Source Of Pulmonary Blood Flow Research Articles

Simulations reveal adverse hemodynamics in patients with multiple systemic to pulmonary shunts.

For newborns diagnosed with pulmonary atresia or severe pulmonary stenosis leading to insufficient pulmonary blood flow, cyanosis can be mitigated with placement of a modified Blalock-Taussig shunt (MBTS) between the innominate and pulmonary arteries. In some clinical scenarios, patients receive two systemic-to-pulmonary connections, either by leaving the patent ductus arteriosus (PDA) open or by adding an additional central shunt (CS) in conjunction with the MBTS. This practice has been motivated by the thinking that an additional source of pulmonary blood flow could beneficially increase pulmonary flow and provide the security of an alternate pathway in case of thrombosis. However, there have been clinical reports of premature shunt occlusion when more than one shunt is employed, leading to speculation that multiple shunts may in fact lead to unfavorable hemodynamics and increased mortality. In this study, we hypothesize that multiple shunts may lead to undesirable flow competition, resulting in increased residence time (RT) and elevated risk of thrombosis, as well as pulmonary overcirculation. Computational fluid dynamics-based multiscale simulations were performed to compare a range of shunt configurations and systematically quantify flow competition, pulmonary circulation, and other clinically relevant parameters. In total, 23 cases were evaluated by systematically changing the PDA/CS diameter, pulmonary vascular resistance (PVR), and MBTS position and compared by quantifying oxygen delivery (OD) to the systemic and coronary beds, wall shear stress (WSS), oscillatory shear index (OSI), WSS gradient (WSSG), and RT in the pulmonary artery (PA), and MBTS. Results showed that smaller PDA/CS diameters can lead to flow conditions consistent with increased thrombus formation due to flow competition in the PA, and larger PDA/CS diameters can lead to insufficient OD due to pulmonary hyperfusion. In the worst case scenario, it was found that multiple shunts can lead to a 160% increase in RT and a 10% decrease in OD. Based on the simulation results presented in this study, clinical outcomes for patients receiving multiple shunts should be critically investigated, as this practice appears to provide no benefit in terms of OD and may actually increase thrombotic risk.

Periscope Modification of Right Ventricle-to-Pulmonary Artery Shunt in Norwood Operation

Given the purported hemodynamic advantages of the right ventricle (RV) to pulmonary artery (PA) conduit, many surgeons have adopted it as their preferred source of pulmonary blood flow during stage I palliation for hypoplastic left heart syndrome. Potential disadvantages of the RV-PA shunt include ventricular dysfunction, pseudoaneurysm formation, arrhythmia, and conduit obstruction, which can lead to a higher rate of unplanned reinterventions. The "dunk" technique was described to reduce the RV incision and proximal conduit obstruction; however, insertion of the ringed graft from the epicardium can be cumbersome and risk RV injury. We introduce a simplified, alternative method of placing the conduit, which we call the periscope technique, whereby the graft is withdrawn from within the RV cavity.

In Search of the Ideal Pulmonary Blood Source for the Norwood Procedure: A Meta-Analysis and Systematic Review

