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Repair for Congenital Mitral Valve Stenosis
Repair for Congenital Mitral Valve Stenosis Eva Maria Delmo Waltera and Roland Hetzerb We report the techniques and long-term outcome of mitral valve (MV) repair to correct congenital mitral stenosis in children. Between 1986 and 2014, 137 children (mean age 4.1 ± 5.0, range 1 month-16.8 years) underwent repair of congenital mitral stenosis (CMS). In 48 patients, CMS is involved in Shone’s anomaly. The typical congenital MS (type I) was seen in 56 patients. Hypoplastic MV (type II, n = 15) was associated with severe left ventricular outflow tract abnormalities and hypoplastic left ventricular cavity and muscle mass. Supravalvar ring (type III, n = 48) ranged from a thin membrane to a thick discrete fibrous ridge. Parachute MV (type IV, n = 10) have 2 leaflets and barely distinguishable commissures, but all chordae merged either into 1 major papillary muscle or asymmetric papillary muscles—1 dominant and the other minuscule. Hammock valve (type IV, n = 8) appeared dysplastic with shortened chordae directly inserted into the posterior left ventricular muscle mass. MV repair was performed using commissurotomy, chordal division, papillary muscle splitting and fenestration, and mitral ring resection, each applied according to the presenting morphology. During the 28-year follow-up period, 23 patients underwent repeat MV repair and 3 underwent MV replacement after failed attempts at repeat repair. At 1 and 15 years postoperatively, freedom from reoperation was 89.3 ± 5.1% and 52.8 ± 11.8%, and cumulative survival rates were 92.3 ± 4.3% and 70.3 ± 8.9, respectively. Mortality unrelated to repair accounted for 9 (20%) deaths. Long-term functional outcome of MV repair in children with CMS is satisfactory. Repeat repair or replacement may be deemed necessary during the course of follow-up. Semin Thorac Cardiovasc Surg Pediatr Card Surg Ann 21:46–57 © 2017 Elsevier Inc. All rights reserved. Keywords: congenital mitral stenosis, parachute-like asymmetric mitral valve, parachute valve, hammock valve, hypoplastic mitral valve, Shone’s anomaly, mitral valve repair
Introduction Congenital mitral stenosis (CMS) is complex1 and is typically associated with other congenital heart diseases. It is rarely found in isolation.2,3 The associated congenital heart lesions may hide, or be hidden by, the mitral valve (MV) stenosis, which is exemplified in Shone’s anomaly,4-7 wherein the additional left heart obstructive lesions complicate its management. As such, surgeons are faced with what optimal strategy to offer to patients with CMS, especially in severe cases wherein medical or interventional therapy entails significant hemodynamic compromise. Over the years, surgical treatment has been focused on a conservative approach, which provides relief of mitral stenosis, albeit for a short duration, depending on its severity and anatomic substrate as well as associated hemodynamically significant cardiovascular anomalies. Interventional treatments, such as percutaneous transcatheter balloon mitral valvuloplasty,8 are utilized for medically refractory CMS, the goal of which is to reduce left ventricular inflow obstruction and left atrial (LA) pressure, hopefully a
Department of Cardiothoracic, Transplantation and Vascular Surgery, Medizinische Hochschule Hannover, Hannover, Germany. b Department of Cardiothoracic and Vascular Surgery, Cardio Centrum Berlin, Berlin, Germany. Presented at the Postgraduate Course on Congenital Heart Disease during AATS Centennial Meeting, April 30, 2017, Boston, MA, USA.
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PEDIATRIC CARDIAC SURGERY ANNUAL • 2018
Appearance of a normal mitral valve (A) in comparison with stenotic mitral valves: parachute-like asymmetric valve (B), parachute valve (C), and hammock valve (D). Central Message For patients with congenital mitral stenosis, a repair strategy using techniques tailored to the presenting morphology demonstrated that repair can be performed in this population with satisfactory long-term survival and freedom from repeat repair and replacement. In patients with successfully repaired valves, adequate mitral valve function is maintained over a long time. Disclosure: No conflicts of interest to report. No funding source has been provided in this paper. Address correspondence to: Eva Maria Delmo Walter, MD, MSc, PhD, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, 30 Hannover, Germany. E-mail: [email protected]
https://doi.org/10.1053/j.pcsu.2017.11.008 1092-9126/© 2017 Elsevier Inc. All rights reserved.
Repair for Congenital Mitral Valve Stenosis producing lasting relief but minimally improving symptoms and delaying MV replacement until the patient is older and larger. This is true for isolated mitral stenosis. However, this approach is not optimal when there are associated left ventricular outflow tract (LVOT) obstructive lesions, such as coarctation of aorta and subaortic stenosis, wherein creation of a widely patent and competent left ventricular inflow leads to concerns about the inadequate loading of the left ventricle, which creates an impedance to left ventricular ejection, decreasing cardiac output and inability to sustain postoperative hemodynamics.9,10 In infants and young children, surgical MV repair improves mitral leaflet mobility and provides adequate and effective inflow area; however, it may not be long lasting and there may be a need for eventual valve replacement. With the advent of excellent diagnostic and imaging modalities, providing optimal guidance to assess the MV and surgically relevant anatomy, as well as the concomitant obstructive lesions, considerable improvements in perioperative management and outcome have been seen in this group of patients. This study reports our institutional experience on surgical strategy to correct CMS, the operative results, and the long-term functional outcome in infants and children.
Patients and Methods The institutional review board approved this retrospective or prospective study and waived the need for patient consent. Between June 1986 and July 2014, 137 infants and children (mean age 4.1 ± 5.0, median 2.9, range 1 month-16.8, years) underwent surgical correction of CMS (Table 1). Medical records including preoperative evaluations, operative notes, and followup data were reviewed. All patients were in modified Ross/ New York Heart Association functional class III. Forty-three of the 58 patients with type I CMS underwent previous balloon mitral valvuloplasty, with 12 having a repeat intervention before the definite surgical procedure. In 48 patients, CMS is involved in Shone’s anomaly (Fig. 1), with multiple left ventricular inflow and outflow tract obstructive lesions (Table 1). In this group, it is very difficult to define which of the associated cardiac lesions is the predominant cause of symptoms. Relief of mitral stenosis unmasks any existing LVOT lesions. In our early years of experience, approach in this group is multistage, that is, treat the presenting lesions as they are unmasked. Later on, the advent of modern imaging modalities made it possible to diagnose all the other concomitant obstructions. Thus, we preferred single-stage surgery, wherein the optimal strategy is governed by the morphology of each obstructive lesion and favored MV repair on all patients with transmitral gradient >5 mm Hg, which, in this population, were underscored. Follow-up outpatient records were provided by written correspondence from the referring physicians. No patients were lost to follow-up.
