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Lumped Parameter Model ◽  
Total Cavopulmonary Connection ◽  
Dynamic Simulations ◽  
Lumped Parameter ◽  
The Impact ◽  
Cavopulmonary Connection

Little is known about the impact of the total cavopulmonary connection (TCPC) on resting and exercise hemodynamics in a single ventricle (SV) circulation. The aim of this study was to elucidate this mechanism using a lumped parameter model of the SV circulation. Pulmonary vascular resistance (1.96 ± 0.80 WU) and systemic vascular resistances (18.4 ± 7.2 WU) were obtained from catheterization data on 40 patients with a TCPC. TCPC resistances (0.39 ± 0.26 WU) were established using computational fluid dynamic simulations conducted on anatomically accurate three-dimensional models reconstructed from MRI ( n = 16). These parameters were used in a lumped parameter model of the SV circulation to investigate the impact of TCPC resistance on SV hemodynamics under resting and exercise conditions. A biventricular model was used for comparison. For a biventricular circulation, the cardiac output (CO) dependence on TCPC resistance was negligible (sensitivity = −0.064 l·min−1·WU−1) but not for the SV circulation (sensitivity = −0.88 l·min−1·WU−1). The capacity to increase CO with heart rate was also severely reduced for the SV. At a simulated heart rate of 150 beats/min, the SV patient with the highest resistance (1.08 WU) had a significantly lower increase in CO (20.5%) compared with the SV patient with the lowest resistance (50%) and normal circulation (119%). This was due to the increased afterload (+35%) and decreased preload (−12%) associated with the SV circulation. In conclusion, TCPC resistance has a significant impact on resting hemodynamics and the exercise capacity of patients with a SV physiology.

Abstract 2207: Significant Impact of the Total Cavopulmonary Connection Resistance on Cardiac Output and Exercise Performance in Single Ventricles

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Kartik S Sundareswaran ◽  
Kerem Pekkan ◽  
Lakshmi Prasad Dasi ◽  
Hiroumi D Kitajima ◽  
Kevin Whitehead ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Vascular Resistance ◽  
Single Ventricle ◽  
Total Cavopulmonary Connection ◽  
Lumped Parameter ◽  
Lp Model ◽  
Surgical Pathway ◽  
The Impact ◽  
Cavopulmonary Connection

Introduction: The resistance of the total cavopulmonary connection (TCPC) in single ventricle (SV) circulation has long been hypothesized as a critical contributing factor to their diminished exercise capacity. We investigate this hypothesis using a lumped parameter (LP) model coupled with cardiac catheterization (cath) and computational fluid dynamics (CFD). Methods: SV pulmonary vascular resistance (1.80 ± 0.83 WU) and systemic vascular resistance (18.4 ± 7.2 WU) were obtained from cath data on 48 pts with a TCPC. TCPC resistances (0.55 ± .24 WU, min=0.24, max = 0.93) were established from CFD simulations (n=13) and in vitro experiments (n=8) conducted on anatomically accurate TCPC models from MRI. Resistance and compliance values for the normal pediatric circulation were obtained from the literature. These values were then used in a LP model developed for both the normal and SV circulation. Results: For a biventricular circulation, the cardiac output (CO) dependence on resistance is negligible, but not for the SV circulation (Fig 1a ). Capacity to increase CO with heart rate is also severely reduced for the SV. At a simulated exercise HR of 140 beats per minute, the SV patient with the highest resistance (0.93 WU) had a significantly lower increase in cardiac output (22%) when compared to an SV patient with the lowest resistance (26%) and the normal circulation (67%) (Fig 1b ). Conclusion: Hemodynamic energy cascade in a SV circulation should not be judged by stereotypes of biventricular circulation. The impact of TCPC surgical pathway resistance on cardiac output at rest and exercise was significantly higher on SVs compared to biventricular circulation. Figure 1. Impact of TCPC resistance in single ventricle vs. normal circulation, specifically (a) resting cardiac output, and (b) exercise cardiac output

Particle Image Velocimetry Measurement and Computational Fluid Dynamic Simulations of the Unsteady Flow Within a Rotating Disk Cavity

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Xiang Luo ◽  
Dongdong Liu ◽  
Hongwei Wu ◽  
Zhi Tao
Keyword(s):  
Particle Image Velocimetry ◽  
Computational Fluid Dynamic ◽  
Particle Image ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Rotating Disk ◽  
Turbine Rotor ◽  
Dynamic Simulations ◽  
Image Velocimetry ◽  
The Impact

In this article a combined experimental and numerical investigation of the unsteady mixing flow of the ingestion gas and rim sealing air inside a rotating disk cavity was carried out. A new test rig was set up, and the experiments were conducted on a 1.5-stage turbine rotor disk and included pressure measurements. The flow structure of the mixing region of the ingestion gas and sealing air in cavity was measured using the particle image velocimetry (PIV) technique. To complement the experimental investigation and to aid in understanding the flow mechanism within the cavity, a three-dimensional (3D) unsteady computational fluid dynamic (CFD) analysis was undertaken. Both simulated and experimental results indicated that near the rotating disk, (i) a large amount of the ingestion gas will turn around and flow out the cavity due to the impact of the centrifugal force and the Coriolis force, (ii) a small amount of ingestion gas will mix transiently with the sealing air inside the cavity, whereas near the static disk, (iii) the ingestion gas will flow into the cavity along the static wall and mix with the sealing air.

