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. Hypo-
plastic 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 pap-
illary 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 pos-
terior 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 cumu-
lative 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 as-
sociated 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 exempli-
fied in Shone’s anomaly,4-7 wherein the additional left heart
obstructive lesions complicate its management. As such, sur-
geons 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. Appearance of a normal mitral valve (A) in comparison with stenotic mitral
Over the years, surgical treatment has been focused on a con- valves: parachute-like asymmetric valve (B), parachute valve (C), and hammock
valve (D).
servative approach, which provides relief of mitral stenosis, albeit
for a short duration, depending on its severity and anatomic sub-
Central Message
strate as well as associated hemodynamically significant
cardiovascular anomalies. Interventional treatments, such as per- For patients with congenital mitral stenosis, a repair strategy using tech-
niques tailored to the presenting morphology demonstrated that repair can
cutaneous transcatheter balloon mitral valvuloplasty,8 are utilized
be performed in this population with satisfactory long-term survival and freedom
for medically refractory CMS, the goal of which is to reduce left from repeat repair and replacement. In patients with successfully repaired valves,
ventricular inflow obstruction and left atrial (LA) pressure, hopefully adequate mitral valve function is maintained over a long time.

a
Department of Cardiothoracic, Transplantation and Vascular Surgery, Medizinische Disclosure: No conflicts of interest to report.
Hochschule Hannover, Hannover, Germany. No funding source has been provided in this paper.
b
Department of Cardiothoracic and Vascular Surgery, Cardio Centrum Berlin, Berlin, Address correspondence to: Eva Maria Delmo Walter, MD, MSc, PhD,
Germany. Medizinische Hochschule Hannover, Carl-Neuberg-Strasse 1, 30 Hannover,
Presented at the Postgraduate Course on Congenital Heart Disease during Germany. E-mail: eva.delmowalter@gmail.com
AATS Centennial Meeting, April 30, 2017, Boston, MA, USA.

46 PEDIATRIC CARDIAC SURGERY ANNUAL • 2018 https://doi.org/10.1053/j.pcsu.2017.11.008

1092-9126/© 2017 Elsevier Inc. All rights reserved.
Repair for Congenital Mitral Valve Stenosis 47

