Robotic Mitral
Valve Surgery
Keywords : mitral valve, repair, replacement, prolapse, robotic
Abstract
Robotic mitral valve surgery was introduced in 1998 to
reproduce excellent conventional sternotomy results with less invasive techniques.
This technology is now routinely performed for delivering complete anatomic
correction of all categories of mitral valve prolapse, regardless of disease
complexity, with or without concomitant tricuspid valve repair and atrial
fibrillation ablation procedures. Recent studies have demonstrated broad
advantages of robotic mitral valve surgery, including reduced bleeding,
extubation on the operating room table, shorter hospital length of stay,
quicker return to normal activities, and a superior cosmetic result. Here we
discuss the current status of robotic mitral valve
surgery techniques.
· The 2014 American College of Cardiology (ACC)/American Heart Association
(AHA) guidelines strongly recommend (class I) prompt
surgical correction of mitral regurgitation (MR) for patients in stages D
(severe symptomatic MR) and C2 (severe asymptomatic MR with left ventricular
ejection fraction [LVEF] < 60% or left ventricular end-systolic diameter
[LVESD] > 40 mm).1 Recently, several studies
have supported the advantages of surgical correction of primary MR, even in patients in stage C1 (severe asymptomatic MR with
LVEF > 60% or LVESD < 40 mm) to prevent excess long-term mortality and
heart failure risks.
· Modified cardiopulmonary bypass techniques were introduced in 1995 and
enabled safe and effective minimally invasive mitral valve surgery. However,
difficulties performing complex mitral valve repair using two-dimensional
vision and long-shafted instruments limited their adoption. During the late
1990s, development of the da Vinci Surgical System (Intuitive Surgical,
Sunnyvale, CA) made safe robotic cardiac surgery possible. The da Vinci
Surgical System has allowed surgeons to perform complex reconstructive
operations using a combination of telemanipulation and three-dimensional (3D) visualization.
The first robotic mitral valve operation was performed by Carpentier et al. in
1998 using the da Vinci Surgical System. In 2000, Dr. Chitwood and colleagues
at East Carolina University (ECU) performed the first mitral valve repair in
the United States as part of the initial US Food and Drug Administration (FDA)
clinical trial.
· The most important benefits of robotic mitral valve surgery include
excellent surgical dexterity with precise movements of instruments in the
closed chest, high-definition 3D visualization with the line of vision parallel
to the flow of the blood into the valve, excellent visualization of the
subvalvular apparatus, and superior cosmetic results, with more rapid recovery
than with the use of conventional approaches.
Step 1. Surgical Anatomy
· The heart is covered anteriorly by the body of the sternum and the third
to sixth costal cartilages of both sides. The coronary sulcus, separating the
atria and ventricles, spans from the upper medial end of the third left costal
cartilage to the middle of the right sixth chondrosternal joint. The anterior
interventricular sulcus spans from the third left intercostal space (ICS) 2.5
cm to the left of the midline to a point 1.2 cm medial to the apex. The aortic
valve is at the level of the third ICS behind the sternum. The pulmonary valve
is at the level of the left third ICS. The tricuspid valve is behind the
sternum at the level of the fourth to fifth intercostal junction. The mitral
valve is located behind the sternum at the level of the fourth intercostal
junction.
· The mitral valve apparatus consists of the anterior and posterior
leaflets, two commissures, which are the areas where the anterior and posterior
leaflets meet, the mitral annulus, and the subvalvular apparatus, including the
chordae tendineae and papillary muscles (Fig. 21.1).
· Each leaflet has three segments including the A1 (anterior segment), A2
(middle segment), and A3 (posterior segment) of the anterior leaflet and P1
(anterior scallop), P2 (middle scallop), and P3 (posterior scallop) of the
posterior leaflet. The anterior mitral annulus shares fibrous continuity with
the aortic valve annulus (left coronary cusp and half of the noncoronary cusp)
and is also adjacent to the atrioventricular node and the bundle of His. The
circumflex artery courses along the posterior annulus and is at risk of injury
during mitral valve repair or replacement (Fig. 21.2). The subvalvular
apparatus includes two papillary muscles (anterolateral and posteromedial) and
the thin fibrous structures chordae tendineae that support both leaflets and
prevent leaflet prolapse. The primary chordae attach to the free margin of the
leaflets, and the secondary and tertiary chordae insert into the leaflet body,
closer to the annulus.
 |
Figure 21.1 Anatomy of
mitral valve apparatus.
