Procedure

Open valvotomy for aortic valve stenosis in newborns and infants

Department of Pediatric Cardiac Surgery, German Pediatric Heart Center, Asklepios Clinic Sankt Augustin, Arnold Jansen Str. 29, 53757 Sankt Augustin, Germany

^* Corresponding author: ^* Tel.: +49 2241-249 603; fax: +49 2241-249 602 v.hraska{at}asklepios.com

	Summary

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The most appropriate management of aortic stenosis in children remains controversial. Both balloon and surgical valvotomy are firmly established as effective initial treatments with encouraging survival rates even in the troublesome neonatal group. Improved early results are based rather on the better understanding of the limits of a biventricular repair than on the method of treatment. Valvotomy of any kind is a palliative procedure and reintervention remains frequent. Direct surgical intervention, where exact splitting of fused commissures and shaving off of obstructing nodules can produce a better valve with maximum valve orifice without causing regurgitation, might offer superior longer-lasting results in comparison with blind ballooning.

Key Words: Aortic stenosis • Congenital heart disease • Surgery

	Introduction

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Isolated valvar aortic stenosis has a wide spectrum of anatomical and clinical variations. Most patients, especially those with a bicuspid aortic valve, will remain asymptomatic during childhood. In later life, as the leaflets become thickened and fibrotic, they may need surgical treatment. At the other end of the spectrum, there are newborns and infants with critical aortic stenosis. They represent a distinct and challenging group of patients with severe obstruction at valvular level and ductus dependent (PDA) systemic circulation. They may become severely ill, when the ductus closes, manifesting with low cardiac output, acute renal failure and severe metabolic acidosis.

Decision making
The key issue is to decide whether left-sided structures are adequate to sustain the systemic circulation, thereby making a biventricular type of repair feasible. Correctly choosing the appropriate surgical pathway at the very beginning is critically important and contributes to an overall improvement in the outcome for patients with critical aortic stenosis [1, 2]. There is no agreement on what combination of left-sided structures would be adequate to perform bi-ventricular correction.

Our treatment protocol
The decision-making protocol for critical aortic stenosis in our institution emphasizes the assessment of the inflow structures of the LV, the length of the LV, flow characteristics in the ascending aorta and the presence and degree of endocardial fibroelastosis (EFE) [1, 3, 4,5,6]. If the mitral valve annulus is <7 mm, or 2Z, and the apex of the heart is not formed by the LV, with diminished left ventricular length, and flow in the ascending aorta is predominantly reversed with developed EFE, one ventricular palliation is contemplated. The left ventricular outflow structures, such as hypoplasia of the aortic annulus (<5 mm) and presence of EFE are not contraindication of biventricular repair if the Ross operation is an option and the EFE can be resected.

Our treatment protocol is surgically driven. If the function of the LV is depressed, a balloon valvotomy (BV) with a balloon not larger than 5 mm in diameter is performed to slightly increase the effective orifice area of the aortic valve with no risk of creating regurgitation. This so-called ‘gentle’ BV is done as an intermittent step to stabilize the patient before surgery.

If LV function is not severely depressed and there is no hypoplastic annulus of the aortic valve, open valvotomy (OV) is the method of choice. In the case of a hypoplastic aortic annulus and developed, but resectable EFE, a Ross-Konno operation is considered. The Ross option is considered if there is failure of the BV or OV as well (Schematic 1).

View larger version (51K): [in this window] [in a new window]   Schematic 1 Treatment protocol of the German Pediatric Heart Center, Sankt Augustin for critical aortic stenosis. AoS – aortic stenosis; LV – left ventricle; EFE – endocardial fibroelastosis; BV – balloon valvotomy; OV – open valvotomy.

	Surgical technique of open valvotomy in neonates and infants

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The operation is performed on cardiopulmonary bypass (CPB) with mild hypothermia (32 °C). The ascending aorta is dissected free as well as the PDA. After systemic heparinization, the patient is cannulated for the CPB (Video 1).

Click on image to view video Video 1 The aorta is cannulated as high as possible to leave enough space for working on the ascending aorta. One venous cannula provides optimal venous drainage without interfering with the operative field.

Click on image to view video Video 2 A purse string is placed. The small angled vent is inserted through an opening at the entrance point of the right pulmonary veins towards the mitral valve into the left ventricle.

Click on image to view video Video 3 An oblique, inverted hockey stick type of incision is made from the anterior aspect of the aorta towards the non-coronary sinus of Valsalva.

Click on image to view video Video 4 The morphology of the valve, the arrangement of the commissures, and the localization of the false raphe and orifices of the coronaries are noted. The degree of peripheral commissural fusion and nodular excrescences on the leaflets composed of myxoid tissue and the thickened part of the leaflets are identified. Insert schematically depicts the anatomy of the valve.