producing lasting relief but minimally improving symptoms and examination before surgery, at the time of discharge from hos-
delaying MV replacement until the patient is older and larger. pital and in a series of follow-ups.
This is true for isolated mitral stenosis. However, this approach Although most patients showed complex structural abnor-
is not optimal when there are associated left ventricular outflow malities in each of the valvular components (leaflets, chordae,
tract (LVOT) obstructive lesions, such as coarctation of aorta and papillary muscles), CMS was defined according to Ruckman and
subaortic stenosis, wherein creation of a widely patent and com- Van Praagh’s classification (Table 1).1 Thickened and rolled leaf-
petent left ventricular inflow leads to concerns about the inadequate lets, short chordae tendineae, partial or complete obliteration of
loading of the left ventricle, which creates an impedance to left interchordal spaces by fibrous tissues, underdeveloped papil-
ventricular ejection, decreasing cardiac output and inability to lary muscles, and commissural fusion (type I, typical congenital
sustain postoperative hemodynamics.9,10 In infants and young MS, Fig. 2A) were seen in 56 patients. Hypoplastic MV (type
children, surgical MV repair improves mitral leaflet mobility and II, Fig. 2B), described as small MV orifice, shortened chordae
provides adequate and effective inflow area; however, it may not tendineae and small papillary muscles, was seen in 15 pa-
be long lasting and there may be a need for eventual valve tients. This form of MS was associated with severe LVOT
replacement. abnormalities, in all cases. Also seen was underdeveloped left
With the advent of excellent diagnostic and imaging modali- ventricular cavity and muscle mass.
ties, providing optimal guidance to assess the MV and surgically Supravalvar mitral ring (type III, Fig. 2C) was seen in 48 pa-
relevant anatomy, as well as the concomitant obstructive lesions, tients; this is described as a circumferential ridge of connective
considerable improvements in perioperative management and tissue that originates at the LA wall overlying the MV leaflets and
outcome have been seen in this group of patients. frequently attached to the annulus. Variable in thickness and
This study reports our institutional experience on surgical strat- extent, it ranged from a thin membrane to a thick discrete fibrous
egy to correct CMS, the operative results, and the long-term ridge. The membrane was often adherent to the anterior MV
functional outcome in infants and children. leaflet. Adhesion to the valve impaired leaflet mobility. This was
associated with variable abnormalities of the MV subvalvar
apparatus.
Patients and Methods Parachute MV (type IV, Fig. 2D), seen in 10 patients, has the
usual 2 leaflets and commissures; however, all chordae tendineae
The institutional review board approved this retrospective or pro- are merged into 1 major papillary muscle, instead of being
spective study and waived the need for patient consent. inserted into 2 papillary muscles. The valve naturally was
Between June 1986 and July 2014, 137 infants and children deformed, and the chordae were short and thick; this, coupled
(mean age 4.1 ± 5.0, median 2.9, range 1 month-16.8, years) with their convergent papillary insertion, allowed restricted
underwent surgical correction of CMS (Table 1). Medical records leaflet mobility, thus creating a stenotic MV as the leaflets were
including preoperative evaluations, operative notes, and follow- closely apposed, greatly reducing the effective mitral orifice
up data were reviewed. All patients were in modified Ross/ area. The only functional communication between the left
New York Heart Association functional class III. atrium and the left ventricle was through the interchordal
Forty-three of the 58 patients with type I CMS underwent pre- spaces. In aggregate, these spaces did not allow free egress of
vious balloon mitral valvuloplasty, with 12 having a repeat blood from the left atrium.
intervention before the definite surgical procedure. Parachute-like asymmetric MV (type IV, Fig. 3) has a large dom-
In 48 patients, CMS is involved in Shone’s anomaly (Fig. 1), inant papillary muscle directly fused with the leaflets, absence
with multiple left ventricular inflow and outflow tract obstruc- of chordae, and presence of only fenestrations. However, the other
tive lesions (Table 1). In this group, it is very difficult to define papillary muscle is very small with just few short chordae, causing
which of the associated cardiac lesions is the predominant cause an asymmetric location of the valve orifice.
of symptoms. Relief of mitral stenosis unmasks any existing LVOT Hammock valve (type IV, Fig. 4), defined as dysplastic with
lesions. In our early years of experience, approach in this group shortened chordae directly inserted in a muscular mass of the
is multistage, that is, treat the presenting lesions as they are un- posterior LV wall resulting in tethering of both leaflets, was
masked. Later on, the advent of modern imaging modalities made seen in 8 patients. The valvar orifice is partially obstructed
it possible to diagnose all the other concomitant obstructions. by intermixed chordae and abnormal papillary muscles, char-
Thus, we preferred single-stage surgery, wherein the optimal strat- acteristically implanted underneath the posterior leaflet. The
egy is governed by the morphology of each obstructive lesion chordae tendineae of the anterior leaflet cross the orifice
and favored MV repair on all patients with transmitral gradient toward the posteriorly implanted papillary muscles, producing
>5 mm Hg, which, in this population, were underscored. the hammock appearance. In extreme cases, the hammock
Follow-up outpatient records were provided by written cor- valve contains a fibrous diaphragm with scattered holes that
respondence from the referring physicians. No patients were lost allow the blood to flow from the left atrium to the left
to follow-up. ventricle.
The left-sided obstructive lesions encountered were coarcta-
tion of the aorta (n = 48), subaortic stenosis (n = 35), and
Anatomical Evaluation of MVs hypoplastic aortic arch (n = 5). Associated cardiac anomalies were
These 137 children and adolescents with CMS were patent ductus arteriosus, atrial septal defect, ventricular septal
submitted to a complete two-dimensional echocardiographic defect, and vascular ring (Table 1).
48 E.M. Delmo Walter and R. Hetzer