Figure 21.2 Cross-sectional
view of the mitral valve.
|
Step 2. Preoperative Considerations
· Degenerative, ischemic, rheumatic, and infectious processes are the
major causes of mitral valve disease and can affect any component of the valve
or subvalvular apparatus. Robotic mitral valve surgery is appropriate for both
degenerative and functional mitral valve disease. However, degenerative mitral
valve disease is the most common indication for robotic surgery. Furthermore,
concomitant left atrial appendage (LAA) closure, ablation for atrial
fibrillation, and tricuspid repair can also be performed
using the same robotic platform.
· Following the 2014 ACC/AHA guidelines,1 in centers with expertise in
both mitral valve and robotic
surgery, most patients with severe primary MR with appropriate vascular and
coronary anatomy may reasonably be considered for early robotic mitral valve
repair, regardless of the complexity of mitral valve disease. Patients should
be screened for comorbid conditions that may preclude the selection of the
robotic technique. Table 21.1 demonstrates plausible and relative contraindications to robotic mitral
valve surgery. However, many of the relative contraindications can be managed
to allow a safe robotic mitral valve operation.
· Repair techniques in patients with functional valve disease relate to
the degree of annular and ventricular dilation, papillary muscle displacement,
dynamic cardiac function, and degree of leaflet tethering.
· Patients at risk for coronary artery disease should undergo a cardiac
catheterization or computed tomography (CT) angiography. Patients with
significant risk factors for carotid or peripheral vascular disease should be
screened by ultrasound and CT. A right heart catheterization may be indicated
for patients who have significant pulmonary hypertension, particularly with
depressed right ventricular function. Finally, patients with sternal or
thoracic deformities should be evaluated by CT to determine whether robotic
instrument trajectories will be compromised. A transthoracic echocardiography
(TTE) or transesophageal echocardiography (TEE) study should be performed to
confirm the diagnosis and determine the repair plan. TEE is also essential in
the operative room to delineate mitral valve anatomy in detail, and
intraoperative femoral ultrasound should be peformed to confirm the adequacy of
vessels for cannulation.
Step 3. Operative Steps
· All patients undergoing robotic mitral valve surgery undergo the
following steps:
1. Patient setup and port placement
2. Cannulation, docking of robotic arms, and exposure of the mitral valve
3. Mitral valve surgery, tricuspid valve repair, and atrial fibrillation
procedures
4. Weaning from bypass, decannulation, and closing of incisions
· The patient is intubated with a double-lumen endotracheal tube, and a TEE
probe is placed. Pulmonary artery vent and retrograde coronary sinus
cardioplegia catheters (CardioVations, Ethicon, Somerville, NJ) may be placed
via the right internal jugular vein under TEE guidance. The patient is
positioned at the right edge of the operating room table with a transverse roll
under the chest and an arm board supporting the right arm. The right femoral
artery and vein are exposed via an oblique incision above the groin crease and
assessed for appropriateness for cannulation.
· Port placement is done after femoral vessel exposure has confirmed
adequacy for use in cannulation for cardiopulmonary bypass. Local anesthetic
may be used at all port sites to aid with postoperative pain control. The
endoscope camera port is placed in the fourth ICS, 2 to 3 cm lateral to the
nipple. In female patients, the breast is retracted superiorly and the incision
is placed in the inframammary crease to enter the chest in the fourth or fifth
ICS. The working port incision (for a 15-mm soft rubber retractor) is placed in
the fourth ICS 4 cm lateral to the camera port. The left instrument port is
placed one interspace above and approximately halfway between the shoulder and
the camera port. The right instrument port is two or three interspaces below
and near the anterior axillary line. The fourth robotic port, for the atrial
retractor instrument, is placed in the fifth ICS medial to the camera port. A
10-G angiocatheter, which can accommodate the so-called crochet hook for suture
retrieval, is placed in the midaxillary line for posterior pericardial traction
sutures. Two other angiocatheters are placed medially and laterally to the
central angiocatheter. A Chitwood transthoracic cross-clamp and a small suction
vent are placed via stab wounds in the axilla (Fig. 21.3).
