Minimally Invasive Aortic Valve Surgery

Abstract

Minimally invasive aortic valve surgery by definition means performing procedures through alternative approaches without the need to divide the sternum completely. Even though this contributes towards lowering the mortality and morbidity of patients, minimally invasive techniques have to be tailored to the unique patient as well as surgeon characteristics. With the advancements made in invasive cardiology techniques, the line between invasive cardiology and minimally invasive cardiac surgery is becoming thinner and thinner. We are presenting state-of-the-art techniques and outcomes for surgical aortic valve replacement via upper mini-sternotomy or anterior right mini-thoracotomy. In addition, aortic valve repair and valve-sparing procedures through a minimally invasive approach are discussed.

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
Chapter
Minimally Invasive Aortic Valve
Surgery
AnzeDjordjevic and IgorKnez
Abstract
Minimally invasive aortic valve surgery by definition means performing
procedures through alternative approaches without the need to divide the sternum
completely. Even though this contributes towards lowering the mortality and mor-
bidity of patients, minimally invasive techniques have to be tailored to the unique
patient as well as surgeon characteristics. With the advancements made in invasive
cardiology techniques, the line between invasive cardiology and minimally invasive
cardiac surgery is becoming thinner and thinner. We are presenting state-of-the-art
techniques and outcomes for surgical aortic valve replacement via upper mini-
sternotomy or anterior right mini-thoracotomy. In addition, aortic valve repair and
valve-sparing procedures through a minimally invasive approach are discussed.
Keywords: aortic valve, valve surgery, minimally invasive surgery, upper
mini-sternotomy, right anterior mini-thoracotomy
. Introduction
Modern and complex aortic valve surgery is dependent on extracorporeal
circulation established first in 1953 by Gibbon [1]. The first, Hufnagel’s aortic
valve was implanted in the descending aorta in 1956 [2] and from then on annual
numbers of aortic valve procedures performed through a full median sternotomy
have risen significantly over the next decades. In 2002, Cribier performed the first
transcatheter aortic valve implantation (TAVI), which paved the way for percutane-
ously resolving patients with prohibitive surgical risk [3]. Although, first minimally
invasive approaches were developed a decade earlier, they gained increased interest
after ever looser indications for TAVI. That dictated a response from the cardiac
surgery society. Cosgrove performed the first minimally invasive aortic valve
replacement (AVR) through a right parasternal approach back in 1996 [4]. In the
same decade, more minimally invasive approaches were developed, such as upper
mini-sternotomy, anterior right mini-thoracotomy (ART) or transverse sternotomy.
Today, most isolated AVRs are performed through either upper mini-sternotomy or
ART (Figure ) with reduced pain, improved respiratory function, early recovery
and an overall reduction in trauma.
Regardless of the approach, some essentials must not be compromised in aortic
valve surgery. These include safe application of a stable aortic cross-clamp, adequate
visualization of the aortic valve, ensuring the same degree of myocardial protection
as in median sternotomy, enabled approach to the aortic root and ascending aorta,
and ability to quickly convert to median sternotomy if needed.

