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Department of Cardiac Surgery, Boston Children's Hospital, Harvard Medical School, Boston, MassDepartment of Cardiothoracic Surgery, Cleveland Clinic Foundation, Cleveland, Ohio
Address for reprints: Sitaram M. Emani, MD, Department of Cardiac Surgery, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA 02115.
Restoration of biventricular circulation is an alternative management strategy in unbalanced atrioventricular canal defects (uAVCDs), especially in patients with risk factors for single-ventricle palliation (SVP) failure. When ventricular volume is inadequate for biventricular circulation, recruitment procedures may accommodate its growth. In this study, we review our uAVCD experience with biventricular conversion (BIVC) after prior SVP.
Methods
This is a single-institution, retrospective cohort study of uAVCD patients who underwent BIVC after SVP, with staged recruitment (staged) or primary BIVC (direct) between 2003 to 2018. Mortality, unplanned reinterventions, imaging, and catheterization data were analyzed.
Results
Sixty-five patients underwent BIVC from SVP (17 stage 1, 42 bidirectional Glenn, and 6 Fontan). Decision for conversion was based on poor SVP candidacy (n = 43) or 2 adequately sized ventricles (n = 22). Of the 65 patients, 20 patients underwent recruitment before conversion. The staged group had more severe ventricular hypoplasia than the direct group, reflected in prestaging end-diastolic volume z scores (–4.0 vs –2.6; P < .01), which significantly improved after recruitment (–4.0 to –1.8; P < .01). Median follow-up time was 1.0 years. Survival and recatheterizations were similar between both groups (hazard ratio, 0.9; 95% CI, 0.2-3.7; P = .95 and hazard ratio, 1.9; 95% CI, 0.9-4.1; P = .09), but more reoperations occurred with staged approach (hazard ratio, 3.1; 95% CI, 1.3-7.1; P = .01).
Conclusions
Biventricular conversion from SVP is an alternative strategy to manage uAVCD, particularly when risk factors for SVP failure are present. Severe forms of uAVCDs can be converted with staged BIVC with acceptable mortality, albeit increased reinterventions, when primary BIVC is not possible.
Staged and primary biventricular conversion from single-ventricle palliation is an alternative strategy to manage unbalanced atrioventricular canal defects, especially when risk factors are present.
Severe forms of unbalanced atrioventricular canal defects are often managed with single-ventricle palliation. We demonstrate that biventricular conversion from prior single ventricle palliation can be achieved with acceptable early and late mortality, and that recruitment procedures promotes significant growth of hypoplastic ventricles and allow for successful conversion to biventricular circulation.
Unbalanced atrioventricular canal defects (uAVCDs) represent 10% to 15% of all patients with complete atrioventricular (AV) canal defects.
Although the definition of an unbalanced AV canal is actively debated, a general anatomic feature is the presence of varying hypoplasia of the inflow valve and/or ventricle.
Echocardiographic features defining right dominant unbalanced atrioventricular septal defect: a multi-institutional congenital heart surgeons' society study.
Echocardiographic definition and surgical decision-making in unbalanced atrioventricular septal defect: a congenital heart surgeons' society multiinstitutional study.
uAVCDs can be further categorized by a left- or right-sided dominance, in reference to the common AV valve positioned predominantly over the left or right ventricle, respectively.
Echocardiographic definition and surgical decision-making in unbalanced atrioventricular septal defect: a congenital heart surgeons' society multiinstitutional study.
Based on the severity of AV valve or ventricle hypoplasia, current management includes biventricular repair or, in severe cases, single-ventricle palliation (SVP).
As widely demonstrated, patients with SVP can develop serious complications later in life such as protein-losing enteropathy, heart failure, and others. Studies report survival outcomes between 60% and 80% at 1 and 5 years.
Furthermore, outcomes were reported to worsen with risk factors such as Down syndrome, younger age, or AV valve regurgitation. An alternative strategy for patients with uAVCD is initial SVP followed by subsequent biventricular conversion following somatic growth.
In circumstances of severe imbalance due to valvular or ventricular hypoplasia, interim ventricular recruitment/staging procedure can be performed to promote inflow into the hypoplastic valve or ventricle, followed by biventricular conversion in patients demonstrating favorable response to recruitment maneuvers.