· A purse-string suture is placed in the anterior surface of the femoral
vein, and then a guidewire is passed through the femoral vein and into the
superior vena cava (SVC) under TEE guidance. Seeing the guidewire pass up into
the SVC is very important to ensure the proper positioning of the venous
cannula. A 25F CardioVations Quickdraw venous cannula is passed over the wire
and positioned so that the tip is several centimeters up the inferior vena cava
(IVC). The femoral artery is cannulated using the Seldinger technique (Fig.
21.4). Cardiopulmonary bypass is
initiated.
· The pericardium is opened with electrocautery anterior to the phrenic
nerve. The pericardiotomy extends from near the IVC to up over the ascending
aorta. Two traction sutures are placed on the posterior pericardial edge to
expose the site of the left atriotomy. A traction stitch on the anterior
pericardium facilitates aortic exposure (Fig. 21.5).
· The table is rotated 15 degrees to the left and placed in reverse Trendelenberg
to lower the hips and gain extra clearance for the right instrument arm of the
robot. The da Vinci robot is brought to the surgical field; the arms are
connected to the ports, and the camera and instruments are introduced into the
chest.
 |
Figure 21.3 Patient setup and port placement.
Figure 21.4 Cannulation of the femoral vessels.
|
◆ Aortic occlusion is
achieved using the endoballoon or Chitwood clamp; cardioplegia is delivered
antegrade and readministered every 15 to 20 minutes throughout the cross-clamp
time.
◆
A left atriotomy
incision is made anterior to the right pulmonary vein (Fig. 21.6). The
intuitive surgical atrial retractor is positioned to elevate the atrial septum
and provide exposure. The atrial retractor position can be adjusted to optimize
exposure for patent foramen ovale closure, closure of the LAA, or exposure of
the mitral valve. The small suction vent is positioned in the left pulmonary
vein to clear the surgical field of blood.
 |
Figure 21.5 Opening of the
precardium.
Figure 21.6 Left
atriotomy.
|
4. Mitral
Valve Repair
· This technique is ideal for patients who need posterior leaflet repair
with prolapsing, redundant, and myxomatous tissue. The mitral valve is exposed
and evaluated. The normal chordae on either side of the prolapsing portion are
identified to determine the extent of resection. A triangular-shaped segment of
tissue, with the base at the free edge of the posterior leaflet and the apex at
or near the annulus, is excised with curved scissors (Fig. 21.7A). Running 4-0
Prolene sutures (see Fig. 21.7B), with or without a ventricularization technique, are used to close the defect in the leaflet.
· The ventricularization technique is performed to normalize the height of
the posterior leaflet and reduce the risk of systolic anterior motion. After
triangular resection, each needle of a double-armed suture is passed through
the free edge of one leaflet remnant and then through the midportion of that
leaflet segment to ventricularize the free edge (i.e., move closer to the
ventricle), thereby reducing the leaflet height (see Fig. 21.7C). Each needle is
then used for a running closure of the posterior leaflet defect (see Fig.
21.7D), and the stitch is tied at the base of the resection (see Fig. 21.7E).
The assistant may tie the suture with a knot pusher or the surgeon can tie it
intracorporeally.
· A quadrangular resection of the posterior leaflet is necessary for the
management of an extensive, redundant, prolapsing leaflet. The excessively tall
posterior leaflet is excised, and then the remaining portions of the posterior
leaflet are detached from the annulus and advanced centrally, sliding it over
to meet the other leaflet component. The leaflet base is reattached to the
annulus with two layers of running 4-0 Prolene sutures, and the leaflet edges are reapproximated with 4-0 Prolene sutures.
 |
Figure 21.7 (A) Triangular resection of the posterior leaflet. (B) Posterior leaflet
repair using running technique. (C) Repair of the posterior
leaflet using ventricularization
technique. (D) Running closure of the posterior defect. (E) Final stitch next
to the annulus.
