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J Thorac Cardiovasc Surg 2007;134:1406-1412
© 2007 The American Association for Thoracic Surgery

Surgery for Congenital Heart Disease

Fate of the right ventricle after fenestrated right ventricular exclusion for severe neonatal Ebstein anomaly

Childrens Hospital Los Angeles and the Keck School of Medicine, Los Angeles, Calif.

Read at the Eighty-seventh Annual Meeting of The American Association for Thoracic Surgery, Washington, DC, May 5-9, 2007.

Received for publication May 2, 2007; revisions received July 10, 2007; accepted for publication July 16, 2007.

^_* Address for reprints: Brian Reemtsen, MD, Childrens Hospital Los Angeles, Cardiothoracic Surgery, 4650 Sunset Blvd, Los Angeles, CA 90027. (Email: breemtsen{at}chla.surgery.edu).

	Abstract

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Objectives: Neonates with Ebstein anomaly can have severe left ventricular dysfunction caused by right ventricular enlargement and ventricular septal displacement. Fenestrated right ventricular exclusion and Blalock–Taussig shunt (Starnes procedure) have been performed to mitigate this problem; however, the fate of the excluded ventricle and its effect on the systemic ventricle have yet to be documented.

Methods: Intermediate-term data have been retrospectively collected on the 12 survivors of neonatal right ventricular exclusion. Echocardiographic examinations were compared from the time of the original right ventricular exclusion and before second-stage Glenn palliation. Measurement of the Great Ormond Street ratio (area of right atrium plus atrialized right ventricle divided by area of trabeculated right ventricle plus left atrium and left ventricle), ratio of right ventricular to left ventricular area, degree of ventricular septal impingement into the left ventricle, and left ventricular shortening fraction have been documented.

Results: In the 12 survivors of right ventricular exclusion, a decrease in the mean Great Ormond Street ratio was observed (before fenestrated right ventricular exclusion: 1.04 ± 0.49 vs before Glenn palliation: 0.31 ± 0.10, P = .01). The average pre-Glenn right ventricular/left ventricular ratio was substantially less than 1.0 (mean, 0.63 ± 0.27), demonstrating right ventricular regression. The degree of left ventricular septal impingement decreased by an average of 38% (P = .008), normalizing left ventricular morphology. At the time of Glenn palliation, the left ventricular shortening fraction was normal in all patients (mean, 42% ± 7%).

Conclusions: After neonatal right ventricular exclusion (Starnes procedure) for severe Ebstein anomaly, there is a reduction in right ventricular size, as demonstrated by echocardiographic evidence of a significant decrease in Great Ormond Street ratios. This regression correlates with ventricular septal realignment and normalization of left ventricular function.

	Introduction

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Neonates presenting with a combination of severe Ebsteinoid changes of the tricuspid valve and variable amount of right ventricular outflow tract (RVOT) obstruction continue to represent a clinical conundrum with low survival.^1,2 Our group has recently published the details of a series of patients who underwent a univentricular repair consisting of fenestrated right ventricular (RV) exclusion and modified Blalock–Taussig (BT) shunt (Starnes procedure) with acceptable survival.³ Our objective in this study was to characterize the effect of fenestrated RV exclusion on both the right ventricle and the systemic ventricle.

We have used standard tomographic and echocardiographic measurements in an attempt to describe the proportional regression of the excluded ventricle and the normalization of the morphology and function of the systemic ventricle.

	Materials and Methods

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A retrospective review of intermediate-term data (median follow-up, 30 months; range, 6–204 months) for 12 of 16 survivors with critical Ebstein anomaly who underwent RV exclusion as neonates was performed. Echocardiographic examinations were compared at the time of the original RV exclusion, before second-stage Glenn palliation, and before the Fontan procedure to determine the fate of the excluded ventricle and its effect on the systemic ventricle. Institutional approval was obtained before the inception of the study.

Demographics and Preoperative Data
Of the 12 survivors, 5 were girls and 7 were boys, with a mean weight of 3.05 ± 0.45 kg. One was premature (36 weeks’ gestation). Seven had a prenatal diagnosis made on the basis of fetal echocardiography. All the survivors had a patent ductus arteriosus and atrial septal defect at the time of the diagnosis. Seven patients had severe pulmonary valve stenosis or atresia. All 12 patients underwent pre-Glenn and 7 underwent pre-Fontan assessment, including echocardiographic analysis and catheterization. All patients showed favorable hemodynamics and were deemed a suitable risk for bidirectional Glenn shunt or progression to completion of the Fontan procedure.