The objective of this study was to review outcomes in a tertiary center of patients with uAVCD with prior SVPs who underwent recruitment and subsequent biventricular repair.
Methods
Study Design
A single-center retrospective review was performed on all patients diagnosed with an uAVCD who had undergone a previous SVP followed by subsequent biventricular conversion at Boston Children's Hospital between January 2003 and December 2018. The hospital institutional review board waived the need for parental consent for patients included in this study and approved this study for publication under protocol No. P00033695 on October 25, 2019.
Patients were separated into 2 groups: staged biventricular conversion: uAVCD with prior SVP who underwent procedures for staged recruitment followed by subsequent biventricular conversion, and primary biventricular conversion: uAVCD with prior SVP who underwent subsequent biventricular conversion without staged recruitment procedures. Patients who are in the process of recruitment were excluded from the current study.
Definitions
An uAVCD was defined as a complete AV septal defect with an AV valve override >60% over either ventricle, the presence of a hypoplastic-/nonapex-forming ventricle, or indexed ventricular volumes with a z score <–2 or 4, and those who were deemed unbalanced and underwent SVP at an outside institution. In determining AV valve override, we measured the area of the common AV valve in diastole, and the left and right AV valve components based on the interventricular septum. SVP was defined as a stage 1 procedure, bidirectional Glenn procedure, or a Fontan procedure. Patients with pulmonary artery banding as sole palliation were not included in this study.
Staging/recruitment procedure was defined as a procedure purposed to redirect or increase blood flow or accommodate growth of the hypoplastic ventricle. Specifically, these comprised a fenestrated atrial septal defect (ASD) creation, septation of AV valve, and/or an aortopulmonary shunt, typically a modified Blalock-Taussig-Thomas Shunt (mBTTS). Techniques for staging/recruitment and biventricular conversion were performed as previously described (Figure E1).
In brief, the size of the ASD fenestration is typically 4 mm. AV valve septation at the time of staged ventricular recruitment is typically done by opposing the superior and inferior leaflets in such a way as to close the central portion of the cleft. The atrial patch is then sutured to the confluence of the common leaflets, thus separating the common valve into right and left components. The atrial patch is essentially similar to the atrial patch of the 2-patch repair and is performed without division of the leaflet. The size of the mBTTS depends on the weight and body surface area of the patient, but it has been our institutional preference to use a 3.5- to 4-mm mBTTS. The index surgery was defined as the biventricular conversion procedure. All index and recruitment procedures were done at our tertiary care center, but the initial SVP may have been performed at an outside institution.
Outcomes and Follow-up
Patient charts were reviewed, and the following data were extracted: patient demographic characteristics, imaging details, prior interventions, operative details, postoperative complications, reinterventions, and mortality. The majority of patients had a cardiac magnetic resonance imaging (CMRI) scan before recruitment and before biventricular conversion. For patients who did not have CMRI data, 3-dimensional echocardiographic data were used to obtain ventricular dimensions from prerecruitment and prebiventricular conversion, to maintain consistency.
Validation of 3D echocardiographic assessment of left ventricular volumes, mass, and ejection fraction in neonates and infants with congenital heart disease a comparison study with cardiac MRI.
Using the Boston Children's Hospital Heart Center database, z scores were calculated for the corresponding MRI and echocardiographic measurements. Mortality was defined as death or transplant occurring after the biventricular conversion. Reoperations were defined as any unplanned operative procedure that occurred after the index procedure. Likewise, reinterventions were defined as any unplanned catheter-based interventions that occurred after the index procedure. Follow-up was measured from the date of the index procedure. All follow-up was performed at our tertiary care center.
