Vena Cava Pressure Research Articles

Noninvasive estimation of central venous pressure after Fontan procedure using biochemical markers and abdominal echography

Patients may develop liver dysfunction, including liver fibrosis, over the long term following Fontan procedure. Therefore, early detection of liver dysfunction is essential to identify those patients who are at risk. We evaluated various laboratory parameters, including liver biochemical markers, hepatic echography findings, and cardiac catheterization outcomes, at an early stage after undergoing Fontan procedure. A total of 56 patients who underwent Fontan procedure were included in the study. All patients underwent cardiac catheterization and biochemical markers were evaluated from the samples. Abdominal echography was performed on a subgroup of patients (n=20) to observe the structure of liver tissues and to measure blood flow in the hepatic vein, portal vein, and hepatic artery. The mean period of time since Fontan procedure was 2.8 ± 2.1 years. There was a significant correlation between venous pressure and serum levels of γ-glutamyltranspeptidase and type IV collagen 7s domain, which indicated a high probability of liver consolidation. The other biochemical markers were normal. Stepwise regression analyses suggested that by using the ratio of hepatic venous flow and type IV collagen 7s collagen domain concentration, inferior vena cava pressure can be predicted. Our study showed that we can predict inferior vena cava pressure using noninvasive abdominal echography and biochemical markers at an early stage after Fontan procedure.

Estimation of central venous pressure using inferior vena caval pressure from a femoral endovascular cooling catheter

PurposeEndovascular cooling using the femoral cooling catheter is widely practiced. Central venous pressure (CVP) monitoring in patients undergoing femoral endovascular cooling may require the placement of another catheter near the right atrium (RA). We sought to estimate the agreement between the CVP recorded from catheters placed in the superior vena caval pressure (SVCP) and the inferior vena caval pressure (IVCP) recorded from the femoral cooling catheter in patients undergoing femoral endovascular cooling. MethodsWe enrolled adult cardiac arrest survivors undergoing femoral endovascular cooling. A commercially available central venous catheter was placed in the SVC (superior vena cava) near the RA via subclavian venous access. Both SVCP and IVCP were recorded every 4 hours during therapeutic hypothermia. Arterial pressure, heart rate, peak inspiratory pressure (PIP), and positive end expiratory pressure (PEEP) at the time of vena caval pressure measurements were obtained. ResultsA total of 323 pairs of SVCP and IVCP measurements were collected. The correlation coefficient between SVCP and IVCP was 0.965 (P < .001). The mean difference between SVCP and IVCP was −0.45 mm Hg (SD, 1.27; 95% confidence interval, −0.59 to −0.31 mm Hg). The limits of agreement were −2.94 to 2.05 mm Hg. Vena caval pressures were significantly correlated with airway pressures (peak inspiratory pressure and positive end expiratory pressure), whereas the difference between SVCP and IVCP did not correlate with airway pressures. ConclusionInferior vena caval pressure measured via the femoral cooling catheter showed excellent agreement with CVP recorded from catheters placed in the SVC, which indicates that the femoral cooling catheter can be used for monitoring CVP.

Pseudotumor Cerebri Associated With Modified Fontan Anatomy

Surgical treatment of functional single-ventricle heart disease with a modified Fontan procedure results in elevated central venous pressure. The case report describes a 19-year-old boy with hypoplastic left heart syndrome and Fontan palliation that resulted in frequent debilitating headaches after transcatheter closure of systemic venous-to-pulmonary venous collaterals. Measured increased intracranial pressure and prompt relief of the headaches with lumbar puncture favored a diagnosis of pseudotumor cerebri. After implantation of a lumboperitoneal shunt, the patient's headaches improved dramatically. Headaches are frequent in patients with Fontan circulation. The current literature supports a pivotal role of elevated dural venous sinus pressure in the pathogenesis of pseudotumor cerebri. The high superior and inferior vena caval pressures characteristic of modified Fontan anatomy may account for headaches in some of these patients.