A clear consensus regarding the optimal source of pulmonary blood flow in patients with hypoplastic left heart syndrome undergoing the Norwood procedure is lacking. A literature search was undertaken to identify relevant articles from 2005 to 2012 using "Norwood, stage 1 palliation," "Modified Blalock Taussig shunt (MBTS)," "right ventricle-to-pulmonary artery shunt (RV-PAS)" alone or in combination. Three end points were selected: early/stage 1 mortality, interstage mortality, and interstage total/shunt intervention. A total of 20 articles, including 19 observational studies and 1 randomized trial (MBTS, n=1,343; RV-PAS, n=1,028), met the inclusion criteria. Mortality after stage 1 was 22% in the MBTS cohort and 16% in RV-PAS cohort. A pooled analysis showed no difference in early mortality between the two groups (risk ratio [RR], 1.20; 95% confidence interval [CI], 0.99 to 1.45; p=0.07). On pooling data from contemporary series (similar era) of 8 studies (MBTS, n=709; RV-PAS, n=631), to minimize variability in surgical and postoperative management practices, early mortality in both cohorts was comparable (RR, 1.14; 95% CI, 0.89 to 1.45; p=0.29). Interstage mortality was 13.8% and 4.6% in the MBTS and RV-PAS cohorts, respectively, and was significantly lower for RV-PAS (RR, 2.85; 95% CI, 1.65 to 4.89; p<0.00002). However, patients with MBTS had fewer shunt interventions (RR, 0.55; 95% CI, 0.44 to 0.68; p<0.001; I2=00%). Our pooled analysis demonstrated no survival benefit for the MBTS or RV-PAS in patients undergoing the Norwood procedure. There appears to be an advantage with the RV-PAS with regard to interstage mortality at the cost of an increased rate of shunt intervention.

Invited Commentary

Jha and associates [1Jha A.K. Gharde P. Devagourou V. Chauhan S. Kiran U. The effect of volume loading on systemic oxygenation after bidirectional superior cavopulmonary anastomosis.Ann Thorac Surg. 2014; 97: 932-937Google Scholar] present a thought-provoking study on the effects of administering intravascular volume early after a superior cavopulmonary connection (SCC). The study is prospectively conducted and controls many patient and procedural variables. Several of the study conditions are worth noting. The study was initiated 10 minutes after cardiopulmonary bypass, with the chest closed and the patients mechanically ventilated. The patients’ median age was 2 years. At the time of the study, each patient had two sources of pulmonary blood flow: a preserved native pulmonary outflow tract, and the SCC (“pulsatile SCC”). Volume administration resulted in increased common atrial pressure (measured in the inferior vena cava), SVC pressure, and blood pressure, with a decrease in heart rate. Systemic oxygen saturation and PO2 increased. Several indicators of cerebral blood flow improved: SVC saturation and cerebral near-infrared spectroscopy signal increased, while upper body arteriovenous saturation difference fell. From the presented data, we can also deduce that the transpulmonary gradient increased (from roughly 3 mm Hg to 10 mm Hg). How do we interpret these findings? Assuming relatively constant pulmonary vascular resistance, the increase in transpulmonary gradient indicates increased pulmonary blood flow. Increased systemic oxygenation is the result. Flow to the lungs likely increased through both sources of pulmonary flow. Increased common atrial pressure and systolic blood pressure will drive more flow through a patent outflow tract, so at least some of the investigators’ findings are due to increased antegrade pulmonary flow. The increased cerebral near-infrared spectroscopy signal and decreased upper body arteriovenous saturation difference also suggest an increase in cerebral blood flow, and therefore SCC flow. An increase in cerebral flow due to increased arterial blood pressure indicates some impairment of cerebral autoregulation. Although mildly hypothermic cardiopulmonary bypass is generally believed to preserve cerebral autoregulation, this issue has not been well studied in children early after SCC. The effects of intravascular volume administration depend on the baseline volume status of the patient. In the study patients, the low mean atrial pressure (inferior vena cava, 6 mm Hg) and SVC pressure (9 mm Hg) at T1, as well as the response of the blood pressure and heart rate to volume administration, suggest that the patients were hypovolemic at baseline. Optimization of volume status at the end of any operation is obviously good practice. Conversely, maintenance of an SVC pressure in the 16 to 20 mm Hg range in an infant is difficult to sustain, and can result in third-spacing with pleural effusions and ascites. Hypoxemia can be an important clinical problem early after SCC. Available approaches include minimization of positive pressure ventilation, judicious hypoventilation, early endotracheal extubation, optimization of cardiac output and hemoglobin level, and (occasionally) the addition of a systemic-pulmonary shunt. The current study specifically examines cardiac output optimization by the addition of intravascular volume. Whether the findings would apply in a more typical patient, such as a 6-month-old with a systemic-pulmonary shunt undergoing a nonpulsatile SCC, will require further study. Jha and colleagues [1Jha A.K. Gharde P. Devagourou V. Chauhan S. Kiran U. The effect of volume loading on systemic oxygenation after bidirectional superior cavopulmonary anastomosis.Ann Thorac Surg. 2014; 97: 932-937Google Scholar] are to be congratulated for carrying out this prospective, well-controlled, and interesting study. The Effect of Volume Loading on Systemic Oxygenation After Bidirectional Superior Cavopulmonary AnastomosisThe Annals of Thoracic SurgeryVol. 97Issue 3PreviewThe unique series arrangement of the cerebral and pulmonary circulation in bidirectional superior cavopulmonary anastomosis (BCPA) makes the pulmonary blood flow dependent upon the cerebral blood flow. Until now, several investigators have tried to correct post-BCPA hypoxemia with various methods such as induced hyperventilation, the addition of carbon dioxide, and inhaled nitric oxide with variable success rates. Full-Text PDF