scholarly journals SERIAL CHANGES IN SINGLE VENTRICLE FLOWS FROM GLENN TO TOTAL CAVOPULMONARY CONNECTION: COMPARISON OF MRI TO LUMPED PARAMETER MODELING

2011 ◽  
Vol 57 (14) ◽  
pp. E478
Author(s):  
Christopher M. Haggerty ◽  
Kartik S. Sundareswaran ◽  
Kerem Pekkan ◽  
Kirk R. Kanter ◽  
Mark A. Fogel ◽  
...  
Keyword(s):  
Single Ventricle ◽  
Total Cavopulmonary Connection ◽  
Lumped Parameter ◽  
Lumped Parameter Modeling ◽  
Cavopulmonary Connection

scholarly journals Assessment of cavopulmonary connections by advanced imaging: value of flat-detector computed tomography

2012 ◽  
Vol 23 (1) ◽  
pp. 18-26 ◽  
Author(s):  
Martin Glöckler ◽  
Andreas Koch ◽  
Julia Halbfaß ◽  
Verena Greim ◽  
Andrè Rüffer ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Diagnostic Accuracy ◽  
Three Dimensional ◽  
Supplementary Information ◽  
Total Cavopulmonary Connection ◽  
Clinical Value ◽  
Flat Detector ◽  
Flat Detector Computed Tomography ◽  
The Impact ◽  
Cavopulmonary Connection

AbstractObjectivesTo investigate the impact of flat-detector computed tomography on the clinical assessment of patients with cavopulmonary connections, and to evaluate the obtained diagnostic accuracy and supplementary information, as well as the value of overlaid three-dimensional reconstructions on fluoroscopic images during catheter-based interventions.MethodsWe analysed 31 consecutive patients retrospectively in whom flat-detector computed tomography was used to visualise the cavopulmonary connection. We investigated patients with cavopulmonary connections either early post-operatively (first group), before converting to a total cavopulmonary connection (second group), and patients with failing total cavopulmonary connection (third group). Flat-detector computed tomography based on a single rotational angiography was used to create a three-dimensional vascular model. The clinical value of flat-detector computed tomography was evaluated using standard categories of diagnostic utility. Used contrast volume and radiation exposure were quantified.ResultsWithin 18 months, flat-detector computed tomography was performed in 31 cases with cavopulmonary connections. The median age was 1.9 years (range 0.3–43 years). In the first group, we found anomalies in 4 out of 8 cases, which led to therapeutic or prophylactic procedures; in the second and third groups, we performed interventions in 14 out of 23 cases. The overall clinical value was always rated superior to conventional biplane angiography. The median dose area product was 91.8 microgray square metres (range 33.0–679.3 microgray square metres). The required contrast medium was 2.08 millilitres per kilogram (range 0.66–4.7 millilitres per kilogram).ConclusionFlat-detector computed tomography improves the diagnostic accuracy in cavopulmonary connections and provides additional diagnostic information, which may lead to therapeutic or prophylactic procedures. Overlaid three-dimensional images on fluoroscopy facilitate and provide security for interventions.

The Effect of Incorporating Vessel Compliance in a Computational Model of Blood Flow in a Total Cavopulmonary Connection (TCPC) with Caval Centerline Offset

2004 ◽  
Vol 126 (6) ◽  
pp. 709-713 ◽  
Author(s):  
J. C. Masters ◽  
M. Ketner ◽  
M. S. Bleiweis ◽  
M. Mill ◽  
A. Yoganathan ◽  
...  
Keyword(s):  
Blood Flow ◽  
Power Loss ◽  
Fluid Dynamic ◽  
Reducing Power ◽  
Pressure Head ◽  
Congenital Defects ◽  
Total Cavopulmonary Connection ◽  
Flow Mixing ◽  
The Right ◽  
Cavopulmonary Connection

Background—The total cavopulmonary connection (TCPC), a palliative correction for congenital defects of the right heart, is based on the corrective technique developed by Fontan and Baudet. Research into the TCPC has primarily focused on reducing power loss through the connection as a means to improve patient longevity and quality of life. The goal of our study is to investigate the efficacy of including a caval offset on the hemodynamics and, ultimately, power loss of a connection. As well, we will quantify the effect of vessel wall compliance on these factors and, in addition, the distribution of hepatic blood to the lungs. Methods—We employed a computational fluid dynamic model of blood flow in the TCPC that includes both the non-Newtonian shear thinning characteristics of blood and the nonlinear compliance of vessel tissue. Results—Power loss in the rigid-walled simulations decayed exponentially as caval offset increased. The compliant-walled results, however, showed that after an initial substantial decrease in power loss for offsets up to half the caval diameter, power loss increased slightly again. We also found only minimal mixing in both simulations of all offset models. Conclusions—The increase in power loss beyond an offset of half the caval diameter was due to an increase in the kinetic contribution. Reduced caval flow mixing, on the other hand, was due to the formation of a pressure head in the offset region which acts as a barrier to flow.

