Superior Vena Cava Pressure Research Articles

Patient-Specific Multiscale Modeling of the Assisted Bidirectional Glenn

First-stage palliation of neonates with single-ventricle physiology is associated with poor outcomes and challenging clinical management. Prior computational modeling and invitro experiments introduced the assisted bidirectional Glenn (ABG), which increased pulmonary flow and oxygenation over the bidirectional Glenn (BDG) and the systemic-to-pulmonary shunt in idealized models. In this study, we demonstrate that the ABG achieves similar performance in patient-specific models and assess the influence of varying shunt geometry. In a small cohort of single-ventricle prestage 2 patients, we constructed three-dimensional in silico models and tuned lumped parameter networks to match clinical measurements. Each model was modified to produce virtual BDG and ABG surgeries. We simulated the hemodynamics of the stage 1 procedure, BDG, and ABG by using multiscale computational modeling, coupling a finite-element flow solver to the lumped parameter network. Two levels of pulmonary vascular resistances (PVRs) were investigated: baseline (low) PVR of the patients and doubled (high) PVR. The shunt nozzle diameter, anastomosis location, and shape were also manipulated. The ABG increased the pulmonary flow rate and pressure by 15% to 20%, which was accompanied by a rise in superior vena caval pressure (2 to 3 mm Hg) at both PVR values. Pulmonary flow rate and superior vena caval pressures were most sensitive to the shunt nozzle diameter. Patient-specific ABG performance was similar to prior idealized simulations and experiments, with good performance at lower PVR values in the range of measured clinical data. Larger shunt outlet diameters and lower PVR led to improved ABG performance.

Optimization of the Assisted Bidirectional Glenn Procedure for First Stage Single Ventricle Repair.

First-stage single-ventricle palliation is challenging to manage, and significant interstage morbidity and mortality remain. Prior computational and in vitro studies of the assisted bidirectional Glenn (ABG), a novel first-stage procedure that has shown potential for early conversion to a more stable augmented Glenn physiology, demonstrated increased pulmonary flow and oxygen delivery while decreasing cardiac work, as compared to conventional stage-1 alternatives. This study aims to identify optimal shunt designs for the ABG to improve pulmonary flow while maintaining or decreasing superior vena caval (SVC) pressure. A representative three-dimensional model of a neonatal bidirectional Glenn (BDG) was created, with a shunt connecting the innominate artery to the SVC. The shunt design was studied as a six-parameter constrained shape optimization problem. We simulated hemodynamics for each candidate designs using a multiscale finite element flow solver and compared performance against designs with taper-less shunts, the standalone BDG, and a simplified control volume model. Three values of pulmonary vascular resistance (PVR) of 2.3, 4.3, and 7.1 WUm2 were studied. Increases in pulmonary flow were generally accompanied by increases in SVC pressure, except at low PVR (2.3 WUm2), where the optimal shunt geometry achieved a 13% increase in pulmonary flow without incurring any increase in SVC pressure. Shunt outlet area was the most influential design parameter, while others had minimal effect. Assisted bidirectional Glenn performance is sensitive to PVR and shunt outlet diameter. An increase in pulmonary flow without a corresponding increase in SVC pressure is possible only when PVR is low.

Superior vena cava replacement combined with venovenous shunt for lung cancer and thymoma: a case series.

Superior vena cava (SVC) replacement is infrequently performed and technically challenging in low-volume centers. Venovenous shunt (VVS) technique is used to reduce SVC pressure during SVC replacement and has not been well reported. This study aimed to add information on this subject and evaluate the surgical outcomes of patients who underwent SVC replacement combined with VVS in our center. A retrospective analysis of six patients who underwent SVC replacement combined with VVS from September 2011 to February 2017 was performed. Clinical characteristics, pathological features, operative characteristics, postoperative outcomes, and the survival of the six patients were reviewed. There were four males and two females with a median age of 44 years (range, 35-69 years). There were three lung cancer patients and three thymoma patients at a stage from IIIA to IVA. Five patients underwent induction therapy. Complete resection was performed on five patients. One patient underwent internal VVS, and the other five patients underwent external VVS. Prosthesis grafts were employed in five cases and autologous pericardium in one case. Three patients underwent single-vein reconstruction, and the other three patients underwent double-vein reconstruction. The median SVC clamping time was 75 minutes. There were no postoperative deaths or major complications. All patients were alive at follow-up, and no thrombosis was found in any of the grafts. SVC replacement combined with VVS is technically feasible and safe. Although VVS technique is not a must, it may make SVC replacement safer in inexperienced centers. Surgery-based multidisciplinary treatment for selected patients with type T4 lung cancer and SVC involvement or thymoma and SVC involvement may achieve a favorable long-term outcome.

