Procedure

Pericardial patch reconstruction of the congenitally diseased aortic valve

Division of Congenital Cardiovascular Surgery, University Hospital and University Children's Hospital, Steinwiesstrasse 75, CH-8032, Zurich, Switzerland

^* Corresponding author: ^* Tel.: +41-44-266 8020; fax: +41-44-266 8021 (Zurich). Tel.: +61-3-9345 5200; fax: +61-3-9345 6386 (Melbourne). hitendu{at}hotmail.com; hitendu.dave{at}rch.org.au

	Summary

Top Summary Introduction Surgical procedure Acknowledgements References

 
Congenital aortic valve disease manifests itself either in the course of its natural history or as a consequence of an intervention (balloon dilatation or surgery). In infancy, a congenital aortic valve presents with stenosis, in childhood and adolescence as slowly evolving regurgitation after primary intervention/surgery and in late adulthood, they re-emerge as stenosis due to natural degeneration and calcification of the fused leaflets. The surgical approach to a congenital aortic valve disease differs depending on whether it is a malformed or a normally laid down (tri-sinusoidal tricuspid) valve; it also differs depending on the type of deformity, dysfunction and valve tissue presenting at surgery. Acutely regurgitant aortic valve in a neonate or an infant after balloon dilatation of congenital aortic stenosis is an infrequently occurring difficult problem with few available options. This video presentation demonstrates a xenopericardial patch repair of the torn fused leaflet (fusion between the right and the noncoronary cusp) of a congenitally stenotic valve, followed by height augmentation of all the three leaflets. Because of the relative hypoplasia of the aortic annulus and the ascending aorta, the aortic root and proximal ascending aorta were enlarged by an oblong xenopericardial patch. The following text includes additional technical issues involved in congenital aortic valve repair. A brief summary of literature is presented.

Key Words: Acute aortic regurgitation • Aortic valve repair • Balloon aortic valvuloplasty • Congenital aortic stenosis • Valve repair in infancy • Xenopericardium

	Introduction

Top Summary Introduction Surgical procedure Acknowledgements References

 
Congenital aortic valve stenosis has an estimated prevalence of 0.86 (95% CI 0.7–1.06) per 10,000 live births [1] and constitutes nearly 3–6% of all congenital cardiac malformations. Congenital aortic stenosis occurs in the setting of either a malformed valve (unicuspid or bicuspid) or a tricuspid valve with commissural fusion. Bicuspid aortic valve, the commonest form (90%) of a congenitally malformed aortic valve has an estimated prevalence of 0.9–1.36% in the general population, and they present at variable times in their lifespan for surgery. The fewer the number of aortic valve cusps, the younger the age at presentation [2, 3]. Balloon valvuloplasty of congenital aortic stenosis has of late been the procedure of choice, because of the limited invasiveness involved [4]. It is effective in reducing trans-valvar gradients with variable duration of palliation [5]. However, the diseased valve eventually presents in the second or third decade of life with pure or predominant aortic regurgitation and a need for repair or replacement. Because of the known limitations of all available alternatives to replace the aortic valve (including the Ross procedure) in the young patient, various groups have strived to evolve reliable techniques of aortic valve repair [6,7,8,9,10,11,12].

Balloon dilatation is a blind uncontrolled technique, which improves the valve opening area by causing tears in the aortic valve, preferentially at the sites of least resistance, which are not always at the site of the fused commissures. The resulting aortic regurgitation is generally well tolerated acutely, but occasionally results in acute left heart decompensation not amenable to pharmacotherapy. Herein we demonstrate the technique of pericardial patch repair for acute aortic regurgitation following balloon dilatation, in a congenitally stenosed tricuspid aortic valve. Because the ascending aorta was relatively small, it was decided to enlarge it simultaneously.

Presentation of the case
A child with critical valvular aortic stenosis underwent balloon dilatation of the aortic valve at the age of two days. The gradient reduced from 45 to 15 mmHg at the cost of mild to moderate aortic regurgitation. This in association with a relatively hypoplastic left ventricle with endocardiofibroelasis and mild mitral stenosis, led to progressive heart failure and severe pulmonary hypertension necessitating a surgical intervention at the age of 29 days. A Ross procedure in the setting of a severe cardiac decompensation and discrepancy between the aortic annulus (6 mm) and the pulmonary annulus (13 mm) was deferred in preference to an aortic valve repair.

