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Eur J Cardiothorac Surg 2005;27:81-85
© 2005 Elsevier Science NL

The influence of valve physiology on outcome following aortic valvotomy for congenital bicuspid valve in children: 30-year results from a single institution

Tara Karamloua,c,*, Irving Shena, Bahaaldin Alsoufiaa, Grant Burchb, Mark Rellerb, Michael Silberbachb, Ross M. Ungerleidera

a Division of Pediatric Cardiothoracic Surgery, Oregon Health and Science University, Portland, OR 97201, USA
b Division of Pediatric Cardiology, Oregon Health and Science University, Portland, OR 97201, USA
c Hospital for Sick Children, Toronto, ON, Canada

Received 15 June 2004; received in revised form 14 October 2004; accepted 25 October 2004.

* Corresponding author. Tel.: +1 503 418 5443; fax: +1 503 418 5443. (E-mail: ungerlei{at}ohsu.edu).


   Abstract
Top
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 
Objective: Aortic valvotomy is widely used for the treatment of congenital aortic stenosis in children. We sought to evaluate whether the predominant post-valvotomy physiology, aortic insufficiency (AI) or aortic stenosis (AS) independently affected patient outcome. Methods: From 1972–2002, 57 children with congenital aortic stenosis underwent valvotomy. We divided age-matched patients with residual lesions based on their predominant pathology into three groups: Group I (n=14), patients with moderate AI; Group II (n=14), patients with moderate AS, and Group III (n=14), patients with combined AI and AS. Fifteen patients with severe AI or mild residual lesions following valvotomy were excluded from analysis. Results: mean freedom from aortic valve replacement (AVR) was 11.2±1.7 years in Group I and 21.5±3.9 years in Group II, P=0.05. AVR was required in 11 patients (79%) in Group I vs. only 5 (36%) in Group II, P=0.05. Group III was intermediate, with 9 (64%) requiring AVR. At the time of AVR, patients with aortic stenosis had significantly higher fractional shortening % than those with insufficiency or combined lesions, (Group 1: 38.2±7.9 vs. Group II: 46.3±5.5 vs. Group III: 39.2±3.7, P=0.007). Patients in Group II also had less severely dilated ventricles (mm) than those in the other groups, (Group 1: 50.2±12.5 vs. Group II: 39.5±8.3 vs. Group III: 49.0±8.1, P=0.030). Conclusions: patients with predominant AI following valvotomy are more likely to need AVR sooner than those with residual stenosis without AI. Therefore, cautious use of repeat valvotomy using maneuvers to avoid AI (small balloons), may prolong freedom from aortic valve replacement in those patients with significant residual AS.

Key Words: Aortic stenosis • Valvotomy • Congenital • Aortic insufficiency • Outcome


   1. Introduction
Top
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 References
 
Aortic valvotomy, whether open or through a percutaneous approach, has become established as an acceptable long-term palliation of congenital aortic stenosis in children. Significant residual aortic stenosis and regurgitation are well known problems after valvotomy, occurring in 10–43% of patients [1–5]. The hemodynamic consequences of these lesions are different, however, with aortic insufficiency (AI) producing chronic volume overload, and aortic stenosis (AS) producing chronic pressure-overload [6–13]. The heart possesses unique morphologic and functional adaptations to volume-overload and pressure-overload, which may influence the clinical course following aortic valvotomy [8–13].

Recent literature has suggested that aortic insufficiency, even if mild initially, is often progressive and may lead to early aortic valve replacement or complicate future surgical intervention [6,7]. In addition, the increased risk of AI following percutaneous valvotomy, secondary to cusp or commissural damage, as compared to surgical valvotomy has renewed interest in defining criteria for timing of repeat intervention and optimizing patient selection [6,14]. Although numerous studies have elucidated risk factors for the development of aortic regurgitation or incomplete relief of obstruction, the natural history of these different post-valvotomy lesions with respect to ventricular function, reintervention, and long-term patient outcome remain uncertain [1–7,14].

The objective of this study was therefore to investigate whether important post-valvotomy aortic insufficiency is associated with more pronounced ventricular dysfunction and the need for earlier aortic valve replacement than significant residual aortic stenosis.


   2. Methods
Top
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 References
 
2.1. Patients
From January 1972 to December 2002, 57 consecutive patients <18 years of age with congenital aortic stenosis and a bicuspid aortic valve who underwent aortic valvotomy (open or percutaneous) at our institution were identified by retrospective review of a prospectively maintained database maintained by the Department of Cardiology at Doernbecher Children's Hospital, Oregon Health and Science University. No patients were excluded because of associated defects.

