LETTER TO THE EDITOR RESPONSE
We thank Dr. Del Giglio et al. for their comments. As it was stated in
our paper1, our primary goal was to describe our
approach and procedural details to MIAVR by way of RALT. For further
reading we would also like to draw attention to our video tutorial
regarding RALT-MIAVR2. Nevertheless, we would like to
congratulate Dr. Del Giglio and his colleagues for their significant
contribution to the field of minimally invasive aortic valve
treatment3 4 56.
We completely agree with Dr. Del Giglio et al. that our statement
regarding preoperative CT-scanning being mandatory is somehow
misleading. However, other colleagues also consider a preoperative CT
scan obligatory for RALT-MIAVR7 providing important
additional information over TEE8. Three-dimensional
reconstructed multidetector CT images allow virtual planning of the
exposure leading to a reduced ischemia time and a reduced conversion
rate9. It has also been shown that systematic
preoperative CT screening in MIMVS is associated with lower risk of
postoperative stroke and a trend towards lower operative
mortality10. Although we agree with Dr. Del Giglio et
al. that CT assessment is helpful at the beginning, it remains
accommodating throughout the complete learning curve and thereafter.
Andre Plass et al.11 wrote that preoperative planning
with multi-slice CT leads to an improved mental preparation and to an
efficient and accurate surgical strategy including the choice of the
optimal ICS. In their Letter to the Editor , Dr. Del Giglio et al.
wrote that surgical access site selection does not require a CT scan,
that the third ICS is the right one in most cases and that the surgeon
could easily change to the second ICS from the same skin incision. We
agree that changing ICS is easily possible, yet it also means added
surgical damage and this should be avoided whenever possible. An
automated method determining the closest ICS to the STJ as the optimal
incision location for MIAVR has already been
introduced12. A novel MIAVR tool that combines 3D
imaging with quantitative planning measures has also been
described13. The access angle is strongly associated
with procedure complexity13 and with CPB time,
x-clamping time and access difficulty13. Moodley et
al.14 reported that mandatory CT-screening of the
chest, abdomen and pelvis revealed significant subclinical aorto-iliac
atherosclerosis resulting in a change in surgical approach in 21% of
asymptomatic or mildly symptomatic patients scheduled for MIMVS (Figures
1 through 3). Regarding the interpreting and reconstructing of CT scans
we agree with Dr. Del Giglio et al. that this means technological
skills, time and financial resources. But with transcatheter cardiac
procedures becoming more popular, it is important for the society of
surgeons to master all aspects of case planning, which not only includes
analysis and measurement but also the reconstruction of CT scans. As
pointed out by Dr. Del Giglio et al. MIAVR has to reproduce the
gold-standard conventional procedure in terms of safety, effectiveness
and especially operative times through a respectful approach; yet in our
opinion, preoperative non-invasive CTA screening in every patient
scheduled for a RALT-MIAVR procedure remains crucial.
In view of truly MIAVR, we believe that arterial and venous central
cannulation both at the same time through the same incision does not
reduce surgical trauma and could lead to central working port
obstruction or significant narrowing. We believe that peripheral
cannulation of the femoral vasculature is as safe and reproducible as
central cannulation if the individualized anatomical characteristics
allow for it. When carrying out percutaneous femoral arterial
cannulation, we never perform a blind puncture of the femoral vessels.
We prefer to have zoomed-in snapshots from our reconstructed CT scans on
display in the OR to accurately puncture the CFA as displayed in figures
1 and 2 for example. Data set published by Eugene A. Grossi et
al.15, suggest that if in older patients a femoral
perfusion technique is chosen, preoperative evaluation of the aorta and
distal vasculature would demonstrate that a given patient would not be
at increased neurological risk15. This would include
CTA of the aorta with runoff and TEE evaluation of the descending
aorta15. They also published that RAP is associated
with an increased risk of stroke in patients with severe PVD and should
be reserved for selected patients without significant atherosclerosis.
Such a thoughtful screening approach has been used also by Murphy and
associates16 in robotic mitral valve surgery for
example15. M. Murzi et al.17 were
able to show that the use of RAP in MIMVS was associated with a higher
incidence of neurological complications in older patients
(>70 years old) with atherosclerotic burden compared with
AAP. Still, their study had several limitations as it was based on a
retrospective analysis of patients undergoing consecutive MIMVS over a
12-year period and potential bias might have been
present17. The observational retrospective analysis of
K. Bedeir et al.18 proved that femoral artery
cannulation may be associated with increased stroke rates in isolated
mitral valve surgery and that antegrade arterial cannulation (direct
aortic or axillary cannulation (figure 2)) may be preferable in MIAVR.
However, their consensus was that these preliminary data should trigger
a larger-scale randomized prospective trial to confirm or refute these
findings18.
In pursuance of reducing hemolysis during CPB19, body
temperature is maintained at around 34°C and
DO2-guidance (goal-directed-perfusion). This is also
helpful in regard to optimal venous drainage as it allows the
surgeon1,2, to safely reduce the calculated pump flow.
Furthermore, we augment venous drainage with the use of vacuum
assistance (−20 to −35 mmHg) to decompress the right
heart1. On one hand,
R.K.
Mathews et al.20 were not able to show a significant
increase in hemolysis or sub-lethal red blood cell membrane damage,
associated with the use of augmented venous drainage. On the other hand,
D. Goksedef et al.21 showed that based on their
results, negative suction at 80 mmHg may cause greater hemolysis than
non-vacuum-assisted drainage or vacuum-assisted drainage at 40 mmHg. For
this reason, we try to keep the vacuum assistance between 0 and -35
mmHg. Besides, it has been proved that application of a controlled,
negative low pressure to the venous return does not cause hemolysis
worse than gravitational CPB22.
At last, Dr. Del Giglio et al. reported concerns about our SLL-PEEP
(maximum 20 cmH2O) technique to inflate the left lung
which pushes the aorta towards the surgical access. It is true that
increased airway pressure or the application of high tidal volumes may
cause damage or disruption of alveolar epithelial cells, by generating
transpulmonary pressures that exceed the elastic properties of the lung
parenchyma above its resting volume23. It has been
demonstrated that the duration of mechanical stress defined as the
stress versus time product affects the development of pulmonary
inflammatory response23. However, in a recent
meta-analysis of postoperative pulmonary complications after
intraoperative ventilation, only a high driving pressure was associated
with an increased incidence24. Therefore, it is highly
unlikely that in an apneic patient on CPB, the elevation of the
PEEP-level of 5 to 20 cmH2O without a resulting change
of driving pressure has any significant negative effect on pulmonary
outcome.
In summary, we agree with the important points addressed by Del Giglio
et al. Central cannulation and its AAP is possible without the need for
preoperative CT scanning. However, for the sake of MIAVR (no rib
resection, no IMA sacrifice) we prefer peripheral percutaneous
cannulation. For such a RAP cannulation strategy, there is sufficient
convincing literature that preoperative CTA scanning should be
considered.