Systemic Venous Blood Flow Research Articles

The Fontan Circulation: From Ideal to Failing Hemodynamics and Drug Therapies for Optimization.

Fontan palliation results in a hemodynamically complex circulation with multisystem consequences, which in the long term adversely affect many body processes. Systemic venous hypertension, nonpulsatilelow-shear pulmonary blood flow, and low cardiac output are the 3 main characteristics of a Fontan circulation, leading to unavoidableslowly progressive failure. An appreciation of how the hemodynamics of a Fontan circulation change with time and relate to the various modes of Fontan circulatory failure is important. Accurate hemodynamic assessment aid this understanding and may permit early identification of potentially treatable drivers of decline. While no evidence-based or guideline-directed pharmacologic management strategy has been established in Fontan patients, understanding the hemodynamics of Fontan circulation failure will assist in the rational selection of potentially helpful drug therapies for individual patients. In this review, we present hemodynamic concepts of the optimal Fontan physiology and Fontan circulatory failure, review practical aspects of invasive hemodynamic assessment, and discuss the role of drug therapies in increasing systemic venous blood flow return and decreasing ventricular filling pressures in Fontan circulation. Oftencomplementary to catheter-based or surgical interventions, pharmacologicmanagement aims at preserving patency of the circuit, adequate systolic and diastolic ventricular function, atrioventricular valve function, an unobstructed ventricular outflow tract, and pulmonary vascular integrity in order to maintain an acceptable cardiac output.

T1 mapping to assess hepatic and myocardial characteristics in children with single ventricle circulation

Abstract Background Single ventricle (SV) palliation, culminating with the Fontan operation, results in passive systemic venous blood flow directly to the pulmonary circulation. Resulting inevitable hepatic venous congestion can lead to hepatic fibrosis. Previous studies suggest hepatic changes can occur prior to the Fontan completion. Besides fibrotic myocardial remodeling may lead to systolic and diastolic ventricular dysfunction, transmitting back pressure to the pulmonary system. Purpose To compare quantitative T1 cardiovascular magnetic resonance (CMR) imaging of the myocardium and liver between SV patients and controls, as a potential measure of myocardial and hepatic fibrosis. Methods Retrospective review of 16 SV patients with dominant single left ventricle (SLV, n=6) or single right ventricle (SRV, n=10), at various stages of palliation (pre-Glenn=6, post-Glenn=3, Fontan=7) underwent CMR with myocardial T1 mapping with the liver also in the plane of view. Biventricular patients found to have structurally normal hearts and normal cardiac function on CMR were used as controls (n=21). Native T1 times using a modified Look-Locker inversion recovery (MOLLI) approach in free-wall of the dominant ventricle at a mid-ventricular short axis in SV and the ventricular septum in controls and, a region of interest in the liver (avoiding any vessels) were measured in all patients. Median and inter-quartile ranges of continuous variables were compared between SV and controls using the Mann-Whitney U test. Results As compared to controls SV patients were (1) significantly younger, (2) had lower ejection fraction, (3) higher median myocardial T1, and (4) higher median liver T1. Also, there was no difference between SLV vs. SRV median myocardial T1 (1056 vs. 1065ms, p=0.43) or liver T1 (678 vs. 729ms, p=0.30) Conclusion Despite younger age, findings of increased myocardial T1 may suggest an element of myocardial fibrosis responsible for the ventricular dysfunction in this population, and that raised liver T1 may be an earlier marker of liver fibrosis, which warrants further study. Funding Acknowledgement Type of funding source: None

