Modified Blalock-Taussig Shunt Operation Research Articles

The Effects of the Mechanical Properties of Vascular Grafts and an Anisotropic Hyperelastic Aortic Model on Local Hemodynamics during Modified Blalock-Taussig Shunt Operation, Assessed Using FSI Simulation.

Cardiovascular surgery requires the use of state-of-the-art artificial materials. For example, microporous polytetrafluoroethylene grafts manufactured by Gore-Tex® are used for the treatment of cyanotic heart defects (i.e., modified Blalock–Taussig shunt). Significant mortality during this palliative operation has led surgeons to adopt mathematical models to eliminate complications by performing fluid–solid interaction (FSI) simulations. To proceed with FSI modeling, it is necessary to know either the mechanical properties of the aorta and graft or the rheological properties of blood. The properties of the aorta and blood can be found in the literature, but there are no data about the mechanical properties of Gore-Tex® grafts. Experimental studies were carried out on the mechanical properties vascular grafts adopted for modified pediatric Blalock–Taussig shunts. Parameters of two models (the five-parameter Mooney–Rivlin model and the three-parameter Yeoh model) were determined by uniaxial experimental curve fitting. The obtained data were used for patient-specific FSI modeling of local blood flow in the “aorta-modified Blalock–Taussig shunt–pulmonary artery” system in three different shunt locations: central, right, and left. The anisotropic model of the aortic material showed higher stress values at the peak moment of systole, which may be a key factor determining the strength characteristics of the aorta and pulmonary artery. Additionally, this mechanical parameter is important when installing a central shunt, since it is in the area of the central anastomosis that an increase in stress on the aortic wall is observed. According to computations, the anisotropic model shows smaller values for the displacements of both the aorta and the shunt, which in turn may affect the success of preoperative predictions. Thus, it can be concluded that the anisotropic properties of the aorta play an important role in preoperative modeling.

Application of a mathematical model of systemic circulation for determination of blood flow parameters after modified blalock-taussig shunt operation in newborns

The problem of infant mortality in children with congenital heart disease is relevant both in Russia and throughout the world. One of the surgical methods for treating congenital heart diseases is bypass surgery using a modified Blalock – Taussig shunt. This operation is used in newborns and infants with congenital heart defects to increase pulmonary blood flow in order to increase the oxygen content in the blood, bring it back to normal and ensure uniform development of the right and left lungs. To improve the efficiency of decision making in surgical practice, the results of a personalized blood flow model can be used. This article presents a conceptual 0D scheme of systemic blood flow, where aorta and pulmonary artery are replaced by a 3D model. A mathematical 0D formulation of the problem of modeling systemic circulation has been developed, which contains 13 differential equations and several dozen algebraic relations. The model parameters in the first approximation are obtained based on real survey data and analysis of literature sources. A numerical implementation is carried out to solve the model relations using the Runge-Kutta methods of 4 orders of magnitude. The simulation results allow to determine the parameters of pressure and blood flow from time to time in any part of the design scheme, as well as the blood flow passing through the shunt, depending on its resistance. Possible ways of further development of the model are to develop an iterative algorithm for coupling 0D and 3D models, develop an algorithm for identifying model parameters based on individual measurements, describe oxygen exchange processes, and formulate criteria based on the obtained hemodynamic characteristics for making decisions in surgical practice.