Statistical Analysis
Continuous variables are expressed as median (interquartile range [IQR]). Categorical variables are presented as absolute and relative frequencies. All continuous variables were normally distributed as tested by Shapiro-Wilk test and graphical represented by histograms and Q-Q plots. Variables were analyzed regarding the need or not for recruitment of the ventricle before biventricular conversion. Between-group comparisons were performed using 2-sided t test. Pearson χ2 test was used for nominal variables. Longitudinal analysis for between-groups comparisons was performed using 2-way repeated-measures analysis of variance within the framework of fitting mixed-effects linear regression models. To reduce the probability of false-positive results (type I error) due to multiple comparisons, Benjamin and Hochberg false discovery rate was applied to control the familywise error to <0.05. Five-year overall, catheterization-free and reoperation-free survival was estimated following generation of Kaplan-Meier curves. The log-rank test was used to perform comparisons of survival between different groups. Cox proportional hazards univariate models were used to identify the variables that were independently predictive of the outcome of interest. All tests reported are 2-tailed. Statistical analyses were performed with Stata version 15.0 (StataCorp LLC) and GraphPad Prism 8 for MacOS (GraphPad Software).
Results
Baseline Characteristics
A total of 65 patients met our inclusion criteria. Of these, 41 patients had right-dominant uAVCD and 24 had left-dominant uAVCD. The median age at biventricular conversion was 3.5 years (IQR, 1.7-6.1 years). The median end-diastolic volume (EDV) z score of the unbalanced ventricle was –3.2. Review of our patient cohort with prior SVP demonstrated that the majority had risk factors for poor SVP candidacy in uAVCDs. Specifically, 54% (35 out of 65) had heterotaxy, 71% (46 out of 65) demonstrated the presence of AV valve regurgitation, 32% (21 out of 65) had pulmonary vein stenosis or partial/total anomalous pulmonary venous return, 9% (6 out of 65) had failing SVP physiology, and 25% (16 out of 65) had trisomy 21. Only 34% (22 out of 65) of patients had no risk factors. Before biventricular conversion, 26% had undergone stage 1/Norwood procedure, 65% had undergone bidirectional Glenn, and 9% had undergone a Fontan procedure. Eighty-five percent of patients (55 out of 65) had their SVP operation at an outside hospital. Baseline patient characteristics are demonstrated in Table 1. The mean left atrial pressure was 7.9 ± 2.3 mm Hg, pulmonary artery pressure was 13.6 ± 3.1 mm Hg, and the mean pulmonary vascular resistance was 2.0 ± 1.1 Woods units (Table 2).
Table 1Baseline patient characteristics and baseline patient characteristics of all biventricular conversions (BIVs)
Table 2Preoperative imaging and hemodynamic characteristics
Variable
All BIVs (N = 65)
Staged BIV (n = 20)
Primary BIV (n = 45)
P value
Presence of AVV regurgitation
46 (71)
12 (60)
34 (76)
.203
Left atrial pressure (mm Hg)
7.9 ± 2.3
7.5 ± 2.1
8.1 ± 12.4
.321
Mean PA pressure (mm Hg)
13.6 ± 3.1
12.8 ± 12.5
13.8 ± 13.3
.308
PVR (Woods Unit)
2.0 ± 1.1
2.2 ± 1.5
1.8 ± 0.8
.311
Right dominant (n = 41)
AVVI
0.33 ± .08
0.29 ± 1.07
0.36 ± 1.06
<.001
LVEDVi (mL/m2)
38.9 ± 18.7
27.7 ± 9.64
46.7 ± 9.6
.001
RVEDVi (mL/m2)
110.1 ± 11.2
97.6 ± 26.5
119.6 ± 26.3
.072
Left dominant (n = 24)
AVVI
0.63 ± 0.03
0.66 ± 0.02
0.62 ± 0.03
.028
LVEDVi (mL/m2)
89.1 ± 43.3
133.6 ± 16.2
80.3 ± 28.9
.048
RVEDVi (mL/m2)
48.4 ± 15.1
36.6 ± 0.8
49.9 ± 15.5
.256
LVEF (%)
55 ± 6
51 ± 6
56 ± 6
.278
Values are presented as n (%) or mean ± SD. BIV, Biventricular conversion; AVV, atrioventricular valve; PA, pulmonary artery; PVR, pulmonary vascular resistance; AVVI, atrioventricular valve index; LVEDVi, index left ventricular end diastolic volume; RVEDVi, index right ventricular end diastolic volume; LVEF, left ventricular ejection fraction.