Bidirectional Glenn procedure with and without cardiopulmonary bypass: Short term results

BackgroundBidirectional superior cavopulmonary anastomosis (BDG) is a palliative surgical procedure for anatomical or physiological univentricular hearts, in which the superior vena cava is anastomosed to the ipsilateral pulmonary artery in an end-to-side manner with or without cardiopulmonary bypass (CPB) support. The objective of this study was to compare the short term results of the BDG procedure performed on CPB or without CPB. MethodsBetween February 2015 and September 2016, 57 consecutive patients (mean age 33.27 ± 18.4 months) undergoing BDG were randomly assigned to either group I: using CPB (n = 27 patients; mean age 30.56 ± 16.47 months) or group II: without using CPB (n = 30 patients; mean age 23.96 ± 14.67 months). In group II two techniques were used (A) A temporary veno-atrial shunt were used (n = 15 cases mean age 23.3 ± 14.58 months), (B) without using veno-atrial shunt (n = 15 cases mean age 24.6 ± 15.24 months). We monitored the superior vena caval (SVC) pressure, O2 saturation, Operative time, mechanical ventilation period, intensive care unit (ICU) stay, hospital stay, operative mortality and postoperative complications. ResultsThere was significant decrease in the operative time in group II (81.63 ± 14.83 min) in comparison to group I (122.33 ± 16.21 min). The differences in the period of mechanical ventilation, ICU stay & hospital stay were insignificant. In addition, the differences between both groups as regard postoperative complications and mortality were insignificant. ConclusionsThe BDG procedure can be performed with no significant differences in operative mortality, morbidity, or use of resources, with or without CPB support.

Bilateral bidirectional Glenn: outcome of off-pump technique.

Off-pump bilateral bidirectional Glenn (b-BDG) poses a surgical challenge and may add complexity to the postoperative outcome especially regarding uniformity of the anastomosis and central pulmonary artery growth. Herein, we report early- and mid-term outcomes after off-pump b-BDG without using superior vena cava decompression techniques. Ninety-seven consecutive patients, between 2009 and 2014, were included in this prospective study. All patients had complete pre- and postoperative clinical and detailed neurological assessments. Diagnosis and follow-up were done by echocardiography and cardiac catheterization for assessment of pulmonary artery anatomically and haemodynamically. Median follow-up period was 3.5 years. Perioperative variables, clinical outcome, morbidity, mortality and follow-up data were recorded. Hypoplastic right ventricle was present in 52 cases (53.6%) and hypoplastic left ventricle was present in 45 cases (46.4%). Mean superior vena cava pressure on clamping was 21.49 ± 3.04 mmHg. Mean total clamping time was 23.11 ± 3.44 min. Mean oxygen saturation increased from preoperative 69.22 ± 6.01% to 83.66 ± 3.97% after b-BDG construction (P-value ≤ 0.0001). The Nakata index increased from 288.47 ± 28.66 mm2/m2 to 303.64 ± 26.85mm2/m2 on follow-up (P-value ≤ 0.05). In-hospital mortality was 4 patients (4.1%) due to low-cardiac output. There were chylothorax in 9 patients (9.3%) and convulsions in 4 patients (4.1%) who were treated conservatively. Off-pump b-BDG can be conducted safely, with a uniform anastomosis that allows a good central pulmonary artery growth for subsequent Fontan completion. Moreover, avoiding the use of cardiopulmonary bypass is more economic and less hazardous.

Stent insertion for malignant superior vena cava syndrome: effectiveness and long-term outcome.