Anatomical Evaluation of MVs These 137 children and adolescents with CMS were submitted to a complete two-dimensional echocardiographic
47 examination before surgery, at the time of discharge from hospital and in a series of follow-ups. Although most patients showed complex structural abnormalities in each of the valvular components (leaflets, chordae, papillary muscles), CMS was defined according to Ruckman and Van Praagh’s classification (Table 1).1 Thickened and rolled leaflets, short chordae tendineae, partial or complete obliteration of interchordal spaces by fibrous tissues, underdeveloped papillary muscles, and commissural fusion (type I, typical congenital MS, Fig. 2A) were seen in 56 patients. Hypoplastic MV (type II, Fig. 2B), described as small MV orifice, shortened chordae tendineae and small papillary muscles, was seen in 15 patients. This form of MS was associated with severe LVOT abnormalities, in all cases. Also seen was underdeveloped left ventricular cavity and muscle mass. Supravalvar mitral ring (type III, Fig. 2C) was seen in 48 patients; this is described as a circumferential ridge of connective tissue that originates at the LA wall overlying the MV leaflets and frequently attached to the annulus. Variable in thickness and extent, it ranged from a thin membrane to a thick discrete fibrous ridge. The membrane was often adherent to the anterior MV leaflet. Adhesion to the valve impaired leaflet mobility. This was associated with variable abnormalities of the MV subvalvar apparatus. Parachute MV (type IV, Fig. 2D), seen in 10 patients, has the usual 2 leaflets and commissures; however, all chordae tendineae are merged into 1 major papillary muscle, instead of being inserted into 2 papillary muscles. The valve naturally was deformed, and the chordae were short and thick; this, coupled with their convergent papillary insertion, allowed restricted leaflet mobility, thus creating a stenotic MV as the leaflets were closely apposed, greatly reducing the effective mitral orifice area. The only functional communication between the left atrium and the left ventricle was through the interchordal spaces. In aggregate, these spaces did not allow free egress of blood from the left atrium. Parachute-like asymmetric MV (type IV, Fig. 3) has a large dominant papillary muscle directly fused with the leaflets, absence of chordae, and presence of only fenestrations. However, the other papillary muscle is very small with just few short chordae, causing an asymmetric location of the valve orifice. Hammock valve (type IV, Fig. 4), defined as dysplastic with shortened chordae directly inserted in a muscular mass of the posterior LV wall resulting in tethering of both leaflets, was seen in 8 patients. The valvar orifice is partially obstructed by intermixed chordae and abnormal papillary muscles, characteristically implanted underneath the posterior leaflet. The chordae tendineae of the anterior leaflet cross the orifice toward the posteriorly implanted papillary muscles, producing the hammock appearance. In extreme cases, the hammock valve contains a fibrous diaphragm with scattered holes that allow the blood to flow from the left atrium to the left ventricle. The left-sided obstructive lesions encountered were coarctation of the aorta (n = 48), subaortic stenosis (n = 35), and hypoplastic aortic arch (n = 5). Associated cardiac anomalies were patent ductus arteriosus, atrial septal defect, ventricular septal defect, and vascular ring (Table 1).
E.M. Delmo Walter and R. Hetzer
48 Table 1 Demographic Profile of Patients with Congenital Mitral Stenosis Lesions Types of congenital mitral stenosis Typical congenital MS* (type I) Mitral valve dysplasia (type II MS) Supravalvular mitral ring (type III MS) Parachute valve (type IV MS) Hammock valve (type IV MS) Associated left ventricular outflow tract obstructive lesions Subaortic stenosis Coarctation of aorta Hypoplastic aortic arch Other concomitant anomalies Patent ductus arteriosus Atrial septal defect Ventricular septal defect Vascular ring Surgical Procedures Performed to Relieve the Congenital Mitral Stenosis
n (%)
Mean Age (Median, Range), y
56 (40.9) 15 (10.9) 48 (35.0) 10 (7.2) 8 (5.8)
3.5 ± 1.4 (3.6, 1.1-4.8) 0.4 ± 0.27 mo (0.32, 0.02-0.96 mo) 8.6 ± 2.0, (8.6, 6.2-9.2) 13.2 ± 1.6 (15.2, 11.2-16.8) 0.7 ± 0.8 (1, 0.58-9)
48 (35.0) 48 (35.0) 5 (3.6) 78 (56.9) 55 (40.1) 41 (29.9) 5 (3.6) Primary MV Repair
Repeat MV Repair
48 10 8 56 38 15
12 1 5 10 5 3
Resection of supravalvular mitral ring Repair of parachute valve Repair of hammock valve Commissurotomy Papillary muscle division Chordal division Surgical Procedures Performed on the Left Ventricular Outflow Tract and Other Associated Congenital Anomalies Repair of coarctation of aorta Enlargement of hypoplastic aortic arch Septal myectomy Resection of subvalvar membrane Konno-Rastan aortoventriculoplasty Aortic valve commissurotomy Aortic valve dilatation Ligation of patent ductus arteriosus Closure of atrial septal defect Closure of ventricular septal defect Resection of vascular ring
Third Intervention 1* 2*
Total 60 10 15 66 25 18
First Intervention
Second Intervention
Third Intervention
Total
40 5 32 23 3 13 9 78 55 41 5
12 1
4
56 6 32 30 3 24 18
7 8† 7‡
3§ 2¶
*MV replacement. † Ross procedure (n = 5), aortic valve replacement (n = 2), ascending aortic replacement (n = 1). ‡ Ross procedure (n = 1), aortic valve repeat dilatation (n = 5), aortic valve replacement (n = 1). § Aortic valve replacement (n = 3). ¶ Aortic valve replacement (n = 2).
Hemodynamic Evaluation
Surgical Technique
A gradient ≥5 mm Hg across the MV was considered significant and was observed in all patients (mean 20.8 ± 4.7 [range 8-30] mm Hg).
A total of 194 procedures to treat the CMS in 137 patients were performed (Table 1). Indications for MV repair are abnormal MV with <2 cm2 orifice area, and mean resting end-diastolic gradient of >5 mm Hg, presence of supramitral ring, and associated left ventricular outflow obstructive lesions. Hemodynamic criteria include pulmonary artery pressure of >25 mm Hg at rest and >30 mm Hg on exertion. Increased LA to left ventricular pressure gradient was an indication for repeat MV surgery. Our approach to the left ventricular inflow and outflow tract obstructive lesions is single-stage surgery whenever possible. In patients with Shone’s anomaly, a single-stage repair was done in 26 patients because all obstructive lesions and intracardiac
Echocardiographic Evaluation Mitral stenosis was quantified by measurement of the MV orifice area (cm2) and mean resting end-diastolic gradient (mm Hg) and was graded from 0 (4-6 cm2, 0 mm Hg), I—mild (2-4 cm2, <5 mm Hg), II—moderate (1-2 cm2, 5-10 mm Hg), to III—severe (<1 cm2, >10 mm Hg). Preoperatively, 34 patients had moderate MS (grade II), whereas 11 had severe (grade III) mitral stenosis.
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Figure 1 Graphical illustration of mitral stenosis in Shone’s anomaly.
defects, which were deemed significant, were diagnosed all at once. This, however, did not preclude eventual re-interventions when necessary. Staged repair were performed in 22 patients, on whom the usual first operations were those that addressed the LVOT obstruction, and the next interventions were performed as the other concomitant lesions appeared hemodynamically significant to warrant surgery. Twenty-five patients in our series presented initially in the neonatal period with coarctation of aorta. The neonatal coarctation presented with severe symptoms which could have masked the other intracardiac pathology until it was repaired. In general, we treat first the most severe obstructive lesions. As there were no patients with hypoplastic, small, or even borderline left ventricle, all patients had biventricular repair. MV repair was performed through a median sternotomy under cardiopulmonary bypass and moderate systemic hypothermia. Antegrade intermittent cold crystalloid cardioplegia with topical hypothermia was used for myocardial protection. Through a left atriotomy along the interatrial groove, the mitral annulus, leaflets, chordae tendineae, and papillary muscles were exposed and meticulously inspected to determine the precise nature of the lesion. Leaflet coaptation is assessed with a forceful transvalvular injection of saline with a bulb syringe. Using a nerve hook, the coaptation of the anterior and posterior leaflets with regard to the presence of sufficient tissues along the coaptation plane was assessed. The valve orifice area was assessed with a Hegar dilator and, more recently, with a Ziemer-Hetzer valve sizer (Fehling Instruments GmbH, Germany). The nomogram published by Rowlatt et al.11 is helpful in determining the normal valve diameter for a specific body surface area.
