Procedure

Surgical closure of a perimembranous ventricular septum defect with a running suture

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

^* Corresponding author: KinderSpital, Steinwiesstrasse 75, 8032 Zürich, Switzerland rene.pretre{at}kispi.uzh.ch

	Summary

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A ventricular septum defect (VSD) is a common defect in congenital surgery, either isolated or associated with other malformations. Most of the defects are located around the membranous septum and hence are called ‘perimembranous’. The less damaging approach to close them is certainly through an incision in the right atrium. In some trunco-arterial malformation, an incision in the infundibulum is necessary to connect the right ventricle to the pulmonary arteries. A perimembranous VSD can then also be closed using the same incision. The videos show the closure of a perimembranous VSD using these two common approaches. Although many surgeons opt for interrupted stitches reinforced with pledgets to close these defects, a running suture can also be used and, in our opinion, is a reliable and rapid alternative technique.

Key Words: Fallot tetralogy • Pulmonary atresia • Rastelli procedure • Truncus arteriosus • Ventricular septum defect

	Introduction

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A ventricular septum defect (VSD) is an anatomic defect between the left and right ventricle which, due to different resistance in their respective circulation, gives rise to a shunt of blood. The shunted blood flows from the left to the right ventricle when there is no obstruction along the right ventricular outflow tract and/or within the lungs. It flows from the right to the left ventricle when there is an obstruction in the pulmonary circulation greater than the overall resistance of the systemic circulation.

The most common location of a VSD is where the membranous septum is normally situated. The term perimembranous VSD is used to describe this type of defect. The defect can be confined in this area or can extend in the inlet, in the muscular or in the outlet part of the septum. It is important to know that in a normal atrio-ventricular connection (by far the most frequent situation) the His bundle of the atrio-ventricular conduction system runs on the left side of the inferior border of a perimembranous VSD (Schematic 1). Knowledge of the precise location of the conducting tissue is crucial to avoid its damage with a resulting complete atrio-ventricular block [1].

View larger version (84K): [in this window] [in a new window]   Schematic 1 Drawing of a typical perimembranous VSD seen through a right atriotomy. The anterior border of the defect is classically hidden by the tricuspid valve leaflets. The conduction tissue runs at the apex of the Koch triangle before it enters the ventricular septum. It then courses on the left side of the septum (insert lower left) before giving off its bundle divisions.

Perimembranous VSD
Perimembranous VSDs are found in 20–30% of congenital heart defects, either in isolation or in association with other defects (especially in trunco-arterial anomalies) [8]. The defect is in close relationship to the aortic valve (under the right coronary cusp or under the commissure between the non-coronary and the right coronary cusp) and the tricuspid valve (centered under the antero-septal commissure). With an inlet extension, the defect spreads underneath the septal leaflet of the tricuspid valve, between the annulus of both atrio-ventricular valves. With an outlet extension, it spreads in the outlet septum along the right coronary sinus of the aortic root. Because of its location between strategic structures, these VSDs are not amenable to percutaneous closure with a device. Most surgeons, when using an atrial approach, close these VSDs with a patch of Goretex or xenopericard, with interrupted stitches of Prolene supported by Teflon pledgets. The chordae of the tricuspid valve leaflets make the exposure of the defect and its closure with a running suture difficult [4]. For many years we have detached part of the tricuspid valve from its annulus to totally expose the borders of the VSD [3, 9]. This has allowed us to close them with a running suture. This technique is shown in Videos 1, 2 ,3, 4, 5, 6, 7, 8, 9. Videos 10, 11, 12, 13, 14, 15 show the closure of a similar perimembranous VSD, using an incision in the right infundibulum in the case of a pulmonary atresia with VSD.

Transatrial closure of the VSD
The child was a two-month-old baby girl (weight: 2.8 kg) with a large perimembranous VSD and equalized pressure in the pulmonary artery and aorta. The indication to perform surgery was given because of clinical signs of overt heart failure, the amount of shunted blood, and the pulmonary hypertension.