ABERNATHY MALFORMATIONS IN CHILDREN. EXPERIENCE IN ENDOVASCULAR AND SURGICAL TREATMENT

Introduction. Congenital portosystemic shunt (SPSS) is a congenital anomaly of the portal system. Blood from the portal system, bypassing the hepatic bloodstream, enters the systemic venous bloodflow. Clinical manifestations are not specific. SPSS can be suspected in patients with arterial hypoxemia and intrapulmonary vascular dilatation, in patients with foci of nodular hyperplasia in the liver, with carbohydrate metabolism disorders in the form of hyperinsulinemia and hypoglycemia, hepatic encephalopathy, hyperammoniemia. Material and methods. Nine patients ( five boys and four girls) , aged 7.7 ± 5.2, were treated in our clinic. All patients had hyperammonemia before surgery 124.5 ± 24.7 μmol / L. Five patients had endovascular SPSS occlusion. Four patients had open SPSS ligation. Results. An immediate technical success was achieved in all patients. There were no complications after endovascular treatment. There was one relapse which required a repeated endovascular occlusion. After endovascular occlusion, the length of hospital stay was shorter, postoperative period was much easier; there were no serious complications compared with the open SPSS ligation. Blood ammonia returned to normal levels in eight patients. In one patient who had multiple shunts and incomplete occlusion, blood ammonia level decreased by twice, up to 82 μmol / L. Conclusion. If SPSS is revealed, a surgical intervention is recommended to separate the portal and systemic venous blood flow. In the surgical treatment for SPSS, X-ray surgical endovascular occlusion is more preferable. If this technique was not possible, surgeons performed open surgical intervention.

False Positive Perfusion/Ventilation SPECT Study for Pulmonary Embolism in a Patient with Fontan Circulation.

Fontan circulation is the consequence of an operation that results in the flow of systemic venous blood to the lungs without passing through a ventricle. An 18-year old man with a history of congenital heart disease surgically treated with Fontan circulation, presented with pleuritic chest pain and a raised D-dimer level. Perfusion/ventilation SPECT was performed to exclude the possibility of pulmonary embolism (PE) that showed unilateral reduced perfusion of the left lung with a mismatched right upper lobe defect, suspicious of PE. However, subsequent computed tomography pulmonary angiogram and clinical follow-up excluded the possibility of PE, emphasizing the need for knowledge of potential pitfalls to avoid false interpretations. Given the fact that adult congenital heart disease population is growing, with the majority having single ventricle/Fontan circulation and being at risk for thromboembolic disease, knowledge of the perfusion pattern pitfalls is important to avoid false interpretation and preventing the misdiagnosis of PE in patients with Fontan physiology.

Interventional Catheterization after Total Cavopulmonary Connection: Experience in 68 Patients

Total cavopulmonary connection (TCPC) is performed in patients having a single ventricle to allow the passive flow of systemic venous blood to the lungs. Interventional catheterization is needed to treat residual defects or complications. We discuss our results concerning 68 patients who had had TCPC from January 1995 to December 2010. Initial and follow-up catheterization data were reviewed retrospectively. Mid-term results were evaluated by means of angiography and/or CT scan. Mean age at TCPC was 5 years (2.5-18); mean interval between TCPC and catheterization was 5.6 years (1.5-15). Sixty-nine catheterizations were performed in 53 patients. Eleven patients (21%) had low venous pressure, did not display a right-to-left shunt, and did not need any intervention. Fifteen patients (28%) had low venous pressure and only needed the closure of the fenestration. The remaining 27 patients (51%) needed the following interventions: embolization of venous vessels prompting right-to-left shunt (n = 15), stenting or reconnection of pulmonary arteries (n = 5), stenting or recanalization of systemic veins (n = 11), other procedures (n = 5). In 3 patients the fenestration could not be closed due to high venous pressure. After the interventions oxygen saturation increased from 90.5%± 4.8% to 94.7% ± 3.6% (P = 0.002). Our data show that 49% of patients with TCPC are in good condition late after surgery. However, half of these patients continue to need interventions generally aimed at suppressing stenoses at various levels of TCPC or at occluding vessels prompting right-to-left shunt. This population should enter a multicenter program aimed at identifying patients at risk.