To determine the clinical effectiveness and long-term outcome of stent insertion for malignant superior vena cava (SVC) syndrome. From June 2010 to April 2016, 47 patients with malignant SVC syndrome were treated with stent insertion in our center. Data regarding the technical success, clinical success, and long-term outcome were collected and analyzed retrospectively. SVC stent insertion was successfully performed in all patients. A total of 65 stents were used. No procedure-related complication occurred in these patients. The mean SVC pressure gradient decreased from 17.8mmHg before stent insertion to 7.6mmHg after stent insertion (P<0.001). Clinical success was 100%. During a mean follow-up period of 6months (range 10days-13months), 25 patients underwent subsequent anti-cancer treatment. Six patients (12.8%) experienced re-obstruction of stent 1 to 189days (median 76days) after stent insertion. All patients died during the follow-up. The median stent patency time and survival were 339 and 167days, respectively. The cumulative 3-, 6-, and 12-month stent patency rates were 93.4, 87.4, and 81.2%, respectively. The cumulative 3-, 6-, and 12-month survival rates were 83, 38.3, and 2.1%, respectively. The independent predictors of prolonging survival after stent insertion were lower tumor stage (P=0.018) and subsequent anti-cancer treatment after stent insertion (P=0.009). Stent insertion is a simple, safe, and effective method for patients with malignant SVC syndrome. Subsequent anti-cancer treatment after stent insertion may increase the survival.

Application of vascular repair and reconstruction in surgical treatment of superior vena cava syndrome caused by thoracic tumor

To summarize the clinical experience of vascular repair and reconstruction for treating superior vena cava syndrome (SVCS) caused by thoracic tumor. Between October 2008 and June 2016, 26 patients with thoracic tumor and SVCS were admitted. There were 18 males and 8 females, aged from 27 to 70 years (mean, 45.9 years). Tumor was typed as B1-B3 thymoma in 13 cases, thymic carcinoma in 6 cases, large B-cell lymphoma in 3 cases, T lymphocytic lymphoma in 1 case, malignant teratoma in 1 case, right lung squamous cell carcinoma in 1 case, and carcinoid in 1 case. The tumor diameter ranged from 8 to 15 cm with an average of 10 cm. The patients had different degrees of neck, face, and upper extremity edema, jugular vein distention, and chest wall collateral venous filling. The superior vena cava pressure was 2.45-5.39 kPa. After excision of tumor and invading superior vena cava, 7 patients underwent superior vena cava reconstruction and 19 patients underwent artificial vascular replacement. There was no perioperative death, and the symptoms of superior vena cava obstruction were eliminated. Postoperative pulmonary infection, respiratory muscle weakness, and right chylothorax occurred in 4 cases, 1 case, and 1 case respectively. Twenty-four patients were followed up 2-92 months (mean, 37 months), and 2 patients failed to be followed up. At 1, 3, and 5 years, the survival rate was 83.3% (20/24), 41.7% (10/24), and 25% (6/24), respectively. In 6 patients with 5-year survival, there were 1 case of type B1 thymoma, 3 cases of type B3 thymoma, and 2 cases of large B-cell lymphoma. For preoperative evaluation of SVCS caused by resectable thoracic tumors, vascular repair and recons-truction technique can be used to quickly and effectively relieve the clinical symptoms and improve the quality of life.

Right atrium and superior vena cava pressure measurements in a novel animal model to study one and a half ventricle repair as compared to Fontan type procedure

Background &amp; Objectives: To evaluate the advantages of the one and a half ventricle repair on maintaining a low pressure in the inferior vena cava district. Also evaluate the competition of flows at the superior vena cava – right pulmonary artery anastomosis site, in order to understand the hemodynamic interaction of a pulsatile flow in combination to a laminar one. Materials &amp; Methods: Adult rabbits (n=30) in terminal anaesthesia with a follow up of 8 h were used, randomly distributed in three experimental groups: Group 1: animals with an anastomosis between superior vena cava and right pulmonary artery, as a model of one and one half ventricle repair; Group 2: animals with the cavopulmonary anastomosis followed by clamping of the right pulmonary artery proximal to the anastomosis; and Group 3: sham animals. Pressures of superior vena cava and pulmonary arteries were afterwards measured, in a resting condition as well as after induced pharmacological stress test.Results: In Group 1, superior vena cava pressure was significantly higher, while venous pressure in the inferior vena cava – right atrium district was constant or lower in comparison with the other groups. After stress test, the pressure in the superior vena cava and the heart rate both increased further, but the right ventricular, right atrial and pulmonary artery pressures remained similar to the values in a resting condition. This proved that the inferior vena cava return was well-preserved, and no venous hypertension was present in the inferior vena cava district even after stress test (good exercise tolerance).Conclusion: One and one half ventricle repair can be considered a good surgical strategy for maintaining a low pressure in the inferior vena cava district with potential for right ventricle growth, restoring the more physiological circulation in borderline or failing right ventricle conditions. The experiment presented a positive finding in favour of one and one half ventricle repair, as compared to Fontan type procedure.