Successful Fontan Completion After Cardiac Resynchronization Therapy

This patient underwent a modified Norwood operation with a right ventricle–pulmonary artery shunt at the age of 7 days following the diagnosis of hypoplastic left heart syndrome with mitral and aortic atresia; this procedure was followed by bidirectional Glenn operation at the age of 5 months. The girl subsequently developed congestive heart failure despite the administration of angiotensin-converting enzyme inhibitors and β-blockers after the initial operation. At the age of 11 months, she required hospitalization and intravenous inotropic support. Coil embolization and surgical ligation of the aortopulmonary collaterals were performed at the age of 1 year but could not control the heart failure. The maximum plasma brain natriuretic peptide level after the second palliative operation was 3823 pg/mL. Cardiac catheterization performed at the age of 1 year and 4 months revealed ventricular dyssynchrony, ventricular ejection fraction of 36.2%, right atrial pressure of 7 mm Hg, superior vena cava pressure of 16 mm Hg, and grade 2 tricuspid regurgitation. QRS duration was 184 ms (Figure 1), and arterial oxygen saturation was 80%. To detect the most delayed and earliest …

Hemorragia presacra durante la resección rectal por cáncer. Consideraciones morfológicas e hidrodinámicas

IntroductionOur aim is to identify the location and size of the anterior foramina of sacral vertebral bodies and analyse the haemodynamic variables that could influence the haemorrhagic severity of the injury of the presacral venous plexus. Materials and methodsUsing computed axial tomography the morphological data of 70 sacral bones in 67 patients with rectal cancer were recorded, as well as measuring the height between the vena cava and S5. After transfemoral catheterisation the inferior vena cava pressure was recorded in 10 patients with rectal cancer. Hydrodynamic principles, according to Bernoulli's Law, were applied to calculate sacral venous plexus pressure, and the flow rate according to the calibre of a hypothetical venous injury. ResultsThe maximum diameter ranged from 0.5mm to 4mm in 22% of the cases. All foramina of 2 or more millimetres were located in the S4-S5 region. Sacral plexus venous pressure in lithotomy was almost double the inferior vena cava pressure in normal position. Blood flow ranged from 498 to 1,994ml/min for injuries of sizes between 2 and 4mm, respectively. ConclusionsLarger calibre foramina are found in vertebral bodies of S4-S5. Venous injury at these levels can reach a flow rate of 2 l/min.

INTACT RIGHT VENTRICLE-PULMONARY ARTERY SHUNT AFTER STAGE II PALLIATION IN HYPOPLASTIC LEFT HEART SYNDROME IMPROVES PULMONARY ARTERY GROWTH

For patients with hypoplastic left heart syndrome who have undergone the Norwood procedure with a right ventricle–pulmonary artery (RV-PA) shunt, the shunt can either be removed or left intact at the time of the stage 2 procedure. This study aimed to determine the effects of an intact shunt on pulmonary artery growth and clinical outcomes after the stage 2 procedure. A retrospective review of patients who underwent Norwood with an RV-PA shunt from 2005 to 2010 was performed. Catheterization data, echocardiographic data, postoperative outcome variables, and mortality data were collected. Pulmonary artery size was measured at pre-stage 2 and pre-Fontan catheterizations using the Nakata Index and the McGoon Ratio. Of the 68 patients included in the study, 48 had the shunt removed at the time of stage 2 (group 1), and 20 had the shunt left intact (group 2). The two groups did not differ in terms of pre-stage 2 hemodynamics or pulmonary artery size. After stage 2, group 2 had higher oxygen saturations. The two groups did not differ regarding duration of chest tube drainage, length of hospital stay, need for unplanned interventions, or mortality. Before Fontan, the group 2 patients had higher superior vena cava (SVC) pressures and more venovenous collaterals closed. There was increased pulmonary artery growth between the pre-stage 2 and pre-Fontan catheterizations in group 2 using both the Nakata Index (+148.5 vs −52.4 mm2/m2; p = 0.01) and the McGoon Ratio (+0.36 vs +0.01; p = 0.01). These findings indicate that patients with an intact RV-PA shunt after stage 2 have greater pulmonary artery growth than patients with the shunt removed, with no increased risk of complications.