Risk factors for mbt shunt thrombosis

Abstract Background The modified Blalock–Taussig shunt (MBTS) is the most commonly created systemic–pulmonary shunt in children with cyanotic heart disease, it continues to be a subject of academic interest, because of persistent risks associated with this simple-looking procedure. The purpose of this study was to determine the risk factors associated with the occurrence of thrombosis complicating modified blalock-taussig shunt. Method Clinical and perioperative variables were examined through prospective study of 45patients who had undergone MBTS construction in one-year period. Results male gender was predominant (33 cases) and females were 12 cases, mean age was 9.58 ±7.45months at the time of surgery. The most common cardiac anomaly was TOF (44.4%), mean duration of post-operative mechanical ventilation was 3.9±4.5 days, mean ICU stay was 5.9±4.5 days and the mean hospital stay was 10±5.4 days, shunt failure rate was 9/45(20%), the analysis revealed that shunt failure is significantly increased in patients aged 7 months at surgery (mean was7.1±6.8 months) (p-value 0.04),failure was more common if the pulmonary arterial diameter was4mm or less(p-value =0,06),shunt failure is significantly related to thoracotomy approach in which 6/45 (13.3%) have been subjected to this approach (p-value=0.02),shunt occlusion was significantly related to use of small shunt size 3.5mm encountered in6/45(13.3%), 4mm in 1/45(2.2%) and 5mm in2/45(4.4%) (p-value=0.02) ,failure rate was (15.55%)7/45 in patients who are deprived from heparin during operation while it was (4.4%)2/45 in heparinized patients (p-value=0.01), use of inotropes and nor-adrenalin are significantly related to shunt occlusion but on expense of poor hemodynamic state in which 6 patients out of 9 occluded shunt patients received inotropes while all occluded shunt cases received nor-adrenalin (p-value =0.02), we didn’t find any relation of other variables (sex, gender, pre-operative coagulation profile and low oxygen saturation) with development of post- operative shunt thrombosis (p-value>0.05),The overall hospital mortality rate was 35.5% (16/45) The rate was significantly higher in patients aged below 10 months (mean 4.3±6.8 months)(p = 0.004),weighing 7kg or less(mean 5.3± 2.5kg) (p = 0.02),low oxygen saturation prior to operation was significantly related to post-operative mortality (mean 53.7±11.9%) while was (69.8 ± 14.5%) in discharged group (p = 0.002), all dead cases(16/16,100%) received nor adrenaline during and after operation that contributed to poor hemodynamic state while 12cases out 16 (75%) received inotropes due to the same reason, the mean Pulmonary artery size was (3.8±1.2mm) in dead cases and(4.3±1.4mm) in discharged cases(p > 0.05), Shunt size was not related to mortality ,mean size was(3.9±0.4mm),( 4.1±0.5mm)in dead and discharged cases respectively(p > 0.05),sternotomy approach was carried out on 29/45 patients9 (56.25%)cases are died and 20(68.96%) discharged while 16/45 underwent thoracotomy 7 of them died (15.55%)and 9(31.03%) discharged(p > 0.05),mortality is encountered in non-heparinized (22/45)cases versus heparinized(23/45) during and after operation in which 10/16 (62.5%) didn’t receive heparin during and after operation while 6/16(37.5%) are heparinized , all patients later on turned to low dose oral aspirin Whether they heparinized or not. Conclusion It is important to assess risk factors associated with the MBTS operation. The results of our study suggest that MBTS thrombosis is associated with many risk factors includes age and presence of small shunt size, small pulmonary artery size, intra. and early post-operative anticoagulation can help to reduce the risk of shunt thrombosis, as well as thoracotomy surgical approach that influence shunt patency. Also, mortality is significantly associated with young age less than 5 months of age and low body weight around 5 kg and oxygen desaturation<60% prior to operation.

Risk Factors for Thrombosis, Overshunting and Death in Infants after Modified Blalock-Taussig Shunt.