Various repair techniques were employed in accordance with the cause of mitral stenosis and the presenting valve morphology. Commissurotomy was performed on both the anterolateral and the posteromedial commissures in children with clearly fused commissures (typical CMS, Fig. 5A). In those with poorly defined commissures, commissurotomy was guided with a stab incision in the assumed commissural area after a hooked clamp is passed through this incision. Commissural incision was started from the papillary muscle on both sides toward the assumed commissures (Fig. 5B), and was performed up to 3-5-mm distance from the annulus. This ensured avoidance of incompetence near the trigones. Mobilization and division of chordae tendineae (Fig. 5C) and division and splitting of papillary muscles (Fig. 5D) were performed in patients with short, fused, and matted chordae. Hypoplastic or dysplastic MV (Fig. 6A) was approached by cautious mobilization of the leaflets, and commissural incision (Fig. 6B-D) to enlarge the orifice. Cautiously dividing the minuscule chordae with careful fenestration in addition to commissurotomy and splitting the papillary muscles (Fig. 7A-D) will likewise increase the mitral opening. Sharp dissection of the supravalvar mitral ring (Fig. 8A-C) was required to initiate the resection. It is very important to remove all components of the ring. As it is usually within the mobile portion of the leaflet, precautions were taken to avoid injuring the leaflet body itself when dissecting the ring off. Parachute valve has the usual 2 MV leaflets and commissures, but all the chordae tendineae cluster into 1 major papillary muscle. It often presented as a funnel-type structure with some distinct fibrous lines at the sites of commissural fusion (Fig. 9A).
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Figure 2 Graphical illustration of classification of congenital mitral stenosis. (A) Type I, typical congenital MS. (B) Type II, hypoplastic mitral valve. (C) Type III, supravalvar mitral ring. (D) Type IV, parachute valve.
The most appropriate site for leaflet-splitting incisions was defined on both sides from the common papillary muscle toward the “assumed” trigones (Fig. 9B). These incisions were extended into the body of the papillary muscle, which was split toward its base assuring sufficient thickness of both new “papillary muscle heads” (Fig. 9C-E).9,12,13 To increase leaflet mobility in parachute-like asymmetric MV with tethered leaflets (Fig. 10A), bilateral commissurotomy is performed, and the large dominant papillary muscle is incised
(Fig. 10B) and split to a length that allows greater coaptation of the anterior and posterior leaflets (Fig. 10C).13 The degree and extent of incision, commissurotomy, and fenestration are measured using a Hegar dilator and more recently a Ziemer-Hetzer valve sizer as determined by the minimal agerelated acceptable MV diameter.11 Hammock valve is the most difficult to correct by reconstructive techniques as its orifice is partially obstructed by intermixed chordae and abnormal papillary muscles, characteristically
Figure 3 Graphical illustration of parachute-like asymmetric valve.
Figure 4 Graphical illustration of a hammock valve.
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Figure 5 Type I congenital mitral stenosis. (A) Point of commissurotomy. (B) Commissural incision starting from the papillary muscle towards the assumed commissures. (C) Chordal division. (D) Papillary muscle splitting.
implanted in the left ventricular wall (Fig. 11A). A suitably thick part of the posterior left ventricular wall carrying the rudimentary chordae is carved off the wall (Fig. 11B).12 Precautions must be observed to ensure that both the remaining LV wall and the “new papillary muscles” include sufficient muscle thickness to maintain their function (Fig. 11C).12,13 To assess the adequacy of repair, saline injection through the valves and intraoperative transesophageal echocardiography were routinely performed. In all the repair strategies we employed, the minimal final MV opening area should not be less than 10% below the norm according to body surface area in children. No mitral insufficiency ensued in 100 patients (72.9%) from the
techniques employed, whereas 37 (27.0%) had trivial or mild insufficiency. Regardless of the underlying pathology and techniques used, no patient was discharged from the hospital with more than mild stenosis or insufficiency. Postoperative transthoracic echocardiography was carried out annually, or if clinically indicated on the basis of symptoms. The degree of MS was estimated by means of standard echocardiographic measurement techniques. Assessment of MV function included planimetric evaluation in mid diastole of MV motion (leaflet mobility), determination of MV and orifice area, and evaluation of valve anatomy as to thickness, commissural fusion, valve pliability, and morphology of the subvalvar apparatus.
Figure 6 Type II congenital mitral stenosis. (A) Hypoplastic mitral valve with minute orifice. (B) Commissural incision starting from the papillary muscle. (C) Commissurotomy. (D) After repair.
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Figure 7 Type II congenital mitral stenosis. (A) Identification of papillary muscles. (B) Commissurale incision. (C) Chordal division and fenestration. (D) Splitting of papillary muscles.
Statistical Analysis All data were analyzed with the SPSS statistical program for Windows, version 16.0 (SPSS Inc., Chicago, IL) software program. Data are expressed as absolute and percentage frequency values and continuous data as mean ± standard deviation, median, and range, as appropriate. Freedom from reoperation and cumulative survival rates were analyzed according to Kaplan-Meier estimates with 95% confidence interval (CI) and Cox proportional hazard regression methods to identify the risk factors for
reoperation and mortality. A value of P ≤ 0.05 was considered significant.
Results Morbidity Five patients (3.6%), who also underwent concomitant closure of ventricular septal defects, developed complete heart block and
Figure 8 Supramitral ring. (A) Atrial view. (B) Sharp dissection of mitral ring. (C) Completed repair.
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Figure 9 Parachute valve. (A) Assumed trigones. (B) Most appropriate site of commissural incision defined on both sides from the common papillary muscle toward the assumed trigones. (C) Commissural incisions extended into the body of the papillary muscle. (D). Papillary muscle is split toward its base, assuring sufficient thickness of both new “papillary muscle heads.” (E) Appearance after commissurotomy, fenestration, and papillary muscle splitting.
required permanent pacemaker implantation performed within 30 days after the operation.
on extracorporeal membrane oxygenator. Eventually, the patient developed capillary leak syndrome and died on the 18th postoperative day.
Early Mortality Early death occurred in a 1-month-old infant with hammock valve, with combined mitral stenosis and insufficiency. After the repair, symptoms of low cardiac output were progressive, refractory to maximal medical therapy; hence, an extracorporeal membrane oxygenation was started. A week later, the patient underwent MV replacement using a 14-mm biological prosthesis but died 10 days postoperatively. Another early death was a 3-month-old infant who underwent urgent single-stage surgery for all the obstructive lesions of Shone’s anomaly with associated pulmonary hypertension (mean pulmonary artery pressure of 32 mm Hg), ventricular septal defect, and patent ductus arteriosus. Postoperatively, the patient had mild residual MS (MV orifice area of 2 cm2, and mean resting end-diastolic gradient <5 mm Hg). The LA pressure was 12 mm Hg. The patient suffered from low output cardiac failure, hemodynamic instability, and hypotension 34 hours after the procedure and was placed
Late Mortality A total of 9 deaths occurred during the postoperative followup. Eight late deaths occurred among patients with Shone’s anomaly who were discharged from the hospital. A 2-monthold infant with the typical congenital MS who underwent repeat MV repair with concomitant repair of coarctation of aorta and repeat septal myectomy 4 months later died from heart failure a year later. A patient with parachute valve, who was 2 years old at the time of the initial MV repair, underwent repeat repair 5 years postoperatively. The patient underwent MV replacement 2 years later, but died 8 years postoperatively. Six patients died of a noncardiac event at 1 (episodes of seizures), 3 (endstage renal failure), 5 (n = 2, end-stage renal failure and pneumonia), 8 (vehicular accident), and 13 (unknown) years postoperatively. A 7-month-old infant with repaired hammock valve died of unknown cause 5 years after the initial repair.
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Figure 10 Parachute-like asymmetric valve. (A) Small papillary muscle with just few short chordae, causing an asymmetric location of the valve orifice. (B) Bilateral commissurotomy and incision of the anterior papillary muscle is incised. (C) Papillary muscle is split to a length allowing greater coaptation of the anterior and posterior leaflets.