The mid-term follow-up of pulmonary perfusion in patients after extracardiac total cavopulmonary connection

To explore the changes of pulmonary perfusion over 5 years in patients who underwent extracardiac total cavopulmonary connection. Forty-three patients who had undergone extracardiac total cavopulmonary connection were examined with pulmonary perfusion 1 month and 5 years following the operation. 99mTc-MAA was used for perfusion imaging; pulmonary perfusion value and blood distribution were measured and calculated. Vena cava pressure and arterial oxygenation were measured using the right cardiac catheter, and the pulmonary arteriole resistance was calculated. The status of the conduit connection was assessed by computed tomography three-dimensional reconstruction. Radionuclide counts of the follow-up group were similar to those of the early postoperative group, and the ratios of right to left pulmonary perfusion and inferior vena cava perfusion were not changed. However, the ratio of the whole pulmonary superior to inferior segment was remarkably reduced (t=2.54, P<0.05), with a significantly higher perfusion rate in the posterior segment of the lower lobe (t=2.16, P<0.05). The pulmonary arteriole resistance of the follow-up group was reduced significantly (t=2.08, P<0.05). The vena cava pressure was also reduced (t=2.69, P<0.05), but oxygenation was not significantly changed. Five patients showed a mismatch between pulmonary angiography and radionuclide scintigraphy soon after the operation. The pulmonary angiography showed that the anastomosis was patent, and both lungs were demonstrated. However, the radionuclide scintigraphy only demonstrated the unilateral lung soon after the operation, and both lungs were demonstrated during follow-up. Radionuclide scintigraphy is superior to the pulmonary angiography in the study of functional pulmonary perfusion. Fontan circulation may lead to gravity-dependent blood redistribution, and its weak pulsation can promote pulmonary vascular development. However, the reduced pulmonary arterial resistance at mid-term follow-up may not lead to an increased amount of pulmonary perfusion or oxygen supply, which is probably because of the massive opening of the arteriovenous shunt and increased futile circulation.

The relationship between plasma concentrations of ionized calcium and magnesium with cardiac energetics and systemic oxygen transport in neonates after the Norwood procedure

We sought to determine the relationship between plasma calcium and magnesium concentrations with postoperative systemic hemodynamics and oxygen transport in neonates after the Norwood procedure. Postoperative systemic oxygen consumption was continuously measured using respiratory mass spectrometry for 72 hours in 17 neonates. Arterial, superior vena caval and pulmonary venous blood gases and pressures, plasma calcium, and lactate levels were measured at 2- to 4-hour intervals to calculate cardiac output, rate pressure product, cardiac power output, systemic oxygen delivery, and oxygen extraction ratio. Plasma magnesium levels were measured at 2- to 8-hour intervals. Plasma calcium levels decreased in the first 8 hours from 1.08±0.13 mmol/L to 0.98±0.08 mmol/L, followed by an increase to 1.10±0.26 mmol/L at 72 hours (P<.0001). Mg2þ change was significantly related to time after logarithmic transformation, rapidly decreasing from 1.62±0.25 mg/L to 0.90±0.15 mg/L in the first 40 hours and further decreasing slowly thereafter to 0.64±0.13 mg/L at 72 hours (P<.0001). Plasma magnesium levels had a significant positive correlation with cardiac output (P=.008) and cardiac power output (P=.01), and a negative correlation with heart rate (P=.05). Plasma magnesium levels correlated positively with systemic oxygen delivery and negatively with systemic oxygen consumption (P=.08 for both), resulting in significant negative correlations with oxygen extraction ratio (P=.04) and lactate levels (P=.05). For a given cardiac power output, plasma magnesium showed a significantly negative correlation with rate pressure product (P=.01). Plasma calcium levels showed the opposite trend, which was statistically insignificant except for lactate (P=.007). Plasma magnesium may exert favorable effects on myocardial energetics and systemic oxygen transport in neonates after the Norwood procedure, whereas plasma calcium may be harmful. Maintaining a relatively high level of plasma magnesium and a low level of plasma calcium may improve myocardial work efficiency and the balance of systemic and myocardial oxygen transport.