Mechanically assisted bidirectional cavopulmonary shunt in neonates and infants: An acute human pilot study

ObjectivePoor survival following surgical palliation for hypoplastic left heart syndrome (HLHS) raises the question of the need for a paradigm shift. This is the first human study to investigate the possibility of primary “in-series” palliation in neonates and infants with HLHS in an acute setting with the aid of 2 types of mechanical assist: superior vena cava (SVC)–to–pulmonary artery (PA) pump assist and SVC–to–right atrium (RA) oxygenation assist. MethodsBy rearranging the cannula sites and flow rates for modified ultrafiltration, 2 types of mechanically assisted bidirectional cavopulmonary shunt (BCPS) circulation were simulated for 20 minutes. Three neonates undergoing a stage I Norwood procedure were assigned to SVC-PA pump assist, and 3 infants undergoing stage II BCPS were assigned to SVC-RA oxygenation assist. Hemodynamic parameters, blood gas values, and arterial (SaO2) and regional cerebral tissue (rCTO2) saturations were analyzed. ResultsAll 6 patients completed the study without hemodynamic compromise. In the SVC-PA pump assist group, a mean arterial pressure >40 mm Hg was maintained. SVC pressure was lower (P = .01) and cerebral perfusion pressure (CPP) was higher (P = .03) during the last 10 minutes of assist compared with Norwood physiology. SaO2 >80%, rCTO2 >60%, and mixed venous saturation ≥59% were maintained, comparable to values with Norwood physiology. In the SVC-RA oxygenation assist group, with full or 50% support, mean blood pressure >50 mm Hg, SVC pressure <15 mm Hg, mixed venous saturation >50%, and CPP >40 mm Hg were maintained, which were comparable to BCPS physiology. ConclusionsTwo types of mechanical assist to support primary in-series palliation are feasible in the acute setting. Both modes of mechanical assist maintained oxygenation, as well as systemic and cerebral perfusion.

Warden repair for superior sinus venosus atrial septal defect and anomalous pulmonary venous drainage in children: Anesthesia and transesophageal echocardiography perspectives.

Objective:Review of intraoperative anesthetic challenges and the role of transesophageal echocardiography in children with sinus venosus atrial septal defect and partial anomalous pulmonary venous drainage undergoing Warden repair.Design:A retrospective observational case series.Methodolgy:Pediatric patients who underwent Warden repair between October 2011-September 2015 were recruited. Their preoperative clinical details, anesthetic techniques, intraoperative TEE findings and postoperative events were recorded from the medical records. The categorical variables and the continuous variables were expressed as number (percentages) and mean ± SD respectively.Results:A total of 35 patients were operated for Warden repair during the study period. Anesthesia was induced with the aim to prevent any fall in pulmonary vascular resistance. The right internal jugular vein was cannulated under ultrasound guidance using a short length cannula to monitor right superior vena cava pressure. Intraoperative TEE revealed the drainage of PAPVC high into RSVC in 22 patients. Persistent LSVC was found in 9 patients. After repair, TEE imaging detected a high gradient at Warden anastomotic site in 5 patients and 3 of them required revision of surgery. Rerouted pulmonary veins required surgical correction in 2 patients in view of obstruction. None of them had pulmonary venous and SVC obstruction in the postoperative period.Conclusion:The primary aim of anesthesia is to avoid any fall in PVR. Right IJV cannulation can be beneficial. The intraoperative TEE can help in delineating the anatomy of lesion and detecting anastomotic site obstruction.

Novel mechanisms for cerebral blood flow regulation in patients with congenital heart disease