Demographic data prior to initial valvotomy and at last follow-up were collected from hospital and clinic charts, diagnostic echocardiographic, electrocardiographic, and cardiac catheterization reports. Follow-up information was obtained from the last clinic visit for each patient.

Patients were then divided into three groups based on the predominant aortic valve pathology immediately following initial valvotomy as follows:

(1) Group I (n=14): patients with moderate aortic insufficiency without significant concomitant aortic stenosis
(2) Group II (n=14): patients with moderate aortic stenosis without significant aortic insufficiency
(3) Group III (n=14): patients with both significant aortic stenosis and significant aortic insufficiency

Two patients had severe AI and required immediate AVR, and 13 had only mild disease, as described below, and were excluded from further analysis.

2.2. Echocardiography and grading of aortic valve pathology
In patients with normal ventricular function, the severity of aortic stenosis was graded according to well-established Doppler gradient measurements, (1). The stenosis was considered to be severe if the peak Doppler gradient was >70mmHg or the mean gradient was >40mmHg. If the maximum gradient was between 50–70mmHg or the mean gradient was between 25–40mmHg, the stenosis was considered moderate. If the maximum gradient was <50mmHg and the mean gradient was <25mmHg, the stenosis was considered mild.

Aortic regurgitation was graded echocardiographically based upon the subjective assessment of the echocardiographer as mild, moderate or severe. In cases where only a numerical grade was reported, the scale described by Moore et al. (2) was used as follows: 0=absent; 1=trivial; 2=mild; 3=moderate; 4=severe.

Presence or absence of left ventricular hypertrophy, left ventricular end-diastolic dimension and left ventricular shortening fraction were also obtained from patients' echocardiographic reports prior to initial valvotomy, when available, and at last follow-up. In patients who underwent aortic valve replacement, echo measurements were obtained prior to the operative procedure.

2.3. Follow-up
Follow-up information, obtained from clinic charts at annual visits, included the presence or absence of symptoms referable to aortic valve disease, need for repeat intervention, and echocardiographic assessment of valvar and ventricular function. Reintervention included repeat balloon dilatation, surgical valvotomy, or valve replacement. Follow-up was 100% for all 42 patients in the study group.

2.4. Statistical analysis
Continuous variables are expressed as mean±SD. Comparisons between groups were made using one-way analysis of variance (ANOVA) with Bonferroni correction for interval data. Categorical data were compared using the {chi}2 or Fisher exact test when appropriate.

Analysis of postoperative time-related events was accomplished by the Kaplan–Meier method, using the log-rank test for group comparisons.

For the entire cohort of patients, the factors related to occurrence of aortic valve replacement were first examined in a univariate model. Univariate variables reaching significance (P<0.05) were then tested in a multivariate logistic regression model and removed using backward stepwise selection if no statistical influence was demonstrated. The postoperative variables were obtained at the most recent follow-up, or immediately prior to aortic valve replacement for those undergoing operation.

The level of statistical significance was set at a P value ≤0.05. Analysis was done using SPSS software (version 11.0; SPSS Inc., Chicago, IL).


   3. Results
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 References
 
Clinical characteristics prior to valvotomy and procedural data for Groups I–III are summarized in Table 1. There were no statistically significant differences between the groups with respect to age at initial valvotomy, sex, duration of follow-up, open vs. percutaneous valvotomy, presence of associated congenital heart defects, or coexistent left ventricular hypertrophy. There were 13 total neonates within the 42 patient cohort. Five of these had moderate aortic insufficiency (AI) following valvotomy, three had moderate aortic stenosis (AS), and six had combined AI/AS. Retrospective measurements of fractional shortening and aortic gradient in patients whose pre-valvotomy echocardiograms were available also were similar between groups.


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  		Table 1. Comparison of preoperative and operative factors between patients in whom aortic valvotomy resulted in aortic insufficiency (Group I), aortic stenosis (Group II), or combined aortic insufficiency and stenosis (Group III)
 
3.1. Mortality and complications
There were no procedural or operative mortality with respect to initial valvotomy or, when required, aortic valve replacement. Late survival (up to 30 years) was also 100% among the 42 study patients. Complications related to balloon valvotomy were uncommon, occurring in only three patients. These included increase in regurgitation grade from mild-to-moderate in 1, patient transient arrhythmia in another, and loss of femoral pulse at the access site requiring intravenous heparin administration. There were two operative complications, both in patients who required a concomitant Konno aortoventriculoplasty procedure for enlargement of the left ventricular outflow tract. One patient developed a sternal wound infection and the other was taken back to the operating room for extensive hemorrhage following removal of an atrial line placement. No patients developed extensive ascending aortic dilatation or aneurysm during the follow-up period.

