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Original Articles: Pediatric Cardiac

Ventricular Scoop in Atrioventricular Septal Defect: Relevance to Simplified Single-Patch Method

^a Cardiac Morphology Unit, National Heart & Lung Institute, Imperial College London, United Kingdom
^b Department of Cardiothoracic Surgery, Royal Brompton and Harefield NHS Trust, London, United Kingdom

Accepted for publication September 11, 2008.

^_* Address correspondence to Dr Ho, Cardiac Morphology Unit, National Heart & Lung Institute, Imperial College London, Guy Scadding Bldg, Dovehouse St, London, SW3 6LY, United Kingdom (Email: yen.ho{at}imperial.ac.uk).

	Abstract

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Background: The simplified single-patch repair for atrioventricular septal defect seems an attractive alternative to conventional methods despite controversies on its suitability in hearts with a large ventricular scoop. Inasmuch as previous anatomic studies were conducted before the advent of this technique, we revisited this malformation with the aim to identify morphologic markers that may aid patient selection.

Methods: We examined 43 heart specimens: 31 with the complete form and 12 with the partial form of the malformation.

Results: In 16 hearts with the complete form, the scoop extended antero-superiorly beyond the atrioventricular junction, resulting in a skewed shape of the scoop. By contrast, none of the other hearts had such an extension and the scoop was nearly symmetric. Hearts with the extension had significantly narrower diameters of the left ventricular outflow tract (median [interquartile range]: 22% [17% to 33%]) than the complete form without the extension (38% [29% to 50%]; p = 0.01) and partial form (43% [25% to 50%]; p = 0.01). However, when the diameters were stratified with scoop depth, no obvious difference was found between the complete form with a deep scoop (defined as the depth of 60% or greater) and those with a shallower scoop (36% [24% to 49%] versus 28% [21% to 36%], respectively; p = 0.146), indicating that antero-superior extension had more impact on the tract size than scoop depth.

Conclusions: The antero-superiorly extended and skewed scoop could lead to asymmetric configuration of the valvar leaflets and outflow tract obstruction if the simplified technique is applied. Therefore, not only scoop depth but also the antero-superior extension should be recognized when repairing this lesion.

	Introduction

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Over many years, the conventional single- [1, 2] and two-patch techniques [3–5] have been the surgical procedures of choice for repairing the so-called complete form of atrioventricular septal defect (AVSD), ie, AVSD with common valvar orifice and both atrial and ventricular levels of shunting. In the late 1990s, an alternative method, later dubbed simplified single-patch technique, was proposed independently by Wilcox and associates [6] and Nicholson and colleagues [7]. This method is unique in its manner of closing the ventricular component of the septal deficiency. The bridging leaflets are approximated to the ventricular crest, converting the anatomy into a lesion akin to the so-called partial or ostium primum form of AVSD. This particular feature has greatly simplified repair for AVSD, shortened operative time, and contributed to the feasibility of earlier repair [8–10] because it does not need exact sizing of the ventricular patch or reattachment of the divided leaflets to a single patch that is required in the conventional methods. Furthermore, its advantages have been endorsed by the impressive midterm results recently reported [8, 9].

However, there remain major concerns regarding this attractive procedure. In particular, the potential for incompetency of the left atrioventricular valve and the risk of left ventricular outflow tract (LVOT) obstruction would be crucial in cases with a large ventricular scoop [6, 7, 9]. Although the rationale behind selective application of this technique is based on careful anatomic consideration [6, 11], its nonselective use [8] raises serious solicitudes from a morphologic standpoint. This is because, conceptually, the surgically partialized form of complete AVSD would carry even higher risks of such morbidities than the naturally occurring partial form that has a smaller scoop [11, 12].

With these considerations in mind and for the very reason that the previous anatomic studies [11–15] were conducted in the days before the advent of this modification, we revisited the morphology of hearts with AVSD, focusing on its relevance to the simplified single-patch technique.

	Material and Methods

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This study has been approved by the institutional ethics committee. From the pathology archive of the Royal Brompton Hospital, we identified 31 hearts with AVSD having common atrioventricular valvar orifice with both atrial and ventricular components of the septal deficiency (so-called complete form) that were suitable for our morphometric assessment. In these hearts, we assessed the configuration of the superior bridging leaflet and its subvalvar apparatus relative to the ventricular crest according to the Rastelli classification. In addition, we examined 12 hearts with separate valvar orifices having only an atrial component (so-called partial or ostium primum form) for comparison. All hearts had concordant atrioventricular and ventriculoarterial connections in the setting of usual atrial arrangement; hearts with abnormal outflow tracts, such as tetralogy of Fallot, and those with abnormal ventriculoarterial connection, such as double outlet from the right ventricle and common arterial trunk, were excluded. In total, 43 hearts with AVSD were examined.