The Fontan Procedure: Anatomy, Complications, and Manifestations of Failure

The Fontan procedure refers to any operation that results in the flow of systemic venous blood to the lungs without passing through a ventricle. It is performed to treat several complex congenital heart abnormalities including tricuspid atresia, pulmonary atresia with intact ventricular septum, hypoplastic left heart syndrome, and double-inlet ventricle. The original Fontan procedure included direct anastomosis of the right atrium to the main pulmonary artery; however, multiple modifications have been employed. Creation of Fontan circulation is palliative in nature, with good results in patients with ideal hemodynamics and substantial morbidity and mortality in those with poor hemodynamics. Complications of Fontan circulation include exercise intolerance, ventricular failure, right atrium dilatation and arrhythmia, systemic and hepatic venous hypertension, portal hypertension, coagulopathy, pulmonary arteriovenous malformation, venovenous shunts, and lymphatic dysfunction (eg, ascites, edema, effusion, protein-losing enteropathy, and plastic bronchitis). Magnetic resonance imaging is best for postoperative evaluation of patients who underwent the Fontan procedure, and cardiac transplantation remains the only definitive treatment for those with failing Fontan circulation.

Cor triatriatum dexter: rare case of neonatal cyanosis

Cor triatriatum dexter is a very rare cardiac anomaly in which a membrane divides the right atrium into two chambers [1]. Depending on the degree of right atrial obstruction, the clinical sign of these anatomic variations may be neonatal cyanosis necessitating urgent surgical intervention; some patients are asymptomatic and reach adulthood without therapy [2]. Echocardiographic diagnosis can be difficult [1, 3]. We report on a newborn referred for severe neonatal cyanosis with the diagnosis of cor triatriatum dexter with obstruction of the right ventricular inflow. Surgical intervention led to complete recovery. The male neonate was spontaneously born at 41 weeks of gestation after an uncomplicated pregnancy with a birth weight of 3550 g. After the initial uncomplicated situation, central cyanosis with a transcutaneous oxygen saturation of 85% led to admission to the neonatal intensive care unit. The echocardiographic evaluation revealed a large, floating membrane within the right atrium connected to the eustachian and thebesian valve at the site of the connection to the inferior vena cava and the atrial septum, respectively, without hemodynamic compromise, but with right-to-left shunting through the secundum atrial septal defect. The membrane formed a ‘‘windsock’’ especially in diastole when it was bulging into the right ventricular inflow tract. Laterally, there was an opening within the membrane permitting turbulent blood flow from the right atrium to the right ventricle (mean pressure gradient 2 mmHg). Surgery was performed then at the age of 4 weeks in a stable patient. After an oblique right atrial opening the membrane was exposed with its attachments to the eustachian valve, thebesian valve, and laterally to the crista terminalis. There were no attachments to the interatrial septum. The membrane could be invaginated completely into the right ventricle, creating an inflow obstruction. The tricuspid valve was normal. The membrane was completely excised and the atrial septal defect (secundum type) was closed directly. The postoperative course was uneventful and the patient was extubated on the day of surgery and discharged home on the 13th day after surgery. Remnants of the right valve of the embryonic sinus venosus are not uncommon and are recognized as the normal eustachian and thebesian valves [3]. In a series of 300 consecutively autopsied patients, almost 70% of the specimens presented such valves [4]. Clinical manifestation of cor triatriatum dexter includes a wide spectrum. It can be completely asymptomatic and detected incidentally or at necropsy. During fetal life, marked nuchal edema may be associated with significant obstruction of the right ventricular inflow [5]. Also, significant obstruction may lead to the underdevelopment of the right heart structures: tricuspid valve abnormalities including Ebstein anomaly, hypoplastic right ventricle and pulmonary stenosis or atresia. After birth, neonatal cyanosis may appear due to the systemic venous blood flow directed toward the atrial septum and consecutively right-to-left shunting [1]. In the M. Loeff R. Kozlik-Feldmann H. Netz R. D. Pozza (&) Department of Pediatric Cardiology, Klinikum Groshadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany e-mail: Robert.DallaPozza@med.uni-muenchen.de

Uncommon Findings in Tc-99m Macroaggregated Albumin Venography in Distal Inferior Vena Cava Obstruction