The Modified Blalock-Taussig shunt procedure can provide increased flow of blood to the lungs for babies born with certain congenital heart defects. We evaluated 44 subjects under 2 years of age who had a Modified Blalock-Taussig shunt (MBTS) procedure performed from 2009-2013, to investigate risk factors for thrombosis, overshunting and death. The study subjects included in our investigation were severely cyanotic newborns with pulmonary stenosis or atresia and duct dependent circulation, and infants having Tetralogy of Fallot with small pulmonary arteries who underwent a MBTS procedure in our facility from 2009-2013. We duly noted patient preoperative characteristics such as hemoglobin, hematocrit, mean platelet volume, prothrombin time and partial thromboplastin time. Our study investigated the risk factors for post-operative overcirculation, thrombosis and death. The age and weight of patients in our study at the time of procedure ranged from 1 day to 20 months old (median 12 days), and 2.4 kg to 12 kg (mean 4.6 kg), respectively. A total of 8 patients died following surgery, and. 4 (9.1%) had shunt thrombosis, of which one died during shunt revision. Partial thromboplastin time was 28.7 seconds in patients with thrombosis, and 35 in all other patients (p = 0.04). Overcirculation was detected in 5 patients; shunt size/body weight was 1.25 in patients who had overcirculation, and 1.06 in all other patients. It is important to assess risk factors associated with the MBTS operation. The results of our study suggest that a preoperative low aPTT value may be an indicator for thrombosis in infants who have undergone MBTS surgery.

Tetralogy of Fallot with unilateral absent pulmonary artery

Tetralogy of Fallot is a common congenital cardiac malformation. A rare subgroup includes unilateral absence of the pulmonary artery, either the left or the right main branch. The literature lacks an established treatment for these cases, and surgical options carry certain mortality and morbidity. There were five patients who had single pulmonary artery and received surgical treatment among the 126 patients with the diagnosis of Tetralogy of Fallot, who were admitted to our institution between July, 2010 and November, 2011. All the patients were male. Ages ranged between 12 months and 8 years. The mean body mass index was 17.1 plus or minus 3.4 kilograms per square metre. Pulmonary artery Nakata index, Nakata index Z-score, and the McGoon index were used for the quantitative assessment of the pulmonary artery and to determine the surgical strategy. Urgent modified Blalock-Taussig shunt operations were performed in two patients with very low oxygen saturation and haemodynamic instability. These patients are scheduled for corrective procedures on an elective basis. There was one patient who received an elective shunt procedure; however, the post-operative course was complicated with the overflow phenomenon and the patient underwent total correction with a check-valved patch used to close the ventricular septal defect. The patient required extracorporeal membrane oxygenator support in the post-operative period. There were two patients who underwent total correction of the pathology uneventfully. Mortality did not occur. Mean durations of hospital stay and follow-up were 14 plus or minus 13.4 days and 184.5 plus or minus 89.3 days, respectively. Our modest series with Tetralogy of Fallot with unilateral absent pulmonary artery indicates the feasibility of surgical correction in patients with appropriate unilateral pulmonary artery size and palliative procedures when the pulmonary artery size is smaller than that predicted for the age. Multi-centre long-term data of larger series are warranted in order to establish a treatment protocol.

Risk factors for acute shunt blockage in children after modified Blalock-Taussig shunt operations

Factors relating to acute blockage of modified Blalock-Taussig shunts (MBTS) have not been well described in the literature. Our aim was to determine the outcomes in patients early after undergoing MBTS operations and to identify potential risk factors for acute shunt blockage in the early postoperative period. A retrospective study was performed in a tertiary referral congenital cardiac unit. All children who underwent first shunt insertion for cyanotic congenital heart disease during the study period from 2002 to 2006 were included. Seventy-six children underwent first shunt insertion with a median age of 37 days (range 2 days-8 years) and median weight of 3.75 kg (range 2.1-17.2 kg). The shunt sizes varied from 3 to 6 mm. The rate of acute shunt blockage was 11.8% (9/76), all within the first 24 h. There were 3 early deaths (3.9%), none of which were associated with shunt blockage. The main risk factors for blockage were preoperative high hemoglobin, weight less than 3 kg, and duct patency on echocardiogram after surgery. This study identifies that high preoperative hemoglobin, a weight less than 3 kg at operation, and the presence of a patent duct are statistically significant risk factors for shunt blockage in the acute postoperative period. Further work is needed to determine if reduction in preoperative hemoglobin concentration and attempts to reduce postoperative ductal patency may alter the outcome.