The mechanisms that regulate cerebral flow in patients after surgery for congenital heart diseases (CHDs) remain poorly understood. We tested our hypothesis that postoperative patients with CHD have disease- or hemodynamic-specific compensatory mechanisms for maintaining cerebral perfusion. A total of 89 children with specific hemodynamics including Glenn (n = 14), Fontan (n = 19), repaired tetralogy of Fallot (n = 24), and control patients (n = 32) were enrolled. The resistance and blood flow distribution between the brain (Rc and CIc) and lower body (Rs and CIs) were calculated by measuring the hemodynamic changes resulting from inferior vena cava occlusion during cardiac catheterization. Despite considerable differences in cardiac index and superior vena cava pressure (SVCp), cerebral blood flow was preserved in all noncontrol groups, with a ratio between the vascular resistances in the cerebral and lower body circulation (Rc/Rs) that was significantly lower than that in controls. Interestingly, the reduced Rc/Rs of Glenn patients was mediated by the reduced Rc, whereas augmented Rs was conducive to the reduced Rc/Rs in the Fontan and tetralogy of Fallot groups. Multivariate analysis revealed that high SVCp was significantly associated with low Rc. Although low cardiac index was significantly associated with increased Rc and Rs, its impact was much greater on Rs than on Rc. Compensatory mechanisms for cerebral flow regulation occur according to hemodynamic abnormality type in postoperative patients with CHD. Because such a regulation mechanism implies cerebral circulation fragility, further investigations are needed to address the impacts of cerebral circulation properties on neurodevelopmental outcomes.

Partial cavopulmonary assist from the inferior vena cava to the pulmonary artery improves hemodynamics in failing Fontan circulation: a theoretical analysis.

Cavopulmonary assist (CPA) for failing Fontan patients remains a challenging issue in the clinical setting. To evaluate the effectiveness of a partial CPA from the inferior vena cava (IVC) to the pulmonary artery (PA), we performed a theoretical analysis using a computational model of the Fontan circulation. Cardiac chambers and vascular systems were described as the time-varying elastance model and the modified three-element Windkessel model, respectively. A rotational pump described as a non-linear function was inserted between the IVC and the PA. When pulmonary vascular resistance index varied from 2.1 to 5.9 Wood units m(2), the partial CPA maintained cardiac index as efficiently as total CPA and markedly reduced the IVC pressure compared with total CPA. However, the partial CPA increased the superior vena cava pressure substantially. The modification from total to partial CPA is potentially an effective alternative in failing Fontan patients suffering from high IVC pressure.

In Vitro Assessment of the Assisted Bidirectional Glenn Procedure for Stage One Single Ventricle Repair.

This in vitro study compares the hemodynamic performance of the Norwood and the Glenn circulations to assess the performance of a novel assisted bidirectional Glenn (ABG) procedure for stage one single ventricle surgery. In the ABG, the flow in a bidirectional Glenn procedure is assisted by injection of a high-energy flow stream from the systemic circulation using an aorta-caval shunt with nozzle. The aim is to explore experimentally the potential of the ABG as a surgical alternative to current surgical practice. The experiments are directly compared against previously published numerical simulations. A multiscale mock circulatory system was used to measure the hemodynamic performance of the three circulations. For each circulation, the system was tested using both low and high values of pulmonary vascular resistance. Resulting parameters measured were: pressure and flow rate at left/right pulmonary artery and superior vena cava (SVC). Systemic oxygen delivery (OD) was calculated. A parametric study of the ratio of ABG nozzle to shunt diameter was done. We report time-based comparisons with numerical simulations for the three surgical variants tested. The ABG circulation demonstrated an increase of 30-38% in pulmonary flow with a 2-3.7 mmHg increase in SVC pressure compared to the Glenn and a 4-14% higher systemic OD than either the Norwood or the Glenn. The nozzle/shunt diameter ratio affected the local hemodynamics. These experimental results agreed with those of the numerical model: mean flow values were not significantly different (p > 0.05) while mean pressures were comparable within 1.2 mmHg. The results verify the approaches providing two tools to study this complicated circulation. Using a realistic experimental model we demonstrate the performance of a novel surgical procedure with potential to improve patient hemodynamics in early palliation of the univentricular circulation.

The assisted bidirectional Glenn: A novel surgical approach for first-stage single-ventricle heart palliation