Pathophysiology and principles of repair
Intraoperative observation of the aortic valve showed that the balloon dilatation had caused a vertical tear in the right and the non-coronary cusps on either side of the intervening commissure (Schematic 1). The commissural fusion remained intact.

View larger version (64K): [in this window] [in a new window]   Schematic 1 Balloon induced tear in the aortic leaflets.

View larger version (63K): [in this window] [in a new window]   Schematic 2 Patch reconstructions of the right and the non-coronary leaflets.

View larger version (58K): [in this window] [in a new window]   Schematic 3 Xenopericardial patch extension of aortic valve leaflets followed by patch enlargement of aorta ascendens.

	Surgical procedure

Top Summary Introduction Surgical procedure Acknowledgements References

Click on image to view video Video 1 Aortotomy, exposure and myocardial protection. After establishing cardiopulmonary bypass, the ascending aorta is clamped and retrograde cold blood hyperkalemic cardioplegia is administered through a directly placed cannula in the coronary sinus. An oblique aortotomy extending up to the annulus in the non-coronary sinus is performed. Commissural stay stitches are placed. Antegrade cardioplegia is administered through direct coronary osteal cannulae.

Click on image to view video Video 2 Inspection and analysis of the defect followed by commissurotomy. The aortic valve is inspected for the valve morphology, quality of cusp tissue, presence and location of tears, etc. The valve is tricuspid in origin with fibrotic commissural fusion. The cusp tissues are dysplastic and thickened. The free edges as well as the torn edges are rolled over. Commissurotomy is performed delicately at all the fused commissures with a fine beveled knife.

Click on image to view video Video 3 Xenopericardial patch repair of the defect in the non-coronary cusp. A fine stay stitch placed at the crest of the right coronary cusp helps exposure of the defect in the non-coronary cusp. The size of the triangular defect is measured using a piece of silk. A xenopericardial patch is fashioned and sutured at the site of defect using continuous prolene stitches.

Click on image to view video Video 4 Xenopericardial patch repair of the defect in the right coronary cusp. This video clip demonstrates a triangular patch repair of the defect in the right coronary cusp with running prolene stitches, starting from the nadir of the defect and working upwards on either sides.

Click on image to view video Video 5 Trimming the excess patch tissue from the reconstructed cusps. The heights of the patches have been deliberately oversized to begin with. Once sutured in place, the excess part is excised using a forward Pott's scissor. This helps to ensure that the reconstructed leaflets have optimum coaptation.

Click on image to view video Video 6 Commissural plasty. A commissural plication at the right non-coronary commissure is performed to correct prolapse of the right coronary cusp. Plication of the free edge fixes the leaflet higher up at the commissure.

Click on image to view video Video 7 Xenopericardial patch extension of the left coronary cusp. The left coronary cusp is relatively shorter than the reconstructed right and non-coronary cusps, thus leading to poor coaptation. Hence it is augmented using a rectangular piece of xenopericardium stacked on top of the native leaflet.

Click on image to view video Video 8 Xenopericardial patch extension of the right coronary cusp. This video clip shows suturing of a rectangular patch to augment the height of the right coronary cusp.

Click on image to view video Video 9 Xenopericardial patch extension of the non-coronary cusp. This video demonstrates a patch augmentation to increase the height of the non-coronary cusp for good coaptation of all the aortic cusps.

Click on image to view video Video 10 Patch reconstruction of the non-coronary sinus followed by trimming of the excess cusp tissue. An oblong xenopericardial patch is fashioned to bridge the aortotomy. The non-coronary sinus is first reconstructed using part of the oval patch. Once the aortic valve geometry is observed in the perspective of the reconstructed aortic root, the excessive leaflet patch tissue is trimmed off.