Comparison of superior vena cava and femoroiliac vein pressure according to intra-abdominal pressure

BackgroundPrevious studies have shown a good agreement between central venous pressure (CVP) measurements from catheters placed in superior vena cava and catheters placed in the abdominal cava/common iliac vein. However, the influence of intra-abdominal pressure on such measurements remains unknown.MethodsWe conducted a prospective, observational study in a tertiary teaching hospital. We enrolled patients who had indwelling catheters in both superior vena cava (double lumen catheter) and femoroiliac veins (dialysis catheter) and into the bladder. Pressures were measured from all the sites, CVP, femoroiliac venous pressure (FIVP), and intra-abdominal pressure.ResultsA total of 30 patients were enrolled (age 62 ± 14 years; SAPS II 62 (52–76)). Fifty complete sets of measurements were performed. All of the studied patients were mechanically ventilated (PEP 3 cmH20 (2–5)). We observed that the concordance between CVP and FIVP decreased when intra-abdominal pressure increased. We identified 14 mmHg as the best intra-abdominal pressure cutoff, and we found that CVP and FIVP were significantly more in agreement below this threshold than above (94% versus 50%, P = 0.002).ConclusionsWe reported that intra-abdominal pressure affected agreement between CVP measurements from catheter placed in superior vena cava and catheters placed in the femoroiliac vein. Agreement was excellent when intra-abdominal pressure was below 14 mmHg.

Non‐invasive assessment of liver fibrosis in patients after the Fontan operation

This study analyzed the change in liver fibrosis markers after the Fontan operation and investigated their clinical usefulness as an index of congestive liver fibrosis. The study enrolled 24 patients who underwent the Fontan operation between January 1994 and December 2008. We subdivided the postoperative period into four intervals and then compared the hepatological markers during each. Eighteen patients underwent postoperative cardiac catheterization and the correlation between hepatological markers and the inferior vena cava (IVC) pressure was analyzed. The mean age of the patients was 138.6 months and the mean interval between the Fontan operation and the examination was 97.8 months. Type IV collagen was extremely high in every interval (I, 286 ± 93; II, 265 ± 93; III, 305 ± 143; IV, 206 ± 70), while none of the laboratory variables changed significantly in each interval. A significant positive correlation was observed between type IV collagen and the IVC pressure, but no significant correlation with any other hepatological marker was detected. No specific parameter that reflects the progress in liver fibrosis was identified in this study. The possibility exists that type IV collagen reflects the degree of hepatic congestion.

Hepatic blood flow distribution and performance in conventional and novel Y-graft Fontan geometries: A case series computational fluid dynamics study

A novel Y-shaped baffle has been proposed for the Fontan operation with promising initial results. However, previous studies have relied either on idealized models or a single patient-specific model. The objective of this study is to comprehensively compare the hemodynamic performance and hepatic blood flow distribution of the Y-graft Fontan baffle with 2 current designs using multiple patient-specific models. Y-shaped and tube-shaped grafts were virtually implanted into 5 patient-specific Glenn models forming 3 types of Fontan geometries: Y-graft, T-junction, and offset. Unsteady flow simulations were performed at rest and at varying exercise conditions. The hepatic flow distribution between the right and left lungs was carefully quantified using a particle tracking method. Other physiologically relevant parameters such as energy dissipation, superior vena cava pressure, and wall shear stress were evaluated. The Fontan geometry significantly influences the hepatic flow distribution. The Y-graft design improves the hepatic flow distribution effectively in 4 of 5 patients, whereas the T-junction and offset designs may skew as much as 97% of hepatic flow to 1 lung in 2 cases. Sensitivity studies show that changes in pulmonary flow split can affect the hepatic flow distribution dramatically but that some Y-graft and T-junction designs are relatively less sensitive than offset designs. The Y-graft design offers moderate improvements over the traditional designs in power loss and superior vena cava pressure in all patients. The Y-graft Fontan design achieves overall superior hemodynamic performance compared with traditional designs. However, the results emphasize that no one-size-fits-all solution is available that will universally benefit all patients and that designs should be customized for individual patients before clinical application.

