1. Staged Left Ventricular Recruitment and Biventricular Conversion for Patients With Borderline Left Heart 
Sitaram M. Emani, MD 
Operative Techniques in Thoracic and Cardiovascular Surgery 
Volume 21, Issue 2, Pages (June 2016)
DOI: /j.optechstcvs
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2. Figure 1
(A) A neonate with a borderline left heart presents with variable degrees of hypoplasia of the left ventricular cavity, mitral and aortic valve, and ascending aorta. Note that the presence of mitral or aortic valvular atresia excludes a patient from the SLVR approach, as techniques for reconstruction of the atretic valves have not yet been developed. Normative Z scores are used to quantitate the size of structures, with Z scores less than −3 being associated with poor prognosis with neonatal biventricular repair, particularly if multiple structures are hypoplastic in tandem. Other factors to take into consideration include the direction of flow across the transverse arch (antegrade vs retrograde) architecture of the mitral valve and the degree of the apex-forming left ventricle (the long axis dimension is probably a better predictor of the success of biventricular repair than the left ventricular end-diastolic volume). Left ventricular function must be taken into consideration as well. In a patient with concerns for left ventricular adequacy (which will differ from institution to institution), stage I palliation may provide a more predictable early outcome. With the SLVR strategy, one is not forced to make a definitive decision about long-term biventricular repair or single-ventricle palliation, permitting a more liberal application of stage I palliation as the first step in patients with an uncertain adequacy of left heart structures. (B) Stage I palliation is performed with aortopulmonary amalgamation and choice of pulmonary blood flow with RV-PA conduit or aortopulmonary shunt. In the neonatal time frame, interventions on the Ao, mitral valve, or left ventricle are difficult due to small size and fragile structures. In select cases, limited Ao commissurotomy or mitral papillary splitting may be performed to improve the mobility of these valves. If the patient has had a previous balloon aortic valvotomy, intervention on the Ao may be necessary if severe aortic insufficiency is present. However, in the presence of mild-to-moderate aortic insufficiency, intervention may not be necessary as long as the mitral valve is competent. Early in the experience, we were performing more rehabilitation maneuvers (EFE resection) at the time of the neonatal stage I procedure but found that these procedures add operative time and risk, and thus have shifted away from significant rehabilitation procedures at the time of the neonatal palliation. The atrial septum is made unrestrictive at this time. Although either form of pulmonary blood flow is acceptable, we prefer the RV-PA conduit with proximal transmural insertion (“dunking”) technique and composite valved femoral vein-ringed GORE-TEX graft. Alternative initial palliation with a hybrid stage I procedure may be an option in patients with very mild hypoplasia but contraindications to neonatal biventricular repair.10 However, in patients who require significant mitral or aortic valvuloplasty or EFE resection, the amount of time delay offered by the hybrid approach is limited (4-6 months). In our experience, this duration of time may not be sufficient to allow adequate left ventricular rehabilitation in patients with significant left heart hypoplasia, and therefore initial hybrid palliation followed by biventricular conversion is performed only in a select population of patients with very mild hypoplasia or unexplained neonatal ventricular dysfunction with otherwise normal left heart structures. EFE = endocardial fibroelastosis; RV-PA = right ventricle-to-pulmonary artery; PA = pulmonary artery; Ao = aortic valve.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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3. Figure 2
(A, B) Between 4 and 6 months of age, the patient returns for second-stage palliation. We prefer bidirectional Glenn procedure at this time. Particularly in patients with hypoplasia of the left PA or left pulmonary vein stenosis, leaving the RV-PA conduit perfusing the left PA with placement of the superior cavopulmonary anastomosis into the RPA allows augmentation of pulmonary blood flow and thus pulmonary venous return to the left heart (A, B). To prevent elevated Glenn pressures from the additional pulmonary blood flow, an obstructing bovine or autologous pericardial membrane is sutured within the PA between the Glenn anastomosis and the RV-PA conduit insertion site (A). A 2.7-mm fenestration is placed in this membrane to allow subsequent balloon dilation in the catheterization laboratory if necessary. PA = pulmonary artery; RPA = right pulmonary artery; RV-PA = right ventricle-to-pulmonary artery.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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4. Figure 2
Continued (C, D) Most of the work in terms of rehabilitation of the LV begins at the second-stage operation. At this stage and size surgical maneuvers to repair valves and resect EFE are technically feasible, and the child is stable from a physiologic standpoint and can tolerate maneuvers to load the left heart. Because the Glenn procedure itself is relatively straightforward, additional procedures performed at this time are relatively well tolerated. Intracardiac work is performed through a right atriotomy and trans-septal approach (C). The right atriotomy is performed (dashed lines) to provide access to the interatrial septum. For patients with HLHS variants, the mitral valve has an appearance of congenital mitral stenosis, including papillary muscle fusion, single papillary muscle, and tethering attachments of muscles between the left ventricular wall and the leaflet and papillary muscle apparatus. This leads to inability of the leaflet to open properly as well as malcoaptation with regurgitation. There is also hypoplasia of the mitral valve annulus. Annular hypoplasia cannot be easily corrected surgically, but inflow into the mitral valve can be improved by splitting of the fused papillary muscles (D). LV = left ventricle; EFE = endocardial fibroelastosis; HLHS = hypoplastic left heart syndrome.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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5. Figure 2