Propulsive Efficiency of the Underwater Dolphin Kick in Humans

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Alfred von Loebbecke ◽  
Rajat Mittal ◽  
Frank Fish ◽  
Russell Mark
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Underwater Video ◽  
Dynamic Simulations ◽  
Slender Body Theory ◽  
Propulsive Efficiency ◽  
Video Footage ◽  
Wide Range ◽  
Dolphin Kick ◽  
Body Theory

Three-dimensional fully unsteady computational fluid dynamic simulations of five Olympic-level swimmers performing the underwater dolphin kick are used to estimate the swimmer’s propulsive efficiencies. These estimates are compared with those of a cetacean performing the dolphin kick. The geometries of the swimmers and the cetacean are based on laser and CT scans, respectively, and the stroke kinematics is based on underwater video footage. The simulations indicate that the propulsive efficiency for human swimmers varies over a relatively wide range from about 11% to 29%. The efficiency of the cetacean is found to be about 56%, which is significantly higher than the human swimmers. The computed efficiency is found not to correlate with either the slender body theory or with the Strouhal number.

A Simple Dynamic Modeling of Head Slap in Hard Disk Drive

2001 ◽  
Author(s):  
Seong-Hun Lee ◽  
Jeong-Hak Lee ◽  
Kwang-Joon Kim
Keyword(s):  
Hard Disk Drive ◽  
Dynamic Modeling ◽  
Structural Design ◽  
Continuous System ◽  
Disk Drive ◽  
Lumped Parameter Model ◽  
Test Results ◽  
Lumped Parameter ◽  
Shock Resistance ◽  
The Impact

Abstract In order to understand mechanism of the impact between head and disk of a HDD subject to a shock and to improve the shock resistance effectively, it is essential to develop a dynamic model which can represent well the head slap. Although motion of the head and disk subject to a shock requires modeling by a continuous system to be rigorous, in this study, a simplified lumped parameter model is developed to understand basic dynamics of the head slap and to determine crucial parameters for the improvement of the structural design. In addition, drop test results of the HDD are presented to back to up the derived model.

The Impact of Modelling Air Compressibility in the Selection of Optimal OWC Design Parameters in Site Specific Wave Conditions

2019 ◽  
Author(s):  
Irene Simonetti ◽  
Lorenzo Cappietti
Keyword(s):  
Fluid Dynamic ◽  
Experimental Tests ◽  
Design Parameters ◽  
Dynamic Simulations ◽  
Regression Approach ◽  
Wave Conditions ◽  
A Site ◽  
The Impact ◽  
Period Wave ◽  
Selection Of

Abstract The importance of properly modelling the effects of air compressibility in the selection of the optimal design parameters for an Oscillating Water Column wave energy converter is investigated. For this purpose, a wide dataset of capture width ratios, obtained from both experimental tests and Computational Fluid Dynamic simulations, is used to formulate an empirical model able to predict the performance of the device as a function of its basic design parameters (chamber width and draught, turbine damping) and of the wave conditions (wave period, wave height). A multiple non-linear regression approach is used to determine the model numerical coefficients. The data used to formulate the model include the effects of air compressibility. The impact of considering such effects on the selection of the optimal geometry of the device is evaluated and discussed by means of the model application for the optimization of a device to be installed in a site located in the Mediterranean Sea (in front of the coast of Tuscany, Italy).

scholarly journals Coupling of a cardiovascular model with a thermoregulation model to predict human blood pressure under unsteady environmental conditions

2019 ◽  
Vol 111 ◽  
pp. 02062
Author(s):  
Yoshito Takahashi ◽  
Masayuki Oata ◽  
Jun-ichi Asaka ◽  
Akihisa Nomoto ◽  
Shin-ichi Tanabe
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Human Blood ◽  
Environmental Conditions ◽  
Lumped Parameter Model ◽  
Cardiovascular Model ◽  
Lumped Parameter ◽  
Gravity Effects ◽  
Vessel Resistance ◽  
Peak Blood

We coupled a cardiovascular model with a thermoregulation model to predict human blood pressure in unsteady environmental conditions. Our cardiovascular model is a lumped parameter model and consists of 42 segments, which include the entire artery and vein system, divided into 18 segments; the heart, divided into 4 segments; and the pulmonary artery and vein. The vessel parameters were adjusted on the basis of local body blood volume and flow of the thermoregulation model in a thermoneutral environment. Blood pressure under unsteady environmental conditions is predicted by changing the heart rate and vessel resistance of the cardiovascular model which is controlled by blood flow that the thermoregulation model predicts. It is possible to predict the increase in blood pressure under cold environmental conditions and the increase in cardiac output under hot environmental conditions and when bathing. The model was validated by simulating bathing experiments. As the result, the model predicted the peak blood pressure later than the experimental data in a cold environment. To improve the accuracy of the model, it is necessary to consider a method for controlling the heart rate, vessel resistance, and gravity effects after a change in posture.

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