A total of 20 patients underwent staged biventricular conversion and 45 underwent primary biventricular conversion (Figure 1). The average age at the time of biventricular conversion was 4.0 years and 3.4 years for the staged biventricular conversion and primary biventricular conversion, respectively. Staged biventricular conversion patients spent a median of 2.91 years with SVP physiology and 1.1 years with recruitment. Primary biventricular conversion patients spent a median of 3.1 years in SVP. Patients in staged biventricular conversion had a significant difference in the proportion of patients with a severely hypoplastic ventricle, demonstrated by EDV z score (–4.0 ± 0.9 vs –2.6 ± 1.4; P < .01), when compared with primary biventricular conversion. All 20 patients in the staged biventricular conversion group underwent 1 or more staged recruitment procedure to promote growth of the hypoplastic ventricle and/or AV valve. Recruitment procedures were performed in 35% (7 out of 20) during stage 1, 60% (12 out of 20) during BDG, and 5% (1 out of 20) during Fontan. During recruitment, 75% (15 out of 20) had a fenestrated ASD, 66% (13 out of 20) had an AV valve partitioning, 40% (8/20) had mBTTS placement, and 60% had concurrent procedures (14 out of 20). Preoperative characteristics of patients who underwent staged biventricular conversion are demonstrated in Table E1. When comparing the preoperative imaging and hemodynamics of staged biventricular conversion and primary biventricular conversion, we found the mean left atrial pressures were 7.5 ± 2.1 mm Hg versus 8.1 ± 2.4 mm Hg (P = .32), mean pulmonary artery pressures were 12.8 ± 2.5 mm Hg versus 13.8 ± 3.3 mm Hg (P = .31), and pulmonary vascular resistances were 2.2 ± 1.5 Woods units vs 1.8 ± 0.8 Woods units (P = .31), respectively (Table 2).
Figure 1Staged and primary biventricular conversion from single-ventricle palliation (SVP) is an alternative strategy to manage unbalanced atrioventricular (AV) canal defects, particularly in those with high-risk factors for SVP failure, with acceptable early and late mortality. ASD, Atrial septal defect; BIV, biventricular conversion; HR, hazard ratio; CI, confidence interval.
Comparison of preoperative characteristics between staged biventricular conversion and primary biventricular conversion groups demonstrated similar incidence of heterotaxy (55% vs 53%; P = .90), pulmonary venous disease (40% vs 29%; P = .38), and trisomy 21 (15% vs 29%; P = .23). In both groups, the majority of the uAVCDs were right-dominant defects (80% vs 55%; P = .50). No significant differences were found between the 2 groups in regard to single-papillary or closely spaced papillary muscles, left ventricular outflow tract obstruction, AV valve regurgitation, and nonapex forming unbalanced ventricle (P = .11) Baseline patient characteristics based on conversion strategy can be found in Table E1. An atrioventricular valve index was calculated for patients undergoing staged biventricular conversion and was determined to be 0.29 ± 0.07 and 0.66 ± 0.02 in right-dominant and left-dominant uAVCD, respectively. In direct biventricular conversion, atrioventricular valve index was calculated to be 0.36 ± 0.06 and 0.62 ± 0.03 for right-dominant and left-dominant patients, respectively (Table 2).
Postoperative Characteristics
Following biventricular conversion, all patients were evaluated and reviewed in terms of early (30 days) and late postoperative outcomes (Table 3). Among all patients, 30-day survival was 95% (62 out of 65), and 1-year survival was 89% (48 out of 54). Median lengths of intensive care unit and hospital stay were 15 and 25 days, respectively. Predischarge echocardiography demonstrated that 23% (15 out of 65) patients developed moderate or more AV valve regurgitation. Left ventricle function was determined to be qualitatively normal in 80% (52 out of 65) patients, whereas 20% (13 out of 65) had mild–moderate or more dysfunction. Comparative analyses of staged versus primary biventricular conversion groups demonstrate no difference between the length of intensive care unit stay (13.5 vs 18.0 days; P = .40) and length of total hospital stay (20.0 vs 27.0 days; P = .46), respectively. Follow-up time was 1.0 year (IQR, 0.3-2.8 years) and 1.1 years (IQR, 0.2-4.3 years) for staged biventricular conversion and primary biventricular conversion, respectively.