Outcomes after a modified Blalock-Taussig shunt (mBTS) in neonates with single-ventricle physiology remain unsatisfactory. However, initial palliation with a superior cavopulmonary connection, such as a bidirectional Glenn (BDG), is discouraged, owing to potential for inadequate pulmonary blood flow (PBF). We tested the feasibility of a novel surgical approach, adopting the engineering concept of an ejector pump, whereby the flow in the BDG is "assisted" by injection of a high-energy flow stream from the systemic circulation. Realistic 3-dimensional models of the neonatal mBTS and BDG circulations were created. The "assisted" bidirectional Glenn (ABG) consisted of a shunt between the right innominate artery and the superior vena cava (SVC), with a 1.5-mm clip near the SVC anastomosis to create a Venturi effect. The 3 models were coupled to a validated hydraulic circulation model, and 2 pulmonary vascular resistance (PVR) values (7 and 2.3 Wood units) were simulated. The ABG provided the highest systemic oxygen saturation and oxygen delivery at both PVR levels. In addition to achieving higher PBF than the BDG, the ABG produced a lower single-ventricular workload than mBTS. SVC pressure was highest in the ABG model (ABG: 15; Glenn: 11; mBTS: 3 mm Hg; PVR = 7 Wood units), but at low PVR, the SVC pressure was significantly lower (ABG: 8; Glenn: 6; mBTS: <3 mm Hg). Adopting the principle of an ejector pump, with additional flow directed into the SVC in a BDG, the ABG appears to increase PBF with a modest increase in SVC and pulmonary arterial pressure. Although multiscale modeling results demonstrate the conceptual feasibility of the ABG circulation, further technical refinement and investigations are necessary, especially in an appropriate animal model.

The effects of dexmedetomidine administration on the pulmonary artery pressure and the transpulmonary pressure gradient after the bidirectional superior cavopulmonary shunt.

The hemodynamic effects of dexmedetomidine (DEX) on pulmonary artery pressure (PAP) are not fully understood in patients with a single-ventricle physiology. The objective of this retrospective study was to characterize the effect of perioperative DEX infusion on PAP and the transpulmonary pressure gradient after a bidirectional superior cavopulmonary shunt (BCPS) operation. We retrieved physiologic data including the heart rate, incidence of cardiac pacing, systolic and diastolic arterial blood pressure (ABP), and superior vena cava (SVC) and inferior vena cava (IVC) pressures from the medical records of all patients <12 months of age who underwent a BCPS operation. Patients with an additional Norwood or Damus-Kaye-Stansel procedure, those with additional pulmonary blood flow, and those without both a SVC and an IVC catheter were excluded from the present study. Following the BCPS operation, the SVC pressure is equivalent to the PAP. Similarly, the IVC pressure is equivalent to the common atrial pressure (CAP). Accordingly, we can directly assess the transpulmonary pressure gradient, defined as the difference between the PAP and the CAP, using simultaneous SVC and IVC pressure measurements. Twenty-nine patients were included in the present study. We did not find any increase in the PAP, CAP, PAP/systolic ABP ratio, or the transpulmonary pressure gradient as of 6 h after admission to the intensive care unit when the patients were treated with DEX infusion at a median (interquartile ranges) dose of 0.6 mcg/kg/h (0.4, 0.64 mcg/kg/h). We concluded that the administration of DEX to children with a single-ventricle physiology is acceptable.

Postoperative visual loss due to complicated mediastinal dissection and haemorrhagic shock treatment during cardiac surgery

We report the case of a patient who underwent third time revision of double heart valve replacement. Mediastinal dissection for right atrium cannulation was complicated by laceration of the superior vena cava; this required temporary rescue clamping of the vessel. The patient suffered complete visual loss related to bilateral retrobulbar haematoma. Acute elevation of superior vena cava pressure due to vascular clamping and administration of large amounts of fluid through the central venous jugular catheter could have caused the postoperative visual loss.

Experimental Measurements of Energy Augmentation for Mechanical Circulatory Assistance in a Patient-Specific Fontan Model

A mechanical blood pump specifically designed to increase pressure in the great veins would improve hemodynamic stability in adolescent and adult Fontan patients having dysfunctional cavopulmonary circulation. This study investigates the impact of axial-flow blood pumps on pressure, flow rate, and energy augmentation in the total cavopulmonary circulation (TCPC) using a patient-specific Fontan model. The experiments were conducted for three mechanical support configurations, which included an axial-flow impeller alone in the inferior vena cava (IVC) and an impeller with one of two different protective stent designs. All of the pump configurations led to an increase in pressure generation and flow in the Fontan circuit. The increase in IVC flow was found to augment pulmonary arterial flow, having only a small impact on the pressure and flow in the superior vena cava (SVC). Retrograde flow was neither observed nor measured from the TCPC junction into the SVC. All of the pump configurations enhanced the rate of power gain of the cavopulmonary circulation by adding energy and rotational force to the fluid flow. We measured an enhancement of forward flow into the TCPC junction, reduction in IVC pressure, and only minimally increased pulmonary arterial pressure under conditions of pump support.