Heart Valve Surgery

The present chapter aims to describe the two most commonly used minimally
invasive approaches to aortic valve surgery (upper mini-sternotomy and ART) with
a special focus on surgical technique and outcomes.
. Upper mini-sternotomy
Skin incision runs over the upper half of the sternum and is usually <10cm long.
Sternotomy can be performed with either the standard (our preference) or oscillat-
ing saw and is performed in a “J” matter into the right 3rd (Maribor preference) or
4th (Graz preference) intercostal space. The selected intercostal space is determined
by the total sternal length, method of myocardial protection delivery (antegrade or
combined ante−/retrograde cardioplegia) and surgeon preference. If exposure of
the aortic valve is not satisfying, the “J” mini-sternotomy can be modified to a “T”
mini-sternotomy or converted to a full median sternotomy. However, care must be
taken during sternotomy osteosynthesis when more than two sternal fragments are
present to avoid excessive postoperative bleeding or sternal dehiscence. In upper “J”
mini-sternotomy, prophylactic division of the right internal thoracic artery (RITA)
is not required.
A small-blade retractor is inserted and the pericardium is opened in a longitu-
dinal matter (Figure ) [5]. Two to three stay sutures on both sides are applied and
the intrapericardial contents are lifted upwards. Care must be taken not to reduce
cardiac preload, which could lead to patient deterioration in the presence of severe
aortic valve stenosis.
The cardiopulmonary bypass could be established centrally or peripherally.
At our institutions, central cannulation remains the preferred option except in
cases of severe ascending aortic calcifications. After systemic heparinization with
300I.U./kg to achieve an activated clotting time (ACT)>480s, the distal ascend-
ing aorta is cannulated through two Prolene 3-0 purse-string sutures with pledgets
placed in a circular fashion. A double-stage venous cannula is placed through a
single Prolene 3-0 purse-string suture either through the right atrial appendage
(Graz preference) or in the superior vena cava (Maribor preference). When can-
nulating the right atrial appendage, the venous cannula could be positioned to the
side of the mini-sternotomy wound or under the undivided sternum and beneath
the xiphoid (Figure ) [6].
Figure 1.
Different approaches for aortic valve surgery. Left: median sternotomy; middle: upper mini-sternotomy;
right: anterior right mini-thoracotomy.

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Minimally Invasive Aortic Valve Surgery
DOI: http://dx.doi.org/10.5772/intechopen.101739
The choice of cardioplegia dictates the type of cannulation. Some cardioplegic
solutions (for example del Nido extracellular crystalloid cardioplegia) require only
antegrade delivery. On the other hand, other solutions (such as blood cardioplegia
or St. Thomas extracellular crystalloid cardioplegia) enhance myocardial protection
when administered via both ante- and retrograde fashion. In that case, the retro-
grade cardioplegic cannula is inserted in the coronary sinus through a single Prolene
3-0 U-suture placed between the venous cannula and the inferior vena cava. The
Figure 2.
Incision of the pericardium through an upper mini-sternotomy [5].
Figure 3.
Upper mini-sternotomy. Operative field and sternal incision [6].

Heart Valve Surgery

antegrade cardioplegic cannula is inserted in the proximal ascending aorta through
a single Prolene 3-0 U-suture.
After placing the patient on cardiopulmonary bypass, a left ventricular vent is
placed through the right superior pulmonary vein or directly through the aorta.
Patients could be safely operated on in normothermia (Maribor preference) or mild
hypothermia (34°C) (Graz preference).
The aorta is cross-clamped, cardioplegia is administered and the intrapericardial
sac is flushed with cold saline to topically cool the heart. An oblique semicircular
incision is made into the ascending aorta and three stay sutures are applied to each
commissure (Figure ) [5].
The aortic valve is excised with a 2-mm margin-left on the aortic annulus. After
flushing the left ventricular outflow tract (LVOT) and ascending aorta to remove
residual calcified particles, an appropriate artificial valve sizer is introduced.
Interrupted Ticron 2-0 U-sutures with pledgets are placed through the annulus with
pledgets on the ventricular side. Care must be taken on the commissure between the
right and a coronary leaflets not to injure the AV node. When an appropriate valve
size is chosen, these sutures are placed on the sewing ring and the valve is lowered
into the aortic annulus. The sutures are tied either by hand or by novel artificial
tying devices (e.g., Cor-Knot). Coronary ostia are carefully inspected to prevent
catastrophic consequences (Figure ).
The aortotomy is closed using two Prolene 4-0 running sutures, both start-
ing at the aortotomy edges. The patient is rewarmed if needed and the heart is
de-aired mostly through a needle incision in the ascending aorta, just distal to the
aortotomy. After removing the aortic cross-clamp, a rhythm check is required.
If ventricular fibrillation, external defibrillation is applied. When sinus rhythm
occurs, an epicardial temporary pacemaker wire is placed on the right ventricle.
This maneuver is facilitated when the heart is actively emptied through the
venous cannula and the wire is then pulled out through the 3rd right
intercostal space.
Also, during active venous drainage, the external drains are placed. Usually,
one retrosternal drain is sufficient placed either through the subxiphoid area or
Figure 4.
Superior view of the aortic valve [5].