We measured the size of the ventricular component of the septal deficiency (scoop) and the LVOT diameter relative to the width of the atrioventricular junction (Fig 1). The junctional width was assessed as the line joining the hinge points of the antero-superior and posteroinferior bridging leaflets at the septum. To assess the shape of scooping, two values were measured: the depth of the deepest point of the scoop and its distance from the posteroinferior margin of the atrioventricular junction. The first value, the depth, was defined as the distance of the deepest point from the level of the anatomic atrioventricular junction. The intersection between the line marking the depth and the line corresponding to the level of the anatomic atrioventricular junction provided the second value. When the intersection reached the posteroinferior or antero-superior end of the junction, it was designated as 0% or 100%, respectively, with 50% indicating the middle of the junction. Additionally, the ventricular component was examined to determine whether it extended beyond the level of the antero-superior end of the atrioventricular junction. The LVOT diameter was defined as the minimum length between a border of the scoop and the ventricular free wall at the left ventricular septal surface. These measurements were standardized with the atrioventricular junction diameter. Because the size of the hearts varied within the series, standardization allowed us to make direct comparisons of these values. Every measurement was repeated twice to minimize potential sources of error from manual maneuvers, and mean values of the two measurements were used as final discrete values.

View larger version (33K): [in this window] [in a new window]   Fig 1. Diagram showing the measurements made on the left ventricular aspect. (Left lower) To assess the shape of a ventricular component, the depth (d) and intersection (i) of the deepest point of the scoop were obtained. The minimum left ventricular outflow tract (LVOT) diameter was measured at the narrowest part between a border of the scoop and the ventricular free wall. The atrioventricular junction diameter (j) was used for standardization of other values. (Right lower) The ventricular component was examined to determine whether it extended beyond the level of the antero-superior end of the atrioventricular junction. (Ao = aorta; LA = left atrium; LV = left ventricle; SBL = superior bridging leaflet; IBL = inferior bridging leaflet.)

	Results

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Antero-superior Extension of the Scoop
Of the 31 hearts with complete form of AVSD, 16 (52%) had the antero-superior extension of a ventricular component of the septal deficiency, whereas the remaining 15 had no extension. By contrast, no hearts with the partial form had such an extension. Pictures of representative specimens are shown in Figure 2.

View larger version (110K): [in this window] [in a new window]   Fig 2. Photographs illustrating the left ventricular surface of two hearts with the complete form of atrioventricular septal defect with the antero-superior extension (a) and without the extension (b) and one heart with the partial form of atrioventricular septal defect (c). In the heart with the partial form, the left ventricular outflow tract (LVOT) area is separately displayed in the inset. The anatomic atrioventricular junction and the narrowest part of the left ventricular outflow tract are marked with a red line and a white arrow, respectively. (Ao = aorta; LA = left atrium; LV = left ventricle.)

View larger version (22K): [in this window] [in a new window]   Fig 3. Measurements on the ventricular component of the septal deficiency (scoop) and the left ventricular outflow tract (LVOT) diameter at the narrowest part in complete forms of atrioventricular septal defect with (C+) and without (C–) antero-superior extension, and partial atrioventricular septal defect (P) are presented as a ratio of the width of the atrioventricular junction. The last column shows no significant difference in the left ventricular outflow tract diameters between hearts with the complete form having a deeper scoop (defined as a depth of 60% or greater) and those having a shallower scoop (depth of less than 60%). p < 0.05. (NS = not significant.)

Diameter of Left Ventricular Outflow Tract
Hearts with the complete form having the antero-superior extension had a significantly narrower LVOT (22% [17% to 33%]) than the complete form without the extension (38% [29% to 50%]; p = 0.01) and the partial form (43% [25% to 50%]; p = 0.01; Fig 3). No statistical difference was observed between the latter two groups (p = 1.00). Combining this finding together with the above findings regarding the depth of the scoop, it seemed reasonable to assume that hearts with the complete form of AVSD with a deeper scoop are more likely to have a narrower LVOT. However, when the LVOT diameters were compared between hearts with the complete form having a deeper scoop (defined as depth of 60% or greater) and those having a shallower scoop (depth of less than 60%), the LVOT diameters did not differ significantly (36% [24% to 49%] versus 28% [21% to 36%], respectively; p = 0.146; Fig 3, right-most columns). This finding suggests that the depth of the scoop is not always a reliable marker for a narrow LVOT.