The Role of Femoral Venous Pressure and Femoral Venous Oxygen Saturation in the Setting Of Intra-Abdominal Hypertension

Femoral venous access is frequently used in critically ill patients. Because raised intra-abdominal pressure (IAP) is also frequently found in this group of patients, we examined the impact of IAP and positive end-expiratory pressure (PEEP) on femoral venous pressure (FVP) and femoral venous oxygen saturation (Sfvo2) in an animal model. Thirteen adult pigs received standardized anesthesia and ventilation. Randomized levels of IAP (3 [baseline], 18, and 26 mmHg) were applied, with levels of PEEP (5, 8, 12, and 15 cmH2O) applied randomly at each IAP level. We measured bladder pressure (IAP), superior vena cava pressure, pulmonary artery pressure, pulmonary artery occlusion pressure, FVP, mixed venous oxygen saturation (Svo2), and Sfvo2. We found that FVP correlated well with IAP (FVP = 4.1 + [0.12 × PEEP] + [1.00 × IAP]; R = 0.89, P < 0.001) with a moderate bias and precision of 5.0 and 3.8 mmHg, respectively. Because the level of agreement did not meet the recommendations of the World Society of Abdominal Compartment Syndrome, FVP cannot currently be recommended to measure IAP, and further clinical trials are warranted. However, a raised FVP should prompt the measurement of the bladder pressure. Femoral venous oxygen saturation did correlate neither with Svo2 nor with abdominal perfusion pressure. Therefore, Sfvo2 is of no clinical use in the setting of raised IAP.

MR Evaluation of Portal Hypertensive Collateral Shunting Vessels for Predicting Outcome after Transjugular Intrahepatic Portosystemic Shunt

We assessed whether magnetic resonance (MR) imaging evaluation of portosystemic collateral shunts can aid prediction of therapeutic effectiveness and complications after creation of a transjugular portosystemic shunt (TIPS), and technical difficulty during the TIPS procedure. We retrospectively reviewed 32 patients (27 men, 5 women; mean age, 56.4 years) who underwent TIPS creation following gadolinium-enhanced MR examination. We measured the diameters of pre-existing portosystemic collateral shunting vessels, added the measurements together to generate a shunting collateral score for each patient, and divided patients into 2 groups by score of 4 or greater or less than 4. We then compared therapeutic effectiveness, technical difficulty and complications of the TIPS procedure, and portal venous (PV) pressure, PV-inferior vena cava (IVC) pressure gradient, and PV diameter between the groups. The patients with a pre-existing large portosystemic shunt showed insignificant trends toward higher technical difficulty of the shunt procedure and rate of shunt dysfunction. The 2 groups showed no significant difference in early mortality rate, onset or worsening rate of hepatic encephalopathy after TIPS creation, PV pressure, PV-IVC pressure gradient, or PV diameter. Gadolinium-enhanced MR imaging may help in predicting technical difficulty and complications of TIPS.

Experimentally modified Fontan circulation in an adolescent pig model without the use of cardiopulmonary bypass

SummaryBackgroundThe feasibility and the hemodynamic outcome of Fontan circulation, without the use of cardiopulmonary bypass, were studied on a beating heart of an adolescent pig model, using a modified total cavopulmonary connection.Material/MethodsEight open-chest anesthetized pigs underwent a successful total cavopulmonary connection with the use of an appropriate Y-shaped Dacron-type conduit. Through a median sternotomy, the distal part of the superior vena cava was anastomosed end-to-end to one side of the conduit. The other side of the graft was anastomosed end-to-side to the main pulmonary artery. The conduit was tailored to an appropriate length and anastomosed end-to-end to the inferior vena cava. The hemodynamic status of the animals was recorded before and after the establishment of the total cavopulmonary connection.ResultsForty-five minutes after completion of total cavopulmonary connection, and for a total of 1 hour, hemodynamic measurements showed a decrease in mean arterial and mean pulmonary artery pressures, heart rate and cardiac output. The inferior vena caval pressure and total pulmonary vascular resistance were increased.ConclusionsA total cavopulmonary connection, performed on a beating heart, without extracorporeal circulation or other means of temporary bypass, although it is technically demanding, is feasible.