Table 1 Demographic Profile of Patients with Congenital Mitral Stenosis

Lesions n (%) Mean Age (Median, Range), y
Types of congenital mitral stenosis
Typical congenital MS* (type I) 56 (40.9) 3.5 ± 1.4 (3.6, 1.1-4.8)
Mitral valve dysplasia (type II MS) 15 (10.9) 0.4 ± 0.27 mo (0.32, 0.02-0.96 mo)
Supravalvular mitral ring (type III MS) 48 (35.0) 8.6 ± 2.0, (8.6, 6.2-9.2)
Parachute valve (type IV MS) 10 (7.2) 13.2 ± 1.6 (15.2, 11.2-16.8)
Hammock valve (type IV MS) 8 (5.8) 0.7 ± 0.8 (1, 0.58-9)
Associated left ventricular outflow tract obstructive lesions
Subaortic stenosis 48 (35.0)
Coarctation of aorta 48 (35.0)
Hypoplastic aortic arch 5 (3.6)
Other concomitant anomalies
Patent ductus arteriosus 78 (56.9)
Atrial septal defect 55 (40.1)
Ventricular septal defect 41 (29.9)
Vascular ring 5 (3.6)
Surgical Procedures Performed to Relieve the Primary MV Repeat Third Total
Congenital Mitral Stenosis Repair MV Repair Intervention
Resection of supravalvular mitral ring 48 12 60
Repair of parachute valve 10 1 1* 10
Repair of hammock valve 8 5 2* 15
Commissurotomy 56 10 66
Papillary muscle division 38 5 25
Chordal division 15 3 18
Surgical Procedures Performed on the Left First Second Third Total
Ventricular Outflow Tract and Other Associated Intervention Intervention Intervention
Congenital Anomalies
Repair of coarctation of aorta 40 12 4 56
Enlargement of hypoplastic aortic arch 5 1 6
Septal myectomy 32 32
Resection of subvalvar membrane 23 7 30
Konno-Rastan aortoventriculoplasty 3 3
Aortic valve commissurotomy 13 8† 3§ 24
Aortic valve dilatation 9 7‡ 2¶ 18
Ligation of patent ductus arteriosus 78
Closure of atrial septal defect 55
Closure of ventricular septal defect 41
Resection of vascular ring 5

*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 signifi- A total of 194 procedures to treat the CMS in 137 patients were
cant and was observed in all patients (mean 20.8 ± 4.7 [range performed (Table 1). Indications for MV repair are abnormal MV
8-30] mm Hg). with <2 cm2 orifice area, and mean resting end-diastolic gradi-
ent of >5 mm Hg, presence of supramitral ring, and associated
left ventricular outflow obstructive lesions. Hemodynamic cri-
Echocardiographic Evaluation teria include pulmonary artery pressure of >25 mm Hg at rest
Mitral stenosis was quantified by measurement of the MV orifice and >30 mm Hg on exertion. Increased LA to left ventricular pres-
area (cm2) and mean resting end-diastolic gradient (mm Hg) and sure gradient was an indication for repeat MV surgery.
was graded from 0 (4-6 cm2, 0 mm Hg), I—mild (2-4 cm2, Our approach to the left ventricular inflow and outflow tract
<5 mm Hg), II—moderate (1-2 cm2, 5-10 mm Hg), to III—severe obstructive lesions is single-stage surgery whenever possible. In
(<1 cm2, >10 mm Hg). Preoperatively, 34 patients had moder- patients with Shone’s anomaly, a single-stage repair was done
ate MS (grade II), whereas 11 had severe (grade III) mitral stenosis. in 26 patients because all obstructive lesions and intracardiac
Repair for Congenital Mitral Valve Stenosis 49

Figure 1 Graphical illustration of mitral stenosis in Shone’s anomaly.