During a mean duration of follow-up of 17.5 ± 1.5 years (range 6.4-27.7 years), cumulative survival rate was 97.6 ± 2.4%, 92.3 ± 4.3%, 83.8 ± 6.1%, 75.7 ± 7.8% and 70.3 ± 8.9%, at 30 days, 1, 5, 10 and 15 years postoperatively, respectively (Fig. 12A).
Functional Outcome of MV Repair Change in Functional Class There was a significant improvement in functional class postoperatively (P < 0.001), and this was sustained until the late follow-up period (Fig. 12B).
the patients with the membranous variety which may not have been detected during the initial resection, as not only was the membrane adherent to the anterior MV leaflet but some tissue components remained proximal to the posterior leaflet. These were also the patients with type I congenital MS with fused commissures and thickened leaflets (n = 10); 2 had hypoplastic MV (type II), of whom one had emphasized shortened chordae and another had miniature papillary muscles. Along with the repeat resection of the membranous ring, they also underwent repeat commissurotomy, chordal division, and papillary muscle splitting. The latest echocardiographic evaluation of these patients showed absence of MS.
Follow-Up Change in Severity of Mitral Stenosis Absence of MS (mean MV orifice area 4.7 ± 0.7 cm2 without mean resting end-diastolic pressure gradient) was noted after the MV repair (P < 0.001) (Fig. 12C). In the course of follow-up, 14 patients have developed significant MS (mean MV orifice area 2.5 ± 0.8 cm2 and mean resting end-diastolic pressure gradient 8.5 ± 1.3 mm Hg) warranting repeat intervention.
Resection of Supravalvular Mitral Ring Twelve patients (27%) who underwent primary resection of supravalvular mitral ring underwent repeat resection. These were
Freedom From Reoperation After MV Repair Mean duration of follow-up was 17.5 ± 1.5 years (range 6.427.7 years). Freedom from reoperation was 97.6 ± 2.4%, 89.3 ± 5.1%, 77.1 ± 7.2%, 72.0 ± 8.3%, and 52.8 ± 11.8% at 30 days, 1, 5, 10, and 15 years postoperatively, respectively (Fig. 12D). We performed 3 MV replacements, and this was on a patient with parachute valve (see section on late mortality), and 2 patients with hammock valves. Thirty-two repeat MV procedures were performed in 14 patients, which were all related to restenosis and repeated MV dysfunction. These procedures were performed mostly for the type I MS and hypoplastic MV.
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Figure 11 Hammock valve. (A) Chordae and abnormal papillary muscles inserted in the left ventricular wall. (B) A suitably thick part of the posterior left ventricular wall carrying the rudimentary chordae is carved off the wall. (C) “New papillary muscles.”
Discussion CMS is the result of abnormalities at multiple levels. This occurrence is primarily the reason why although new techniques have been developed specifically for children and have been introduced to repair the MV during the last decades, surgical methods of MV repair for congenital MS still remain limited and extremely challenging. With the aforementioned complexity of MV stenosis, surgical management in infants and children still remains a formidable issue. It is an enormously demanding and considerable task for the surgeon to reconstruct and repair MVs in infants and children, primarily because of their size, the immature and fragile leaflet tissues in infants, as well as the associated congenital cardiac abnormalities, which take particular hemodynamic consideration. MV repair in children is guided by the same surgical rules as in adults, but the anatomic substrate differs greatly. The technical difficulties vary according to the anatomy, size, and age of the patient. The indications for surgery and the
timing of surgery have to take into account a large range of concerns and are therefore less straightforward than in adults. Our present surgical strategy in infants and children with CMS are merited mostly from previous experiences ranging from catheter-based relief of mitral stenosis through surgical repair and eventual replacement, when necessary, from the modern diagnostic and imaging modalities which could precisely define the anatomy and morphology of the MV as well as immediate uncovering of other left-sided obstructive lesions, and from enhanced surgical skills. The repair strategy for CMS patients using a variety of repair techniques tailored to the presenting morphology of each patient demonstrated that repair can be performed in this population with satisfactory long-term survival and freedom from repeat repair and replacement. In patients with a successfully repaired valve, adequate MV function is maintained over the longterm with minimal need for replacement. The typical CMS was ingenuous to repair. Simple commissurotomy, chordal division, and splitting the papillary muscles
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Figure 12 Kaplan-Meier estimates showing (A) cumulative survival; (B) comparison of preoperative, postoperative, early, and late follow-up as to functional class; (C) degree of CMS; and (D) freedom from reoperation.
created an effective orifice area. Although some leaflets were cautiously mobilized, we did not see the need to touch the thickened and rolled leaflets but left them as they were seen. Determining the surgical approach to the hypoplastic MV, with a minuscule leaflet and subvalvar apparatus, complemented with immensely delicate and underdeveloped, if not insufficient, tissues seen in infants, is arduous. Repair is the only available option that provides a functional MV, although perhaps not a longlasting one. Even when the primary repair result is not optimal, time is gained for repeated repair until an adult-sized prosthesis can be implanted. Hypoplastic MV is a very rare congenital defect and is mostly combined with an underdeveloped left ventricle. Opening the MV orifice promotes growth of the left ventricular cavity and mass. Some moderate mitral incompetence may even promote this process. The degree of mitral hypoplasia ranging from normal size MV toward mitral atresia determines the rationale of this concept. The cornerstones are still undetermined between valve repair and eventually a univentricular strategy. The presence of a parachute valve does not automatically warrant a surgical indication. Some are functionally adequate. The parachute valves, associated with significant subaortic stenosis, were amenable to repair because the main obstructive mitral
element was subvalvar. Outcomes in this subgroup are related to the degree to which MS can be relieved. MV stenosis with abnormal papillary muscles also includes hammock valve, which refers to the atrial aspect of various subvalvar anomalies. The valvar orifice is partially obstructed by intermixed chordae and abnormal papillary muscles, characteristically implanted underneath the posterior leaflet. The chordae tendineae of the anterior leaflet cross the orifice toward the posteriorly implanted papillary muscles, producing the hammock appearance. In extreme cases seen, the hammock valve contains a fibrous diaphragm with scattered holes that allow the blood to flow from the left atrium to the left ventricle. This malformation is the most difficult to correct by reconstructive techniques. This study comprises an institutional series of MV repair in 48 children with Shone’s anomaly.9 The challenge presented by these patients is amplified by the coexistence of restrictive and often surgically unfavorable MV morphology with other obstructive lesions at an early age. The optimal surgical approach in this group is governed by the morphology of each obstructive lesion. One complicating factor is that the degree of MS can be underestimated owing to the coexistence of LVOT obstruction, which may mask the need for surgical intervention on the MV.
Repair for Congenital Mitral Valve Stenosis The single-stage operative approach did not prove to have a significant positive effect on long-term outcome in these patients, even in terms of reoperation, as relief of mitral stenosis unmasked any existing left ventricular inflow tract lesions. We found no difference in reoperation rate between those who underwent single- or multistaged approach.
Conclusion We have demonstrated that an aggressive functional repair approach to the MV and relief of the LVOT obstruction (single or multistage) lead to long-term event-free survival in these children. Outcomes in this population are related to the degree which mitral stenosis can be relieved.
Acknowledgments We thank Diana Kendall for literature search, Julia Stein for statistical analysis, and Helge Haselbach for graphical illustrations.