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Minimally Invasive Aortic Valve Surgery
DOI: http://dx.doi.org/10.5772/intechopen.101739
the 3rd right intercostal space lateral to the RITA. Another viable option is also
placement of transpleural drainage tubes.
Weaning from cardiopulmonary bypass follows after complete reperfusion with
step-by-step decannulation and oversewing all cannulated spots with Prolene 5-0.
Simultaneously with aortic decannulation, protamine is administered in a 1:1 ratio
to reverse the effects of heparine. With the pericardium left open, sternal osteosyn-
thesis is performed with one obliquely placed wire between the non-divided lower
sternum and the 2nd right intercostal space and one figure-of-eight placed wire
around the manubrio-sternal joint. Finally, fascia, subcutaneous tissue and skin are
sutured, respectively.
. Anterior right mini-thoracotomy
To consider this approach, a preoperative chest computed tomography (CT)
scan is mandatory to assess the relationship of intrathoracic structures, especially
the distance of the aortic root to the right-sided rib cage. The main criteria are: (1)
the position of more than half of the ascending aorta is over the pulmonary artery
on the right side of the sternum and (2) the distance of the ascending aorta from the
sternum is <10cm [7, 8]. Over the 2nd right intercostal space, a <10cm long incision is
made with the medial portion at the sternal edge. The intercostal muscles are sharply
divided using electrocautery. Upon entering the thoracic cavity, the superior right
pulmonary lobe is retracted using selective bilateral lung intubation and prophylactic
division of the RITA is necessary to prevent extensive blood loss. A small-blade retrac-
tor is inserted and the pericardium is opened in a longitudinal matter (Figure ) [5].
It is of paramount importance to identify the phrenic nerve before pericardial incision
to avoid postoperative delayed mechanical ventilation due to respiratory disturbances.
Two stay sutures on both sides are applied and the intrapericardial contents are lifted
upwards. We advise against routine rib resection. In most ART cases, visualization is
already satisfactory after intercostal muscles’ division.
The cardiopulmonary bypass could be established centrally or peripherally. At
our institutions, central cannulation remains the preferred option. The rest of the
operation commences in a similar fashion as previously described in the chapter on
upper mini-sternotomy [9, 10].
Figure 5.
Probing the coronary ostia (courtesy of Medical University of Graz).

Heart Valve Surgery

. Outcomes
Both already described minimally invasive approaches to the aortic valve were
developed in the 1990s. The Cleveland group developed the upper mini-sternotomy
technique in 1996 [4] and the first published data on the ART are from New Delhi
group from 1993 [9].
The first large published article regarding minimally invasive aortic valve
surgery was written by the Boston group. They reported their experience with 526
consecutive minimally invasive aortic valve procedures, which were mostly done
through an upper mini-sternotomy (93%). Their publication has shown excellent
results with short- and long-term mortality at 2% and 5%, respectively. Freedom
from reoperation at 6years was 99% [6].
Encouraged by these data, the number of minimally invasive aortic valve surgery
have risen significantly in the following years. A report was recently published on
the clinical trends between median sternotomy and minimally invasive approaches
for aortic valve stenosis in three high volume aortic valve surgery centres in the
USA (Houston, Atlanta, and Miami). In the observed three-year period, the overall
number of AVRs increased by 107% owing to improved diagnostics and TAVIs for
previously denied patients. Minimally invasive AVRs increased by 57% and median
sternotomy AVRs decreased by 15% [11].
Outcomes of minimally invasive aortic valve surgery are similar or even superior
in some reports to those of conventional median sternotomy surgery [12].
. Mortality
Mortality rates are similar when comparing ART [13–15] or upper mini-sternot-
omy [6, 16, 17] with median sternotomy, respectively. One-year survival is reported
to be >95%, whereas 5-year survival ranges from 80–95%, respectively.
Figure 6.
Pericardial incision through an anterior right mini-thoracotomy [5].