defects, which were deemed significant, were diagnosed all at Various repair techniques were employed in accordance with
once. This, however, did not preclude eventual re-interventions the cause of mitral stenosis and the presenting valve morphology.
when necessary. Staged repair were performed in 22 patients, Commissurotomy was performed on both the anterolateral
on whom the usual first operations were those that and the posteromedial commissures in children with clearly
addressed the LVOT obstruction, and the next interventions were fused commissures (typical CMS, Fig. 5A). In those with poorly
performed as the other concomitant lesions appeared hemody- defined commissures, commissurotomy was guided with a stab
namically significant to warrant surgery. incision in the assumed commissural area after a hooked clamp
Twenty-five patients in our series presented initially in the neo- is passed through this incision. Commissural incision was started
natal period with coarctation of aorta. The neonatal coarctation from the papillary muscle on both sides toward the assumed
presented with severe symptoms which could have masked the commissures (Fig. 5B), and was performed up to 3-5-mm
other intracardiac pathology until it was repaired. In general, we distance from the annulus. This ensured avoidance of incom-
treat first the most severe obstructive lesions. As there were no petence near the trigones. Mobilization and division of chordae
patients with hypoplastic, small, or even borderline left ventri- tendineae (Fig. 5C) and division and splitting of papillary
cle, all patients had biventricular repair. muscles (Fig. 5D) were performed in patients with short, fused,
MV repair was performed through a median sternotomy under and matted chordae.
cardiopulmonary bypass and moderate systemic hypothermia. Hypoplastic or dysplastic MV (Fig. 6A) was approached by
Antegrade intermittent cold crystalloid cardioplegia with topical cautious mobilization of the leaflets, and commissural incision
hypothermia was used for myocardial protection. Through a left (Fig. 6B-D) to enlarge the orifice. Cautiously dividing the mi-
atriotomy along the interatrial groove, the mitral annulus, leaf- nuscule chordae with careful fenestration in addition to
lets, chordae tendineae, and papillary muscles were exposed and commissurotomy and splitting the papillary muscles (Fig. 7A-D)
meticulously inspected to determine the precise nature of the will likewise increase the mitral opening.
lesion. Leaflet coaptation is assessed with a forceful transvalvular Sharp dissection of the supravalvar mitral ring (Fig. 8A-C) was
injection of saline with a bulb syringe. Using a nerve hook, the required to initiate the resection. It is very important to remove
coaptation of the anterior and posterior leaflets with regard to all components of the ring. As it is usually within the mobile
the presence of sufficient tissues along the coaptation plane was portion of the leaflet, precautions were taken to avoid injuring
assessed. The valve orifice area was assessed with a Hegar dilator the leaflet body itself when dissecting the ring off.
and, more recently, with a Ziemer-Hetzer valve sizer (Fehling In- Parachute valve has the usual 2 MV leaflets and commis-
struments GmbH, Germany). The nomogram published by sures, but all the chordae tendineae cluster into 1 major papillary
Rowlatt et al.11 is helpful in determining the normal valve di- muscle. It often presented as a funnel-type structure with some
ameter for a specific body surface area. distinct fibrous lines at the sites of commissural fusion (Fig. 9A).
50 E.M. Delmo Walter and R. Hetzer

Figure 2 Graphical illustration of classification of congenital mitral stenosis. (A) Type I, typical congenital MS. (B) Type II, hy-
poplastic mitral valve. (C) Type III, supravalvar mitral ring. (D) Type IV, parachute valve.

The most appropriate site for leaflet-splitting incisions was defined (Fig. 10B) and split to a length that allows greater coaptation
on both sides from the common papillary muscle toward the of the anterior and posterior leaflets (Fig. 10C).13
“assumed” trigones (Fig. 9B). These incisions were extended into The degree and extent of incision, commissurotomy, and fen-
the body of the papillary muscle, which was split toward its base estration are measured using a Hegar dilator and more recently
assuring sufficient thickness of both new “papillary muscle heads” a Ziemer-Hetzer valve sizer as determined by the minimal age-
(Fig. 9C-E).9,12,13 related acceptable MV diameter.11
To increase leaflet mobility in parachute-like asymmetric MV Hammock valve is the most difficult to correct by reconstruc-
with tethered leaflets (Fig. 10A), bilateral commissurotomy is tive techniques as its orifice is partially obstructed by intermixed
performed, and the large dominant papillary muscle is incised chordae and abnormal papillary muscles, characteristically

Figure 3 Graphical illustration of parachute-like asymmetric valve. Figure 4 Graphical illustration of a hammock valve.
Repair for Congenital Mitral Valve Stenosis 51

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 techniques employed, whereas 37 (27.0%) had trivial or mild
part of the posterior left ventricular wall carrying the rudimen- insufficiency. Regardless of the underlying pathology and tech-
tary chordae is carved off the wall (Fig. 11B).12 Precautions must niques used, no patient was discharged from the hospital with
be observed to ensure that both the remaining LV wall and the more than mild stenosis or insufficiency.
“new papillary muscles” include sufficient muscle thickness to Postoperative transthoracic echocardiography was carried out
maintain their function (Fig. 11C).12,13 annually, or if clinically indicated on the basis of symptoms.
To assess the adequacy of repair, saline injection through the The degree of MS was estimated by means of standard
valves and intraoperative transesophageal echocardiography were echocardiographic measurement techniques. Assessment of MV
routinely performed. In all the repair strategies we employed, function included planimetric evaluation in mid diastole of MV
the minimal final MV opening area should not be less than 10% motion (leaflet mobility), determination of MV and orifice area,
below the norm according to body surface area in children. No and evaluation of valve anatomy as to thickness, commissural
mitral insufficiency ensued in 100 patients (72.9%) from the 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.
52 E.M. Delmo Walter and R. Hetzer

Figure 7 Type II congenital mitral stenosis. (A) Identification of papillary muscles. (B) Commissurale incision. (C) Chordal di-
vision and fenestration. (D) Splitting of papillary muscles.