A Coronary–Pulmonary Artery Fistula with Giant Aneurysm in a Child with Ventricular Septal Defect with Pulmonary Atresia

Mini‐AbstractPulmonary atresia with ventricular septal defect accounts for about 2% of all congenital heart diseases. Aortopulmonary collaterals are the usual source of pulmonary blood flow. Coronary–pulmonary artery fistula is a rare and sole source of pulmonary blood flow. We are reporting a case of a 6‐year‐old girl who presented with severe cyanosis, clubbing, and effort intolerance. Echocardiography demonstrated a large subaortic ventricular septal defect and pulmonary atresia with confluent pulmonary arteries. It also revealed the presence of a coronary–pulmonary artery fistula along with a giant coronary artery aneurysm. These findings were confirmed by an aortic root angiogram. She was referred for intra‐ cardiac repair.

The use of the Berlin Heart EXCOR in patients with functional single ventricle

The frequency and successful use of pediatric ventricular assist devices (VADs) as a bridge to cardiac transplantation have been steadily increasing since 2003, but the experience in patients with complex congenital heart disease has not been well described. Using a large prospectively collected dataset of children supported with the Berlin Heart EXCOR VAD, we have reviewed the experience in children with single ventricular anatomy or physiology (SV), and compared the results with those supported with biventricular circulation (BV) over the same time period. The EXCOR Investigational Device Exemption study database was retrospectively reviewed. VAD implants under the primary cohort and compassionate use cohort between May 2007 and December 2011 were included in this review. Twenty-six of 281 patients supported with a VAD were SV. The most common diagnosis was hypoplastic left heart syndrome (15 of 26). Nine patients were supported after neonatal palliative surgery (Blalock-Taussig shunt or Sano), 12 after a superior cavopulmonary connection (SCPC), and 5 after total cavopulmonary connection (TCPC). Two patients received biventricular assist devices, 1 after stage I surgery and 1 after stage II. SV patients were supported for a median time of 10.5 days (range, 1-363 days) versus 39 days (range, 0-435 days) for BV (P = .01). The ability to be bridged to transplant or recovery in SV patients is lower than for BV patients (11 of 26 [42.3%] vs 185 of 255 [72.5%]; P = .001). Three of 5 patients with TCPC were successfully bridged to transplant and were supported with 1 VAD. Seven of 12 patients with SCPC were bridged to transplant, and only 1 of 9 patients supported after a stage I procedure survived. The EXCOR Pediatric VAD can provide a bridge to transplant for children with SV anatomy or physiology, albeit less successfully than in children with BV. In this small series, results are better in patients with SCPC and TCPC. VAD support for patients with shunted sources of pulmonary blood flow should be applied with caution.

