Mitral Valve Replacement
Keywords : mitral valve, mitral valve replacement
· The mitral valve is a complex structure comprised of an anterior and
posterior leaflet that is connected to the left ventricle via attachments to
papillary muscles through the chordae tendineae.
· It is anchored to the mitral annulus, which is in close relation to the
circumflex coronary artery laterally, coronary sinus medially, and aortic valve
anteriorly.
· Shown in Fig. 19.1 is the mitral annulus in a lateral view, along with
view of the mitral valve from the top of the heart showing its proximity to the
aortic and tricuspid valves.
· Exposure of the mitral valve must be optimized to facilitate efficient
and effective surgery. Although not described in detail, complete drainage of
the right atrium must be achieved prior to arresting the heart and opening the
left atrium.
· Left atriotomy via Sondergaard’s groove: The interatrial plane is
dissected to separate a portion of the right atrium that overhangs the left
atrium toward the septum. This incision is extended superiorly toward the left
atrial roof. It is extended inferiorly anterior to the inferior pulmonary
veins, but posterior to the inferior vena cava (Fig. 19.2).
· Extended vertical transseptal biatriotomy: The right atrium is opened
from the right atrial appendage
toward the inferior vena cava. The interatrial septum is then incised down to
the fossa ovalis and extended cephalad onto the dome of the left atrium. This
approach is particularly useful in the setting of reoperative valve surgery
with an aortic valve prosthesis in place (Fig. 19.3)
· Khonsari biatriotomy: This extends from the right atrial appendage
toward the right superior pulmonary vein to expose the interatrial septum,
which is then incised transversely through the fossa ovalis (Fig. 19.4)
· Continuous suture: This approach to anchoring a prosthesis is typically
performed when the mitral annulus is tough and fibrous without much annular
calcification. The major advantage of this technique relates to surgical speed,
which may be advantageous in robotic or minimally invasive mitral surgery. This
is performed with a 3-0 Prolene or Gore-Tex sutures (Fig. 19.5).
· Interrupted sutures without pledgets: This technique is performed in the
setting of mitral annular calcification or following failed prosthesis removal
at the time of reoperative mitral replacement. The major advantage of this
technique is that the sewing cuff of the mitral prosthesis will be seated
precisely within the plane of the mitral annulus, without any distortion. This
is performed with 3-0 Ethibond sutures (Fig. 19.6).
· Interrupted sutures with pledgets: These sutures can be placed from the
atrium toward the ventricle (pledgets sitting on the atrial surface of the
mitral valve) or vice versa (pledgets sitting on the ventricular surface of the
mitral valve; Fig. 19.7).
· Although both approaches can be applied for bioprosthetic or mechanical
valve replacement, it is advantageous to place pledgets on the atrial surface
when using a mechanical valve. This minimizes the risk of pledget embolization
into the left ventricle if a suture tears during tying.
· Bioprosthesis: The largest leaflet cusp should face the left ventricular
outflow tract to prevent outflow
obstruction (Fig. 19.8).
· Mechanical prosthesis: Modern bileaflet valves are positioned in an
antianatomic position with the pivot
guards orientated in an anterior-posterior direction (Fig. 19.9).
◆ Maintenance of
the ventricular-annular continuity at the time of mitral valve replacement has
been associated with more favorable ventricle remodeling and better survival
compared to nonchordal sparing valve replacement.
· The most common approach to chordal preservation involves complete
resection of the anterior leaflet in which the posterior leaflet is retained.
Replacement sutures are placed through the annulus and through a portion of the
posterior leaflet (Fig. 19.10).3
· Some have also described resection of the central portion of the
posterior leaflet, with reattachment of the posterior leaflet free edge with
the valve replacement sutures.
· This has been described with excision of a central trapezoidal segment
of the anterior leaflet. The remaining tissue is taken by the valve suture.
Others have described using Prolene sutures to reapproximate the remaining
leaflet tissue to the annulus before valve suture placement (Fig. 19.11A).4
· Others have also described complete detachment of the anterior leaflet
with resection of the middle portion of the leaflet. The remaining leaflet
tissue is that reapproximated to the anterolateral and posteromedial
commissures, respectively.5
· Initially described for implantation of a tilting disk mechanical
prosthesis, reattachment of the detached anterior leaflet to the posterior
annulus has been used by some.
