Right Ventricle-to-pulmonary Artery Shunt Research Articles

Introduction to the Single Ventricle Reconstruction trial

The Single Ventricle Reconstruction (SVR) trial, sponsored by the National Heart, Lung, and Blood Institute and carried out by 15 clinical centers, randomized 549 neonates and showed that transplantation-free survival at 14 months was significantly higher overall with the right ventricleto-pulmonary artery shunt (RVPAS) compared with the modified Blalock-Taussig shunt (MBTS). Any surgical procedure that does not exceed 65% survival at 1 year deserves to be studied and scrutinized relentlessly. Although the primary outcome was clear when considering the entire study cohort, many questions remained regarding the impact of comorbidities; intraoperative, postoperative, and interstage management strategies on morbidity and mortality; and the mechanisms of death throughout the study period. The compilation of 5 follow-up articles represents secondary analyses of the SVR trial, and their main value is that they provide a more detailed analysis of areas that could not be covered in the New England Journal of Medicine article. The SVR trial fortunately included enough study patients, and collected a vast amount of data, to permit analysis of the interaction of risk factors with shunt type; the risk factors of hospital morbidity and mortality after the Norwood; the impact of shunt type and other risk factors on interstage mortality; the cause, timing, and location of death after the Norwood; as well as a descriptive study on practice variation in perioperative care found across centers. Some of the findings confirm the findings of previous retrospective studies or database extraction studies, such as the impact of center/surgeon volume, the major and independent role of extracardiac anomalies, genetic syndromes, low gestational age and birth weight, smaller ascending aorta, obstructed pulmonary venous return, and lower socioeconomic status play on outcomes. Patients with aortic stenosis/mitral stenosis did better than any other subgroup, presumably because of the presence of antegrade aortic flow, and patients with aortic atresia/mitral stenosis did not exhibit a higher mortality, although the presence or

Interstage mortality after the Norwood procedure: Results of the multicenter Single Ventricle Reconstruction trial

For infants with single ventricle malformations undergoing staged repair, interstage mortality is reported at 2% to 20%. The Single Ventricle Reconstruction trial randomized subjects with a single morphologic right ventricle undergoing a Norwood procedure to a modified Blalock-Taussig shunt (MBTS) or a right ventricle-to-pulmonary artery shunt (RVPAS). The aim of this analysis was to explore the associations of interstage mortality and shunt type, and demographic, anatomic, and perioperative factors. Participants in the Single Ventricle Reconstruction trial who survived to discharge after the Norwood procedure were included (n=426). Interstage mortality was defined as death postdischarge after the Norwood procedure and before the stage II procedure. Univariate analysis and multivariable logistic regression were performed adjusting for site. Overall interstage mortality was 50 of 426 (12%)-13 of 225 (6%) for RVPAS and 37 of 201 (18%) for MBTS (odds ratio [OR] for MBTS, 3.4; P<.001). When moderate to severe postoperative atrioventricular valve regurgitation (AVVR) was present, interstage mortality was similar between shunt types. Interstage mortality was independently associated with gestational age less than 37 weeks (OR, 3.9; P=.008), Hispanic ethnicity (OR, 2.6; P=.04), aortic atresia/mitral atresia (OR, 2.3; P=.03), greater number of post-Norwood complications (OR, 1.2; P=.006), census block poverty level (P=.003), and MBTS in subjects with no or mild postoperative AVVR (OR, 9.7; P<.001). Interstage mortality remains high at 12% and is increased with the MBTS compared with the RVPAS if postoperative AVVR is absent or mild. Preterm delivery, anatomic, and socioeconomic factors are also important. Avoiding preterm delivery when possible and close surveillance after Norwood hospitalization for infants with identified risk factors may reduce interstage mortality.

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.