Early Cyanosis After Stage II Palliation for Single Ventricle Physiology

In the early postoperative period after stage II palliation, patients with single ventricle physiology can have cyanosis due to a variety of causes. This cyanosis can be significant and necessitate cardiac catheterization to determine etiology and attempt treatment. Our objective was to determine the etiology of early postoperative cyanosis and outcomes in patients referred to the catheterization laboratory from the cardiac intensive care unit (CICU) after stage II palliation. We performed a retrospective analysis of all patients referred for cardiac catheterization from the CICU for evaluation of early cyanosis after stage II palliation. Etiology for hypoxemia, treatment strategy, and patient outcomes were examined for each patient. Between January 1, 2006, and December 31, 2011, 244 patients underwent stage II palliation of which 22 required cardiac catheterization during the early postoperative period because of severe cyanosis. The etiologies for cyanosis were venovenous collaterals (n = 12), cavopulmonary pathway thrombosis (n = 3), hemi-Fontan pathway baffle leak (n = 2), and undetermined (n = 5). Overall, transplant-free survival to hospital discharge was 50% and survival to hospital discharge with stage II physiology was 32%. Venovenous collateral occlusion, cavopulmonary anastomosis takedown, and addition of a second source of pulmonary blood flow were not associated with improved outcome. Regardless of the etiology or treatment strategy, severe cyanosis in the early postoperative period after stage II palliation imparts high mortality and usually indicates failing stage II physiology. Venovenous collateral occlusion and thrombectomy are usually futile, and those who survive have a low likelihood of having stage II physiology at hospital discharge.

Coronary artery to pulmonary artery communications in pulmonary atresia with ventricular septal defect

Coronary artery to pulmonary artery communications (CAPAC) are an important source of pulmonary blood flow in approximately 10% of patients with pulmonary atresia and ventricular septal defect (PA-VSD). A diligent look for these abnormal communications is important to prevent perioperative complications and achieve a complete repair. We present two cases of PA-VSD with CAPAC, one in a 7-year-old child and the other in a 33-year-old adult. The method of occlusion of these communications could be either surgical or catheter based.

Giant aorto-pulmonary collaterals in pulmonary atresia and ventricular septal defect

The association of pulmonary atresia and ventricular septal defect (PA/VSD) can be considered the most severe form of tetralogy of Fallot. The main feature of this congenital heart disease is represented by discontinuity between the right ventricle and pulmonary trunk or its branches; the anatomy of central pulmonary arteries is often abnormal, consequently the type and the amount of sources of pulmonary blood flow are variable. Due to evolution in surgical techniques, definitive correction is now also considered in more complex cases. A small rate of unoperated patients with PA/VSD can survive until adulthood and the arterial blood supply to the lungs, provided by major aorto-pulmonary collateral arteries (MAPCAs), is one of the main determinants of survival. We report two unoperated cases of PA/VSD and MAPCAs with long-term survival. Giant MAPCAs can occasionally be found by chest radiography in adults with unrepaired PA/VSD. Moreover, non-invasive assessment of the pulmonary arterial bed with computer tomography or MRI is helpful in these patients during follow-up. Finally, we discuss the use of oral anticoagulants and/or 5-phosphodiesterase inhibitors in these patients.

Outcomes and Predictors of Reintervention in Patients With Pulmonary Atresia and Intact Ventricular Septum Treated With Radiofrequency Perforation and Balloon Pulmonary Valvuloplasty