Continued (E-G) In addition, the PL can be detached from the annulus at its base, exposing the underlying secondary chordal attachments, EFE, and muscle bundles (E, F). Abnormal attachments are divided, and papillary muscle EFE is resected, thus freeing up both the PL and papillary muscles. The goal is to improve the mobility of the leaflets and the orifice size, not necessarily to normalize orifice size. Time and flow through the valve will ultimately lead to further growth of the annulus and valve apparatus. Because the PL may be deficient from chronic tethering, augmentation of the base may be necessary using autologous or bovine pericardium (G). In patients with HLHS variants (no VSD), EFE frequently impairs both the diastolic and systolic ventricular functions. In these patients, a transmitral approach is utilized for the removal of EFE. This approach begins on the papillary muscles and extends down toward the apex of the LV posteriorly. Along the septum, a thick layer of EFE is often present, and removal may necessitate detachment of the anterior leaflet from the annulus to access this portion of the septum. EFE is a thick, almost cartilaginous material that is quite adherent to the underlying muscle fibers and requires sharp dissection to develop the appropriate layer. From histologic examination, it is clear that EFE often has fimbriae that extend into the underlying myocardium, so EFE may recur despite resection (F). A = anterior; P = posterior; PL = posterior leaflet; LV = left ventricle; EFE = endocardial fibroelastosis; HLHS = hypoplastic left heart syndrome; VSD = ventricular septal defect.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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6. Figure 3
(A, B) In patients with an unbalanced AV canal defect and a borderline left ventricle, left ventricular recruitment involves mitral valve redistribution and atrial septation, but not necessarily ventricular septation. The most common left-sided valvular abnormalities in patients with unbalanced AV canal defect are deficiency of the left-sided superior and inferior bridging leaflets, and single papillary muscle with tethering of the superior and inferior bridging leaflets (A). Right atriotomy is performed (dashed lines) to access the common atrioventricular valve. Splitting of the papillary muscle begins the process of separation into 2 separate distinct papillary heads and ultimately facilitates cleft closure, which cannot be performed in the presence of a single papillary muscle abnormality (B). IV = interventricular; AV = atrioventricular; CS = coronary sinus.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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7. Figure 3
Continued (C, D) Although superior and inferior bridging leaflets on the left side of the AV valve are frequently deficient, redistribution of leaflet is possible by the placement of an atrial septal patch onto the right-sided portion of the AV valve, thus essentially “stealing” the leaflet from the right-sided AV valve. Autologous or bovine pericardium can be utilized for this atrial septation. If 2 papillary muscles are present, closure of the left cleft as well as the left cleft and the right cleft prepares the valve for ultimate separation at the time of biventricular conversion for ultimate biventricular conversion. Closure of the ventricular septal defect at the time of this procedure is reasonable but may not be necessary to achieve the goal of left ventricular growth. The risk of heart block with closure of the ventricular septal defect must be taken into consideration, especially in a patient who may ultimately require single-ventricle palliation if the left heart does not grow (C). In patients with both hypoplastic left heart syndrome variant and an unbalanced AV canal defect, closure of the atrial septal defect with a fenestrated patch (4-5 mm) is performed. The size of the fenestration is determined based upon the age and weight of the patient. In a 4-month-old (approximately 5-6 kg) child, a 4- to 5-mm fenestration allows for unrestrictive atrial septal flow early after surgery. This is preferable, so as to ensure that the left atrial pressures are low in the early postoperative period. Over time as a child grows and fibrin deposits on the fenestration, the defect becomes restrictive. As the defect becomes more restrictive, it gradually promotes increasing proportion of the pulmonary venous return to enter into the left heart, thus promoting growth of the left heart structures. Frequent interrogation of the gradient across the atrial septal defect by echocardiogram is warranted to ensure that left atrial hypertension does not develop, and head circumference must be monitored as a surrogate for Glenn pressures. If the gradient across the atrial septal defect increases above 8 mmHg, or concerns for superior vena cava syndrome develop, catheterization must be performed to measure pressures and dilate or stent the atrial septal defect. At catheterization, the atrial septal fenestration can be calibrated to decrease the gradient across the fenestration to 5 mmHg, and this is better controlled with a stent that can be adjusted based upon hemodynamic measurements during the catheterization procedure (D). AV = atrioventricular.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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8. Figure 4