Right ventricle-to-pulmonary artery shunt related complications after Norwood procedure☆

The right ventricle-to-pulmonary artery (RV-PA) shunt in the Norwood procedure (NP) for children with hypoplastic left-heart syndrome (HLHS) provides stable early hemodynamics and improves survival in many centers. However, lower pulmonary-to-systemic flow ratio causes early cyanosis and may require earlier second-stage procedure. The aim of the study was to present shunt-related results after NP with RV-PA shunt and our technique of RV-PA shunt construction. Between June 2001 and August 2010, 236 children with HLHS and variants underwent NP with RV-PA shunt, and were operated on by the same surgeon. The medical records were retrospectively reviewed. To date, 180 children at a mean age of 7.0 ± 1.6 months with a mean weight of 6.4 ± 0.9 kg underwent second-stage procedure. The mean systemic oxygen saturation before stage 2 operation was 74.8 ± 6.6% and mean arterial partial oxygen pressure was 32.8 ± 6.7 mm Hg. These two parameters were significantly lower than after NP (p = 0.029, p < 0.001, respectively). Between stage 1 and 2 operation, three children (1.3%) died due to the shunt obstruction. Four children (1.7%) underwent re-operations due to shunt problems (one of them died), and the other four (1.7%), stent implantation in RV-PA shunt. Two infants (1.1%) developed aneurysm of the right ventricle infundibulum, which was resected during stage 2 without complications. One child required early (before fifth month of age) second-stage procedure due to the shunt obstruction. The patients with right-sided to the neo-aorta course of the RV-PA shunt had significantly more frequent delayed sternal closure after NP than children with left-sided shunt (35.5% vs 14.1%; p = 0.008). The RV-PA shunt can be a safe and efficient technique in providing optimal pulmonary blood flow in the children with HLHS after Norwood procedure, performed with minimal rate of complications. In our experience, the use of RV-PA shunt in NP does not require earlier second-stage procedure.

Comparison of Norwood Shunt Types: Do the Outcomes Differ 6 Years Later?

A modification to the Norwood procedure involving a right ventricle-to-pulmonary artery (RV-PA) shunt may improve early postoperative outcomes. Concerns remain about the effect of the right ventriculotomy required with this shunt on long-term ventricular function. Between January 2000 and April 2005, 76 patients underwent the Norwood procedure, 35 with a modified Blalock-Taussig shunt (mBTS) and 41 with a RV-PA shunt. Patients were monitored until death or September 1, 2009, with an average follow-up of 6.8 years. Cardiac catheterization, echocardiograms, perioperative Fontan courses, and need for cardiac transplantation were compared between groups. Cumulative survival was 63% (22 of 35) in the mBTS group vs 78% (32 of 41) in the RV-PA group (p = 0.14). Pre-Fontan echocardiography revealed poorer ventricular function in RV-PA patients (p = 0.03). Cardiac transplantation was required in 6 of 32 (19%) patients with a prior RV-PA shunt vs 1 of 23 (4%) in the mBTS group (p = 0.06). This results in an almost identical cumulative transplant-free survival between groups; 60% (21 of 35) in the mBTS group and 63% (26 of 41) in the RV-PA group (p = 0.95). Neither shunt offers a clear survival advantage through an average follow-up of 6.8 years. The RV-PA shunt results in impaired late ventricular function that may result in an increased need for cardiac transplantation.

Right Ventricle-to-Pulmonary Artery Shunt in Norwood Procedure: Early Results

The aim of this study was to evaluate experience and predictors of early mortality in patients with hypoplastic left heart syndrome (HLHS)-type defects undergoing Norwood procedure (NP) with right ventricle-to-pulmonary artery (RV-PA) shunt. Between 2001 and 2009, a consecutive series of 229 children with HLHS-type single ventricle underwent NP with application of RV-PA shunt. Demographic, echocardiographic, and clinical perioperative data were retrospectively analyzed. The mean duration of follow-up of survivors was 4.5 ± 2.1 years (60 days to 8.1 years). Follow-up was complete for 92.1% of patients. Major early postoperative complications included sepsis/generalized infection in 40 (17.5%), pericardial effusion in 9 (3.9%), and wound infection in 8 (3.5%). The early (30-day) survival was 87.8% (n = 201). In the late postoperative period, 12 (5.9%) died. Early nonsurvivors were more frequently older than 14 days (P = .045) at initial surgery, had lower operative weight (P = .024), had more frequent associated cardiac (P < .001) and/or extracardiac anomalies (P < .001), and were more likely to have a restrictive interatrial communication before operation (P = .024). Use of the right RV-PA shunt has helped to mitigate some previously described predictors of early death after NP. Longer follow-up will be required to determine whether the RV-PA shunt modification confers an important survival benefit.

