Discussion
In recent years, significant improvements have been made in minimally
invasive aortic valve surgery, including direct right
mini-incision[4] and thoracoscopic-assisted right
mini-incision[5], and robotic-assisted aortic
valve surgery[6], all of which are characterized
by less trauma, less bleeding, and better recovery compared with
conventional aortic valve surgery[7]. With similar
repair results, total thoracoscopic AVR can also be used for complex
valvular lesions, with the advantage of minimally invasive valve
surgery. The upper mini-sternotomy group had significantly reduced 24h
chest drainage, reduced pain, decreased ICU stay and hospital stay when
compared to conventional AVR, which was consistent with the previous
findings of Totaro P et al.[8] and Paparella D et
al[4]. Furthermore, total thoracoscopic AVR had
more favorable perioperative assessment data compared to the upper
mini-sternotomy group, in except for a prolonged CPB as well as AC time.
However, a study by Tokoro M et al. indicated that all-thoracoscopic AVR
had similar CPB and AC times compared to conventional
AVR[9]. Cresce GD et al. showed that the type of
valve may have a significant effect on CPB and AC time, and we were
failed to perform a subgroup analysis because of the insufficient number
of procedures[10]. In addition, since Vola et al.
first reported total thoracoscopic AVR in 2014, only a few centers have
performed further studies on this procedure. We think that factors
including the anatomical characteristics of the patient’s aorta, the
insufficient number of aortic valve procedures performed by the surgeon,
and the insufficient exposure of the surgical field by the assistant
during the procedure limit the development of total thoracoscopic AVR
procedures.
The first is patient selection based on the anatomical characteristics
of the aortic valve structure, in our experience, a wider sinotubular
junction region may be more favorable for thoracoscopic exploration, and
a narrower junction region may result in poorer surgical field of view
exposure. The severity of calcification of the diseased aortic valve may
also render total thoracoscopic AVR more difficult, leading to slightly
unfavorable surgical outcomes. In addition, the height of the aortic
valve position may be another factor affecting the exposure of the
surgical field. In contrast, the conventional AVR, upper mini-sternotomy
AVR, is less demanding on the anatomical characteristics of the aortic
valve and is generally applicable. Technical improvements in
thoracoscopic devices may be a viable solution in the future.
The second is the limitation on the number of heart valve procedures the
surgeon has completed. Based on the valve surgery learning curve
assessment, after completing a sufficient number of right heart valve
procedures, one can attempt mitral valve surgery and subsequently aortic
valve surgery[11], which is also a process of
re-familiarization with the cardiac anatomy. Our previous study
identified the safety as well as reliability of total thoracoscopic
mitral valve repair with superior early postoperative outcomes, with the
exception of prolonged AC and CPB times[12].
Similarly, the increased AC and CPB times are reasonable due to the
limitations of the aortic valve anatomic region as well as the
sinotubular junction region. Our study identified that total
thoracoscopic MVP provided equally satisfactory surgical results
compared to conventional MVP and that stabilization could be achieved
gradually after completion of the 75th procedure, which was similar to
the results of previous learning curve studies of minimally invasive
valve surgery. Although there were significant differences between
different studies, the overall tendency of change in CUSUM was similar,
with the number of total thoracoscopic MVPs required to overcome the
learning curve ranging from 64 to 116[13-15].
However, we failed to perform an assessment of the learning curve of
CUSUM (Cumulative Sum) based on total thoracoscopic AVR due to the
insufficient number.
The third is the insufficient cooperation between the surgeon and the
assistant, decreased cooperation will directly lead to inferior surgical
field exposure, which in turn will affect suturing and knotting results.
It maybe noteworthy that one case of perivalvular leak was observed in
the total thoracoscopic group at the 3-month follow-up, as the incidence
of perivalvular leakage after AVR was less than 0.01 in our center, this
may be the result of inferior suture angles and weak knotting.