In inferior vena cava obstruction, collateral pathways allow the retrograde flow of venous blood from the lower part of the body. Unanticipated findings of Tc-99m macroaggregated albumin (MAA) venography in 3 cases with deep vein thrombosis of the legs and infrarenal inferior vena cava obstruction are presented. Apart from extensive collateral networks in the legs and the abdomen, the visualization of the liver indicates a shunt of the systemic venous blood flow through the paraumbilical vein to the portal vein. The visualization of lumbar and thoracic vertebrae is attributed to venous flow through a dilated vertebral plexus, resulting in trapping of tracer in the neighboring bone marrow.

Liver and Vertebral Uptake of Tc-99m Macroaggregated Albumin (MAA)

An unusual phenomenon during lung scintigraphy is presented. Besides visualization of the lungs, accumulation of Tc-99m macroaggregated albumin (MAA) was seen in a small part of the liver and in and around several thoracic vertebrae. Contrast-enhanced radiographic computed tomography revealed extensive collateral pathways, which were caused by a partially obstructed superior vena cava. Shunting of systemic venous blood flow through chest wall veins to the portal system was responsible for accumulation of MAA in the liver. Retrograde blood flow through dilated thoracic vertebral veins resulted in visualization of the bone marrow.

Individualized total cavopulmonary connection technique for patients with Asplenia syndrome

Background. Outcomes after univentricular repair for patients with asplenia syndrome remain unsatisfactory, not only because of clinical difficulties in patient selection, but also secondary to technical difficulties in the separation of the systemic and pulmonary circulations, particularly with the rerouting technique for the inferior systemic veins.Methods. Between February 1995 and May 2000, a total of 14 consecutive patients with asplenia syndrome underwent bidirectional cavopulmonary connection with obliteration of additional pulmonary blood flow, followed by a total cavopulmonary connection. The rerouting technique for inferior systemic venous blood flow was individualized to optimize laminar nonturbulent flow characteristics in the pathway, and to minimize prosthetic load and suture load on the atrial wall. The lateral tunnel or tube conduit technique was used in an extraatrial, intra-extraatrial, or intraatrial fashion. No fenestration was applied.Results. No hospital mortality was observed. Systemic venous flow was evaluated using magnetic resonance angiography, revealing no signs of obstruction, turbulence, or stasis either in or near the reconstructed pathways, irrespective of the rerouting technique. Postoperative catheterization revealed favorable hemodynamics including an inferior vena cava pressure of 13 ± 2 mm Hg and arterial oxygen saturation of 93.4% ± 3.5% at room air. All patients have remained free of symptoms, although 1 patient died of acute septic complications 3.5 years after the procedure.Conclusions. The complexity of cardiac anomalies in asplenia syndrome warrants individualization of the total cavopulmonary connection technique used in reconstruction of the inferior systemic venous pathway. Optimizing flow characteristics in the pathway should be a priority. A staging approach allows suitable selection of candidates for univentricular repair.

WS06: Fetal echocardiography WS06‐01Human fetal cardiac function during the first trimester of pregnancy

IntroductionThe hypothesis was tested whether the improvement in the human fetal cardiac diastolic and systolic functions are associated with changes in the cardiac volume blood flow, inflow blood velocity waveform characteristics, systemic venous blood flow parameters, umbilical artery velocimetry and fetal nuchal translucency. By a longitudinal study protocol the inflow and outflow blood velocity waveforms were obtained in 16 uncomplicated pregnancies at 6, 7, 8, 9 and 10 weeks.ResultsThe proportion of isovolumetric relaxation time decreased and the proportions of filling and ejection times of the cardiac cycle increased significantly from 6 to 7 weeks. The proportion of isovolumetric contraction decreased between 8 and 9 weeks. Every inflow waveform was monophasic before 9 weeks but it was biphasic in all cases at 10 weeks. Mean velocity of inflow and outflow increased between 6 and 7 weeks and Vmean of inflow increased further after 8 weeks. At 9 and 10 weeks, atrioventriculu valve recurgitation (AVVR) was present in 4 and 7 fetuses, respectively. Nuchal translucency was greater in fetuses with AVVR present at 10 weeks compared with non‐AVVR cases.ConclusionImprovement in the diastolic function of fetal heart between 6 and 7 weeks is accompanied by simultaneous increase in the mean velocities across inflow and outflow tracts. Appearance of biphasic inflow pattern is associated with significant change in systolic function between 8 and 9 weeks. AVVR is a common finding at 10 weeks of gestation.