Management of a Stenotic Right Ventricle-Pulmonary Artery Shunt Early After the Norwood Procedure

Inadequate pulmonary blood flow through a right ventricle-to-pulmonary artery (RV-PA) shunt early after the Norwood operation can be remedied by adding a modified Blalock-Taussig (mBT) shunt. We used multiscale computational modeling to determine whether the stenotic RV-PA shunt should be left in situ or removed. Models of the Norwood circulation were constructed with (1) a 5-mm RV-PA shunt, (2) a RV-PA shunt with 3- or 2-mm stenosis at the RV anastomosis, (3) a stenotic RV-PA shunt plus a 3.0- or 3.5-mm mBT shunt, or (4) a 3.5-mm mBT shunt. A hydraulic network that mathematically describes an entire circulatory system with pre-stage 2 hemodynamics was used to predict local dynamics within the Norwood circulation. Global variables including total cardiac output, mixed venous oxygen saturation, stroke work, and systemic oxygen delivery can be computed. Proximal stenosis of the RV-PA shunt results in decreased pulmonary blood flow, total cardiac output, mixed venous saturation, and oxygen delivery. Addition of a 3.0- or 3.5-mm mBT shunt leads to pulmonary overcirculation, lowers systemic oxygen delivery, and decreases coronary perfusion pressure. Diastolic runoff through the stenotic RV-PA shunt dramatically increases retrograde flow into the single ventricle. Removal of the stenotic RV-PA shunt balances systemic and pulmonary blood flow, eliminates regurgitant flow into the single ventricle, and improves systemic oxygen delivery. Adding a mBT shunt to remedy a stenotic RV-PA shunt early after a Norwood operation can lead to pulmonary overcirculation and may decrease systemic oxygen delivery. The stenotic RV-PA shunt should be taken down. Conversion to an optimal mBT shunt is preferable to augmenting a stenotic RV-PA shunt with a smaller mBT shunt.

Two-Year Survival and Mental and Psychomotor Outcomes After the Norwood Procedure

The Norwood procedure for stage 1 palliation of hypoplastic left heart syndrome is performed with either the modified Blalock-Taussig (MBTS) or the right ventricle-to-pulmonary artery (RVPA) shunt. In our institution, surgical practice changed from use of the MBTS to use of the RVPA shunt in 2002. We analyzed survival and mental and psychomotor outcomes of the 2 consecutive surgical eras. Between September 1996 and July 2005, 94 neonates with hypoplastic left heart syndrome underwent the Norwood procedure. Patients were recruited as neonates and followed up prospectively. Health, mental, and psychomotor outcomes (Bayley Scales of Infant Development-II) were assessed at 2 years. The study subjects were from the Norwood-MBTS era (n=62; 1996 to 2002) or the Norwood-RVPA era (n=32; 2002 to 2005). In the MBTS era, early and 2-year mortality rates were 23% (14/62) and 52% (32/62); the mean (SD) mental and psychomotor developmental indices were 79 (18) and 67 (19). In the RVPA era, early and 2-year mortality rates were 6% (2/32) and 19% (6/32); the mean (SD) mental and psychomotor developmental indices were 85 (18) and 78 (18). The 2-year mortality rate (P=0.002) and the psychomotor developmental index (P=0.029) were improved in the more recent surgical era. On multivariable Cox regression analysis, postoperative highest serum lactate independently predicted 2-year mortality in the MBTS and RVPA eras. Analysis of 2 consecutive surgical eras of hypoplastic left heart syndrome patients undergoing the Norwood procedure showed a significant improvement in 2-year survival and psychomotor development in the more recent era. Adverse neurodevelopmental outcome in this patient population remains a concern.