Statistical Analysis reoperation and mortality. A value of P ≤ 0.05 was considered

All data were analyzed with the SPSS statistical program for significant.
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 Results
range, as appropriate. Freedom from reoperation and cumula-
tive survival rates were analyzed according to Kaplan-Meier Morbidity
estimates with 95% confidence interval (CI) and Cox propor- Five patients (3.6%), who also underwent concomitant closure
tional hazard regression methods to identify the risk factors for 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.
Repair for Congenital Mitral Valve Stenosis 53

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 papil-
lary 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 on extracorporeal membrane oxygenator. Eventually, the patient
30 days after the operation. developed capillary leak syndrome and died on the 18th post-
operative day.

Early Mortality
Early death occurred in a 1-month-old infant with hammock Late Mortality
valve, with combined mitral stenosis and insufficiency. After the A total of 9 deaths occurred during the postoperative follow-
repair, symptoms of low cardiac output were progressive, re- up. Eight late deaths occurred among patients with Shone’s
fractory to maximal medical therapy; hence, an extracorporeal anomaly who were discharged from the hospital. A 2-month-
membrane oxygenation was started. A week later, the patient un- old infant with the typical congenital MS who underwent repeat
derwent MV replacement using a 14-mm biological prosthesis MV repair with concomitant repair of coarctation of aorta and
but died 10 days postoperatively. Another early death was a repeat septal myectomy 4 months later died from heart failure
3-month-old infant who underwent urgent single-stage surgery a year later. A patient with parachute valve, who was 2 years
for all the obstructive lesions of Shone’s anomaly with associ- old at the time of the initial MV repair, underwent repeat repair
ated pulmonary hypertension (mean pulmonary artery pressure 5 years postoperatively. The patient underwent MV replace-
of 32 mm Hg), ventricular septal defect, and patent ductus ar- ment 2 years later, but died 8 years postoperatively. Six patients
teriosus. Postoperatively, the patient had mild residual MS (MV died of a noncardiac event at 1 (episodes of seizures), 3 (end-
orifice area of 2 cm2, and mean resting end-diastolic gradient stage renal failure), 5 (n = 2, end-stage renal failure and
<5 mm Hg). The LA pressure was 12 mm Hg. The patient suf- pneumonia), 8 (vehicular accident), and 13 (unknown) years
fered from low output cardiac failure, hemodynamic instability, postoperatively. A 7-month-old infant with repaired hammock
and hypotension 34 hours after the procedure and was placed valve died of unknown cause 5 years after the initial repair.
54 E.M. Delmo Walter and R. Hetzer

Figure 10 Parachute-like asymmetric valve. (A) Small papillary muscle with just few short chordae, causing an asymmetric lo-
cation 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 the patients with the membranous variety which may not have
6.4-27.7 years), cumulative survival rate was 97.6 ± 2.4%, been detected during the initial resection, as not only was the
92.3 ± 4.3%, 83.8 ± 6.1%, 75.7 ± 7.8% and 70.3 ± 8.9%, at 30 membrane adherent to the anterior MV leaflet but some tissue
days, 1, 5, 10 and 15 years postoperatively, respectively (Fig. 12A). components remained proximal to the posterior leaflet. These
were also the patients with type I congenital MS with fused com-
missures and thickened leaflets (n = 10); 2 had hypoplastic MV
(type II), of whom one had emphasized shortened chordae and
Functional Outcome of another had miniature papillary muscles. Along with the repeat
MV Repair resection of the membranous ring, they also underwent repeat
commissurotomy, chordal division, and papillary muscle split-
Change in Functional Class ting. The latest echocardiographic evaluation of these patients
There was a significant improvement in functional class post- showed absence of MS.
operatively (P < 0.001), and this was sustained until the late
follow-up period (Fig. 12B).