References 1. Ruckman RN, Van Praagh R. Anatomic types of congenital mitral stenosis and surgical implications. Am J Cardiol 1978;42:592601 2. Carpentier A, Brizard C. Congenital malformation of the mitral valve. In: Stark J, de Leval M, Tsang VT (eds): Surgery for Congenital Heart Defects. Ed 3. England; John Wiley & Sons, Ltd; 2006: pp 573-590
57 3. Ferencz C, Johnson AL, Wigglesworth FW. Congenital mitral stenosis. Circulation 1954;9:161-179 4. Shone JD, Sellers RD, Anderson RC, et al: The developmental complex of “parachute mitral valve”, supravalvular ring of left atrium, subaortic stenosis and coarctation of the aorta. Am J Cardiol 1963;11:714-725 5. Bolling SF, Lannettoni MD, Dick M II, et al: Shone’s anomaly: operative results and late outcome. Ann Thorac Surg 1990;49:887893 6. Brauner R, Laks H, Drinkwater DC Jr, et al: Multiple left heart obstruction (Shones’s anomaly with mitral valve involvement: longterm surgical outcome. Ann Thorac Surg 1997;64:721-729 7. Brown J, Ruzmetov M, Vijay P, et al: Operative results and outcomes in children with Shone’s anomaly. Ann Thorac Surg 2005;79: 1358-1365 8. McElhinney DB, Sherwood MC, Keane JF, et al: Current management of severe congenital mitral stenosis: outcomes of transcatheter and surgical therapy in 108 infants and children. Circulation 2005;112:707-714 9. Delmo Walter EM, Komoda T, Siniawski H, et al: Long-term surgical outcome of mitral valve repair in infants and children with Shone’s anomaly. Eur J Cardiothorac Surg 2013;43:473-481. discussion 481-2 10. Delmo Walter EM, Van Praagh R, Miera O, et al: Repair of left ventricular inflow tract lesions in Shone’s anomaly: valve growth and long-term outcome. Ann Thorac Surg 2013;95:948-955 11. Rowlatt U, Rimoldi H, Lev M. The quantitative anatomy of the normal child’s heart. Pediatr Clin North Am 1963;10:499588 12. Hetzer R, Delmo Walter EMB, Huebler M, et al: Modified surgical techniques and long term outcome of mitral valve reconstruction in 111 children. Ann Thorac Surg 2008;86:604-613 13. Delmo Walter EM, Javier M, Hetzer R. Repair of parachute and hammock valve in infants and children: early and late outcomes. Semin Thorac Cardiovasc Surg 2016;28:448-459
Introduction Congenital mitral stenosis (CMS) is complex1 and is typically associated with other congenital heart diseases. It is rarely found in isolation.2,3 The associated congenital heart lesions may hide, or be hidden by, the mitral valve (MV) stenosis, which is exemplified in Shone’s anomaly,4-7 wherein the additional left heart obstructive lesions complicate its management. As such, surgeons are faced with what optimal strategy to offer to patients with CMS, especially in severe cases wherein medical or interventional therapy entails significant hemodynamic compromise. Over the years, surgical treatment has been focused on a conservative approach, which provides relief of mitral stenosis, albeit for a short duration, depending on its severity and anatomic substrate as well as associated hemodynamically significant cardiovascular anomalies. Interventional treatments, such as percutaneous transcatheter balloon mitral valvuloplasty,8 are utilized for medically refractory CMS, the goal of which is to reduce left ventricular inflow obstruction and left atrial (LA) pressure, hopefully a
Department of Cardiothoracic, Transplantation and Vascular Surgery, Medizinische Hochschule Hannover, Hannover, Germany. b Department of Cardiothoracic and Vascular Surgery, Cardio Centrum Berlin, Berlin, Germany. Presented at the Postgraduate Course on Congenital Heart Disease during AATS Centennial Meeting, April 30, 2017, Boston, MA, USA.
46
PEDIATRIC CARDIAC SURGERY ANNUAL • 2018
Appearance of a normal mitral valve (A) in comparison with stenotic mitral valves: parachute-like asymmetric valve (B), parachute valve (C), and hammock valve (D). Central Message For patients with congenital mitral stenosis, a repair strategy using techniques tailored to the presenting morphology demonstrated that repair can be performed in this population with satisfactory long-term survival and freedom from repeat repair and replacement. In patients with successfully repaired valves, adequate mitral valve function is maintained over a long time. Disclosure: No conflicts of interest to report. No funding source has been provided in this paper. Address correspondence to: Eva Maria Delmo Walter, MD, MSc, PhD, Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, 30 Hannover, Germany. E-mail: [email protected]
https://doi.org/10.1053/j.pcsu.2017.11.008 1092-9126/© 2017 Elsevier Inc. All rights reserved.
Repair for Congenital Mitral Valve Stenosis producing lasting relief but minimally improving symptoms and delaying MV replacement until the patient is older and larger. This is true for isolated mitral stenosis. However, this approach is not optimal when there are associated left ventricular outflow tract (LVOT) obstructive lesions, such as coarctation of aorta and subaortic stenosis, wherein creation of a widely patent and competent left ventricular inflow leads to concerns about the inadequate loading of the left ventricle, which creates an impedance to left ventricular ejection, decreasing cardiac output and inability to sustain postoperative hemodynamics.9,10 In infants and young children, surgical MV repair improves mitral leaflet mobility and provides adequate and effective inflow area; however, it may not be long lasting and there may be a need for eventual valve replacement. With the advent of excellent diagnostic and imaging modalities, providing optimal guidance to assess the MV and surgically relevant anatomy, as well as the concomitant obstructive lesions, considerable improvements in perioperative management and outcome have been seen in this group of patients. This study reports our institutional experience on surgical strategy to correct CMS, the operative results, and the long-term functional outcome in infants and children.
Patients and Methods The institutional review board approved this retrospective or prospective study and waived the need for patient consent. Between June 1986 and July 2014, 137 infants and children (mean age 4.1 ± 5.0, median 2.9, range 1 month-16.8, years) underwent surgical correction of CMS (Table 1). Medical records including preoperative evaluations, operative notes, and followup data were reviewed. All patients were in modified Ross/ New York Heart Association functional class III. Forty-three of the 58 patients with type I CMS underwent previous balloon mitral valvuloplasty, with 12 having a repeat intervention before the definite surgical procedure. In 48 patients, CMS is involved in Shone’s anomaly (Fig. 1), with multiple left ventricular inflow and outflow tract obstructive lesions (Table 1). In this group, it is very difficult to define which of the associated cardiac lesions is the predominant cause of symptoms. Relief of mitral stenosis unmasks any existing LVOT lesions. In our early years of experience, approach in this group is multistage, that is, treat the presenting lesions as they are unmasked. Later on, the advent of modern imaging modalities made it possible to diagnose all the other concomitant obstructions. Thus, we preferred single-stage surgery, wherein the optimal strategy is governed by the morphology of each obstructive lesion and favored MV repair on all patients with transmitral gradient >5 mm Hg, which, in this population, were underscored. Follow-up outpatient records were provided by written correspondence from the referring physicians. No patients were lost to follow-up.