Right Ventricle-to-Pulmonary Artery Shunt: Alternative Palliation in Infants With Inadequate Pulmonary Blood Flow Prior to Two-Ventricle Repair

Traditional palliation of infants with biventricular hearts and inadequate pulmonary blood flow is a modified Blalock-Taussig shunt. The aim of this report is to assess the results of an alternative, right ventricle-to-pulmonary artery (RV-PA) shunt. Between August 2004 and July 2007, 10 infants with biventricular hearts and inadequate pulmonary blood flow underwent palliation with an RV-PA shunt. Median age was 9 days (range, 4 to 86), weight was 3.0 kg (1.7 to 4.5), and 4 of 10 patients weighed less than 2.5 kg. Shunts were nonvalved Gore-Tex (W.L. Gore Assoc, Flagstaff, AZ), and size was 6 mm (n = 5) or 5 mm (n = 5). There were no operative deaths. Median oxygen saturation at hospital discharge was 95% (87 to 98). In 2 patients the shunt was partially narrowed with a metal clip; they underwent successful balloon dilation 6 months after shunt placement. Eight patients have undergone two-ventricle repair 6 to 17 months after shunt placement. At the time of complete repair, oxygen saturation was 86 +/- 1% and weight was 7.7 +/- 1.7 kg. Repairs included a valved RV-to-PA conduit, 14 to 16 mm in diameter. There was one interstage death. The RV-PA shunt provides successful palliation in infants with biventricular heart disease and inadequate pulmonary blood flow. It can be used in low birth weight infants and allows significant growth with protection of oxygen saturation prior to complete repair. Partial clipping of the shunt with subsequent balloon dilation is an option to prolong palliation. These results compare favorably with those of a modified Blalock-Taussig shunt or single stage complete repair.

Follow-up study of pulmonary artery configuration in hypoplastic left heart syndrome

Pulmonary artery (PA) distortion significantly compromises the outcome of the staged approach to the Fontan operation in patients with hypoplastic left heart syndrome (HLHS). This retrospective study was designed to investigate the influence of the initial operation on postoperative PA anatomy. Forty-nine patients with HLHS and its variant were enrolled in this study. As an initial palliation, the Norwood operation with a modified Blalock-Taussig (BT) shunt was performed in 12, the Norwood operation with a right ventricle to pulmonary artery (RV-PA) shunt in 31, and bilateral PA banding in 6. The incidence and risk factors of postoperative central pulmonary artery stenosis (PS) were investigated, and the PA configuration was followed up until post-Fontan status. Twenty-two patients (51.2%) had developed central PS after the Norwood operation (33.3% with a BT shunt vs. 58.1% with a RV-PA shunt). The RV-PA shunt with a polytetrafluoroethylene (PTFE) patch at the distal pulmonary stump significantly decreased the central PS (P = 0.035). The PA index after the Norwood operation was not statistically different between the BT and RV-PA shunt groups, although in the RV-PA group it was significantly higher in patients with a PTFE patch on the distal PA stump. PA plasty was performed in 16 patients in the second-stage palliation and in 15 with the Fontan completion. Freedom from PA plasty was significantly lower in the RV-PA shunt group than in the BT shunt group (63.5% vs. 31.1% at 5 years, P = 0.034). Six patients initially palliated with bilateral PA banding had no stenosis at the banding site in the Norwood + Glenn operation, and one patient required stent placement for left PS in the Fontan completion. Post-Fontan catheterization (n = 31) showed central venous pressure of 11.5 +/- 2.6 mmHg, cardiac index of 3.6 +/- 0.8 l/kg/min, and PA index of 194.0 +/- 58.4 mm(2)/m(2); there was no difference between the groups. The incidence of central PS after the Norwood operation was significant, and the shunt type and procedure for the distal PA stump influenced the postoperative configuration of the central PA. With an aggressive surgical approach to central PS, PA anatomy was satisfactory with good hemodynamic variables after Fontan completion. Bilateral PA banding did not cause later vascular deformity.