Table 3Postoperative patient characteristics
Variable
Staged BIVC
Primary BIVC
P value
Early postoperative complication
ECMO
0 (0)
6 (13)
.087
Heart block
3 (15)
9 (20)
.835
Follow-up time
1.0 (0.3-2.8)
1.1 (0.2-4.3)
.096
ICU stay
13.5 (5.8-20.5)
18.0 (8.0-25.0)
.396
Hospital stay
20.0 (12.3-37.8)
27.0 (14.0-40.0)
.462
Late postoperative complication
Death
3 (15)
7 (16)
.350
Reoperation
10 (50)
13 (29)
.147
Catheter-based reintervention
10 (50)
17 (38)
.356
Values are presented as n (%) or median (range). BIVC, Biventricular conversion; ECMO, extracorporeal membrane oxygenation; ICU, intensive care unit.
Among all patients, 10 deaths occurred and none of the cohort underwent transplantation. There were 3 deaths among staged biventricular conversion patients, and 7 deaths occurred in patients undergoing primary biventricular conversion (15% vs 16%; P = .35). A large portion of the mortalities was due to systolic or diastolic ventricular dysfunction leading to heart failure and multiorgan dysfunction (80%; 8 out of 10 patients), whereas others developed severe AV valve regurgitation and subsequent mortality (20%; 2 out of 10 patients). Of these patients, 1 patient was listed for transplantation. The other 9 patients succumbed to multiorgan failure and were not transplant candidates or died before listing. Characteristics of patients with mortality are described in Table E2. Overall/transplant-free survival between the 2 groups were not statistically different (hazard ratio [HR], 0.9; 95% CI, 0.2-3.7; P = .95) (Figure 2, A). Reoperations were more frequent in staged biventricular conversion (HR, 3.1; 95% CI, 1.3-7.1; P = .01), but no statistical significance was found in catheterized reinterventions (HR, 1.9; 95% CI, 0.9-4.1; P = .09) (Figure 2, B and C).
Figure 2A, Overall survival of staged biventricular conversion (BIVC) and primary BIVC (hazard ratio [HR], 0.9; 95% CI, 0.2-3.7; P = .95). B, Freedom from any reoperation of staged BIVC and primary BIVC (HR, 3.1; 95% CI, 1.3-7.1; P = .01). C, Freedom from any recatherization of staged BIVC and primary BIVC (HR, 1.9; 95% CI, 0.9-4.1; P = .09).
Subgroup analyses for staged biventricular conversion demonstrate that single papillary muscle in the hypoplastic ventricle was associated with increased reoperation rate (HR, 2.1; 95% CI, 1.1-4.3; P = .03) (Table 4). Other preoperative factors were not found to be associated with mortality, reoperation, or recatheterization. For primary biventricular conversion, preoperative AV valve regurgitation was found to be a predictor for both reoperation (HR, 3.2; 95% CI, 1.2-8.6; P = .02) and mortality (HR, 8.1; 95% CI, 1.6-41.9; P = .01).
Review of CMRI and echocardiographic data from prerecruitment and postrecruitment/prebiventricular conversion demonstrated significant growth of the recruited ventricle following the staged recruitment procedure. EDV of the recruited ventricle was found to be 43.8 mL/m2 before recruitment and was 61.9 mL/m2 after recruitment (z score, –4.0 to –1.8; P < .01) (Figure 3, A). Review of pre- and postbiventricular conversion volumetric data demonstrated a nonsignificant increase EDV of the hypoplastic ventricle (staged biventricular conversion: z score, –1.8 to –1.3; P = .31 and primary biventricular conversion: z score, –2.6 to –2.14; P = .45) (Figure 3, B).
Figure 3A, Prerecruitment (before) and postrecruitment/pre-biventricular conversion (BIV) (after) end-diastolic volumes (EDV) for the recruited ventricle. B, Recruited ventricle end-diastolic volumes for staged versus primary BIV before recruitment, before BIV, and at discharge.