	Surgical technique for transatrial VSD closure

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After a median sternotomy and opening of the pericardium, the aorta and both vena cava were cannulated and cadiopulmonary bypass was established. The ascending aorta was cross-clamped underneath the aortic cannula and warm blood cardioplegia was administered every 10 min in the aortic root [10]. A vent was inserted in the left ventricle. After establishment of full cardiopulmonary bypass, the right atrium was opened with an antero-inferior incision and the tricuspid valve exposed with three stay stitches. If the borders can be identified completely through the tricuspid aperture, the VSD is closed using this approach, with a patch and a running suture. If, however, as it is frequently the case, the anterior and superior part of the VSD cannot easily be identified (because of an overriding aortic annulus or because of chordae of the tricuspid valve) the anterior leaflet of the tricuspid valve is detached from its annulus [3, 9] as illustrated here.

Click on image to view video Video 1 Detachment of the anterior leaflet. The leaflet is detached from its annulus, down to the inferior border of the VSD.

Click on image to view video Video 2 The patch is inserted in the remote part of the septum, and the running suture is performed down the inferior border of the VSD. On this part of the VSD, full thickness bites are taken on the septum.

Click on image to view video Video 3 On the inferior border of the septum, near the tricuspid annulus, shallow bites are taken on the septum to avoid damage to the conducting tissue.

Click on image to view video Video 4 The patch is then inserted on the superior border of the VSD. Separate bites are taken on the patch (forehand move) and on the VSD (backhand move). Pulling the patch caudally, nicely unfold and expose the border of the VSD around the aortic annulus.

Click on image to view video Video 5 When the insertion of the patch reaches the tricuspid valve annulus, the suture is pulled and held on a rubber shod.

Click on image to view video Video 6 The patch is trimmed from excessive tissue.

Click on image to view video Video 7 The patch is sandwiched between the tricuspid annulus and the anterior leaflet, starting at the lower part of the VSD with shallow bites on the annulus.

Click on image to view video Video 8 The suture is pursued to the superior border of the VSD and knocked down.

Click on image to view video Video 9 The tricuspid valve is checked for competence with saline.

A patch of Goretex or xenopericard is then cut to the size of the VSD. The insertion of the patch on the septum is started at the most remote part (from the surgeon) of the septum, taking full-thickness bites on the septum (Video 2). After two stitches, the patch is lowered down on the septum, and the suture proceeds toward the inferior border of the VSD up to the junction between the ventricular septum and the leaflet detachment. After a few stitches, the bites become more superficial, ‘endocardial’, and are taken on the right side of the septum to avoid disturbing the conducting tissue (Schematic 1 and Video 3).

The anterior part of the VSD closure is then performed. To facilitate the suturing around the aortic annulus, we recommend taking separate bites in the patch and then in the border of the VSD. By gently pulling on the patch, the border of the defect progressively comes in view and can be sutured precisely with adequate bites (Video 4). This part of closure is also terminated when the suture reaches the annulus of the tricuspid valve (Video 5). The excess of patch is trimmed (to avoid any fold under the tricuspid valve) (Video 6).

The last part of the closure (the part where the VSD is in direct relationship with the tricuspid valve annulus) is performed last. Here, the patch is sandwiched between the tricuspid annulus and the detached leaflet (Video 7). Once the closure is completed, the suture threads are knotted together (Video 8). The remaining (superior) part of the detachement of the anterior leaflet of the tricuspid valve is closed with a running suture of resorbable thread (not shown).

The competence of the tricuspid valve is checked by injection of saline in the right ventricle (Video 9). If a prolapsus of the antero-septal commissure is identified (something sometimes present in perimembranous VSD), the two corresponding leaflets can be adapted with one or two separate stitches of Prolene 6/0.

The atrial septum is checked for any defects like a patent foramen ovalis, which would be closed. The heart is deaired and the aortic cross-clamp is removed. During the early reperfusion phase, the right atrium is closed with a running stitch of fine resorbable suture. Sinus rhythm recovers within a few seconds with warm blood cardioplegia and after 10 min reperfusion, weaning from cardiopulmonary bypass is possible.

Closure of a perimembranous VSD using an infundibulotomy
An incision in the infundibulum is rarely performed to close a VSD. VSD located in the outlet septum can still be approached with a right atriotomy (our preferred approach) or an incision in the pulmonary artery. A transverse infundibulotomy can also be performed. It gives direct access to the VSD.

A longitudinal infundibulotmy, or a longitudinal incision in the upper part of the right ventricle (when there is no infundibulum) is necessary to connect the right ventricle to the pulmonary artery in case of pulmonary artresia with VSD, truncus arteriosus or some transposition of the great arteries with pulmonary stenosis. The VSD can then be closed using this ventricular incision and avoiding an additional atriotomy. This approach is presented in the second video sequences.