An infected pseudoaneurysm following a modified Blalock-Taussig shunt

A two-month-old male infant with tetralogy of Fallot underwent a right-sided modified Blalock-Taussig shunt using a 4 mm expanded polytetrafluoroethylene graft through a right thoracotomy. Five months later, the patient developed otitis media, followed by repeated relapses of pneumonia and fever of unknown origin. Multidetector-row computed tomography and angiography, performed at 12 months of age, revealed a pseudoaneurysm of the subclavian artery at the insertion of the modified Blalock-Taussig shunt. After 20 days of antibiotic therapy, the pseudoaneurysm and infected graft were successfully resected through a median sternotomy approach. This report describes the treatment strategy of this rare but potentially fatal complication after a modified Blalock-Taussig shunt operation.

Right ventricle-dependent coronary circulation demonstrated with 64-slice computed tomography

A 12-year-old female patient, who had emergency left modified Blalock–Taussig shunt operation during neonate and a total cavo-pulmonary shunt operation performed at the age of 5 years following a diagnosis of pulmonary atresia with intact ventricular septum (PAIVS), was under regular follow-up. At her last visit, she was admitted with exercised-induced anginal symptoms. …

Effects of Hemodilution on Outcome After Modified Blalock-Taussig Shunt Operation in Children With Cyanotic Congenital Heart Disease

Cyanotic congenital heart diseases (CCHD) with secondary polycythemia and hyperviscosity state are associated with a reduction in blood flow, stagnation of blood, and thrombosis. Sufficient hemodilution in cyanotic children results in higher blood flow and significant reductions in perioperative blood loss. The aim of this study was to investigate similar beneficial effects of hemodilution in preventing shunt thrombosis and decreasing postoperative blood loss after modified Blalock-Taussig (BT) shunt operations in children with CCHD. Prospective, randomized, controlled study. Cardiac center of a tertiary care, referral hospital. Fifty children with CCHD undergoing modified BT shunt operations. Patients were randomized into 2 groups. The study group (n = 25) received a calculated amount of 6% hydroxyethyl starch (200/0.5) solution to bring down the hematocrit to 45%, whereas the control group (n = 25) received 5% dextrose solution intraoperatively as per the authors' normal protocol. Effects of hemodilution on shunt patency, postoperative blood loss at 24 hours, blood and blood component usage, and re-exploration rates were recorded. The shunt patency rate was significantly higher in the study group than the control group (100% and 84%, respectively, p < 0.05). Postoperative blood loss at 24 hours was significantly higher in the control group than in the study group (14.4 +/- 11.8 mL/kg and 9.9 +/- 8 mL/kg, respectively, p < 0.05). The number of recipients and the amount of blood and blood components administered were higher in the control group, but they were not statistically significant. The re-exploration rate (for excessive postoperative chest-tube drainage) was significantly higher in the control group than the study group (12% and 0%, respectively, p < 0.05). Hemodilution in CCHD patients undergoing modified BT shunt surgery has beneficial effects including improved shunt patency because of higher blood flow through the graft and less postoperative blood loss, which may be attributed to the lower viscosity produced by hemodilution.

The value of end-tidal carbon dioxide monitoring during systemic-to-pulmonary artery shunt insertion in cyanotic children

Objective To investigate the relationship between end-tidal carbon dioxide levels and augmentation of pulmonary blood flow achieved by insertion of systemic-pulmonary shunts. Design Prospective clinical study. Settings University hospital. Participants Nineteen cyanotic children with tetralogy of Fallot. Interventions Modified Blalock-Taussig shunt operations were performed on the left side in 14 patients and on the right side in 5 patients. Measurements and Main Results End-tidal carbon dioxide tension was recorded, and an arterial blood gas sample was obtained simultaneously after thoracotomy (T0) and after completion of systemic-pulmonary shunt (T1). End-tidal carbon dioxide tension was significantly higher ( p < 0.01), and arterial to end-tidal carbon dioxide tension difference was significantly lower ( p < 0.01) at T1 when compared with T0. The increase in end-tidal carbon dioxide showed a statistically significant correlation with the response of arterial oxygen saturation ( r = 0.61, p < 0.01). The fall in arterial to end-tidal carbon dioxide tension difference correlated inversely with the change of oxygen saturation ( r = −0.81, p < 0.0001). Conclusion It is concluded that end-tidal carbon dioxide tension alterations offer an alternative intraoperative tool to monitor pulmonary blood flow during modified Blalock-Taussig shunt procedures.