Diagnosis of Inadvertent Cannulation of the Azygos Vein During Cardiopulmonary Bypass

Cardiac surgery with cardiopulmonary bypass demands diligence and attention to detail to prevent neurologic injury. Arterial and venous cannulae are used to facilitate cardiopulmonary bypass. The assessment of adequate decompression of the venous circulation is an essential duty of the cardiac surgical team. Modalities for the assessment of adequate regional venous drainage are limited, however communication between the team and increased awareness of certain pathologic states can be useful. These modalities include cerebral oximetry and superior vena caval pressure monitoring, which were employed during a case with bicaval venous cannulation. Malposition of the superior vena cava cannula was detected after a series of events alerted the team that superior vena cava drainage may be compromised.

Azygos Vein to Pulmonary Vein Fistula Is a Pathway for Cerebral Embolism

A 43-year-old man was admitted for right upper and lower limb weakness and aphasia. He had suffered dizziness and transient blindness 6 months ago and had also been found lying in the bathroom on another occasion. Multiple cerebral infarctions were confirmed by brain CT scan and MRI. Diffuse nodes in the mediastinum and postperitoneum had been found in pulmonary CT scans and MRI scans since 1999. Pulmonary CT scan revealed multiple bilateral pneumatoceles in the lungs. Contrast CT scan showed an enlarged azygos vein on the right side of the spinal column and an enlarged azygos arch. CT scan-guided biopsy revealed a few fibers, fat, and vascular tissues in the mass. Transcranial Doppler bubble test showed gas microembolic signals in both middle cerebral arteries. Pulmonary digital subtraction angiogram confirmed an enlarged azygos vein. A fistula was found between the pulmonary and azygos veins with turbulent flow from pulmonary to azygos at rest. Cavography revealed that the pulmonary vein appeared simultaneously with the superior cava vein during Valsalva maneuver. In summary, the pathway of cerebral embolism was based on three pathologic mechanisms: (1) increased inferior vena cava pressure, (2) enlarged right azygos aneurysm, and (3) the presence of a fistula between the azygos and pulmonary veins.

Increasing abdominal pressure with and without PEEP: effects on intra-peritoneal, intra-organ and intra-vascular pressures.

BackgroundIntra-organ and intra-vascular pressures can be used to estimate intra-abdominal pressure. The aim of this prospective, interventional study was to assess the effect of PEEP on the accuracy of pressure estimation at different measurement sites in a model of increased abdominal pressure.MethodsCatheters for pressure measurement were inserted into the stomach, urinary bladder, peritoneal cavity, pulmonary artery and inferior vena cava of 12 pigs. The pressures were recorded simultaneously at baseline, during 10 cm H20 PEEP, external abdominal pressure (7 kg weight) plus PEEP, external abdominal pressure without PEEP, and again under baseline conditions.Results (mean ± SD)PEEP alone increased diastolic pulmonary artery and inferior vena cava pressure but had no effect on the other pressures. PEEP and external abdominal pressure increased intraperitoneal pressure from 6 ± 1 mm Hg to 9 ± 2 mm Hg, urinary bladder pressure from 6 ± 2 mm Hg to 11 ± 2 mm Hg (p = 0.012), intragastric pressure from 6 ± 2 mm Hg to 11 ± 2 mm Hg (all p ≤ 0.001), and inferior vena cava pressure from 11 ± 4 mm Hg to 15 ± 4 mm Hg (p = 0.01). Removing PEEP and maintaining extraabdominal pressure was associated with a decrease in pulmonary artery diastolic but not in any of the other pressures. There was a significant correlation among all pressures. Bias (-1 mm Hg) and limits of agreement (3 to -5 mm Hg) were similar for the comparisons of absolute intraperitoneal pressure with intra-gastric and urinary bladder pressure, but larger for the comparison between intraperitoneal and inferior vena cava pressure (-5, 0 to -11 mm Hg). Bias (0 to -1 mm Hg) and limits of agreement (3 to -4 mm Hg) for pressure changes were similar for all comparisonsConclusionsOur data suggest that pressure changes induced by external abdominal pressure were not modified by changing PEEP between 0 and 10 cm H20.