Click on image to view video Video 5 The incision is short, usually 1–2 mm in length. Even a short incision may result in adequate opening of the outflow orifice, because the flow is a function of the fourth power of the radius. The height and base of the interleaflet triangle, which is significantly reduced, is developed.

Click on image to view video Video 6 Obstructive myxomatous and fibrous nodules on the leaflets are removed. This implies careful and meticulous thinning/shaving of the leaflets with a knife.

Click on image to view video Video 7 Frequently, a cleavage plane is identified between the fibrosis and what seems to be a thin pliable aortic leaflet tissue. Correctly performed ‘shaving’ greatly improves mobility of the leaflets and the effective orifice area of the aortic valve.

Click on image to view video Video 8 It is important to remove fibrose nodules located at the hinge point of the leaflets to enlarge the outflow tract.

Click on image to view video Video 9 The effective orifice area is checked by ‘olive’ and the commissurotomy and shaving are extended if necessary.

Click on image to view video Video 10 A final assessment of the opening of the valve and mobility of the leaflets is performed.

Click on image to view video Video 11 The aortotomy is closed with a running suture.

Click on image to view video Video 12 The left part of the heart is de-aired through the vent, using retrograde filling of the left ventricle with saline. The aortic cross-clamp is removed and de-airing is completed.

	Results

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Recent results achieved either with balloon or open valvotomy, incorporating only large series of patients with critical aortic stenosis, are summarized in Tables 1 and 2. The varying design of these studies does not allow a valid comparison of OV and BV. On the other hand, the surgical approach tends to exhibit a lower mortality rate, higher freedom from reintervention and lower incidence of significant aortic regurgitation.

	Discussion

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Percutaneous dilatation relieves aortic stenosis by causing rupture along the lines of least resistance, either along the underdeveloped commissures or into the leaflet tissue. Usually the transvalvar gradient is effectively reduced but there is increased risk of progressing aortic regurgitation, pre-disposing to an early or late re-operation, which does not seem to be prevented by the use of small balloons [11]. Reintervention is almost inevitable [12]. The incidence of aortic regurgitation is up to 40% at least, at 10 years of follow-up [13]. Reintervention rates are 50% at 8 years after the initial valvotomy. In the neonatal group, the results are worse with <0% of patients surviving to 14 years without reintervention [14]. The incidence of procedure-related mortality up to 2% is certainly not negligible, demonstrating that the ‘less invasive’ approach is not necessarily the safest [15]. There is high incidence of procedural femoral artery damage [11]. Despite treatment, the majority of children have evidence of obstructive lesions of iliofemoral vessels after balloon valvuloplasty [11].

Open surgical valvotomy, allows more accurate fashioning of commissurotomies, with the attempted construction of leaflet anatomy as close to normal as possible. Shaving of thickened leaflets, excision of obstructive myxomatous nodularities, and mobilization of leaflets effectively increase the orifice area of the valve with minimal risk of creating regurgitation. This is not achievable with the ‘blind’ BV, where cusps are likely to get torn or perforated while trying to relieve the obstruction. Overall, early mortality after OV is between 5% and 10%, with the mortality rate approaching zero among the infants over one month and older children. Early mortality in critical neonates is associated with adverse prognostic factors such as mitral stenosis, small-sized left ventricle, small aortic annulus, depressed fractional shortening (FS), low aortic gradient, EFE, and other co-existing defects [16]. The overall 10-year survival rate is approximately 90% with nearly 100% survival rate for isolated aortic stenosis. There is a late death-hazard with a 70% survival rate for neonates and infants with other severe associated lesions. The 10-year freedom from recurrent aortic stenosis is approximately 80% [17, 18]. Mild aortic stenosis is stable and non-progressive and, should it be so, is amenable to repair [19]. Development of severe aortic regurgitation after open valvotomy is unlikely with 10 years freedom from severe aortic regurgitation up to 90%. Usually, post-surgical aortic regurgitation is related to monocuspid valves, or a technically inadequate commissurotomy with rather over-enthusiastic incisions in the valve [17]. Overall, the 10-year survival rate, free from reintervention, is between 75% and 90%, reflecting the underlying age at repair, being less favorable for critical newborns [17, 18].

The underlying anatomy of the left ventricular outflow tract and associated lesions determines the outcome of critical aortic stenosis more than the method of treatment. Aortic BV is safe and effective. The major long-term problem is progressive aortic regurgitation [11], converting the physiology of aortic stenosis to aortic regurgitation with a detrimental effect on ventricular performance [10]. The reintervention rate is higher and the need for an aortic valve replacement occurs sooner than after a direct surgical OV [20]. Superior longer-lasting results can be achieved by direct surgical intervention, where the exact splitting of fused commissures and shaving off of obstructing nodules can better produce a valve with a maximum valve orifice without causing regurgitation [17]. Open valvotomy is the method of choice in our institution.

	References

Top Summary Introduction Surgical technique of open... Results Discussion References

 

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