Article
Minimally Invasive aortic valve replacement gained growing consent in
the last years [1] based om associated minimal surgical trauma,
faster rehabilitation, better pain control and patient compliance. Since
the beginning of our experience, we focused on simplification and
optimization of the technique to make the MiAVR as versatile and as
reproducible as the conventional median sternotomy approach. Our aim was
to reach the result of the gold-standard approach through a smaller
incision[2], [3]. The key elements to realize a true minimally
invasive procedure include sparing the right mammary artery, avoiding
rib fractures, adopting a total central cannulation[4] – of
paramount importance to improve both perfusion and drainage while on
cardiopulmonary bypass (CPB) - and a short operative time to make that
procedure minimally invasive from a biological point of view too. We
strongly believe that minimally invasive surgery should spread across
the developing country as well, because it holds advantages in terms of
blood transfusion rate, intubation and Intensive Care Unit (ICU) times
and pain control: a simple technique would be extremely reproducible
even in Centres working on a limited budget.
After more than 1200 RAT-Aortic Valve Replacement, we were able to
optimize our technique (Central Picture). The patient lies in supine
decubitus and an inflatable bag is placed behind the right scapula to
tilt the thorax toward the left side. Double lumen intubation is
provided to exclude the right lung. The second or third intercostal
space is opened through a 5-cm skin incision, paying attention to
preserve the right mammary artery and avoiding any rib damage. We do not
perform routinely a CT-scan to plan the operation: the chest X-ray and
the aortography during the coronary artery catheterization, in our
experience, are reliable to highlight the presence of worrisome aortic
calcification or unusual anatomic variants; on the other hand, we do
recognize the value of a pre-operative CT-scan when starting a MiAVR
program: in the first cases, that allows to rule out patients who are
more demanding in terms of surgical skills [5]. The correct site to
carry out the thoracotomy is identified looking for position of the
angle of Louis and, from there, that of the third rib: we perform a 5 cm
long incision along its edge, starting at a distance of 5 cm from the
jugular-xiphoid line (Fig. 1). The third intercostal space (just below
the incision line) is most of the times the appropriate space to gain
access to the thorax: the right superior pulmonary vein should be
appreciated in the middle of the surgical field. However, if the
exposition seems to be not adequate for the patient’s individual
anatomy, it is nonetheless easy to switch from the 3rd to the 2nd space
upon the same incision. To further improve the view throught the
intercostal space, a soft tissue retractor and an appropriate spreader
are adopted. The pericardium is opened as medial as possible, almost as
in median sternotomy, keeping a safe distance from the phrenic nerve.
This incision in extended up to the pericardial reflection and down
towards the diaphragm, to pursue the best right atrial exposure. This
correct exposure is critical to secure an easy procedure. Then, to
further improve the exposure and to cope with the anatomical variances
as well, we use three pericardial retractions, making a deep
figure-of-eight stitch with a strong and thick wire: one is positioned
at the level of the right superior pulmonary vein, the second as cranial
as possible and the last as caudal as possible from the first
respectively. Those stitches are passed through the thoracic wall with
an EndoClose and pulled to bring the aortic root closer to the
thoracotomy, especially in case of deep and left-sided aorta (Fig. 2).
Our technique strictly relies on a totally central and direct arterial
and venous cannulation. Central cannulation not only reduces surgical
trauma, but also avoids the potential complications related to the
femoral approach, at the same time providing a more physiological
perfusion flow and better venous drainage. Furthermore, retrograde
arterial flow demonstrated a strong correlation with femoral and aortic
dissection, ipsilateral limb ischemia and cerebrovascular and renal
events. For arterial cannulation, the EOPA cannula is inserted through a
double purse-string suture placed at the pericardial aortic (Fig. 3),
while a three-stage 29-Fr cannula is placed in the right atrium for the
venous drainage. Both the optimal view and control of the target spot
are critical to perform a harmless aortic cannulation: one useful trick
is to push the aorta down and towards the operating surgeon using sponge
and forceps. Regarding the venous cannulation, as it might be difficult
to engage the inferior cava vein with a straight cannula, we use a metal
spindle (e.g. the one included in the intracavitary venting small
cannula) to obtain a rounded shaped venous cannula (Fig. 4). Aside the
hydrodynamic advantage, the venous cannulation through the right
appendage may further improve the exposure. Indeed, we use a snare that
is strongly and safely fastened around the venous cannula next to the
right appendage, which is also passed through the thoracic wall: a
gentle pull on this snare will move the right atrium away, improving the
exposure of the aortic root. The left ventricle is vented via a small
cannula inserted through the right upper pulmonary vein into the left
ventricle. Continuous carbon dioxide flow at a rate of 3L/min is
routinely delivered throughout the procedure. A Chitwood-DeBakey aortic
cross clamp is placed at right below the origin of the innominate,
avoiding the dissection between the ascending aorta and the pulmonary
trunk. A separate small incision just below the lateral clavicular side,
measuring less than 1 cm, is used to insert the clamp across the
transverse sinus, so as to achieve the least crowded operative field
(Fig. 5). Blood cold cardioplegia is administered in an antegrade
fashion. Blood cold St.Thomas Cardioplegia, which is enriched with
procaine, is administered in an antegrade fashion to guarantee an
ischemic time of about 40 min. The use of sutureless bioprostheses or a
running suture technique for the implant usually bewares the need for a
second cardioplegic infusion. In case of significant aortic
regurgitation, part of the cardioplegic solution is delivered
antegradely to arrest the heart, while the rest of the dose is
admnistered directly into the coronary ostia: the left main stem ostium
can be easily reached through the aortotomy, albeit the identification
of the access to the right ostium might require the use of a small
dentist looking glass; whether a second shot is needed, the coronary
ostia are used for this purpose. We routinely use a transverse aortic
incision to excise the diseased aortic valve en bloc (Fig.6). Thus,
either a sutureless or a sutured prosthesis can be implanted. In case of
a sutured prosthesis, the preferred technique forecasts three running
2/0 Prolene (120 cm) sutures with 3/4 big steps along each sinus:
according to our experience, this technical tool warrants better
hemodynamics, faster implant and marginal risk of paravalvular leaks. In
addition, we use a silked thread placed at the middle of the suture to
apply counter traction and stretch the suture properly, thus reducing
the occurrence of paravalvular leaks to a greater degree. The dearing is
done gently filling the heart, with the surgical table in
anti-Trendelenburg position, and in the meanwhile the aortotomy is
closed using a single or double 4/0 Prolene suture. Ventricular pacing
wires are placed on the right ventricle. The aortic clamp is removed and
the patient is weaned from cardiopulmonary bypass; the intracavitary
venting line is removed as soon as the echocardiographic monitoring
demonstrated the absence of bubbles within the cardiac chambers.
Finally, it is imperative to realize an exhaustive hemostasis in the
relatively narrow space of the surgical access. Therefore, we use PTFE
pledgets on every purse-string.