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Minimally Invasive Aortic Valve Surgery
DOI: http://dx.doi.org/10.5772/intechopen.101739
. Postoperative bleeding
The incidence of re-exploration due to excessive bleeding ranges from 3.8% up to
12% [15–18]. The latter high number was reported by Semsroth et al. in a subgroup
of 167 patients who were operated through an ART. One explanation could be that
they already experienced lots of issues with intraoperative bleeding, which resulted
in the fact that bleeding was the predominant cause for conversion to median
sternotomy [18]. Most often significant bleeding occurs on the aortotomy edges,
on cannulation sites, especially the right superior pulmonary vein, on sternotomy
edges or if the RITA is injured.
. Transfusion
Blood product transfusion is reported to be significantly lower in minimally
invasive aortic valve surgery compared to traditional median sternotomy. Reported
incidences are from 21.3% to 48.8% [13–18]. The highest reported incidence was
by Stolinski et al. in a series of 211 patients who undergone an ART, which is still
significantly lower than in the median sternotomy group (67.3%, p<0.001) [15].
. Postoperative atrial fibrillation
Rhythm disturbances often accompany cardiac valvular procedures. The
reported incidences of postoperative atrial fibrillation (POAF) are from 12.8% to
32.2% [13, 15–17].
. Mechanical ventilation
Mechanical ventilation is significantly shorter in patients undergoing minimally
invasive aortic valve surgery (5 vs. 6h; p=0.04) [17] and only 4.3% required
prolonged ventilation >24h [16].
. Intensive care unit and hospital stay
Intensive care unit (ICU) and hospital length of stay are perhaps the most
evident advantages of minimally invasive aortic valve surgery. Both parameters are
shorter in comparison to median sternotomy aortic valve surgery [15]. Semsroth
et al. reported a mean duration of ICU to stay 22h for upper mini-sternotomy and
21h for ART patients [18]. Although, Ghanta et al. reported longer ICU stays, early
discharge defined by discharge by the 4th postoperative day (POD) was achieved
in 15.8% in the minimally invasive group compared to only 4.2% in the median
sternotomy group (p<0.01) [17]. About 52.8% of minimally invasive surgery
patients are discharged by the 6th POD and only 7.9% have a prolonged stay over
12days [16].
. Acute kidney injury
Acute kidney injury (AKI) incidence ranges from 1% to 4.7% [16, 17] with
hemodialysis from 0.5% to 13.2% [15, 18]. The large differences are a consequence
of different AKI definitions and acquired protocols for renal replacement therapy.
The highest reported incidence of hemodialysis comes from the report by Semsroth
et al. Their explanation lies in the necessity of a preoperative CT imaging for
patients receiving minimally invasive aortic valve surgery through ART, as contrast
enhancement is nephrotoxic and might increase the risk for AKI [18].