Radiofrequency perforation and valvuloplasty (RFV) is an effective initial treatment in patients with pulmonary atresia and intact ventricular septum (PA-IVS) and mild to moderate right ventricle and tricuspid valve hypoplasia. Outcomes and risk factors for the need for additional interventions in these patients are poorly defined. All patients with PA-IVS who underwent RFV at our center between January 2000 and July 2011 were reviewed. Twenty-three patients met the inclusion criteria. All patients underwent successful valvuloplasty with no procedural deaths and one major complication. Excluding two patients with limited follow-up, 6 (29%) patients underwent no subsequent interventions, whereas 9 (42%) patients underwent surgical right-ventricular outflow tract augmentation. All except one patient with adequate follow-up have a biventricular circulation with saturation >92%. Patients who did not undergo any right-ventricular outflow tract intervention after valvuloplasty had a significantly lower gradient across the pulmonary valve after valvuloplasty (9.9mmHg±8.4 vs. 19.1mmHg±10.4, p=0.05). Significantly more patients who received a supplemental source of pulmonary blood flow had a tricuspid valve z-score <-0.7 compared with patients who did not receive supplemental blood flow [2 (15%) vs. 7 (70%), p=0.008]. In our cohort of patients with PA-IVS, radiofrequency perforation with valvuloplasty was an effective and safe first step in establishing a biventricular circulation. Postvalvuloplasty pulmonary valve gradient may be predictive of subsequent outflow tract intervention, and tricuspid hypoplasia may be predictive of the need for a supplemental source of pulmonary blood flow.

Is there any need for a shunt in the treatment of tetralogy of Fallot with one source of pulmonary blood flow?†

In symptomatic patients, performing a primary repair of tetralogy of Fallot (TOF), irrespective of age or placing a shunt, remains controversial. The aim of the study was to analyse the policy of primary correction. Between May 2005 and May 2012, a total of 87 consecutive patients with TOF, younger than 6 months of age, underwent primary correction. All patients had one source of pulmonary blood flow, with or without a patent ductus arteriosus. The median age at surgery was 106 ± 52.3 days (8-180 days). Twelve patients (13.8%) were newborns. Two groups were analysed: group I, patients <1 month of age; group II, patients between 2-6 months of age. There was no early or late death at 7 years of follow-up. There was no difference in bypass time or hospital stay between the two groups, but the Aristotle comprehensive score (P < 0.0001), ICU stay (P = 0.030) and the length of ventilation (P = 0.014) were significantly different. Freedom from reoperation was 87.3 ± 4.3% and freedom from reintervention was 85.9 ± 4.2% at 7 years, with no difference between the two groups. Neurological development was normal in all patients, but 1 patient in Group II had cerebral seizures and showed developmental delay. Growth was adequate in all patients, except those with additional severe non-cardiac malformations that caused developmental delay. Eighty-five per cent of the patients were without cardiac medication. Even in symptomatic neonates and infants <6 months of age, primary repair of TOF can be performed safely and effectively. One hundred per cent survival at 7 years suggests that early primary repair causes no increase in mortality in the modern era. Shunting is not necessary, even in symptomatic newborns, thus avoiding the risk of shunt-related complications and repeated hospital stays associated with a staged approach.

Invited Commentary

Invited Commentary

Systemic to pulmonary collateral blood flow influences early outcomes following the total cavopulmonary connection

BackgroundSystemic to pulmonary collaterals (SPCs) represent an additional and unpredictable source of pulmonary blood flow in patients with single ventricle physiology following bidirectional superior cavopulmonary connection (BCPC). Understanding their influence...

Pulse oximetry home monitoring in infants with single-ventricle physiology and a surgical shunt as the only source of pulmonary blood flow

Shunt occlusion is a major cause of death in children with single ventricle. We evaluated whether one daily measurement of oxygen saturation at home could detect life-threatening shunt dysfunction. A total of 28 infants were included. Parents were instructed to measure saturation once daily and if less than or equal to 70% repeat the measurement. Home monitoring was defined as positive when a patient was admitted to Queen Silvia Children's Hospital because of saturation less than or equal to 70% on repeated measurement at home. A shunt complication was defined as arterial desaturation and a narrowing of the shunt that resulted in an intervention to relieve the obstruction or in death. Parents' attitude towards the method was investigated using a questionnaire. A shunt complication occurred out of hospital eight times in eight patients. Home monitoring was positive in five out of eight patients. In two patients, home monitoring was probably life saving; in one of them, the shunt was replaced the same day and the other had an emergency balloon dilatation of the shunt. In three out of eight patients, home monitoring was negative; one had an earlier stage II and survived, but two died suddenly at home from thrombotic shunt occlusion. On seven occasions in three patients home monitoring was positive but there was no shunt complication. The method was well accepted by the parents according to the results of the questionnaire. Home monitoring of oxygen saturation has the potential to detect some of the life-threatening shunt obstructions between stages I and II in infants with single-ventricle physiology.