Current management for uAVCDs depends on the severity of imbalance of the AV valve and ventricles. This descriptive study demonstrates a single institutional experience with biventricular conversion following initial SVP for uAVCD, and demonstrates the feasibility of biventricular conversion in a select subset of patients. Many patients undergoing this approach frequently had risk factors for poor outcomes related to SVP. The approach included primary biventricular conversion in patients with favorable ventricular morphology, and staged approach in patients with more significant hypoplasia, with the goal of the staged recruitment being to retain candidacy for biventricular circulation in patients with single-ventricle physiology. The series demonstrates that this approach is feasible in select patients, although mortality and reoperation remain a significant concern in patients with the highest risk.
In this series, biventricular conversion was performed in patients with a hypoplastic, unbalanced ventricle, as demonstrated by a median EDV z score of –3.2. Moreover, most patients presented with 1 or more risk factors for SVP failure, such as heterotaxy; trisomy 21; and, in some cases, symptoms of failing single-ventricle physiology.
The presence of left ventricular systolic dysfunction would be a contraindication to biventricular conversion, but none of the patients in this series had this issue. Although hypoplasia of right or left heart structures may be a deterrent for biventricular circulation, previous studies have reported feasibility and success in biventricular repair and conversion in patients with borderline hypoplasia.
When presented with a patient with uAVCD who had undergone previous SVP, the decision regarding ongoing SVP management versus biventricular conversion should be made based on the risk assessment of each strategy. The majority of patients who underwent biventricular conversion with or without recruitment had undergone a previous bidirectional Glenn procedure (65%), which permitted delay of the conversion to age beyond early infancy.
Previous studies have shown that primary repair of uAVCD carries the highest risk in neonates and young infants.
In our institution, we have tended to utilize neonatal Norwood operations more liberally in patients with favorable anatomy, with the understanding that staged biventricular conversion is feasible.
Still, the decision regarding primary versus staged approach to biventricular conversion requires careful consideration. The staged procedures can be done at the time of bidirectional Glenn, although in this series, the majority of recruitment procedures were performed after the bidirectional Glenn (before Fontan) because they were referred from other institutions. Biventricular conversion is typically performed 12 to 18 months after staged recruitment to allow sufficient time for growth, which has been demonstrated in various pathologies with hypoplastic ventricles.
In this present study, comparison of staged and primary biventricular conversion groups demonstrated that the unbalanced ventricle was likely to have greater degree of hypoplasia in those undergoing staged biventricular conversion, demonstrated by a lower ventricular EDV (z score, –4.0 vs –2.6) at initial presentation. This finding reflects our institutional practice of staged recruitment in patients with severely hypoplastic heart structures followed by biventricular conversion in those who demonstrate progressive valvular and ventricular growth.
In patients with severe AV valve hypoplasia and single papillary muscles, a staged approach may be preferred as it allows optimization of the AV valve before biventricular conversion. However, variables such as single papillary muscle or parachute valve, nonapex forming ventricle, heterotaxy, or pulmonary venous disease, were not statistically different between the 2 groups.
Although biventricular conversion by primary or staged approach is feasible, the series demonstrates 15% mortality associated with biventricular conversion. This is clearly higher than mortality associated with primary repair of balanced AVCD, but may be similar to mortality in other series of primary repair for uAVCD.
This may reflect the advanced levels of preoperative illness, presence of high-risk features, genetic abnormalities, or inadequate circulatory reserve. Given the small number of patients in this study, we were unable to detect clear risk factors for mortality to allow for better patient selection and risk mitigation. Certainly, when considering management of a patient with uAVCD who had undergone SVP, the risk of ongoing SVP should be weighed against the risk of biventricular conversion. The risk of mortality with biventricular conversion should be compared with long-term survival for patients with uAVCD who completed or are undergoing SVP, with literature suggesting survival as low as 60%.
The risk of reoperation following biventricular conversion reflects persistent AV valvular dysfunction, which is characteristic of uAVCDs. Certain anatomic features in uAVCDs, including unusual AV cleft, abnormalities of papillary muscle architecture, annular hypoplasia, and leaflets dysplasia can pose significant challenges for repair.