Follow-Up
Change in Severity of Mitral Stenosis Freedom From Reoperation After MV Repair
Absence of MS (mean MV orifice area 4.7 ± 0.7 cm2 without mean Mean duration of follow-up was 17.5 ± 1.5 years (range 6.4-
resting end-diastolic pressure gradient) was noted after the MV 27.7 years). Freedom from reoperation was 97.6 ± 2.4%,
repair (P < 0.001) (Fig. 12C). In the course of follow-up, 14 pa- 89.3 ± 5.1%, 77.1 ± 7.2%, 72.0 ± 8.3%, and 52.8 ± 11.8% at
tients have developed significant MS (mean MV orifice area 30 days, 1, 5, 10, and 15 years postoperatively, respectively
2.5 ± 0.8 cm2 and mean resting end-diastolic pressure gradient (Fig. 12D). We performed 3 MV replacements, and this was on
8.5 ± 1.3 mm Hg) warranting repeat intervention. 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 pa-
Resection of Supravalvular Mitral Ring tients, which were all related to restenosis and repeated MV
Twelve patients (27%) who underwent primary resection of dysfunction. These procedures were performed mostly for the
supravalvular mitral ring underwent repeat resection. These were type I MS and hypoplastic MV.
Repair for Congenital Mitral Valve Stenosis 55

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 timing of surgery have to take into account a large range of con-
cerns and are therefore less straightforward than in adults.
CMS is the result of abnormalities at multiple levels. This oc- Our present surgical strategy in infants and children with CMS
currence is primarily the reason why although new techniques are merited mostly from previous experiences ranging from
have been developed specifically for children and have been in- catheter-based relief of mitral stenosis through surgical repair and
troduced to repair the MV during the last decades, surgical eventual replacement, when necessary, from the modern diag-
methods of MV repair for congenital MS still remain limited and nostic and imaging modalities which could precisely define the
extremely challenging. With the aforementioned complexity of anatomy and morphology of the MV as well as immediate un-
MV stenosis, surgical management in infants and children still covering of other left-sided obstructive lesions, and from enhanced
remains a formidable issue. It is an enormously demanding and surgical skills. The repair strategy for CMS patients using a variety
considerable task for the surgeon to reconstruct and repair MVs of repair techniques tailored to the presenting morphology of
in infants and children, primarily because of their size, the im- each patient demonstrated that repair can be performed in this
mature and fragile leaflet tissues in infants, as well as the associated population with satisfactory long-term survival and freedom from
congenital cardiac abnormalities, which take particular hemo- repeat repair and replacement. In patients with a successfully
dynamic consideration. MV repair in children is guided by the repaired valve, adequate MV function is maintained over the long-
same surgical rules as in adults, but the anatomic substrate differs term with minimal need for replacement.
greatly. The technical difficulties vary according to the anatomy, The typical CMS was ingenuous to repair. Simple commis-
size, and age of the patient. The indications for surgery and the surotomy, chordal division, and splitting the papillary muscles
56 E.M. Delmo Walter and R. Hetzer

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 cau- element was subvalvar. Outcomes in this subgroup are related
tiously mobilized, we did not see the need to touch the thickened to the degree to which MS can be relieved.
and rolled leaflets but left them as they were seen. MV stenosis with abnormal papillary muscles also includes
Determining the surgical approach to the hypoplastic MV, with hammock valve, which refers to the atrial aspect of various
a minuscule leaflet and subvalvar apparatus, complemented with subvalvar anomalies. The valvar orifice is partially obstructed by
immensely delicate and underdeveloped, if not insufficient, tissues intermixed chordae and abnormal papillary muscles, character-
seen in infants, is arduous. Repair is the only available option istically implanted underneath the posterior leaflet. The chordae
that provides a functional MV, although perhaps not a long- tendineae of the anterior leaflet cross the orifice toward the pos-
lasting one. Even when the primary repair result is not optimal, teriorly implanted papillary muscles, producing the hammock
time is gained for repeated repair until an adult-sized prosthe- appearance. In extreme cases seen, the hammock valve con-
sis can be implanted. Hypoplastic MV is a very rare congenital tains a fibrous diaphragm with scattered holes that allow the blood
defect and is mostly combined with an underdeveloped left ven- to flow from the left atrium to the left ventricle. This malfor-
tricle. Opening the MV orifice promotes growth of the left mation is the most difficult to correct by reconstructive techniques.
ventricular cavity and mass. Some moderate mitral incompe- This study comprises an institutional series of MV repair in
tence may even promote this process. The degree of mitral 48 children with Shone’s anomaly.9 The challenge presented by
hypoplasia ranging from normal size MV toward mitral atresia these patients is amplified by the coexistence of restrictive and
determines the rationale of this concept. The cornerstones are often surgically unfavorable MV morphology with other ob-
still undetermined between valve repair and eventually a structive lesions at an early age. The optimal surgical approach
univentricular strategy. in this group is governed by the morphology of each obstruc-
The presence of a parachute valve does not automatically tive lesion. One complicating factor is that the degree of MS can
warrant a surgical indication. Some are functionally adequate. be underestimated owing to the coexistence of LVOT obstruc-
The parachute valves, associated with significant subaortic ste- tion, which may mask the need for surgical intervention on the
nosis, were amenable to repair because the main obstructive mitral MV.
Repair for Congenital Mitral Valve Stenosis 57