	Comment

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Undoubtedly, the simplified single-patch repair for the complete form of an AVSD is an attractive procedure with many advantages over previous techniques [10]. Avoidance of insertion of a ventricular patch or attachment of the divided leaflets to a single patch substantially shortens cross-clamp and bypass times, facilitating earlier repair that is crucial to prevent irreversible changes in the pulmonary vasculature [8, 9, 16]. Accordingly, this simplified technique could provide further advantages with respect to lowering early mortality. Nowadays, however, the mortality rate has decreased dramatically even with conventional approaches. Reflecting this change, interest has shifted toward prevention of late morbidities, especially incompetence of the left atrioventricular valve and LVOT obstruction. In this regard, recent reports from Backer and associates [9] and Nunn [8] describing midterm results of this technique are encouraging. In their article, Backer and associates [9] concluded that the simplified method produced outcomes comparable (at least not inferior) to the conventional two-patch technique in younger patients with a similar size of the scoop. Their conclusion has been further endorsed with the amazing result from Nunn [8], involving 128 patients undergoing the simplified technique. In particular, unlike the other authors [6, 9], he has used this technique nonselectively since 1995. Despite this policy of universal application, there was a low incidence (2.3%) of reoperation on the left atrioventricular valve and no instances of LVOT obstruction requiring resection during a median follow-up period of 7.3 years. These results were identical or even better than his own experience in repair of the complete form of AVSD using the two-patch method (46 cases) and repair of the partial form (126 cases), yielding incidences of reoperation on the left atrioventricular valve (13% and 1.6%, respectively) and LVOT obstruction (15% and 6.4%, respectively) during a median follow-up period of 14.4 and 9 years, respectively. According to the review article by Backer and coworkers [10], Nunn's result with the simplified technique is perhaps the best ever reported for AVSD. These figures, especially the difference of the incidences of LVOT obstruction between the simplified and two-patch methods, are somehow surprising in view of a particular concern regarding LVOT obstruction in the simplified technique. Nunn commented that the lack of rigid synthetic material in LVOT after the simplified single-patch technique might prevent turbulence and reduce the potential for fibrotic overgrowth or deposition on an inherently narrow LVOT. Although a direct verification of his assumption is difficult at present time, the impressive result would further attract surgeons who are not currently using this technique toward this newer procedure. The results would also encourage surgeons who are already using this technique in selected patients to broaden their inclusion criteria.

The important issue to be discussed would be, therefore, the indication for this technique. Even if this procedure is much more broadly applicable than initially thought, are all patients encountered in the operating theater suitable for this modification? We doubt it. In fact, we know of one case in which hemodynamically significant LVOT obstruction developed intraoperatively, and the patient could be weaned from the cardiopulmonary bypass only after conversion to the conventional two-patch method. From a morphologic point of view, the LVOT diameter would inevitably become narrower with the simplified technique, as the nature of this procedure is to make the anatomy equivalent to that of the partial form of AVSD, which inherently has a narrower LVOT than the complete form. Furthermore, the complete form of AVSD is known to have a more deformed cardiac mass than the partial form, accompanying a more elongated LVOT [11, 12]. Accordingly, it is highly likely that once hearts with the complete form are surgically partialized, they are at an even higher risk of developing LVOT obstruction than those with the naturally partial form. Although the development of LVOT obstruction can be multifactorial, the LVOT diameter is the most significant variable that is directly affected by surgical maneuvers. For these reasons, we believe that surgeons should carefully select candidates based on the anatomy.

