CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 5, June 2012
AFRICA
e9
(ring or leaflet), residual cleft/prolapse or residual annular
dilatation, systolic anterior motion of the mitral valve causing
left ventricular outflow tract obstruction, rupture of previously
shortened or transferred chordae, elongations or ruptures of
chordae from previously shortened papillary muscles, flail
or perforated leaflet]. Late failure however is usually valve
related (progressive degenerative disease, valvular retractions,
or endocarditis).
3,4
In their study, Dumont
et al
.
3
observed that suture dehiscence
was the most common cause (42%) for procedure-related
early failure of mitral valve repair, occurring at the sites of
leaflet resection and at the annuloplasty ring. This early suture
dehiscence can occur due to a fragile mitral annulus, superficial
sutures, regurgitation due to leaflet problem causing undue
stress on the rings, or increased tension on suture lines,
3
and due
to endocarditis
5
or blunt chest trauma.
6,7
This underscores the
importance of the creation of a tension-free repair, especially
in large posterior leaflet resection. A sliding repair to reduce
tension on the suture lines is suggested.
3
Clinically, dehiscence of the annuloplasty ring can result
in significant MR, heart failure or haemolysis.
8
Our patient
had gross dehiscence of the Duran ring secondary to suture
dehiscence, occurring very late after surgery (without a history
of endocarditis or chest trauma), which is uncommon. Late
dehiscence of an annuloplasty ring at one year has previously
been reported.
5
In our patient, ring dehiscence as well as its attachment to the
lateral commissural area of the annulus was clearly demonstrated
with transthoracic and transoesophageal echocardiography.
Recently, three-dimensional transoesophageal echocardiography
has been reported to provide detailed anatomical information in
patients with mitral ring dehiscence.
8
Kronzon
et al
.
8
reported
eight patients with ring dehiscence and they observed that
dehiscence occurred mainly in a posterior or lateral location.
There was only one anterior dehiscence.
The reasons postulated for increased occurrence of posterior
dehiscence of the ring are: the posterior annulus is in the far
surgical field, thus limiting the view while suturing, performance
of a more superficial suturing posteriorly by the surgeon to avoid
the circumflex artery, or due to calcifications and fibrosis of the
mitral annulus, which are more prevalent posteriorly, making it
less amenable to suturing.
8
In our patient it was a circumferential
dehiscence, but it was in the lateral commissural location, which
is uncommon.
Recently, it has been observed that saddle-shaped mitral
rings, compared to presently available flat rings, may reduce
systolic strain in both the radial and circumferential directions,
leading to reduction in loading on the suture lines and potentially
improving repair durability and preventing dehiscence.
9,10
In
another study, complete rings increased the non-planarity angle
of the mitral valve (making the native mitral annulus less saddle
shaped), compared with partial rings. Neither of the two types of
rings was found to restore the non-planarity angle to the normal
range.
11
In a meta-analysis, Chee
et al
.
12
observed that flexible
annuloplasty rings demonstrated comparable outcomes for
patients with MR secondary to degenerative mitral valve disease,
compared to semi-rigid/rigid annuloplasty rings. With regard
to ischaemic MR, it was observed that there was continued
global and regional left ventricular remodelling with subsequent
dilatation of the anterior and posterior mitral ring segments,
together with asymmetrical ventricular dilatation, causing
tethering and therefore MR.
13
It was noted that annuloplasty
using flexible rings may not completely remodel the native valve
and, in particular, neglect the insertion area of the anterior mitral
leaflet.
Silberman
et al
.
14
analysed long-term outcomes in 169
patients who had undergone mitral valve annuloplasty and
coronary artery bypass grafting. Over a mean clinical follow
up of almost 58 months, 34% in the patient group with flexible
rings had residual MR to a moderate or greater degree, compared
with 15% in the group with rigid rings. Therefore we feel that
a rigid or semi-rigid ring would cause significant reduction
in the antero-posterior diameter and thus reduce residual MR,
compared to a using flexible ring.
Another novel surgical procedure with promising results is
the use of biodegradable annuloplasty rings, which remodel
the shape, reinforce the repair, restore the function of the atrio-
ventricular valves, and maintain the three-dimensional dynamic
motion and geometry of the mitral valve annulus.
15
Conclusion
The exact cause for such late suture dehiscence in our patient is
not known, but the above drawbacks of the flexible ring would
have played a significant role.
References
1.
Chung CH, Kim JB, Choo SJ,
et al.
Long-term outcomes after mitral
ring annuloplasty for degenerative mitral regurgitation: Duran ring
versus Carpentier-Edwards ring.
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2007;
16
: 536–544.
2.
Makhija Z, Desai J. Early and mid-term functional and survival benefits
in ischemic versus degenerative mitral valve repair using Duran flexible
ring: a single surgeon series.
Interact CardioVasc Thorac Surg
2009;
9
:
471–475.
3.
Dumont E, Gillinov AM, Blackstone EH,
et al.
Reoperation after
mitral valve repair for degenerative disease.
Ann Thorac Surg
2007;
84
: 444‒450.
4.
Agricola E, Oppizzi M, Maisano F,
et al.
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immediate failure by transesophageal echocardiography in quadrangu-
lar resection mitral valve repair technique for severe mitral regurgita-
tion.
Am J Cardiol
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9
1: 175–179.
5.
Alexioua C, Doukasa G, Swanevelderb J, Sosnowski A. Late dehis-
cence of a mitral
annuloplasty band in an asymptomatic patient: the
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Eur J Cardiothorac Surg
2004;
25
: 642.
6.
Ramakrishna H. Incidental TOE finding – Carpentier mitral annulo-
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Ann Card Anaesth
2008;
11
: 49–50.
7.
Kolowca M, Domaradzki W, Biernat J,
et al.
Mitral annuloplasty ring
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2007;
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: 575–576.
8.
Kronzon I, Sugeng L, Perk G,
et al.
Real-time 3-dimensional
transesophageal echocardiography in the evaluation of post-operative
mitral annuloplasty ring and prosthetic valve dehiscence.
J Am Coll
Cardiol
2009;
53
: 1543–1547.
9.
Jensen MO, Jensen H, Smerup M,
et al.
Saddle-shaped mitral valve
annuloplasty rings experience lower forces compared with flat rings.
Circulation
2008;
118
: S250–255.
10. Padala M, Hutchison RA, Croft LR,
et al
. Saddle shape of the mitral
annulus reduces systolic strains on the P2 segment of the posterior
mitral leaflet.
Ann Thorac Surg
2009;
88
: 1499–1504.
11. Mahmood F, Subramaniam B, Gorman JH 3rd,
et al.
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valve repair.
Ann Thorac Surg
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88
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