Invited Commentary

Invited Commentary

A Large Coronary‐Pulmonary Artery Fistula in a Cyanotic Patient Leading to Severe Biventricular Dysfunction and Heart Failure

In cases of pulmonary atresia (PA) with ventricular septal defect (VSD), the commonest source of pulmonary blood flow is via major aortoplumonary collaterals. Collaterals may also arise from the coronary arteries and the reported prevalence of such coronary-pulmonary artery fistulas (CPAF) in PA with VSD is 10%. However gross congestive heart failure (CHF) and ventricular dysfunction is extremely rare in such cases. We report a 17-year-old male with PA with VSD and a large CPAF from the anterior right aortic sinus connecting to the left pulmonary artery, who presented with severe CHF. The left anterior descending and the right coronary artery both arose from the proximal part of the CPAF, possibly leading to extensive coronary steal and biventricular dysfunction.

Norwood with right ventricle-to-pulmonary artery conduit is more effective than Norwood with Blalock–Taussig shunt for hypoplastic left heart syndrome: mathematic modeling of hemodynamics

The introduction of right ventricle to pulmonary artery (RV-PA) conduit in the Norwood procedure for hypoplastic left heart syndrome resulted in a higher survival rate in many centers. A higher diastolic aortic pressure and a higher mean coronary perfusion pressure were suggested as the hemodynamic advantage of this source of pulmonary blood flow. The main objective of this study was the comparison of two models of Norwood physiology with different types of pulmonary blood flow sources and their hemodynamics. Based on anatomic details obtained from echocardiographic assessment and angiographic studies, two three-dimensional computer models of post-Norwood physiology were developed. The finite-element method was applied for computational hemodynamic simulations. Norwood physiology with RV-PA 5-mm conduit and Blalock-Taussig shunt (BTS) 3.5-mm shunt were compared. Right ventricle work, wall stress, flow velocity, shear rate stress, energy loss and turbulence eddy dissipation were analyzed in both models. The total work of the right ventricle after Norwood procedure with the 5-mm RV-PA conduit was lower in comparison to the 3.5-mm BTS while establishing an identical systemic blood flow. The Qp/Qs ratio was higher in the BTS group. Hemodynamic performance after Norwood with the RV-PA conduit is more effective than after Norwood with BTS. Computer simulations of complicated hemodynamics after the Norwood procedure could be helpful in establishing optimal post-Norwood physiology.

Gadolinium-Enhanced Three-Dimensional Magnetic Resonance Angiographic Assessment of the Pulmonary Artery Anatomy in Cyanotic Congenital Heart Disease With Pulmonary Stenosis or Atresia: Comparison With Cineangiography

Pulmonary stenosis (PS) or pulmonary atresia (PA) is an important component of complex cyanotic congenital heart disease, especially in tetralogy of Fallot or lesions with ventricular septal defect (VSD)-PS physiology. Management strategy in these patients depends on accurate assessment of PAs and identification of all sources of pulmonary blood flow. X-ray cineangiography is the "gold standard" for this purpose, but it has the inherent risks of an invasive procedure. Gadolinium-enhanced three-dimensional magnetic resonance angiography (Gd-MRA) has been shown to noninvasively and accurately evaluate various lesions of the vascular system. This study was undertaken to evaluate the accuracy of Gd-MRA compared with cineangiography in the evaluation of pulmonary anatomy. Nineteen patients having complex cyanotic heart disease with PS or PA were included in the study. All patients underwent Gd-MRA and cineangiography. Catheterisation and MRA findings regarding the anatomic variable of interest were analysed for agreement by Bland-Altman analysis. There was total agreement between the two modalities in the delineation of confluent PAs. McGoon's ratio and the Nakata index, which are standard measures of the adequacy of PA size, also showed excellent agreement between the two modalities. MRA was able to delineate all aorto-pulmonary collaterals in the setting of PA. MRA can delineate all sources of pulmonary blood supply in cyanotic congenital heart disease with PS and/or PA as well as provide accurate assessment of PA size for planning corrective surgery.