Pulsed Doppler echocardiographic assessment of patterns of venous flow after the modified Fontan operation: potential clinical implications.

To assess the effect of a modified Fontan operation on systemic venous blood flow and the hepatic circulation, we compared 11 patients having an atriopulmonary connection and 35 with total cavopulmonary anastomosis. The Doppler echocardiographic study of the caval venous, hepatic venous and portal venous flow was performed so as to calculate the pulsatility ratio and the variation of flow with respiration. All patients had undergone cardiac catheterization. In addition, we included specific laboratory investigations to assess function of various organs. Significantly lower maximum velocities of flow at inspiration (0.31+/-0.12 m/sec vs 0.45+/-0.14 m/sec) and expiration (0.23+/-0.09 m/sec vs 0.32+/-0.11 m/sec), less pulsatility (0.43 vs 0.16) and a lower ratio of systolic to diastolic velocity (1.22 vs 1.85) were found in the patients having a cavopulmonary as compared to an atriopulmonary anastomosis. Peak velocities of hepatic venous flow during inspiration and expiration were significantly lower in those with a cavopulmonary anastomosis (p = 0.001 and p < 0.001, respectively). In these patients, forward flow was extremely dependent on respiration, with decrease or cessation of antegrade flow during expiration in 22 patients. The velocity of portal venous flow was also significantly lower in these patients, although the pulsatility ratio did not differ significantly between the groups (0.5+/-0.21 and 0.57+/-0.23, respectively). The ratio of inspiratory and expiratory velocities showed no significant difference between the groups, nor was there any correlation between the pulsatility ratio of the venous vessels or the ratio of peak flow velocities during expiration and the mean systemic venous/right atrial pressure on postoperative cardiac catheterization. Hypoproteinemia was found in 8 patients after total cavopulmonary anastomosis; 9 of 10 patients with protein C deficiency belonged to this group. The dependence of hepatic venous flow on respiration in the presence of a chronically elevated systemic venous pressure in patients after the total cavopulmonary anastomosis may influence hepatic function in the postoperative period.

Formation of thrombus in the residual pulmonary trunk and regurgitation of the pulmonary valve after total cavopulmonary connection

AbstractThe procedure of total cavopulmonary connexion includes trans-section and closure of the pulmonary trunk, the systemic venous blood flow being directed to the pulmonary vascular bed by an anastomosis of the superior caval vein with the right pulmonary artery. Following this procedure, there remains a small residual pulmonary trunk. The purpose of our study was to obtain information about the fate of this residual trunk and its contained pulmonary valve. Using transthoracic echocardiography, we examined 29 patients (mean age 7 years 4 months) after a total cavopulmonary connexion (mean interval 17 months). We were able to obtain adequate visualization of the pulmonary valve and the pulmonary trunk in 23 of the patients. Pulmonary regurgitation was demonstrated by colour Doppler echocardiography in 13 pts (57%). Formation of thrombus in the residual pulmonary trunk was detected in one patient (4%) 6 months after the operation. One cerebrovascular embolic event occurred in a patient who had pulmonary regurgitation without formation of thrombus in the residual trunk 3 months after the total cavopulmonary connexion. Our findings show that pulmonary regurgitation is frequently present in patients after total cavopulmonary connexion. Although formation of thrombus in the residual pulmonary trunk seems to be less common, we recommend surgical closure of the pulmonary valve during this procedure so as to exclude the residual pulmonary trunk as a possible source of systemic emboli.