The child was a four-month-old boy with pulmonary atresia and perimembranous VSD. Three weeks after birth, he underwent a unifocalization of all identified MAPCAs with establishment of a right ventricle-pulmonary artery (RV-PA) connection with a 4.5 mm diameter Goretex graft. He subsequently showed a satisfactory growth of the reconstructed pulmonary arteries, which allowed closure of the VSD and insertion of a valved conduit between the right ventricle and pulmonary arteries.

	Surgical technique for transventricular VSD closure

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After establishment of CPB between the two vena cava and the ascending aorta, the ascending aorta was cross-clamped and warm blood cardioplegia was administered in the aortic root [10]. A vent was inserted in the left ventricle through the right superior pulmonary vein.

The graft between the right ventricle and pulmonary arteries was dissected and removed. The borders of the previous infundibulotomy were trimmed, leaving firm fibrotic tissues for insertion of the valved conduit. Using the incision in the infundibulum, the VSD is exposed and its size appreciated (Video 10). A corresponding patch of xenopericard is cut out. The suture of the patch is started at the deepest point of the VSD (which is the inferior border of the VSD, which corresponds to the junction of the lower limb of the septo-marginal trabecula with the infundibular fold) (Video 11). There, the border of the VSD typically appears fibrotic and is in close relationship with the tricuspid valve annulus (near the antero-septal commissure). Small bites are taken on the septum to avoid stretching the tissues surrounding the conduction tissues. The suture is performed toward the surgeon on the lower limb of the septomarginal trabecula (Video 12). Rapidly, larger bites can be taken on the septum as one gets away from the conducting tissue. The suture is stopped close to the beginning of the conal septum.

Click on image to view video Video 10 The borders of the VSD are shown.

Click on image to view video Video 11 A patch is trimmed to the size of the VSD and is anchored on the lowest part of the VSD (inferior border of the VSD).

Click on image to view video Video 12 The suture is performed on the inferior border of the VSD.

Click on image to view video Video 13 The patch is then inserted on the ventriculo-infundibular fold.

Click on image to view video Video 14 The opposite part of the patch is inserted on the opposite part of the septum and sutured first towards the anterior limb of the septo-marginal band.

Click on image to view video Video 15 And then to the ventriculo-infundibular fold.

	Results

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From 2001 to 2006, 152 children underwent closure of an isolated (98 patients) VSD or of a VSD associated with Fallot tetralogy (54 patients) using a running suture after detachment of the anterior leaflet of the tricuspid valve in our unit. This analysis is concentrated on this subset of patients which represents 70% of the total cohort of patients with these pathologies and does not include direct closure of VSD, closure of VSD in atrio-ventricular canal, or closure of VSD in other locations.

Median age was five months and median weight 5.6 kg. The median cardiopulmonary bypass and cross-clamp times for isolated VSD were 61 and 32 min, respectively. All patients were controlled peri- and post-operatively with echocardiography. Follow-up was complete.

There was no early or late death. One child required ECMO support after Fallot repair but survived. This patient required reoperation to reinsert a torn anterior leaflet of the tricuspid valve and implantation of a valved conduit on the RVOT. A residual VSD was found in postoperative transthoracic echocardiography at three months in three patients with isolated VSD and in two patients with Fallot tetralogy. These were all restrictive, smaller than 3 mm and none required a reoperation. One patient after Fallot tetralogy required a permanent pace-maker because of persisting complete atrio-ventricular block. Except for the ECMO patient, the tricuspid valve never showed more than trivial or mild residual valvular insufficiency.