Anatomical Evaluation of MVs These 137 children and adolescents with CMS were submitted to a complete two-dimensional echocardiographic
47 examination before surgery, at the time of discharge from hospital and in a series of follow-ups. Although most patients showed complex structural abnormalities in each of the valvular components (leaflets, chordae, papillary muscles), CMS was defined according to Ruckman and Van Praagh’s classification (Table 1).1 Thickened and rolled leaflets, short chordae tendineae, partial or complete obliteration of interchordal spaces by fibrous tissues, underdeveloped papillary muscles, and commissural fusion (type I, typical congenital MS, Fig. 2A) were seen in 56 patients. Hypoplastic MV (type II, Fig. 2B), described as small MV orifice, shortened chordae tendineae and small papillary muscles, was seen in 15 patients. This form of MS was associated with severe LVOT abnormalities, in all cases. Also seen was underdeveloped left ventricular cavity and muscle mass. Supravalvar mitral ring (type III, Fig. 2C) was seen in 48 patients; this is described as a circumferential ridge of connective tissue that originates at the LA wall overlying the MV leaflets and frequently attached to the annulus. Variable in thickness and extent, it ranged from a thin membrane to a thick discrete fibrous ridge. The membrane was often adherent to the anterior MV leaflet. Adhesion to the valve impaired leaflet mobility. This was associated with variable abnormalities of the MV subvalvar apparatus. Parachute MV (type IV, Fig. 2D), seen in 10 patients, has the usual 2 leaflets and commissures; however, all chordae tendineae are merged into 1 major papillary muscle, instead of being inserted into 2 papillary muscles. The valve naturally was deformed, and the chordae were short and thick; this, coupled with their convergent papillary insertion, allowed restricted leaflet mobility, thus creating a stenotic MV as the leaflets were closely apposed, greatly reducing the effective mitral orifice area. The only functional communication between the left atrium and the left ventricle was through the interchordal spaces. In aggregate, these spaces did not allow free egress of blood from the left atrium. Parachute-like asymmetric MV (type IV, Fig. 3) has a large dominant papillary muscle directly fused with the leaflets, absence of chordae, and presence of only fenestrations. However, the other papillary muscle is very small with just few short chordae, causing an asymmetric location of the valve orifice. Hammock valve (type IV, Fig. 4), defined as dysplastic with shortened chordae directly inserted in a muscular mass of the posterior LV wall resulting in tethering of both leaflets, was seen in 8 patients. The valvar orifice is partially obstructed by intermixed chordae and abnormal papillary muscles, characteristically implanted underneath the posterior leaflet. The chordae tendineae of the anterior leaflet cross the orifice toward the posteriorly implanted papillary muscles, producing the hammock appearance. In extreme cases, the hammock valve contains a fibrous diaphragm with scattered holes that allow the blood to flow from the left atrium to the left ventricle. The left-sided obstructive lesions encountered were coarctation of the aorta (n = 48), subaortic stenosis (n = 35), and hypoplastic aortic arch (n = 5). Associated cardiac anomalies were patent ductus arteriosus, atrial septal defect, ventricular septal defect, and vascular ring (Table 1).
E.M. Delmo Walter and R. Hetzer
48 Table 1 Demographic Profile of Patients with Congenital Mitral Stenosis Lesions Types of congenital mitral stenosis Typical congenital MS* (type I) Mitral valve dysplasia (type II MS) Supravalvular mitral ring (type III MS) Parachute valve (type IV MS) Hammock valve (type IV MS) Associated left ventricular outflow tract obstructive lesions Subaortic stenosis Coarctation of aorta Hypoplastic aortic arch Other concomitant anomalies Patent ductus arteriosus Atrial septal defect Ventricular septal defect Vascular ring Surgical Procedures Performed to Relieve the Congenital Mitral Stenosis
n (%)
Mean Age (Median, Range), y
56 (40.9) 15 (10.9) 48 (35.0) 10 (7.2) 8 (5.8)
3.5 ± 1.4 (3.6, 1.1-4.8) 0.4 ± 0.27 mo (0.32, 0.02-0.96 mo) 8.6 ± 2.0, (8.6, 6.2-9.2) 13.2 ± 1.6 (15.2, 11.2-16.8) 0.7 ± 0.8 (1, 0.58-9)
48 (35.0) 48 (35.0) 5 (3.6) 78 (56.9) 55 (40.1) 41 (29.9) 5 (3.6) Primary MV Repair
Repeat MV Repair
48 10 8 56 38 15
12 1 5 10 5 3
Resection of supravalvular mitral ring Repair of parachute valve Repair of hammock valve Commissurotomy Papillary muscle division Chordal division Surgical Procedures Performed on the Left Ventricular Outflow Tract and Other Associated Congenital Anomalies Repair of coarctation of aorta Enlargement of hypoplastic aortic arch Septal myectomy Resection of subvalvar membrane Konno-Rastan aortoventriculoplasty Aortic valve commissurotomy Aortic valve dilatation Ligation of patent ductus arteriosus Closure of atrial septal defect Closure of ventricular septal defect Resection of vascular ring
Third Intervention 1* 2*
Total 60 10 15 66 25 18
First Intervention
Second Intervention
Third Intervention
Total
40 5 32 23 3 13 9 78 55 41 5
12 1
4
56 6 32 30 3 24 18
7 8† 7‡
3§ 2¶
*MV replacement. † Ross procedure (n = 5), aortic valve replacement (n = 2), ascending aortic replacement (n = 1). ‡ Ross procedure (n = 1), aortic valve repeat dilatation (n = 5), aortic valve replacement (n = 1). § Aortic valve replacement (n = 3). ¶ Aortic valve replacement (n = 2).
Hemodynamic Evaluation
Surgical Technique
A gradient ≥5 mm Hg across the MV was considered significant and was observed in all patients (mean 20.8 ± 4.7 [range 8-30] mm Hg).
A total of 194 procedures to treat the CMS in 137 patients were performed (Table 1). Indications for MV repair are abnormal MV with <2 cm2 orifice area, and mean resting end-diastolic gradient of >5 mm Hg, presence of supramitral ring, and associated left ventricular outflow obstructive lesions. Hemodynamic criteria include pulmonary artery pressure of >25 mm Hg at rest and >30 mm Hg on exertion. Increased LA to left ventricular pressure gradient was an indication for repeat MV surgery. Our approach to the left ventricular inflow and outflow tract obstructive lesions is single-stage surgery whenever possible. In patients with Shone’s anomaly, a single-stage repair was done in 26 patients because all obstructive lesions and intracardiac
Echocardiographic Evaluation Mitral stenosis was quantified by measurement of the MV orifice area (cm2) and mean resting end-diastolic gradient (mm Hg) and was graded from 0 (4-6 cm2, 0 mm Hg), I—mild (2-4 cm2, <5 mm Hg), II—moderate (1-2 cm2, 5-10 mm Hg), to III—severe (<1 cm2, >10 mm Hg). Preoperatively, 34 patients had moderate MS (grade II), whereas 11 had severe (grade III) mitral stenosis.
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49
Figure 1 Graphical illustration of mitral stenosis in Shone’s anomaly.
defects, which were deemed significant, were diagnosed all at once. This, however, did not preclude eventual re-interventions when necessary. Staged repair were performed in 22 patients, on whom the usual first operations were those that addressed the LVOT obstruction, and the next interventions were performed as the other concomitant lesions appeared hemodynamically significant to warrant surgery. Twenty-five patients in our series presented initially in the neonatal period with coarctation of aorta. The neonatal coarctation presented with severe symptoms which could have masked the other intracardiac pathology until it was repaired. In general, we treat first the most severe obstructive lesions. As there were no patients with hypoplastic, small, or even borderline left ventricle, all patients had biventricular repair. MV repair was performed through a median sternotomy under cardiopulmonary bypass and moderate systemic hypothermia. Antegrade intermittent cold crystalloid cardioplegia with topical hypothermia was used for myocardial protection. Through a left atriotomy along the interatrial groove, the mitral annulus, leaflets, chordae tendineae, and papillary muscles were exposed and meticulously inspected to determine the precise nature of the lesion. Leaflet coaptation is assessed with a forceful transvalvular injection of saline with a bulb syringe. Using a nerve hook, the coaptation of the anterior and posterior leaflets with regard to the presence of sufficient tissues along the coaptation plane was assessed. The valve orifice area was assessed with a Hegar dilator and, more recently, with a Ziemer-Hetzer valve sizer (Fehling Instruments GmbH, Germany). The nomogram published by Rowlatt et al.11 is helpful in determining the normal valve diameter for a specific body surface area.