Early Determinants of Pulmonary Vascular Remodeling in Animal Models of Complex Congenital Heart Disease

In this article, we review the current state of knowledge about early changes in the pulmonary vasculature that result from persistent systemic-to–pulmonary arterial shunting in newborn lambs. Data generated in this model system may be important in children with various forms of congenital heart disease (CHD), but perhaps most so in those with single-ventricle anomalies. Children born with a functional single ventricle (eg, hypoplastic left heart syndrome, tricuspid atresia, or pulmonary atresia) represent a subgroup of patients with CHD with the poorest outcome, with 5-year mortality rates up to 50%.1 Although functionally single-ventricle heart disease comprises many structural variants, a shared physiological feature is that both systemic and pulmonary circulations are supplied in parallel by a functionally single pumping chamber. Immediately after birth, the pulmonary vasculature of these infants is exposed to abnormal conditions, such as increased flow or pressure.2,–,4 Over time, if these abnormal forces are not modified, they can lead to progressive functional and morphological abnormalities in the pulmonary vasculature that are characterized by altered reactivity, increased resistance, and structural alterations (remodeling).3 Clinically, these abnormalities can have an important impact on surgical options and perioperative outcome. The current approach to neonates with a functional single ventricle is to establish a controlled, low-pressure source of pulmonary blood flow that facilitates systemic oxygen delivery sufficient to permit somatic growth and development without excessive ventricular volume loading, typically by means of a surgical systemic-to–pulmonary artery or ventricle-to–pulmonary artery conduit or by restricting the main or branch pulmonary arteries.2 The pulmonary-to-systemic blood flow balance can be difficult to achieve, and the infant runs the gauntlet between pulmonary blood flow that is too low (resulting in chronic hypoxemia and the potential consequences thereof) or …

Impact of Shunt Type on Growth of Pulmonary Arteries After Norwood Stage I Procedure

The past decade has seen a substantial improvement in the outcome following surgical palliation for hypoplastic left heart syndrome. This has been attributed to modifications in the surgical as well as postoperative management strategies. One such modification is the reemergence of the right ventricle to pulmonary artery (RV-PA) shunt as an alternative to the modified Blalock-Taussig (mBT) shunt as the source of pulmonary blood flow. The RV-PA shunt has been shown to improve the immediate surgical outcome compared with the classic Norwood procedure with an mBT shunt. Despite the several reported advantages, the impact of the RV-PA shunt on growth of the pulmonary arteries and incidence of late development of central PA stenosis remains unclear. This systematic review evaluates the current best available evidence to address this issue and concludes that the evidence from retrospective studies and only available randomized controlled trial (RCT) is conflicting. The retrospective studies predominantly suggest that the Norwood procedure with RV-PA shunt may have favorable effects on the development of the pulmonary arteries due to even distribution of pulmonary blood flow with greater distal left pulmonary artery growth, resulting in more balanced distal branch pulmonary artery size albeit with a greater degree of central pulmonary artery hypoplasia needing surgical attention. On the contrary, the RCT reports that the overall size of the pulmonary artery on angiography before the stage II procedure was smaller in the RV-PA shunt group than in the mBT shunt group, with no information available on incidence of central pulmonary hypoplasia.