The single-stage operative approach did not prove to have a 3. Ferencz C, Johnson AL, Wigglesworth FW. Congenital mitral ste-
significant positive effect on long-term outcome in these pa- nosis. Circulation 1954;9:161-179
4. Shone JD, Sellers RD, Anderson RC, et al: The developmental
tients, even in terms of reoperation, as relief of mitral stenosis
complex of “parachute mitral valve”, supravalvular ring of left atrium,
unmasked any existing left ventricular inflow tract lesions. We subaortic stenosis and coarctation of the aorta. Am J Cardiol
found no difference in reoperation rate between those who un- 1963;11:714-725
derwent single- or multistaged approach. 5. Bolling SF, Lannettoni MD, Dick M II, et al: Shone’s anomaly: op-
erative results and late outcome. Ann Thorac Surg 1990;49:887-
893
6. Brauner R, Laks H, Drinkwater DC Jr, et al: Multiple left heart
Conclusion obstruction (Shones’s anomaly with mitral valve involvement: long-
term surgical outcome. Ann Thorac Surg 1997;64:721-729
We have demonstrated that an aggressive functional repair ap- 7. Brown J, Ruzmetov M, Vijay P, et al: Operative results and out-
proach to the MV and relief of the LVOT obstruction (single or comes in children with Shone’s anomaly. Ann Thorac Surg 2005;79:
1358-1365
multistage) lead to long-term event-free survival in these chil- 8. McElhinney DB, Sherwood MC, Keane JF, et al: Current man-
dren. Outcomes in this population are related to the degree which agement of severe congenital mitral stenosis: outcomes of
mitral stenosis can be relieved. transcatheter and surgical therapy in 108 infants and children. Cir-
culation 2005;112:707-714
9. Delmo Walter EM, Komoda T, Siniawski H, et al: Long-term sur-
Acknowledgments gical outcome of mitral valve repair in infants and children with
Shone’s anomaly. Eur J Cardiothorac Surg 2013;43:473-481. dis-
We thank Diana Kendall for literature search, Julia Stein for sta- cussion 481-2
tistical analysis, and Helge Haselbach for graphical illustrations. 10. Delmo Walter EM, Van Praagh R, Miera O, et al: Repair of left ven-
tricular 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
References the normal child’s heart. Pediatr Clin North Am 1963;10:499-
1. Ruckman RN, Van Praagh R. Anatomic types of congenital mitral 588
stenosis and surgical implications. Am J Cardiol 1978;42:592- 12. Hetzer R, Delmo Walter EMB, Huebler M, et al: Modified surgi-
601 cal techniques and long term outcome of mitral valve reconstruction
2. Carpentier A, Brizard C. Congenital malformation of the mitral in 111 children. Ann Thorac Surg 2008;86:604-613
valve. In: Stark J, de Leval M, Tsang VT (eds): Surgery for Con- 13. Delmo Walter EM, Javier M, Hetzer R. Repair of parachute and
genital Heart Defects. Ed 3. England; John Wiley & Sons, Ltd; 2006: hammock valve in infants and children: early and late outcomes.
pp 573-590 Semin Thorac Cardiovasc Surg 2016;28:448-459