Click on image to view video Video 11 Closure of the aortotomy. The left lateral part of the aortotomy is suture closed primarily with a running absorbable suture; while the extension of the elongated sinus patch is used to augment the tubular part of aorta ascendens along the non-coronary sinus.

Click on image to view video Video 12 Postoperative echocardiography. Postoperative echocardiography of the reconstructed tri-leaflet aortic valve showed good physiology with a laminar flow on colour Doppler and only mild regurgitation.

View larger version (76K): [in this window] [in a new window]   Schematic 4 Schematic representation (overview) of the original valve morphology and the steps to tricuspidization. (Reproduced with permission from The European Association for Cardio-Thoracic Surgery and Elsevier Inc. [13].) Partial detachment of the fused (right plus non-coronary) leaflet from the annulus, followed by fashioning of a non-coronary cusp from the native tissue. The right coronary cusp is created from a patch of xenopericardium. (L=left, R=right, NC=non-coronary.)

View larger version (71K): [in this window] [in a new window]   Schematic 5 Side view as well as a saggital view of the aortic root. (Reproduced with permission from The European Association for Cardio-Thoracic Surgery and Elsevier Inc. [13].) Opened up view of the aortic root between the left and the non-coronary cusps showing detachment of the fused leaflet, followed by reinsertion of a non-coronary cusp, wholly created from it. The right coronary cusp is fashioned out of a patch of xenopericardium (orange coloured). A saggital section of the aortic root (on the right of the diagram) explains the morphology (with an emphasis on coaptation and annular insertion), before and after repair.

View larger version (92K): [in this window] [in a new window]   Photo 1 Operative picture showing completed correction with a schematic explanation (inset). (Reproduced with permission from The European Association for Cardio-Thoracic Surgery and Elsevier Inc. [13].) Intraoperative picture after tricuspidisation of a bicuspid aortic valve with creation of a complete right coronary cusp carved out of a patch of xenopericardium. The free edges of both the native leaflets have been stabilized by a simple weaving Goretex suture. Lower left inset explains the leaflets made of native tissue (white) and a leaflet made of xenopericardium (coloured).

Reduction plasty of the dilated sinus: vertical sinus plication
In contrast to the exemplified case of neonatal repair where the aorta has had no time to dilate, patients presenting with predominant chronic regurgitation have a dilated aorta. The best way to deal with the dilated annulus and the aortic sinuses is yet to emerge. Some groups [15] have proposed using Teflon felt reinforced annuloplasty to plicate the membranous part (most part of the non-coronary sinus) of the aortic annulus. We have not found it necessary in our younger patient population, who present early on before developing significant annular-aortic dilatation.

A dilated annulus, sinus and sino-tubular junction lead to a widened inter-commissural distance, stretched-out leaflets and coaptation deficit. While severe aortic dilatation may necessitate replacement of the supra-coronary aorta; mild localized dilatation could be tackled with vertical plication of the dilated sinus. This in turn helps to improve coaptation of the aortic leaflets. In occasional cases of relatively smaller left or right aortic leaflets, a similar plication of the non-coronary sinus may also be effectively used to improve coaptation. Although more conveniently performed from inside the opened up aorta, in selected circumstances, we have applied this technique externally, based on trans-esophageal echocardiographic findings of residual regurgitation due to specific coaptation deficit, after removal of the aortic cross clamp. This technique may preserve the advantage of having a dynamic aortic root participating in the valve function mechanism.

Stabilization of the free edge of the reconstructed leaflets
In cases where part of the leaflet is made up of native tissue and the rest from a patch of xenopericardium, the difference in stiffness/compliance of both the tissues may require that the free edge of the leaflet be stabilized with a simple run over of non-absorbable suture. Reinforcement and elevation of the level of free margin of a prolapsing cusp by weaving fine Gore-Tex along the free margin has been described by others [15].