	Review of the literature

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The results of VSD closure have been consistently excellent for many years, with mortality rates nowadays approaching 0 percent in the case of isolated malformation [5, 11]. In one of the largest retrospective surveys spanning from 1976 to 2001, the mortality rate was 1.5% [1]. The risk of complete atrio-ventricular block in normal atrio-ventricular configuration ranges from 0 to 1% [1, 3, 5, 11]. The presence of residual VSD is difficult to appreciate because of the various methods used to establish diagnosis and the different timings of analysis (most minor defects close within a few days). Using the sensitive transesophageal echocardiography perioperatively, a residual VSD jet was found in 12% of patients in our experience [1]. Most of these jets were consecutive to the needle holes in the Goretex patch and closed spontaneously within a few days [3]. Persistent residual VSD, typically larger than 2 mm in diameter, are seen in about 1% of perimembranous VSD [12, 13] and only a few of them, those over 4–5 mm, require a reoperation. The liberal detachment of the tricuspidal valve leaflet seems to have even reduced the incidence of residual VSD by providing better visualization of the defect borders [3, 9, 13]. The incidence of tricuspid valve insufficiency is, for the same reasons, difficult to appreciate, but does not exceed 3% of patients long-term [3, 5, 13, 14]. A valvular insufficiency exists already in about 5% of patients with a perimembranous VSD due to prolapsus of the antero-septal commissure induced by the jet of shunted blood. The insufficiency regresses after VSD closure as a result of the reduced pressure in the right ventricle but is usually not entirely eliminated unless the surgeon adds a plasty at the commissure [3]. A new valvular insufficiency can be induced with inappropriate tailoring or suturing of the patch. The detachment of the tricuspid valve leaflet, with the improved exposition of the VSD and the avoidance of stretch on the subvalvular apparatus, has led to better preservation of the valve function [3, 5, 9, 13]. In our opinion, the technique with a running suture further allows the progressive trimming of the patch and avoids any tension or patch redundancy which could interfere with the tricuspid valve function [3, 9].

	Discussion

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Closure of a ventricular septum defect is one of the most common procedures performed by congenital surgeons. Many approaches and techniques have been described, not only for unusual locations, but also for the most common ones. We have concentrated our presentation on the most common perimembranous VSD, using a transatrial approach and an infundibular approach. We believe that practically all perimembranous VSDs can be closed using the transatrial approach, especially after detachment of the appropriate part of the tricuspid valve, which greatly enhances exposure [3, 5, 9, 13].

Detachment of the tricuspid valve leaflets has been described for a long time for the septal leaflet [5, 15]. Gaining experience with Fallot tetralogy showed us that most perimembranous VSD can be approached with a detachment of the anterior leaflet [3, 9]. The detachment is typically started in the mid part of the anterior leaflet and is pursued inferiorly close to the point where the inferior border of the defect is visible. The detachment of the leaflet is prolonged superiorly if necessary. This detachment has several advantages. The exposure of the VSD is always optimal, and the risk of damage to the conducting tissue (which is substantial when the detachment is made on the septal leaflet) is reduced. Furthermore, this approach gives a complete exposure of the aortic annulus in case of overriding aorta. Because of the full exposure of the VSD (without any structure overriding it), the defect can be easily closed with a running suture. Finally, the patch can be trimmed to exactly fit the defect. An excessively small patch can induce a tear on the suture line with a subsequent residual defect, and an excessively large patch can create a fold either underneath the aortic valve or underneath the tricuspid valve.

Concerns can be raised regarding the solidity of the reattachement of the fragile valvular tissue of neonates. We have liberally used this technique in this group of patients, with the same excellent results. We insert the patch on the septum with a 7/0 non-resorbable suture and readapt the detached leaflet on its annulus with a running 7/0 resorbable suture or an 8/0 Prolene suture. The leaflet readaptation is performed on a cardioplegic heart in neonates and on a beating heart in larger kids.

Classical perimembranous VSDs sometimes result in a prolapsus of the antero-septal commissure of the tricuspid valve induced by the jet of blood. In such a situation, a tricuspid valve insufficiency or a left ventricular to right atrium shunt is detected in preoperative echocardiography. We always check this part of the tricuspid valve and correct it by a short adaptation of the two adjacent leaflets with one of two interrupted stitches of Prolene 6/0.

In our practice, an incision in the right ventricle is used only to close perimembranous VSDs associated with a pulmonary atresia and MAPCAs, with a truncus arteriosus or to connect the left ventricle to the aorta during a Rastelli procedure. We close the VSD through the right atrium in Fallot tetralogy to minimize the incision in the infundibulum necessary to enlarge the stenotic right ventricular outflow tract. In the infundibular approach too, we have stuck to our closure technique with a running suture, which allows a progressive and precise fashioning of the patch. The patch is inserted first on the most inferior part of the VSD, usually on a fibrotic part of the defect border. The bites should be shallow there, because of the proximity of the His bundle. Once this part is completed, larger bites are used to firmly anchor the patch on the VSD. The aortic valve should also be clearly identified to avoid suturing the patch too far away from the valve, on trabecula (which could result in residual shunt), or too close to the leaflets. Infusion of cardioplegia in the aortic root spreads the aortic valve out and precisely shows the location for the patch insertion.

	References

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