Pulmonary ventricular outflow reconstruction with a size-reduced cryopreserved pulmonary valve allograft: mid-term follow-up.

Surgical reduction of pulmonary allografts is being performed because of the shortage of allografts of suitable size for pediatric use. However, the outcome of size-reduced pulmonary allografts for pulmonary conduits is unknown. In the present study, cryopreserved pulmonary allografts harvested from adults at the time of kidney donation were size-reduced and used in 4 children, 2 with pulmonary atresia and ventricular septal defect and 2 with atrioventricular discordance, pulmonary atresia and ventricular septal defect. They all had undergone right and/or left modified Blalock-Taussig shunt operations with a 5-mm synthetic graft prior to the reparative operations. They underwent definitive repair with a size-reduced cryopreserved pulmonary allograft valved conduit and were followed up for 2-5 years. Postoperative echocardiographic and cineangiographic assessments revealed excellent function of the pulmonary bicuspidalized valves with a minimal pressure gradient and no, or only trivial, regurgitation. Although the long-term result of a cryopreserved bicuspid pulmonary valved conduit remains unknown, the remodeled bicuspid pulmonary allograft conduits showed excellent hemodynamic characteristics in mid-term follow-up and appear to be a reasonable alternative to other types of conduits when an appropriate-sized allograft is not available.

術前および術中に高度低酸素血症を呈したＢｌａｌｏｃｋ‐Ｔａｕｓｓｉｇ短絡術

術前および術中に高度低酸素血症を呈したＢｌａｌｏｃｋ‐Ｔａｕｓｓｉｇ短絡術

Modified Blalock-Taussig shunt following long-term administration of prostaglandin E1 for ductus-dependent neonates with cyanotic congenital heart disease

In the treatment of cyanotic heart diseases in neonates who are ductus dependent, the small size of the pulmonary artery and/or subclavian artery often precludes construction of a sufficient Blalock-Taussig shunt. To avoid an emergency operation and to obtain pulmonary and subclavian arteries of adequate size (3 mm), a low dose of prostaglandin E1 was given to 16 neonates for a mean of 47 days (range 26 to 65 days), and a modified Blalock-Taussig shunt operation was performed in neonates whose mean age was 50 days. The pulmonary artery grew significantly (mean 4.5 mm) and the mean diameter of the subclavian artery was 3 mm, which was large enough for a good shunt at the time of operation. There were two late deaths and one operative death. All surviving patients shunts at the mean follow-up period of 22 months. The shunt was constructed on the same side as the ductus arteriosus so that the ductus could be ligated at the same operation in selected cases; the ductus may not close after discontinuation of prostaglandin E1 infusion and may cause uncontrollable congestive heart failure because of excessive pulmonary blood flow, particularly in patients with a univentricular heart. The ductus, dissected in nine patients, was enlarged and elongated in all and was ligated in four patients without complication.

Modified blalock-taussig shunt operation without cardiac catheterization: Two-dimensional echocardiographic preoperative assessment in cyanotic infants

Between May 1981 and December 1983, 25 infants with cyanotic congenital heart defects underwent 26 Blalock-Taussig shunt operations without cardiac catheterization and angiocardiography. In these infants, the diagnosis was established by 2-dimensional echocardiography (2-D echo) supplemented with clinical findings, chest x-ray and electrocardiography. The right and left pulmonary artery measurements, a prerequisite for a shunt operation, determined by 2-D echo were compared with those at surgery and had an excellent correlation (r = 0.94). No infant died as a consequence of an early shunt failure, and only 1 died of postoperative pyothorax. In conclusion, 2-D echo may eliminate the need for invasive investigation in selected patients undergoing the Blalock-Taussig anastomosis.