Tomographic Assessment
Standard anterior–posterior tomographic analysis was performed preoperatively, at the time of Glenn palliation, and at the time of final Fontan palliation. The cardiac silhouette was measured and compared with the length of the thoracic cage at the same level. This number determines the preoperative ratio of the cardiac silhouette to the thoracic cage (CT ratio).

Echocardiographic Assessment
The echocardiographic assessment was performed preoperatively before the original RV exclusion, the Glenn procedure, and Fontan completion respectively. Four separate variables were measured for evaluation of the excluded right ventricle and systemic ventricle at both time points.

First, a Great Ormond Street (GOS) ratio was calculated, as described by Celermajer and associates.⁴ The GOS ratio is determined as a product of the combined area of the right atrium and atrialized portion of the right ventricle divided by the area of the trabeculated right ventricle plus the left atrium and ventricle. As an arbitrary expression of the GOS ratio, the score represents a graded severity correlate of the mortality risk. Grade 1 is characterized as a ratio of less than 0.5, grade 2 as a ratio of 0.5 to 0.99, grade 3 as a ratio of 1.0 to 1.49, and grade 4 as a ratio of equal to or greater than 1.5. A GOS score of grade 3 has been associated with a substantially higher mortality.⁴

Second, to measure the degree of the effective remodeling of the trabeculated RV area in relation to the functional left ventricle, the RV/left ventricular (LV) ratio was calculated. The RV and LV areas were measured in an apical 4-chamber echocardiographic view. This ratio correlates with the degree of the RV regression during the time interval. Because of the "redefinition of the RV" at initial palliation, the RV/LV ratio was calculated before Glenn palliation and before the Fontan procedure only.

Third, the degree of septal remodeling in relation to the LV morphology was assessed by using the LV septal impingement ratio. This ratio is the product of the upper septal curvature vertical dimension from the RV wall (length connoted by a in Figure 1) divided by the lower septal curvature vertical dimension from the LV wall (length connoted by b in Figure 1), as measured in the short-axis, left parasternal echocardiographic view. This ratio indirectly correlates with the degree of LV morphology normalization as a result of the LV septal impingement regression (Figure 1).⁵

View larger version (17K): [in this window] [in a new window]   Figure 1. Schematic illustration of the parasternal short-axis view. The septal impingement ratio is calculated at the end-systolic phase and equals a/b values measured in the left ventricle (LV). Values approaching 1.0 indicate circular morphology, and values of less than 1.0 connote septal impingement. RV, Right ventricle.

Surgical Technique
A univentricular (fenestrated RV exclusion) strategy was undertaken as the original first-stage palliative approach for all the patients who eventually qualified for the bidirectional Glenn procedure. All 12 survivors had a tricuspid valve not amenable to repair with an inadequate functional portion of the right ventricle associated with variable amounts of RVOT obstruction not amenable to a hemodynamically acceptable reconstruction.

Standard aortic and bicaval cannulation are used. During moderate hypothermia, the heart is arrested with cold blood cardioplegia. The tricuspid valve is approached through an oblique right atriotomy incision. The RV fenestrated exclusion was accomplished by patching the tricuspid valve at the "anatomic" level of its annulus by using glutaraldehyde-fixed autologous pericardium. The coronary sinus is not incorporated under the pericardial exclusion and therefore is left in the anatomic position in the morphologically right atrium. A 4- to 5-mm fenestration is performed on the patch by using a coronary punch. Free atrial communication is ensured, and a right atrial reduction plasty is carried out as a standard component of the fenestrated RV exclusion strategy. If pulmonary artery insufficiency exists, pulmonary artery interruption is performed. Early RV exclusion did incorporate RV plication, if necessary, but we have abandoned this practice in the current era because of RV involution observed after palliation. Finally, pulmonary blood flow is provided by a modified BT shunt (3.5–4.0 mm).

	Results

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From 1992 to the present, 16 patients with severe Ebstein anomaly have undergone RV exclusion with a modified BT shunt at a single institution, with 12 survivors. The first survivor had an unfenestrated tricuspid patch, and all other survivors had the fenestration. Eleven of 12 survivors have gone on to a bidirectional Glenn shunt, and 6 patients have been completely palliated with total caval pulmonary connection. There have been no interstage deaths. No hospital mortality has been observed in this treatment group since 1996. To this point, all patients have been evaluated and deemed acceptable candidates for bidirectional Glenn and Fontan procedures at the age-appropriate time. One patient has a pacemaker for complete heart block after RV exclusion and underwent a modified maze procedure for severe preoperative tachyarrythmias.

CT Ratio
The CT ratio was observed to be 0.84 ± 0.09. At the time of the Glenn shunt, the ratio had decreased to 0.56 ± 0.10; this difference was statistically significant to a P value of .003. The CT ratio did not significantly change in the time between the Glenn and Fontan operations (Table 1).