(A, B) The ascending aorta above the aortopulmonary amalgamation (DKS) is opened, and the aortic valve is examined. Frequently, the valve is either commissural or unicommissural. Fused commissures are opened (A). The aortic valve is opened by incising from fused leaflet toward the commissure (white arrow, A). Thickened leaflets are debrided. In patients with aortic valvular regurgitation, more complex repairs including leaflet augmentation or replacement may be necessary. Subvalvular stenosis should be resected at this time as well, and provides visualization for endocardial fibroelastosis and the left ventricular outflow tract that may not have been visualized through the mitral valve. Even though the aortic annulus may be hypoplastic, we have seen a significant growth of the annulus promoting flow through the left ventricle in many patients. Ultimately, in patients with severely deformed aortic valves, valve replacement may be necessary to accomplish biventricular circulation, but that commitment is not made until the next stage (B). DKS = Damus-Kaye-Stansel connection.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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9. Figure 5
Over the period of the next year to two, as the atrial septum gradually restricts, more flow is directed through the mitral valve, left ventricle, and aortic valve. Echocardiogram is used to document the increase in the size of structures over time, and should be performed every 2-4 months to document the atrial septal defect gradient, and low threshold for cardiac catheterization if concerns of left atrial hypertension arise. Even in patients who require dilation of the atrial fenestration, flow is promoted through the left heart as documented by MRI. Typically, all patients undergo interval cardiac catheterization and MRI with flow measurements every 12 months following the recruitment procedure to establish trends in flow and hemodynamics. At cardiac catheterization, balloon occlusion of the atrial septal defect is performed to force all pulmonary venous return to enter into the left heart. Flow measurements across the mitral and tricuspid valve are compared by MRI. The total flow across the left heart may reach a full cardiac output by 2 years of age because it includes flow from Glenn plus right ventricle-to-pulmonary artery conduit and aortopulmonary collaterals. A left ventricular end-diastolic pressure less than 13 mmHg in the setting of a full cardiac output signals adequate left heart structures for biventricular conversion. The decision to ultimately commit to biventricular or single-ventricle palliation is made based upon the response of the left heart structures to left ventricular recruitment procedures and reassessment of risk of single-ventricle palliation. In patients with hypoplastic left heart syndrome variants, our experience has been that approximately one-third of patients will favorably respond with growth of left heart structures. MRI = magnetic resonance imaging.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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10. Figure 6
The decision to proceed to biventricular repair is based upon the response of the left heart structures to recruitment maneuvers. Although no absolute value of LV end-diastolic volume is utilized, an indexed LV volume greater than 20 mL/m2 in patients with an unbalanced AV canal defect and an indexed LV volume greater than 40 mL/m2 in patients with hypoplastic left heart syndrome variants are generally associated with favorable outcomes. Biventricular conversion surgery entails takedown of the aortopulmonary amalgamation with either direct reconstruction of main pulmonary artery to branch pulmonary arteries or Ross procedure. The Ross procedure may be necessary in patients with significant mixed aortic valve disease. However, patients who demonstrate significant improvement in the annulus of the aortic valve may be managed with native aortic re-anastomosis. The pulmonary artery is disconnected from the amalgamation, and the native aortic root is directed into the ascending aorta. Reconstruction of the native main pulmonary artery to the branch pulmonary arteries may require augmentation with an anterior patch. (6B). The RV to PA conduit is taken down, and the SVC connection to the pulmonary artery is disconnected. The branch pulmonary arteries may require reconstruction with patch as well. Establishment of continuity between SVC to right atrium may require a posterior flap (6A) of atrial appendage with anterior augmentation using pericardium or Gore-Tex graft material (6B). Rarely, the right atrial appendage has enough redundancy to directly reach the SVC. Generally, the fenestration is left in atrial septal patch to allow decompression of the left atrium in the early postoperative recovery. LV = left ventricle; AV = atrioventricular.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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11. Figure 7
A general algorithm for patient management according to the SLVR strategy is demonstrated. Mitral and aortic annular Z scores greater than −3 are acceptable. End-diastolic pressure measured at catheterization is used to risk stratify patients, with EDP less than 13 mmHg being associated with favorable outcomes after conversion. EDP = end-diastolic pressure.
Operative Techniques in Thoracic and Cardiovascular Surgery  , DOI: ( /j.optechstcvs )
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