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Ann Thorac Surg 1997;63:1657-1663
© 1997 The Society of Thoracic Surgeons
Divisions of Cardiothoracic Surgery and Pediatric Cardiology, University of California at San Francisco, San Francisco, California
Accepted for publication December 3, 1996.
| Abstract |
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Methods. Five consecutive neonates and young infants (age range, 23 days to 5 months; median age, 3 months) with right-dominant unbalanced complete AV canal underwent biventricular repair. Preoperative and postoperative echocardiographic measurements of left (LV) and right ventricular size and AV valve component size were made. Potential LV volume was assessed preoperatively using a theoretic model that assumed a normalization of septal bowing.
Results. There was no perioperative mortality; 1 patient died 71 days postoperatively of problems related to the left AV valve. Preoperatively, all patients had severe LV hypoplasia, with a mean end-diastolic indexed true LV volume of 14.8 ± 9.1 mL/m2, indexed potential LV volume of 32.0 ± 18.8 mL/m2, left AV valve to total AV valve ratio of 0.30 ± 0.06, and LV to right ventricular long-dimension ratio of 0.65 ± 0.1. Postoperatively, all patients had indexed true LV volumes greater than 30 mL/m2 (mean volume, 35.6 ± 3.9 mL/m2), and the left AV valve to total AV valve ratio and the LV to right ventricular long-dimension ratio increased to 0.42 ± 0.03 and 0.88 ± 0.11, respectively. Both preoperative potential and true LV volumes correlated well with postoperative true LV volumes: r = 0.90 (p = 0.040) and r = 0.93 (p = 0.023), respectively. Increases in LV length and left AV annulus size indicated contributions of volume loading and surgical patching to the right of the ventricular crest to the increase in LV size.
Conclusions. In our small series, preoperative indexed potential LV volume of 15 mL/m2 or greater (present in all patients) allowed biventricular repair of right-dominant unbalanced AV canal. Any previous criteria for LV hypoplasia in this condition need to be reconsidered. This study also has implications for other right-sided volume-loaded lesions in which the left ventricle initially is judged to be hypoplastic but in which biventricular repair may be feasible.
| Introduction |
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Repair of complete atrioventricular canal (CAVC) has evolved from an often staged approach with a relatively high morbidity and mortality to one-stage complete repair in young infants with generally low morbidity and mortality [16]. Ventricular balance relates to the commitment of the left and right part of the atrioventricular (AV) junction to the respective ventricles. If the AV junction is connected preponderantly to either one or the other ventricle, then right ventricular (RV) or left ventricular (LV) dominance is considered to exist [7]; the ventricle associated with the smaller portion of the AV valve orifice is often correspondingly hypoplastic. Right dominance is considerably more frequent than left dominance [810].
In intermediate and even highly unbalanced cases of CAVC, there are no proven guidelines for deciding between biventricular repair or univentricular palliation. Cohen and co-workers [10] recently emphasized the importance of the relative sizes of the AV valve areas and of the ventricular septal defect size in the outcome of patients with unbalanced CAVC. However, the definition of "balance" as determined preoperatively remains unclear, and presumably, criteria are used that have been applied to other conditions with small left ventricles [1113].
We challenge the notion that unbalanced CAVC may always require univentricular palliation and believe that biventricular repair, if feasible, remains the best option. For right-dominant unbalanced CAVC, we hypothesized that RV volume overload results in right-to-left septal bowing and contributes to the appearance of a small left ventricle, which can actually accommodate a greater potential volume. Therefore, surgical decision-making depends not only on the absolute LV volume but also on the potential LV volume preoperatively. To test this hypothesis, we retrospectively analyzed our experience with 5 consecutive neonates and young infants with right-dominant unbalanced CAVC who all underwent biventricular repair.
| Patients and Methods |
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| Echocardiographic Measurements |
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Four patients underwent cardiac catheterization to further assess LV size, the reason for systemic arterial desaturation, or both; noninvasive testing could not clarify the contributions of intracardiac right-to-left shunting versus pulmonary venous desaturation. Patients 1, 2, and 4 had pulmonary hypertension and at least some bidirectional shunting at either the atrial or (less likely) ductal level (minimal postductal saturation, 97%). Patients 1, 2, and 3 had decreased pulmonary venous saturation causing systemic arterial desaturation.
| Surgical Technique |
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| Statistical Analysis |
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| Results |
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One patient died (patient 4: Tables 2, 3![]()
). Morphologically, this patient had a marked tissue deficiency of the bridging leaflets of the left AV valve and a rudimentary posteromedial papillary muscle. The cleft between the left-sided bridging leaflets had been closed only partially, as complete closure would have resulted in undue tension on the edges of the leaflets. After a relatively uneventful early postoperative course, severe left AV valve regurgitation developed, necessitating further cleft closure and annuloplasty of the left AV valve 22 days after the initial operation. Because of residual left AV valve regurgitation, a 17-mm St. Jude Medical prosthesis was placed in the supraannular position. Despite adequate anticoagulation, recurrent thrombus formation on the prosthesis necessitated thrombectomy; ultimately, refusal of an additional operation led to the patient's death 71 days after the initial operation. In this patient, the left ventricle had been able to sustain the systemic circulation during the entire postoperative course despite the severe AV valve regurgitation; the unfavorable outcome was not related to LV inadequacy.