Various repair techniques were employed in accordance with the cause of mitral stenosis and the presenting valve morphology. Commissurotomy was performed on both the anterolateral and the posteromedial commissures in children with clearly fused commissures (typical CMS, Fig. 5A). In those with poorly defined commissures, commissurotomy was guided with a stab incision in the assumed commissural area after a hooked clamp is passed through this incision. Commissural incision was started from the papillary muscle on both sides toward the assumed commissures (Fig. 5B), and was performed up to 3-5-mm distance from the annulus. This ensured avoidance of incompetence near the trigones. Mobilization and division of chordae tendineae (Fig. 5C) and division and splitting of papillary muscles (Fig. 5D) were performed in patients with short, fused, and matted chordae. Hypoplastic or dysplastic MV (Fig. 6A) was approached by cautious mobilization of the leaflets, and commissural incision (Fig. 6B-D) to enlarge the orifice. Cautiously dividing the minuscule chordae with careful fenestration in addition to commissurotomy and splitting the papillary muscles (Fig. 7A-D) will likewise increase the mitral opening. Sharp dissection of the supravalvar mitral ring (Fig. 8A-C) was required to initiate the resection. It is very important to remove all components of the ring. As it is usually within the mobile portion of the leaflet, precautions were taken to avoid injuring the leaflet body itself when dissecting the ring off. Parachute valve has the usual 2 MV leaflets and commissures, but all the chordae tendineae cluster into 1 major papillary muscle. It often presented as a funnel-type structure with some distinct fibrous lines at the sites of commissural fusion (Fig. 9A).
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Figure 2 Graphical illustration of classification of congenital mitral stenosis. (A) Type I, typical congenital MS. (B) Type II, hypoplastic mitral valve. (C) Type III, supravalvar mitral ring. (D) Type IV, parachute valve.
The most appropriate site for leaflet-splitting incisions was defined on both sides from the common papillary muscle toward the “assumed” trigones (Fig. 9B). These incisions were extended into the body of the papillary muscle, which was split toward its base assuring sufficient thickness of both new “papillary muscle heads” (Fig. 9C-E).9,12,13 To increase leaflet mobility in parachute-like asymmetric MV with tethered leaflets (Fig. 10A), bilateral commissurotomy is performed, and the large dominant papillary muscle is incised
(Fig. 10B) and split to a length that allows greater coaptation of the anterior and posterior leaflets (Fig. 10C).13 The degree and extent of incision, commissurotomy, and fenestration are measured using a Hegar dilator and more recently a Ziemer-Hetzer valve sizer as determined by the minimal agerelated acceptable MV diameter.11 Hammock valve is the most difficult to correct by reconstructive techniques as its orifice is partially obstructed by intermixed chordae and abnormal papillary muscles, characteristically
Figure 3 Graphical illustration of parachute-like asymmetric valve.
Figure 4 Graphical illustration of a hammock valve.
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Figure 5 Type I congenital mitral stenosis. (A) Point of commissurotomy. (B) Commissural incision starting from the papillary muscle towards the assumed commissures. (C) Chordal division. (D) Papillary muscle splitting.
implanted in the left ventricular wall (Fig. 11A). A suitably thick part of the posterior left ventricular wall carrying the rudimentary chordae is carved off the wall (Fig. 11B).12 Precautions must be observed to ensure that both the remaining LV wall and the “new papillary muscles” include sufficient muscle thickness to maintain their function (Fig. 11C).12,13 To assess the adequacy of repair, saline injection through the valves and intraoperative transesophageal echocardiography were routinely performed. In all the repair strategies we employed, the minimal final MV opening area should not be less than 10% below the norm according to body surface area in children. No mitral insufficiency ensued in 100 patients (72.9%) from the
techniques employed, whereas 37 (27.0%) had trivial or mild insufficiency. Regardless of the underlying pathology and techniques used, no patient was discharged from the hospital with more than mild stenosis or insufficiency. Postoperative transthoracic echocardiography was carried out annually, or if clinically indicated on the basis of symptoms. The degree of MS was estimated by means of standard echocardiographic measurement techniques. Assessment of MV function included planimetric evaluation in mid diastole of MV motion (leaflet mobility), determination of MV and orifice area, and evaluation of valve anatomy as to thickness, commissural fusion, valve pliability, and morphology of the subvalvar apparatus.
Figure 6 Type II congenital mitral stenosis. (A) Hypoplastic mitral valve with minute orifice. (B) Commissural incision starting from the papillary muscle. (C) Commissurotomy. (D) After repair.
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Figure 7 Type II congenital mitral stenosis. (A) Identification of papillary muscles. (B) Commissurale incision. (C) Chordal division and fenestration. (D) Splitting of papillary muscles.
Statistical Analysis All data were analyzed with the SPSS statistical program for Windows, version 16.0 (SPSS Inc., Chicago, IL) software program. Data are expressed as absolute and percentage frequency values and continuous data as mean ± standard deviation, median, and range, as appropriate. Freedom from reoperation and cumulative survival rates were analyzed according to Kaplan-Meier estimates with 95% confidence interval (CI) and Cox proportional hazard regression methods to identify the risk factors for
reoperation and mortality. A value of P ≤ 0.05 was considered significant.
Results Morbidity Five patients (3.6%), who also underwent concomitant closure of ventricular septal defects, developed complete heart block and
Figure 8 Supramitral ring. (A) Atrial view. (B) Sharp dissection of mitral ring. (C) Completed repair.
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Figure 9 Parachute valve. (A) Assumed trigones. (B) Most appropriate site of commissural incision defined on both sides from the common papillary muscle toward the assumed trigones. (C) Commissural incisions extended into the body of the papillary muscle. (D). Papillary muscle is split toward its base, assuring sufficient thickness of both new “papillary muscle heads.” (E) Appearance after commissurotomy, fenestration, and papillary muscle splitting.
required permanent pacemaker implantation performed within 30 days after the operation.
on extracorporeal membrane oxygenator. Eventually, the patient developed capillary leak syndrome and died on the 18th postoperative day.
Early Mortality Early death occurred in a 1-month-old infant with hammock valve, with combined mitral stenosis and insufficiency. After the repair, symptoms of low cardiac output were progressive, refractory to maximal medical therapy; hence, an extracorporeal membrane oxygenation was started. A week later, the patient underwent MV replacement using a 14-mm biological prosthesis but died 10 days postoperatively. Another early death was a 3-month-old infant who underwent urgent single-stage surgery for all the obstructive lesions of Shone’s anomaly with associated pulmonary hypertension (mean pulmonary artery pressure of 32 mm Hg), ventricular septal defect, and patent ductus arteriosus. Postoperatively, the patient had mild residual MS (MV orifice area of 2 cm2, and mean resting end-diastolic gradient <5 mm Hg). The LA pressure was 12 mm Hg. The patient suffered from low output cardiac failure, hemodynamic instability, and hypotension 34 hours after the procedure and was placed
Late Mortality A total of 9 deaths occurred during the postoperative followup. Eight late deaths occurred among patients with Shone’s anomaly who were discharged from the hospital. A 2-monthold infant with the typical congenital MS who underwent repeat MV repair with concomitant repair of coarctation of aorta and repeat septal myectomy 4 months later died from heart failure a year later. A patient with parachute valve, who was 2 years old at the time of the initial MV repair, underwent repeat repair 5 years postoperatively. The patient underwent MV replacement 2 years later, but died 8 years postoperatively. Six patients died of a noncardiac event at 1 (episodes of seizures), 3 (endstage renal failure), 5 (n = 2, end-stage renal failure and pneumonia), 8 (vehicular accident), and 13 (unknown) years postoperatively. A 7-month-old infant with repaired hammock valve died of unknown cause 5 years after the initial repair.
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Figure 10 Parachute-like asymmetric valve. (A) Small papillary muscle with just few short chordae, causing an asymmetric location of the valve orifice. (B) Bilateral commissurotomy and incision of the anterior papillary muscle is incised. (C) Papillary muscle is split to a length allowing greater coaptation of the anterior and posterior leaflets.