RV/LV Ratio
The RV/LV ratio was measured as 0.63 ± 0.27 at the time of the Glenn shunt. This value continued to decrease to a mean of 0.44 ± 0.05 measured at the time of the Fontan procedure. Both of these values are significantly less than the expected 1:1 ratio expected with normal anatomy. This value represents the continued comparative regression of the right ventricle from the left ventricle during the interim between the Glenn and Fontan procedures.

Septal Impingement
As shown in Figure 1, A, a calculated a/b ratio approaching 1.0 connotes a circular structure, whereas a value approaching zero connotes a flattened structure. This ratio helps to identify the degree of septal impingement and its effect on the shape and presumed function of the left ventricle. As shown in Figure 2, preoperative septal impingement was calculated preoperatively at a mean of 0.58 ± 0.09, whereas the values increased significantly to 0.93 ± 0.13 and 1.01 ± 0.17, respectively, at the Glenn and Fontan procedures (P = .008, Figure 3). This difference clearly establishes the RV dilation’s effect on the LV morphology seen in severe neonatal Ebstein anomaly, as well as documenting the normalization of the left ventricle after palliation.

View larger version (102K): [in this window] [in a new window]   Figure 2. Two-dimensional echocardiogram of the parasternal short axis. This is a preoperative view demonstrating septal impingement, with a/b approaching zero. RV, Right ventricle; LV, left ventricle.

View larger version (137K): [in this window] [in a new window]   Figure 3. Two-dimensional echocardiogram of the parasternal short axis. This is a pre-Glenn view demonstrating lack of septal impingement, with a/b approaching 1.0, suggesting normal morphology of the left ventricle (LV). RV, Right ventricle.

We observed a decrease in the relative and net size of the right ventricle after exclusion. With this measurable regression, we have documented normalization of both morphology and function of the left ventricle, leading to effective palliation and increased survival.

	Discussion

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Although the fenestrated RV exclusion approach to palliation for severe Ebstein anomaly has demonstrated improved survival, no documentation of the physiologic effect has been published.⁷ Our study has implied 2 major ideas. First, children with severe Ebstein anomaly have not only severe right-sided failure but also biventricular failure. The dilation of the right side of the heart causes septal impingement and resultant left-sided heart failure. Second, the fenestrated RV exclusion induces a durable regression of the right-sided structures, thereby restoring the systemic ventricular morphology and function. The postoperative reestablishment of normal ventricular function clearly demonstrates the ventricular interplay that leads to severe heart failure in these neonates.

Although others contend that all patients with severe Ebstein anomaly can have this condition repaired, we continue to believe that patients with poor valve delamination and the combination of a diminutive trabeculated right ventricle with RVOT obstruction are better served with a single-ventricle repair.⁸ At the severe end of the spectrum, maximal decompression and subsequent involution of the right-sided structures after RV exclusion should not only allow patients to survive the neonatal period but also make them excellent candidates for future total cavopulmonary connection.

Other derivations of the RV exclusion have favored wide plication and even excision of the atrialized portion of the right ventricle seen in severe Ebstein anomaly.^9,10 The involution of the right-sided structures seen after fenestrated RV exclusion obviates the need for RV manipulation. This process should serve to decrease operative times and spare any possible injury to the right coronary artery made possible with RV excision or excessive plication.¹¹ Other processes, apart from severe Ebstein anomaly, causing RV failure cannot be commented on based on our current study.

No study to date has described RV function or its effect on the systemic ventricle after valve repair for severe neonatal Ebstein anomaly. Chauvaud and colleagues¹² have described increased LV ejection fraction correlating with decreased end-diastolic RV volume after plication and valve repair in adult patients; however, long-term follow-up has not been included. The majority of valve repair articles describe postoperative patients as asymptomatic in New York Heart Association Class I, without physiologic parameters of ventricular function. To date, we have seen uniform RV regression in our patients and normalization of the LV function, which is durable. In the short term, this leads to better systemic ventricular mechanics in these critically ill children and improves survival. We have encountered and expect excellent Fontan candidates because of this normalization of the LV morphology and function.

	References

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8. Knott-Craig CJ, Overholt ED, Ward KE, Ringewald JM, Baker SS, Razook JD. Repair of Ebstein’s anomaly in the symptomatic neonate: an evolution of technique with 7-year follow-up. Ann Thorac Surg 2002;73:1786-1793.[Abstract/Free Full Text]
   
9. Yun IT, Lee SH, Ko JK. Neonatal stenotic Ebstein’s anomaly: a novel technique of right ventricular exclusion. J Thorac Cardiovasc Surg 2005;131:469-471.
   
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