Symptoms referable to aortic valve disease at last follow-up were slightly more common among patients with AI (71%) and combined lesions (64%) than in those with residual AS (43%), P=0.71.

3.2. Reintervention
Actuarial freedom from AVR for the entire study population at 5, 10, and 20 years was 87, 58, and 11%, respectively, (Fig. 1). Aortic valve replacement was required in 11/14 (79%) of the patients in Group I, compared to 5/14 (36%) in Group II, and 9/14 (64%) in Group III, (P=0.04 for Groups I and II). One patient in Group II required both an initial Konno procedure followed 7 years later by a repeat AVR to allow placement of a larger prosthetic valve.



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  		Fig. 1. Actuarial freedom from aortic valve replacement for all 42 patients.

 
Mean freedom from AVR (Fig. 2) at 1, 10, and 15 years was 85, 58, and 20% for Group I and 80, 65 and 65% for Group II, P=0.05. Mean time to replacement was significantly shorter in Group I than in Group II (11.2±1.74 years vs. 21.5±3.9 years), P=0.05. The freedom from AVR for patients with combined aortic insufficiency and stenosis was slightly less (9.7±1.3 years) than Groups I and II, although statistical significance was not reached. Four patients who had valvotomy within the neonatal period underwent later surgical intervention directed at the aortic valve. Three had a Ross operation, and one underwent a Ross–Konno procedure within the follow-up period.



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  		Fig. 2. Actuarial freedom from aortic valve replacement (AVR) between patients with residual aortic stenosis (AS) and patients with aortic insufficiency (AI).

 
Repeat balloon valvuloplasty was performed more frequently in Groups II and III (29 and 21%) than in Group I (7%), (Table 2). Repeat percutaneous dilatation likely contributed to the improved freedom from AVR in Group II, since those patients in Group I with significant AI were not candidates for this intervention.


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  		Table 2. Reinterventions required in patients following initial valvotomy
 
3.3. Echocardiographic results of left ventricular function
Patients with aortic stenosis had significantly higher fractional shortening % at the time of AVR than those with insufficiency or combined lesions, (Group I: 38.2±7.9 vs. Group II: 46.3±5.5 vs. Group III: 39.2±3.7, P=0.007). Patients in Group II also had less severely dilated ventricles (mm) than those in the other groups, (Group I: 50.2±12.5 vs. Group II: 39.5±8.3 vs. Group III: 49.0±8.1, P=0.030).

3.4. Analysis of risk factors
The preoperative and postoperative factors tested in the univariate model are listed in Table 3. The only pre-valvotomy correlate for aortic valve replacement was the presence of additional congenital heart defects, (P=0.014). Univariate correlates for AVR included the presence of symptoms attributable to aortic valve disease, (P=0.006), left ventricular hypertrophy, (P=0.046), and important aortic regurgitation, (P=0.021). We were unable to demonstrate independent risk factors for aortic valve replacement on multivariate analysis.


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  		Table 3. Univariable risk factors for need for aortic valve replacement
 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
References
 
Significant aortic regurgitation is a well-recognized complication following aortic valvotomy, occurring between 0 and 43% in many series [2,5,14]. Balloon dilatation can also exacerbate pre-existing AI. Moore and colleagues reported an increase in AI grade in 58.1% of their 142 patients [14]. The method of dilatation (either surgical or catheter-based) produces equivalent outcomes with regard to reintervention and survival, although the lack of prospective randomized trials evaluating these techniques hampers direct comparison [15]. Recent data from the Congenital Heart Surgeons Society multi-institutional study of 110 patients demonstrated that percutaneous valvuloplasty, currently the preferred approach in most institutions, may preferentially exacerbate AI compared to surgical valvotomy [2]. Other risk factors for the development of AI following percutaneous valvotomy include an increased balloon: annulus ratio, larger valves, unicommissural valve morphology, and the presence of preexisting aortic regurgitation [5,16].