During a mean duration of follow-up of 17.5 ± 1.5 years (range 6.4-27.7 years), cumulative survival rate was 97.6 ± 2.4%, 92.3 ± 4.3%, 83.8 ± 6.1%, 75.7 ± 7.8% and 70.3 ± 8.9%, at 30 days, 1, 5, 10 and 15 years postoperatively, respectively (Fig. 12A).
Functional Outcome of MV Repair Change in Functional Class There was a significant improvement in functional class postoperatively (P < 0.001), and this was sustained until the late follow-up period (Fig. 12B).
the patients with the membranous variety which may not have been detected during the initial resection, as not only was the membrane adherent to the anterior MV leaflet but some tissue components remained proximal to the posterior leaflet. These were also the patients with type I congenital MS with fused commissures and thickened leaflets (n = 10); 2 had hypoplastic MV (type II), of whom one had emphasized shortened chordae and another had miniature papillary muscles. Along with the repeat resection of the membranous ring, they also underwent repeat commissurotomy, chordal division, and papillary muscle splitting. The latest echocardiographic evaluation of these patients showed absence of MS.
Follow-Up Change in Severity of Mitral Stenosis Absence of MS (mean MV orifice area 4.7 ± 0.7 cm2 without mean resting end-diastolic pressure gradient) was noted after the MV repair (P < 0.001) (Fig. 12C). In the course of follow-up, 14 patients have developed significant MS (mean MV orifice area 2.5 ± 0.8 cm2 and mean resting end-diastolic pressure gradient 8.5 ± 1.3 mm Hg) warranting repeat intervention.
Resection of Supravalvular Mitral Ring Twelve patients (27%) who underwent primary resection of supravalvular mitral ring underwent repeat resection. These were
Freedom From Reoperation After MV Repair Mean duration of follow-up was 17.5 ± 1.5 years (range 6.427.7 years). Freedom from reoperation was 97.6 ± 2.4%, 89.3 ± 5.1%, 77.1 ± 7.2%, 72.0 ± 8.3%, and 52.8 ± 11.8% at 30 days, 1, 5, 10, and 15 years postoperatively, respectively (Fig. 12D). We performed 3 MV replacements, and this was on a patient with parachute valve (see section on late mortality), and 2 patients with hammock valves. Thirty-two repeat MV procedures were performed in 14 patients, which were all related to restenosis and repeated MV dysfunction. These procedures were performed mostly for the type I MS and hypoplastic MV.
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Figure 11 Hammock valve. (A) Chordae and abnormal papillary muscles inserted in the left ventricular wall. (B) A suitably thick part of the posterior left ventricular wall carrying the rudimentary chordae is carved off the wall. (C) “New papillary muscles.”
Discussion CMS is the result of abnormalities at multiple levels. This occurrence is primarily the reason why although new techniques have been developed specifically for children and have been introduced to repair the MV during the last decades, surgical methods of MV repair for congenital MS still remain limited and extremely challenging. With the aforementioned complexity of MV stenosis, surgical management in infants and children still remains a formidable issue. It is an enormously demanding and considerable task for the surgeon to reconstruct and repair MVs in infants and children, primarily because of their size, the immature and fragile leaflet tissues in infants, as well as the associated congenital cardiac abnormalities, which take particular hemodynamic consideration. MV repair in children is guided by the same surgical rules as in adults, but the anatomic substrate differs greatly. The technical difficulties vary according to the anatomy, size, and age of the patient. The indications for surgery and the
timing of surgery have to take into account a large range of concerns and are therefore less straightforward than in adults. Our present surgical strategy in infants and children with CMS are merited mostly from previous experiences ranging from catheter-based relief of mitral stenosis through surgical repair and eventual replacement, when necessary, from the modern diagnostic and imaging modalities which could precisely define the anatomy and morphology of the MV as well as immediate uncovering of other left-sided obstructive lesions, and from enhanced surgical skills. The repair strategy for CMS patients using a variety of repair techniques tailored to the presenting morphology of each patient demonstrated that repair can be performed in this population with satisfactory long-term survival and freedom from repeat repair and replacement. In patients with a successfully repaired valve, adequate MV function is maintained over the longterm with minimal need for replacement. The typical CMS was ingenuous to repair. Simple commissurotomy, chordal division, and splitting the papillary muscles
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Figure 12 Kaplan-Meier estimates showing (A) cumulative survival; (B) comparison of preoperative, postoperative, early, and late follow-up as to functional class; (C) degree of CMS; and (D) freedom from reoperation.
created an effective orifice area. Although some leaflets were cautiously mobilized, we did not see the need to touch the thickened and rolled leaflets but left them as they were seen. Determining the surgical approach to the hypoplastic MV, with a minuscule leaflet and subvalvar apparatus, complemented with immensely delicate and underdeveloped, if not insufficient, tissues seen in infants, is arduous. Repair is the only available option that provides a functional MV, although perhaps not a longlasting one. Even when the primary repair result is not optimal, time is gained for repeated repair until an adult-sized prosthesis can be implanted. Hypoplastic MV is a very rare congenital defect and is mostly combined with an underdeveloped left ventricle. Opening the MV orifice promotes growth of the left ventricular cavity and mass. Some moderate mitral incompetence may even promote this process. The degree of mitral hypoplasia ranging from normal size MV toward mitral atresia determines the rationale of this concept. The cornerstones are still undetermined between valve repair and eventually a univentricular strategy. The presence of a parachute valve does not automatically warrant a surgical indication. Some are functionally adequate. The parachute valves, associated with significant subaortic stenosis, were amenable to repair because the main obstructive mitral
element was subvalvar. Outcomes in this subgroup are related to the degree to which MS can be relieved. MV stenosis with abnormal papillary muscles also includes hammock valve, which refers to the atrial aspect of various subvalvar anomalies. The valvar orifice is partially obstructed by intermixed chordae and abnormal papillary muscles, characteristically implanted underneath the posterior leaflet. The chordae tendineae of the anterior leaflet cross the orifice toward the posteriorly implanted papillary muscles, producing the hammock appearance. In extreme cases seen, the hammock valve contains a fibrous diaphragm with scattered holes that allow the blood to flow from the left atrium to the left ventricle. This malformation is the most difficult to correct by reconstructive techniques. This study comprises an institutional series of MV repair in 48 children with Shone’s anomaly.9 The challenge presented by these patients is amplified by the coexistence of restrictive and often surgically unfavorable MV morphology with other obstructive lesions at an early age. The optimal surgical approach in this group is governed by the morphology of each obstructive lesion. One complicating factor is that the degree of MS can be underestimated owing to the coexistence of LVOT obstruction, which may mask the need for surgical intervention on the MV.
Repair for Congenital Mitral Valve Stenosis The single-stage operative approach did not prove to have a significant positive effect on long-term outcome in these patients, even in terms of reoperation, as relief of mitral stenosis unmasked any existing left ventricular inflow tract lesions. We found no difference in reoperation rate between those who underwent single- or multistaged approach.
Conclusion We have demonstrated that an aggressive functional repair approach to the MV and relief of the LVOT obstruction (single or multistage) lead to long-term event-free survival in these children. Outcomes in this population are related to the degree which mitral stenosis can be relieved.
Acknowledgments We thank Diana Kendall for literature search, Julia Stein for statistical analysis, and Helge Haselbach for graphical illustrations.
References 1. Ruckman RN, Van Praagh R. Anatomic types of congenital mitral stenosis and surgical implications. Am J Cardiol 1978;42:592601 2. Carpentier A, Brizard C. Congenital malformation of the mitral valve. In: Stark J, de Leval M, Tsang VT (eds): Surgery for Congenital Heart Defects. Ed 3. England; John Wiley & Sons, Ltd; 2006: pp 573-590
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