A New Multiparameter Approach to Computational Simulation for Fontan Assessment and Redesign

Despite an abundance of prior Fontan simulation articles, there have been relatively few clinical advances that are a direct result of computational methods. We address a few key limitations of previous Fontan simulations as a step towards increasing clinical relevance. Previous simulations have been limited in scope because they have primarily focused on a single energy loss parameter. We present a multi-parameter approach to Fontan modeling that establishes a platform for clinical decision making and comprehensive evaluation of proposed interventions. Time-dependent, 3-D blood flow simulations were performed on six patient-specific Fontan models. Key modeling advances include detailed pulmonary anatomy, catheterization-derived pressures, and MRI-derived flow with respiration. The following performance parameters were used to rank patients at rest and simulated exercise from best to worst performing: energy efficiency, inferior and superior vena cava (IVC, SVC) pressures, wall shear stress, and IVC flow distribution. Simulated pressures were well matched to catheterization data, but low Fontan pressure did not correlate with high efficiency. Efficiency varied from 74% to 96% at rest, and from 63% to 91% with exercise. Distribution of IVC flow ranged from 88%/12% (LPA/RPA) to 53%/47%. A "transcatheter" virtual intervention demonstrates the utility of computation in evaluating interventional strategies, and is shown to result in increased energy efficiency. A multiparameter approach demonstrates that each parameter results in a different ranking of Fontan performance. Ranking patients using energy efficiency does not correlate with the ranking using other parameters of presumed clinical importance. As such, current simulation methods that evaluate energy dissipation alone are not sufficient for a comprehensive evaluation of new Fontan designs.

Relationship between ventilatory change of the inferior vena cava and central venous pressure (author's transl)

Relationship between ventilatory change of the inferior vena cava and central venous pressure (author's transl)

Flow in lymphatic networks: interaction between hepatic and intestinal lymph vessels.

Lymph from both the liver and intestine flows into the cisterna chyli. We hypothesized that increasing liver lymph flow would increase cisterna chyli pressure and, thereby, decrease intestinal lymph flow, potentiating intestinal edema formation. Anesthetized dogs were instrumented to measure and manipulate portal vein pressure and cisterna chyli pressure. The effects of directly increasing portal pressure with and without directly increasing cisterna chyli pressure on intestinal wet-to-dry ratio and intestinal ascites formation rate were determined. Target values for portal and cisterna chyli pressures were determined following elevation of inferior vena caval pressure to levels seen in patients with obstructive caval disease. Direct elevation of portal pressure (P(port)) alone to 17.5 mm Hg caused a significant increase in intestinal wet-to-dry ratio (3.98 +/- 0.24 vs. 3.40 +/- 0.43) and the rate of ascites formation (0.36 +/- 0.12 vs. 0.05 +/- 0.03 mL/g dry wt/h). Simultaneous direct elevation of cisterna chyli pressure to 6.0 mm Hg and P(port) to 17.5 mm Hg caused further increases in intestinal wet-to-dry ratio (5.52 +/- 1.20) and ascites formation (0.57 +/- 0.11 mL/g dry wt./h). Inferior vena caval hypertension increases liver lymph flow that elevates cisterna chyli pressure, which inhibits intestinal lymph flow and augments intestinal edema formation.