· The Khonsari I technique is applied for rheumatic valves in which the
primary chordate are destroyed and subvalvular apparatus are thickened. In this
technique, second-order chords are preserved in bundles and then reattached
radially to the annulus in their anatomic position using pledgetted valve
sutures.6,7
◆ Polytetrafluoroethylene
sutures are placed on the papillary muscles and attached to the mitral annulus at 2, 5, 7, and 10 o’clock positions (Fig. 19.12).
· In patients with destruction of the posterior annulus, secondary
endocarditis, or following radical débridement in patients with severe annular
calcification, a pericardial patch is sewn into the left ventricle cavity with
Prolene sutures. Valve sutures are then secured to the patch before the atrial
surface is reapproximated (Fig. 19.13).
· Mitral annular calcification is common and represents a challenging
cardiac lesion.
· Mitral annular calcification in younger patients with degenerative
disease tends to involve the posterior annulus (Fig. 19.14). In these patients,
the calcification is dense and can be removed en bloc, with subsequent
reconstruction of the annulus, described previously.
· In patients with a history of renal dysfunction requiring renal
replacement therapy, or mediastinal irradiation, or those of advanced age, the
calcification of the mitral annulus may be friable, with extension into the
ventricle cavity.
· In these patients, valve explants may be challenging. I recommend that
resection begin with the anterior leaflet, thereby facilitating visualization
of the subvalvular structures. Importantly, this aids in the identification of
the mitral annulus, which may not be obvious. Débridement of the annulus is
performed with sharp dissection using a no. 11 blade and bluntly with a
rongeur. Mitral replacement with interrupted suture placement is useful because
it allows the mitral prosthesis to be seated within the mitral annulus. Also,
interrupted suture placement may mitigate tension on the annulus, which can
result in calcium fracturing when tying.
· For impenetrable calcium involving the portion of the mitral annulus
from the 12 to 3 o’clock positions, sutures may be placed across the
interatrial septum via the right atrium. Impenetrable calcium involving the
mitral annulus from the 9 to 12 o’clock positions may require suture placement
externally on the left atrial roof onto the mitral annulus (Fig. 19.15).
· Another strategy for mitral prosthesis implantation involves the
intraatrial insertion of the prosthesis, as described by Gandjbakhch.8 In this
technique, a Dacron collar is sewn onto a valve prosthesis. An inner row of
interrupted pledgetted valve sutures (pledgets on the atrial surface) are
placed before the free end of the collar is sewn to the left atrium with
running Prolene sutures.
References
· Guiraudon GM, Ofiesh JG, Kaushik R. Extended vertical
transatrial septal approach to the mitral valve. Ann Thorac Surg.
1991;52(5):1058–1060; discussion 1060–1062.
· Khonsari S, Sintek CF. Transatrial approach revisited.
Ann Thorac Surg. 1990;50:1002.
· Feikes HL, Daugharthy JB, Perry JE, et al.
Preservation of all chordae tendinae and papillary muscles during mitral valve
replacement with a tilting disc valve. J Cardiac Surg. 1990;2:81.
· David TE. Mitral valve replacement with preservation
of chordae tendinae: Rationale and technical consideration. Ann Thorac Surg.
1986;41:680.
· Miki S, Kusuhara K, Ueda Y, et al. Mitral valve
replacement with preservation of chordae tendinae and papillary muscles. Ann
Thorac Surg. 1988;45:28.
· Okita Y, Miki S, Ueda Y, Tahata T, Sakai T, Matsuyama
K. Mitral valve replacement with maintenance of mitral annulopapillary muscle
continuity in patients with mitral stenosis. J Thorac Cardiovasc Surg.
1994;108:42–51.
· Wasir H, Choudhary SK, Airan B, Srivastava S, Kumar
AS. Mitral valve replacement with chordal preservation in a rheumatic
population. J Heart Valve Dis. 2001;10:84–89.
· Nataf P, Pavie A, Jault F, Bors V, Cabrol C,
Gandjbakhch I. Intraatrial insertion of a mitral prosthesis in a destroyed or
calcified mitral annulus. Ann Thorac Surg. 1994;58(1):163–167.