· Gore-Tex (WL Gore & Associates, Newark, DE) neochordae placement is
greatly facilitated by the robotic approach due to the excellent exposure and
magnified view of the subvalvular apparatus. The anterior leaflet is lifted
upward using a dynamic left atrial retractor. The neochordae are created using
5-0 polytetrafluoroethylene (PTFE) sutures. One arm of the suture is passed
twice through the fibrous tip of the papillary muscle and then twice through the
free edge of the corresponding prolapsing segment. The second arm is then
passed twice through the free edge of the prolapsing segment. The length of the
chordae is adjusted based on the height of the nearest normal segment of the
posterior leaflet, and the sutures are tied on the atrial
side of the mitral valve leaflet (Fig. 21.8).
 |
Figure 21.8 Repair of the mitral
valve using artificial chordae.
Annuloplasty
· All repairs are completed using a flexible, standard-length annuloplasty
band. The band is first secured at the right (A3–P3) trigone, and additional
sutures are placed from the medial to lateral part of the annulus using either
running or interrupted Ethibond sutures.
· For the interrupted suture technique, 10 to 12 2-0 braided polyester
sutures are used to secure the annuloplasty ring in the standard fashion (Fig.
21.9). For the running suture technique, three 2-0 braided polyester sutures
(Ticron, Covidien, MA) are used to secure the annuloplasty ring as follows. The
first suture is tied down between right trigone and the ring and run clockwise
to the midportion of the ring. The second suture (14 cm in length) is then
passed through the ring and annulus in running fashion to the level of the
midportion of the annulus. The second suture is started at this point with a
single interrupted stitch and tied to the first suture. The remainder of the
second suture is then run clockwise to the left trigone. The third suture (9 cm
in length) is passed through the ring, through the left trigone, and then back
through the ring. This third suture is tied down, and the tail is used to
secure the second suture (Fig. 21.10).
· The subvalvular apparatus and chordae are preserved whenever possible.
Appropriate sizing is performed and 10 to 12 everting, double-armed, mattress
sutures with Teflon pledgets are placed counterclockwise from the 11 o’clock
position and fixed sequentially outside the incision with a small hemostat. The
sutures are placed in the prosthesis sewing ring outside the chest. The
prosthesis is lowered into the chest and positioned, and the knots are tied
using the knot pusher or Cor-Knot device (LSI Solutions, Victor, NY) through
the working port.
◆
All lesions are
created by applying the CryoMaze probe (ATS Medical, Minneapolis, MN) for 2
minutes directly to myocardial tissue, with temperatures reaching –140° to
–160°C (–284° to –320°F). Following lesion creation, the probe is separated
from the surrounding tissue by administering warm saline solution.
◆
The pulmonary veins
are isolated with a single wide box lesion around all four veins. The first
cryolesion extends from the right inferior pulmonary vein to the mitral
annulus. The next lesion extends from the mitral annulus around the left
pulmonary veins, reaching the upper border of the atriotomy. Great care is
taken to ensure complete contact between the probe and atrial tissue. The
complete box lesion can be constructed with two or three cryolesions; however,
if the left atrium is particularly large and redundant, more lesions may be
required. Additional lesions might be required from the pulmonary vein
isolation box to the LAA if this area is not completely ablated.
◆
The final left atrial
lesion is an epicardial lesion across the coronary sinus to ensure complete
transmurality at the mitral valve annulus.
◆ The LAA is routinely
closed as part of the CryoMaze operation unless there are significant
pericardial adhesions keeping the appendage patent. The LAA is closed in a
two-layer fashion using 3-0 Gore-Tex sutures.
 |
Figure 21.9 Band
annuloplasty using interrupted stitches.
Figure 21.10 Band
annulolasty using running stitches.
|
7. Atrial
Closure
· Once the mitral surgery is complete, the left atriotomy is closed with
running 4-0 Gore-Tex sutures, beginning a suture at each end of the atriotomy
and meeting in the middle. The heart is allowed to fill and de-air via the
atriotomy before tying the suture.