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| Echocardiographic Data |
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Postoperatively, all patients had indexed true LV volumes exceeding 30 mL/m2 (see Table 3
). All indices of relative LV size also increased substantially postoperatively. The increase in LV dimensions with reversal of septal bowing and the increase in LV long dimension were dramatic in most patients (Fig 4
).
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| Comment |
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Surgical manipulation is also a factor in the increase in LV size. The volume of the left ventricle can be increased by attachment of the ventricular septal patch slightly more to the right of the ventricular crest than is usually done in the repair of CAVC; in addition, if a single-patch repair is performed, the superior or inferior bridging leaflet, or both leaflets, can be divided more to the RV side than is usually done. Utmost discipline must be exerted in the sizing of the patch, as oversizing results in patch redundancy with the potential for left AV valve regurgitation. Although it is our bias to close the cleft whenever possible, closure of the cleft can lead to stenosis of the left AV valve orifice, especially in the setting of closely spaced or single papillary muscles. In the setting of a tissue-deficient left AV valve, pericardial patch augmentation of the superior and inferior bridging leaflets may be a valuable technique to restore a competent neoseptal leaflet [14]. In our opinion, corroborated by the findings of this study, the determinant of successful biventricular repair of right-dominant unbalanced CAVC appears to be related more to competence of the left AV valve than to LV size. Indeed, at a median follow-up of 33 months, 3 of our 4 surviving patients had no left AV valve regurgitation, and 1 had mild regurgitation; no patient had any restriction to inflow.
Because all 5 patients in this series underwent biventricular repair sustained by an adequate left ventricle postoperatively, we were not able to determine all the factors related to outcome. However, an RVforming apex and the appearance of a small left ventricle on the preoperative echocardiogram were clearly not predictors of failure. Also, a left AV valve to total AV valve diameter ratio as low as 0.23 and an LV to RV area ratio as low as 0.14 did not preclude successful biventricular repair. Cohen and colleagues [10] recently emphasized the importance of the relative sizes of the AV valves and the size of the interventricular communication in relation to patient outcome. Although our findings cannot be compared directly with theirs, we agree that the preoperative true LV size may be misleading and that a small interventricular communication, present in all 5 of our patients, appears to carry a more favorable prognosis. Our series, however, does suggest that the size of the left AV valve may be less important because surgical manipulation may be able to alter the relative AV valve size.
Morphometric data, no matter how concerning, may be less important than physiologic data. In the presence of a restrictive interventricular communication, antegrade ascending aortic flow with left-to-right ductal flow or an obliterated ductus arteriosus and oxygen saturations in the upper and lower extremities matched at 100% indicate that biventricular repair can be accomplished. In contrast, when there is retrograde flow in the ascending aorta in the presence of right-to-left ductal flow, univentricular palliation is generally indicated because of inadequacy of the left ventricle to sustain the systemic circulation. All 5 patients in our series showed antegrade flow in the ascending aorta, and the 3 patients with a patent ductus arteriosus exhibited left-to-right ductal shunting. In situations of documented antegrade flow in the ascending aorta with ductal flow being right to left or bidirectional and a differential oxygen saturation between the upper extremities, the decision making may be more complex. In this situation, cardiac catheterization may be of value in differentiating between pulmonary venous desaturation and major intracardiac right-to-left shunting, as it did in 4 of our patients.
In summary, in this small series of patients with right-dominant unbalanced CAVC, biventricular repair was successfully accomplished despite severe LV hypoplasia with indexed true LV volumes as low as 7 mL/m2 and indexed potential LV volumes as low as 15 mL/m2. We do not believe that the criteria for absolute LV volumes in the setting of critical aortic stenosis or hypoplastic left heart syndrome [11, 13] are valid in the setting of LV compression by a volume-loaded right ventricle. We believe that the lower limit of LV size must be reconsidered in the context of ventricular geometry. The indexed potential LV volume of 15 mL/m2, or higher, even in the presence of a relatively small aortic annulus, is nevertheless consistent with the lower limits on absolute LV size set by previous investigators [11, 13]. Surgical augmentation of the left AV valve annulus may also increase LV size and adequacy. Further studies with larger patient populations are needed to determine the value of preoperative echocardiography in predicting postoperative LV adequacy. This study has broad implications for the management of right-dominant unbalanced CAVC and other right-sided volume lesions in which the left ventricle initially is judged to be hypoplastic but for which biventricular repair may be feasible.
| Acknowledgments |
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| Footnotes |
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| References |
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