Our data demonstrated 23% had AV valve regurgitation postoperatively. Not surprisingly, reinterventions in both groups were required primarily to address recurrent AV valve regurgitation and, to a lesser extent, outflow tract obstruction. Subgroup analyses demonstrated a greater risk for reoperation in patients with single papillary muscle and in those with preoperative AV valve regurgitation. Presence of a single papillary or parachute valve and preoperative AV valve regurgitation are known to be associated with increased risk of reoperation after primary repair of AVCDs. Improvements in surgical valve repair techniques in patients with severe valve deformities are necessary to reduce the risk of reoperation in this patient population.
The majority of catheter reinterventions were performed to address stenosis of pulmonary artery branches. Because most conversions occurred after a bidirectional Glenn procedure, these reinterventions are likely to result from the manipulation of these branches during SVP or Glenn takedown.
Staged biventricular conversion and primary biventricular conversion have similar early and late postoperative outcomes, but staged conversion is associated with an increased risk of reoperation, especially related to the AV valve. Freedom from recatherization were not statistically significant, although the trend may favor primary biventricular conversion over staged biventricular conversion. However, overall survival for both groups were similar. These outcomes suggest that recruited ventricles are functional and can provide adequate systemic cardiac output, with the acceptable risk of future reintervention, particularly in patient groups who may have unfavorable outcomes in single-ventricle physiology. It also supports an alternative strategy for recruitment in patients with uAVCDs that require optimization before conversion, particularly those who may require additional growth of the hypoplastic ventricle.
The rationale underlying staged recruitment is that fluid forces provide a stimulus for growth of hypoplastic structures.
In patients with uAVCDs, ventricular recruitment consisted of ASD fenestrated closure, AV valve partitioning, and/or additional inflow using a mBTTS in patients with hypoplastic left heart structures. After a median of 1.1 years with staging, staged biventricular conversion patients showed significant growth of the ventricle before conversion. By the end of the recruitment period, the EDV of the staged biventricular conversion group was similar to that of the primary biventricular conversion group.
Limitations
This study is a retrospective review from a single institution. The biventricular conversion and recruitment strategies are still novel, and this series includes patients in our early experience. The number of staged biventricular conversions in uAVCD continue to be small and do not have a clear comparison group. Another limitation may be that volumetric measurements were extracted from 3-dimensional echocardiograms due to missing CMRI data, in a minority of patients. However, studies demonstrate that measurements taken from either modality are reliable and compare well, even in hypoplastic ventricles.
Validation of 3D echocardiographic assessment of left ventricular volumes, mass, and ejection fraction in neonates and infants with congenital heart disease a comparison study with cardiac MRI.
Many patients were referred to our center, and thus indications for SVP and preoperative volumetric data were unavailable. A final limitation is that many patients returned to outside institutions for their follow-up visits, leading to decreased numbers of completed follow-up data.
Conclusions
Patients with uAVCD and severe forms of ventricle hypoplasia continue to experience management challenges and may initially require SVP. Although long-term studies will be required, our study demonstrates that biventricular conversion is an alternative to SVP, with acceptable mortality given the high-risk profile for SVP failure in our patient cohort. Our study also demonstrates that ventricular recruitment provides significant growth of the hypoplastic ventricles and those undergoing staged recruitment before conversion. Conversion to a biventricular circulation is feasible albeit with nontrivial mortality and risk of reintervention.
The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.
Appendix E1
Figure E1Schema of staged biventricular conversion. A, Diagram of an unrepaired unbalanced atrioventricular canal defect. B, Stage 1 procedure is performed. C, Staging procedures such as atrial septation and/or modified Blalock-Taussig-Thomas shunt is performed to promote growth of hypoplastic ventricle during single ventricle palliation state. D, Single ventricle circulation is converted to a biventricular circulation after the ventricle demonstrates adequate growth and function.
Echocardiographic features defining right dominant unbalanced atrioventricular septal defect: a multi-institutional congenital heart surgeons' society study.
Echocardiographic definition and surgical decision-making in unbalanced atrioventricular septal defect: a congenital heart surgeons' society multiinstitutional study.
Validation of 3D echocardiographic assessment of left ventricular volumes, mass, and ejection fraction in neonates and infants with congenital heart disease a comparison study with cardiac MRI.
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