Superior vena cava syndrome caused by a swollen absorbable haemostat after repair of ischaemic mitral regurgitation

Surgicel, an absorbable haemostat, is widely used in cardiovascular surgery. An 81-year-old woman, who was diagnosed with ischaemic mitral regurgitation, underwent mitral valve plasty and coronary artery bypass grafting. On postoperative day two, her superior vena cava (SVC) pressure gradually rose to 38 mmHg and she developed low output syndrome. Emergent surgery revealed that the cause of SVC syndrome was external compression from a haematoma at the posterior surface of the SVC, which formed around the Surgicel.

Intracranial Pressure and Optic Nerve Sheath Diameter as Cephalic Venous Pressure Increases in Swine

Nontraumatic, nonhydrocephalic increases in intracranial pressure (ICP) are often difficult to diagnose and may underlie spaceflight-related visual changes. This study looked at the utility of a porcine animal model of increasing cephalic venous pressure to mimic acute changes in ICP and optic nerve sheath diameter (ONSD) from cephalic venous fluid shifts observed during spaceflight. Anesthetized juvenile piglets were assigned to groups of either naïve (N = 10) or elevated superior vena cava pressure (SVCP; N = 20). To elevate SVCP, a 6F custom latex balloon catheter was inserted and inflated to achieve SVCP of 20 and 40 mmHg for 1 h at each pressure. In both groups, serial measurements of ICP, internal jugular pressure (IJP), and external jugular pressure (EJP) were made hourly for 3 h, and ONSD of the right eye was measured hourly by ultrasound (US). There was a significant linear correlation between IJP and ICP (slope: 0.9614 +/- 0.0038, r = 0.9683). With increasing SVCP, resulting ONSD was also well correlated with the ICP (slope: 0.0958 +/- 0.0061, r = 0.7841). The receiver operating characteristic curve for ONSD in diagnosing elevated ICP had an area under the curve of 0.9632 with a sensitivity and specificity of 92% and 91%, respectively, for a cutoff of 5.45 mm. Increases in SVCP result in ICP changes that are well correlated with alteration in ONSD. These changes are consistent with observed ONSD changes monitored during spaceflight.

Obstruction of the Superior Vena Cava After Neonatal Extracorporeal Membrane Oxygenation

Obstruction of the superior vena cava is one of the potential complications of neonatal extracorporeal membrane oxygenation. Chylothorax is a known complication of surgery involving the thoracic cavity in children, and of extracorporeal membrane oxygenation. The aim of this study was to evaluate the association between chylothorax and superior vena cava obstruction after neonatal extracorporeal membrane oxygenation. Twenty-two patients diagnosed with superior vena cava obstruction at ≤ 6 months of age (median 1.8 months) after neonatal extracorporeal membrane oxygenation were compared with a randomly selected cohort of 44 neonatal extracorporeal membrane oxygenation patients without superior vena cava obstruction. Among patients with superior vena cava obstruction, 18 underwent extracorporeal membrane oxygenation for respiratory disease and four for cardiac insufficiency. Chylothorax was more prevalent among patients with superior vena cava obstruction than controls (odds ratio 9.4 [2.2-40], p = .01) and was associated with extension of obstruction into the left innominate vein. Patients with superior vena cava obstruction were supported by extracorporeal membrane oxygenation for a longer duration than controls. Nineteen patients with superior vena cava obstruction (86%) underwent transcatheter balloon angioplasty and/or stent implantation (median 7 days after diagnosis), which decreased the superior vena cava pressure and superior vena cava-to-right atrium pressure gradient and increased the superior vena cava diameter (all p < 0.001). There were no serious procedural adverse events. Six study patients died within 30 days of the diagnosis of superior vena cava obstruction (including three of nine with chylothorax), which did not differ from controls. During a median follow-up of 2.7 yrs, two additional patients died and nine underwent 14 superior vena cava reinterventions. Among neonates treated with extracorporeal membrane oxygenation, superior vena cava obstruction is associated with an increased risk of chylothorax. In neonates with chylothorax after extracorporeal membrane oxygenation, evaluation for superior vena cava obstruction may be warranted. Although mortality is high in this population, transcatheter treatment can relieve superior vena cava obstruction and facilitate symptomatic improvement.