Material for patch augmentation
While the technique of pericardial patch augmentation of the aortic valve is yet to be standardized so as to be consistently reproducible, one of the important impediments to achieving satisfactory long-term result is the available patch material. The commercially available xenopericardial patch materials, although good to handle, are far from ideal. They do not grow, have no self repair function, are relatively thick, stiff and virtually non-elastic to allow any comparison to the native valve tissue. The dynamic abilities, such as stretching and elongation of the native valve tissue [17] that actively contribute to the size and function of the aortic valve are not compensated for by the non-compliant xenopericardial patches. We have recently attempted to revisit the idea of using native untreated pericardium for aortic valve repair. Although our initial experience is encouraging, it is too early to make a statement. Realization of full potential of aortic valve repair techniques will be best served by availability of a growing tissue with greater resemblance to the native valve [18, 19]. In spite of this handicap, valve repair continues to be appealing in various clinical scenarios. In neonates and infants with need for acute intervention as a salvage procedure after balloon dilatation, valve repair with pericardial patch augmentation continues to be the procedure of choice. In teenaged children and young adults, the prospect of having a functional native aortic and a pulmonary valve, which delays a Ross procedure, will remain attractive if we can prove that aortic valve repair with the evolving techniques and the available material remains durable over medium to long term. Availability of such a procedure would allow these children to be subjected to surgery early enough, thus preserving the precious left ventricular function.

Contemporary experience
Although aortic valve reconstructive procedures were sporadically described right through the 1990s [20, 21], no one technique imposed itself over the others, with stable reproducible results and over longer term follow-up. Valve repair for aortic stenosis in the setting of a bicuspid aortic valve in particular, has specifically experienced a revival of late [9, 12, 22, 23]. The description of a variety of techniques indigenous to each group, however, aptly summarizes the nascence of the evolving strategies. Broadly summarized, the surgical philosophy hinges on either attaining sufficiency while maintaining the bicuspid morphology of the valve [12, 23] or reconfiguring the valve annulus by opening the fused raphae and creating a tri-sinusoidal tricuspid aortic valve. The proponents of the latter school of thought [8, 9, 22] obviously claim the advantages of restoring a normal anatomy with a larger valve orifice area and reduced valve stress.

Tolan et al. [9] described a technique dividing the raphae (in the fused leaflet) and use of a folded triangular piece of bovine pericardium to supplement the deficient leaflets, thus creating a tri-sinusoidal valve. Various other groups more or less mimicked this type of repair with minor modifications. Odim et al. [22], additionally advocated reduction plasty of the dilated sino-tubular aorta ascendens either with resection of a strip of aorta, or using a wrap of Dacron mesh. A few groups [12] advocate augmenting the fused cusp with a glutaraldehyde fixed pericardial patch, while retaining the bicuspid structure.

Massetti et al. [24] used a sliding leaflet technique to pull up the prolapsing leaflet and reinsert higher up along the adjoining commissures to treat isolated leaflet prolapse. We have no experience with this technique and have difficulties to imagine that a whole sinus can be surgically ‘isolated’ and brought higher up without interfering with the important surrounding anatomic structures.

The fused leaflet in a bicuspid valve is not laid down along a normal deep crown-like annulus, but instead along a more superficial flat plane, thus reducing the area of coaptation. Moreover, one fused leaflet is not equal to a sum of two leaflets – as far as the span, height and the concavity are concerned. We therefore detach the fused leaflet and set it onto a fictitious neo-annulus, which is deeper to the existing annulus. We thus aim to restore the anatomical crown-like form of the annulus. We use a patch of xenopericardium to recreate the third leaflet. The long-term fate (shrinkage, fibrosis, stiffness and calcification) of the available material will be an important predictor which will decide the longitivity of this repair. From our modest experience of 12 cases, freedom from reoperation and freedom from severe regurgitation was 100%, at a median follow-up of 13 months [13]. The adjoining Table 1 enlists the results of contemporary series of bicuspid valve repairs from various groups.

To summarize, with the limited experience that has been accumulated so far, it appears fair enough to say that longer follow-up, standardization of techniques and reproducibility of results would be a key to further democratization of this procedure.

	Acknowledgements

Top Summary Introduction Surgical procedure Acknowledgements References

 
We thank Dr. Achim Haeussler for the help in preparing the video clips and Mr. Stefan Schwyter for preparing the graphic artwork for this manuscript.

	References

Top Summary Introduction Surgical procedure Acknowledgements References

 

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