Heart Valve Surgery

However, a word of caution is proper. Not all patients are suitable for minimally
invasive approaches, especially for ART which is technically more demanding. The
reported exclusion criteria for ART are concomitant ascending aortic aneurysms,
ascending aorta located completely retrosternal or relatively left lateral, pathologi-
cal calcification of the ascending aorta (soft plaques) or prior cardiac surgery, his-
tory of right-sided pleuritis, a deep chest or women with large breasts [10, 19]. On
the other hand, this approach is highly beneficial for disabled patients on crutches
or those with deformed sternum due to radiation or injury.
. Aortic valve repair and valve-sparing procedures through a minimally
invasive approach
All of the information on minimally invasive approaches so far have been
regarding AVR. In recent years, some authors have published their experience with
performing aortic valve repair or aortic valve-sparing procedures through minimally
invasive approaches.
The Beijing group reported their results in upper mini-sternotomy aortic root
surgery. A relatively small sample of 18 patients was matched with an equally large
median sternotomy group. There were no differences in the categories of surgery, as
aortic root surgery was combined with ascending aorta replacement or aortic arch
replacement. Aortic cross-clamp was significantly longer in the minimally invasive
group. Regarding postoperative outcomes, fewer transfusions, lower drainage
volume, shorter mechanical ventilation time as well as shorter ICU and hospital stay
were observed [20].
The ART approach was tested for the treatment of ascending aortic pathology.
The Houston group compared 74 patients who operated through an ART with 103
patients with median sternotomy. In a matched cohort, a trend towards longer
aortic cross-clamp time as well as significantly higher numbers of the bicuspid
aortic valves in the ART group was observed. Again, fewer transfusions, shorter
ventilation time, shorter ICU and hospital stay were experienced. Interestingly,
short-term mortality was similar between the two groups [21].
A systematic review of the results of the minimally invasive aortic root, ascend-
ing aorta or aortic arch performed by the Bristol group revealed similar mortality,
decreased length of cardiopulmonary bypass, shorter ICU and hospital stay, fewer
reoperations due to bleeding and lower incidence of postoperative AKI in the
minimally invasive group. A major limitation of this review is very low-quality
non-randomized evidence [22].
The Warsaw group reported their experience with 167 upper mini-sternotomy
aortic root or ascending aorta operations. About 49% undergone ascending aortic
replacement, 26% a combination of ascending aortic and aortic valve replacement
and 25% one of the aortic valve-sparing procedure (reimplantation/remodeling).
Short- and long-term mortality was 1% and 5%, respectively. Seven % reopera-
tions for bleeding, 1.7% prolonged ICU stays and 4.8% postoperative AKIs were
observed [23].
. Pitfalls in minimally invasive surgery
As already mentioned in the text above, there are some specific pitfalls encoun-
tered in minimally invasive aortic valve surgery. Let us summarize and emphasize
the most frequently seen:

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Minimally Invasive Aortic Valve Surgery
DOI: http://dx.doi.org/10.5772/intechopen.101739
• injury to the RITA (prophylactic division is recommended in ART, sharp
tissue division and electrocautery use should prevent RITA injury in upper
mini-sternotomy),
• poor exposure (excision of the prepericardial fatty tissue),
• difficult ascending aortic cannulation (always be prepared for peripheral can-
nulation, most often through the femoral artery),
• difficult de-airing (using a gauze-covered long instrument and additional CO2
inflation during the procedure can help aid against air embolisms),
• reoperation (we strongly advocate against using minimally invasive approaches
for redo surgery),
• do not jeopardize the patient’s safety—if severe difficulties occur during a
minimally invasive approach, do not hesitate to convert it into full median
sternotomy.
. Conclusions
Minimally invasive aortic valve surgery carries substantial benefits to patients
with aortic valve disease. Fewer transfusions, shorter ICU and hospital stay, shorter
mechanical ventilation alongside similar survival, POAF and AKI incidence are the
main advantages when compared to conventional median sternotomy. The cardiac
surgery society should aim at providing additional training to all cardiac surgeons
to implement minimally invasive approaches in the majority of patients. Only by
doing so, the cardiac surgery society can offer a counter-balance to ever-increasing
numbers of TAVI, which will undoubtedly spread also in moderate or even low-risk
patients in the following years [24].
Acknowledgements
The authors report not received funding.
Conflict of interest
The authors report no conflicts of interest.

Heart Valve Surgery

Author details
AnzeDjordjevic1* and IgorKnez2
1 Department of Cardiac Surgery, University Medical Center Maribor, Maribor,
Slovenia
2 Department of Cardiac Surgery, Medical University of Graz, Graz, Austria
*Address all correspondence to: anze.djordjevic@ukc-mb.si;
anze.djordjevic@gmail.com
© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms
of the Creative Commons Attribution License (http://creativecommons.org/licenses/
by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly cited.

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Minimally Invasive Aortic Valve Surgery
DOI: http://dx.doi.org/10.5772/intechopen.101739
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