· After bicaval cannulation, the caval cannulas are backed into the SVC
and IVC, and the tapes around the cavae are tightened. A vertical right
atriotomy is made, and the dynamic atrial retractor is used to retract the
anterior right atrial wall. Tricuspid valve repair has evolved from a classic
De Vega repair (double-armed, running, vertical mattress purse-string sutures
of 4-0 PTFE, tied over pledgets) to an annuloplasty band sewn into place with
interrupted 2-0 polyester sutures. The right atrium is then closed in two
layers with PTFE, and the caval tapes are released.
· All repairs are assessed using saline insufflation to fill and
pressurize the left ventricle before closure, de-airing, and cross-clamp
removal. Integrity of the repair (less than or mild residual MR) and adequacy
of deairing should be confirmed with the patient off cardiopulmonary bypass
before decannulation. Once the heart is beating (and preliminary evaluation of
the repair by TEE looks good), the antegrade cardioplegia catheter is removed
from the aorta, and the puncture site is closed with pledget-reinforced 4-0
Gore-Tex or Prolene mattress sutures.
· The pericardium is loosely closed with two sutures to prevent cardiac
torsion. A 19F Blake drain (Ethicon) is brought into the chest via the atrial
retractor and the right instrument ports.
· The instruments and ports are all removed, and both lungs are
ventilated. The patient is then separated from cardiopulmonary bypass, and the
repair is evaluated by TEE. While a protamine is administered, the cannulas are
removed, the purse-string sutures in the femoral vein are tied, and the femoral
arteriotomy is repaired primarily.
· After a protamine is administered, the right lung is deflated, and the
camera is reintroduced into the chest to examine the aortic cardioplegia site,
as well as all port and angiocatheter sites, to ensure good hemostasis.
Step 4. Postoperative Care
· Postoperative care is routine for cardiac surgery, with special
attention to arrhythmia prevention and maintaining afterload reduction. In the
area of postoperative pain control, several factors should be considered. Pain
control after robotic surgery may be achieved with intercostal nerve block or
using cryothermia to freeze the intercostal nerves prior to incision closure.
Compared to sternotomy, patients who have robotic surgery require less
intravenous narcotic, which may allow earlier extubation. All patients should
undergo repeated TTE before discharge from hospital. Lifelong annual
echocardiographic surveillance is necessary after mitral valve repair.
Step 5. Pearls and Pitfalls
· Operating inside the heart with robotic instruments does not allow
tactile feedback. However, this has not been a limitation in practice. Highly
disciplined movement of robotic instruments, advanced echocardiographic
imaging, and gaining ocular tactility through experience have addressed this
issue. Furthermore, although cross-clamp and operative times are longer
compared to those of conventional median sternotomy, there has been no
significant difference with regard to postoperative morbidity and mortality.
· There are several potential advantages of robotic mitral valve repair in
comparison to thoracotomy and thoracoscopic approaches. The robot facilitates
precise movements of instruments in the closed chest and avoids the
difficulties of using long, shafted, endoscopic instruments that may be
experienced during minimally invasive procedures. The high-definition 3D view
facilitates the visualization of the subvalvular apparatus and enables repair
of any type of myxomatous pathology. The cosmetic results are appreciated by
female and male patients, particularly in patients with prior breast
reconstruction. Finally, the requirements for heterologous blood products, the
incidence of atrial fibrillation, and postoperative pain have been reported to
be lower, likely due to the reduced surgical trauma.
· The collective results of robotic mitral valve repair in experienced
groups have now reported a hospital mortality rate of less than 0.9%, stroke
rate of 0.6% to 1.7%, reexploration for bleeding of 2.2% to 4.7%, and rare
chest wall infections. Furthermore, the incidence of iatrogenic aortic
dissection, phrenic nerve palsy, and groin infections have all decreased to
almost 0%.
· In summary, robotic mitral valve repair is now routinely performed, with
or without concomitant tricuspid valve repair and atrial fibrillation ablation
procedures. This approach is safe, effective, and durable for complete
correction of all categories of mitral valve leaflet prolapse, regardless of
complexity. Furthermore, robotic repair offers reduced blood loss, lower risk
of incisional infection and atrial fibrillation, shorter hospital length of
stay, quicker return to normal activities, and a superior cosmetic
result. Therefore, the procedure may be particularly appealing in
asymptomatic stage C1 patients according to ACC/AHA class IIa guideline
recommendations.