Consequences of Right Ventricle–to–Pulmonary Artery Shunt at the First Stage for the Fontan Operation

The evidence of the advantageous physiology associated with right ventricle-to-pulmonary artery (RV-PA) shunt in the early postoperative period after the Norwood procedure for hypoplastic left heart syndrome has been recently widely reported. We investigated the late consequences of this modification from the perspective of the third-stage palliation, the Fontan operation. Between September 1995 and November 2006, a consecutive series of 50 children with hypoplastic left heart syndrome from a single institution underwent a fenestrated Fontan operation (lateral tunnel technique): group 1 (n = 19) after the modified Blalock-Taussig shunt, and group 2 (n = 31) after RV-PA shunt during the Norwood procedure. Hemodynamic, echocardiographic, electrocardiographic, and clinical operative and perioperative data were analyzed. Children after the RV-PA shunt were characterized by higher preoperative partial oxygen tension in pulmonary arteries (p = 0.018) and the aorta (p = 0.028), as well as lower systolic, diastolic, and mean aortic pressure (p = 0.005, p = 0.004, p = 0.019). After administration of 100% oxygen, this group additionally showed a lower value for systemic resistance (p = 0.013). The analyzed angiograms revealed a higher incidence of systemic-to-pulmonary collateral vessels (p = 0.003) in group 2. At the discharge after Fontan operation, children after the RV-PA shunt demonstrated higher arterial partial oxygen tension (p = 0.004). The two groups did not differ significantly with respect to the mortality, ventricular function, incidence of pleural effusions or rhythm disturbances, intensive care unit stay, and hospitalization time. The Norwood procedure with the RV-PA shunt provides satisfactory late hemodynamics. Children who underwent this method of palliation were more prone to the development of systemic-to-pulmonary arterial collaterals.

Hemodynamic status after the Norwood procedure: A comparison of right ventricle–to–pulmonary artery connection versus modified blalock-taussig shunt

Background The aim of this study is to compare hemodynamic status, in particular systemic oxygen delivery, in patients undergoing a Norwood procedure with a right ventricle–to–pulmonary artery (RV-PA) versus a modified Blalock-Taussig (mBT) shunt. Methods From June 2000 to November 2003, 44 consecutive neonates with hypoplastic left heart syndrome underwent a Norwood procedure. The first 25 patients received an mBT shunt; the subsequent 19 an RV-PA shunt. Hemodynamic data, including mixed venous oxygen saturation, was determined during the first 48 hours after surgery. Results The mBT and RV-PA shunt patients had no significant differences in systemic oxygen saturation, mixed venous oxygen saturation, arteriovenous oxygen saturation difference, or oxygen excess factor during the first 48 hours. Mixed venous saturation declined to a nadir in both groups at 6 to 12 hours. The RV-PA patients had significantly higher diastolic and mean blood pressures, and lower systolic blood pressure. Mean heart rate, common atrial pressure, and inotrope score did not differ between the two groups. The RV-PA patients received higher fraction of inspired oxygen and minute ventilation to achieve partial pressures of arterial oxygen and carbon dioxide, and pH, similar to mBT patients. Durations of mechanical ventilation, intensive care unit stay, and hospital stay did not differ between mBT and RV-PA patients. Operative survival in the mBT versus RV-PA group was 20 of 25 (80%) versus 17 of 19 (89%; p = 0.7). Conclusions Indicators of postoperative systemic oxygen delivery are equivalent in neonates who have undergone a Norwood procedure with an mBT or RV-PA shunt. Both mBT and RV-PA patients undergo similar declines in hemodynamic status 6 to 12 hours after surgery. Any advantages of one approach over the other lie in areas other than systemic oxygen delivery, such as resistance to physiologic insults, or preservation of ventricular function.