We currently refer all neonates with critical aortic stenosis for balloon valvotomy if they are candidates for biventricular repair. Although randomized studies comparing surgical valvotomy to transcatheter valvotomy are lacking, we believe that balloon valvotomy is superior to an open procedure in the neonatal population. In patients who have pre-existing aortic regurgitation, those in which vascular access cannot be reliably achieved, or those requiring surgery to repair other cardiac lesions, open valvotomy would be considered. Our current practice regarding older patients is similar, with the important exception that we utilize the Ross operation aggressively as a durable alternative to valvotomy. Despite the inevitable need for conduit reoperation, the Ross procedure is preferable because of the potential normalization of hemodynamics, avoidance of residual lesions, and theoretical long-term preservation of ventricular function [2]. Bhabra and colleagues [3] recently published their analysis of 54 infants who underwent open commisurotomy, suggesting a benefit in those in whom a trileaflet valve could be fashioned. Although we agree with the notion that surgical commisurotomy is more accurate and certainly a trileaflet valve might have salutary effects, there is no reliable method to prospectively identify patients in whom a trileaflet valve could be constructed, and compelling evidence of benefit that outweighs the substantial risk of an open procedure are currently unavailable. Therefore we currently do not use leaflet anatomy per se as a criterion for recommending surgical valvotomy over balloon valvotomy.

The natural history of AI following valvotomy is variable [6,17,18]. Acute severe AI, though uncommon in the modern era, generally leads to early surgical intervention [20].The long-term outcome for milder AI is less well understood. Balmer and colleagues used serial echocardiographic assessment to demonstrate that the course of aortic regurgitation following BAV is progressive over time, even in cases of mild or trivial initial lesions [6]. This finding is in agreement with another recent report by Pedra et al. in which AI appeared or worsened in 38% (27/71) of their patients following balloon valvotomy [7]. Several small series have further shown that progressive AI leads, predictably, to earlier surgical intervention [7,17–19]. In contrast, although the incidence of residual AS is comparable, the clinical evolution appears to be slower, suggesting that valvuloplasty can have long-lasting beneficial effects in patients >1 year of age [16,20–22]. Borghi and colleagues reviewed their 12-year experience of 90 children and documented that the Doppler gradients remained stable in 75%[20]. In addition, stenotic lesions are amenable to repeat balloon dilatation, which can further reduce the incidence of valve replacement in this patient population.

We have demonstrated that aortic insufficiency is less well tolerated than residual aortic stenosis following valvotomy in young patients. Patients with residual significant AI had more symptoms referable to aortic valve disease, required aortic valve replacement more often, and at an earlier time than those with AS. Furthermore, left ventricular function at the time of AVR was significantly worse in this group of patients.

This information may be useful in planning a treatment algorithm for patients with significant residual AS following initial valvotomy. In those patients at higher risk for the development of post-valvotomy AI, such as those with previous open valvotomy or any preexisting regurgitation, a smaller balloon: annulus ratio ≤1.0 should be used if repeat percutaneous intervention is considered.

The reasons that patients with AI have different outcomes than those with AS are multifactorial. Volume overload (VO) hypertrophy is associated with several adaptations that are different than those found in pressure overload (PO)-induced hypertrophy [8–13,23,24]. Chronic adaptation may also play a role. In children with congenital aortic stenosis, the ventricle is primed to deal preferentially with pressure-overload as this is the pathology to which it has been (subacutely or chronically) exposed. In contrast, the myocardium may not be well-adapted to volume-overload. This may in turn lead to maladaptive remodeling and earlier intervention in the subset of patients with predominant aortic regurgitation following aortic valvotomy for congenital aortic stenosis.

There are several limitations to this retrospective review. The study population is heterogeneous and includes the results of procedures performed in neonates, who are at disproportionate risk for adverse outcome, as well as older children. The results cover a long time interval, and thus may include those performed during the evolution and refinement of percutaneous valvotomy techniques and indications. In addition, the echocardiographic assessment of the grade of aortic regurgitation and the criteria used to determine the need for repeat intervention were not standardized.

Multiple studies have demonstrated that successful aortic valvotomy delays the need for surgical intervention [16,25]. Our results confirm this finding and show that the predominant post-valvotomy pathology is an important predictor of long-term outcome. This information may be useful in establishing a treatment algorithm for children with congenital AS. Those patients with residual severe AS and the absence of AI are ideal candidates for repeat catheter dilatation, which can prolong the need for AVR if maneuvers to minimize iatrogenic regurgitation are employed. In contrast, young patients with even mild regurgitation, especially if other AI specific risk-factors are present, are at risk for progressive insufficiency and ventricular dysfunction and should be considered for earlier aortic valve replacement.


   Acknowledgments
 
The authors would like to thank Dawn Peters, PhD, in the Department of Biostatistics, Oregon Health and Science University for her invaluable assistance with statistical analysis.


   Footnotes
 
{star} Presented at the joint 18th Annual Meeting of the European Association for Cardio-thoracic Surgery and the 12th Annual Meeting of the European Society of Thoracic Surgeons, Leipzig, Germany, September 12–15, 2004.


   References
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 

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