Another issue would be how the surgeon can determine the suitability or unsuitability of this procedure. Hearts with the aortic valve originating exclusively from the right ventricle (eg, double outlet from the right ventricle) clearly are unsuitable. This is not because of a larger scoop in such complex hearts [6] but because of the fact that the only outlet for the left ventricle is the space between the bridging leaflets and the ventricular crest. Applying the simplified technique for such hearts will diminish the space and thereby cause complete obstruction of the LVOT. Nevertheless, even in hearts with normal ventriculoarterial connections, anatomic consideration would still be of critical importance. Wilcox and coworkers [6] raised the size issue of the scoop as one potential pitfall of this technique. Their concern was based on an anatomically reasonable speculation that distortion of leaflets and the tension required to bring the leaflets to the septum would be of consequence if the scoop were too deep (extensive toward the apex). In fact, 6 patients in their series were judged unsuitable in this respect. Backer and associates [9] have also described the importance of the scoop depth for decision-making. Using transesophageal echocardiography, they measured the depth of the scoop, which is defined as the distance from the ventricular crest to the atrioventricular valve during end-diastole. If the depth were 10 mm or less, they would not hesitate to use the simplified technique, but would consider the two-patch technique for patients with a deeper ventricular component. This cutoff value seems to be based on their experience in a case that had a deep (12 mm) component. In that case, they had to convert to the two-patch method, because an attempt of the simplified technique produced malcoaptation of the superior bridging leaflet with the other two leaflets in the left valvar orifice.

We agree that the depth of the scoop is one of the important factors to be considered in terms of valvar function. With respect to the risk of LVOT obstruction, however, the presence or absence of the antero-superior extension of the scoop should not be ignored. As shown in our morphometric analysis, it is not the depth of the scoop but its antero-superior extension that directly affects the size of the LVOT. A deep scoop does not necessarily indicate the presence of a narrow LVOT, and, interestingly, a relatively shallow scoop does not always exclude the risk of LVOT obstruction. This finding can be explained when we appreciate the anatomic relationship between the ventricular component of the septal deficiency and the LVOT. It is not the apical part (depth of the scoop) but the antero-superior border of the defect that constitutes a substantial portion of the LVOT. Furthermore, the antero-superior extension might also affect the valvar competency unfavorably. As described above, the scoop is unequivocally skewed antero-superiorly in the presence of the extension. If the bridging leaflets are surgically attached to the ventricular crest, their configuration will be determined by the shape of the scoop. It is, therefore, highly likely that the valvar leaflets inevitably become asymmetric, if the simplified technique is applied in hearts with the extension. We suppose that the above-mentioned case in the report by Backer and colleagues [9] in which the superior bridging leaflet did not coapt with other two leaflets might be associated with such a skewed scoop. Although the antero-superior extension itself is not a revelation [17], the importance of such an extension in determining the suitability of the simplified technique has never been highlighted in the literature. Unfortunately, unlike the depth, the extension of the septal defect may not be easy to assess using echocardiography or even with direct inspection, particularly when the superior bridging leaflet is adherent to the septum as in the so-called Rastelli type A variant. The very location of the extension, beyond the extreme end of the atrioventricular junction, also adds to the difficulty in clear visualization. Our study suggests that identification of the deepest point of the scoop would help the surgeon predict the presence of such an extension. This is because the location of the deepest point beneath the superior bridging leaflet is a fairly sensitive and specific finding in hearts with the antero-superior extension, as opposed to approximately the middle location in those without the extension. In addition, it might be possible to say that the presence of a free-floating superior bridging leaflet as seen in the so-called Rastelli type C variant should raise a suspicion of the presence of the antero-superior extension, because the majority of type C cases were associated with antero-superior extension in our series. Nevertheless, this observation needs further confirmation considering the small number of type C cases in our series.

An obvious limitation of this study is the lack of physiologic consideration. We believe, nonetheless, our morphometric analysis will be able to provide an additional insight for this attractive procedure. The evolution of surgical repair for AVSD has been largely related to better understanding of its morphology, and for this reason there are few cardiac anomalies that have benefited more from thorough anatomic observation than AVSD [6].

The current study has suggested not only the depth but also the presence or absence of the antero-superior extension is of surgical significance and hence requires recognition when determining the suitability of the simplified single-patch technique. The presence of such an extension unequivocally results in a skewed shape of the scoop, which potentially could lead to asymmetric configuration of the atrioventricular valvar leaflets and LVOT obstruction, if the simplified method is applied.

	Acknowledgments

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This study is supported by the Francis Fontan prize of the European Association of Cardio-Thoracic Surgery awarded to Iki Adachi and a grant from The Uehara Memorial Foundation. The Cardiac Morphology Unit receives funding from the Royal Brompton and Harefield Hospital Charitable Fund. The authors wish to express appreciation for statistical advice from Mr Joseph Eliahoo at the Statistical Advisory Service, Imperial College London. We also appreciate Ms Manveer Sroya and Ms Carina Lim for their technical and secretarial assistances.

	References

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

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