3.5 Incidence of major adverse events per surgeon
Six surgeons (total number of procedures during the three-year period of
72, 36, 23, 14, 13, and 10, respectively) have completed 168 transaortic
septal myectomy procedures. A total of 11 major adverse events were
recorded, including surgical death (one patient), complete
atrioventricular block (5), residual obstruction (3), and moderate
residual MR (2). As shown in Table 3, no significant difference was
found among all surgeons regarding the incidence of major adverse events
(p=0.739).
Discussion
In the 1960s, Morrow et al have reported transaortic resection of a
small amount of muscle from the proximal ventricular septum, a technique
generally described as classic Morrow operation. Over the next decades,
myectomy has evolved from the classic Morrow operation to a more
extended septal myectomy guided by preoperative cardiovascular magnetic
resonance and intraoperative TEE [15-18]. High
technical difficulty, however, limited clinical application of the
extended septal myectomy procedure. In 2015, Ferrazzi et al proposed the
transaortic secondary chordae cutting in addition to a shallow septal
myectomy for the treatment of HOCM [8]. It was
reported to be associated with favorable results [8,
19]. However, such an approach remained controversial because the
secondary chordae maintains ventricular geometry and enhances wall
thickening, which may be helpful in the presence of left ventricular
dilation and systolic dysfunction [20]. In this
study, with the aid of special surgical instruments, transaortic septal
myectomy was performed in 168 patients with HOCM and drug refractory
symptoms. Favorable results were achieved, including a low surgical
mortality (<1%) with no occurrences of deaths or
re-interventions at follow-up, a significant improvement of quality of
life with recovery from symptoms and NYHA functional class I and II, an
effective relief of LVOT obstruction, and a reliable reduction of MR.
The observed good survival and a significant improvement in NYHA
functional status coincided with an effective relief of LVOT obstruction
and a reliable reduction of MR, which confirmed the safety and efficacy
of transaortic septal myectomy with the aid of special surgical
instruments in the treatment of symptomatic HOCM.
In this series including 168 transaortic myectomy procedures with the
aid of special surgical instruments, the mean duration of aortic
cross-clamping was 36.0 ± 8.1 minutes (median, 35.0 min), which was
significantly lower than the value (median, 68 min) reported from a
famous and experienced myectomy center in the same country[21]. The reason for this difference may be that
the application of special surgical instruments may be beneficial in
reducing the technical challenges of myectomy and shortening operation
time.
Note that 7 HOCM patients in this series suffered from midventricular
obstruction and underwent transaortic septal myectomy with the aid of
special surgical instruments. Favorable results suggested that the
application of special surgical instruments made it easy to remove the
myocardium at the base of PMs, even to extend to the apex of the left
ventricle. The surgical comfort of the operator is essential for a
myectomy surgeon, especially for an inexperienced myectomy surgeon.
These may attribute to the small operational radius of the special
instruments. Moreover, the application of special surgical instruments
is beneficial for an adequate length of septal excision, which is
extremely important to surgical effect [14].
In addition, six surgeons with greatly varied operation volume have
completed 168 myectomy procedures. Favorable results were achieved, and
no significant difference was found among six surgeons regarding the
incidence of major adverse events, which suggested that the application
of special surgical instruments during transaortic septal myectomy may
be a promising treatment option for HOCM, with good and reproducible
results.
Complete atrioventricular block, left ventricular free wall rupture,
aortic valve injury and iatrogenic septal perforation were the main
complications of septal myectomy. In the present cohort, the incidence
of pacemaker implantation (3.0%) was greater than expected based on
other large series [22, 23]. This elevated
incidence was attributed to the excessive subaortic resection to the
side of the noncoronary valve when the incision beginning just to the
right of the nadir of the right aortic sinus was made. More than 41.0%
of patients developed complete left bundle branch block after myectomy,
which allowed the adoption of conservative surgical strategies in
patients with preoperative right bundle branch block. In this series,
left ventricular free wall rupture, a rare complication after myectomy,
occurred in 2 (1.2%) patients, and was successfully treated under
cardiopulmonary bypass and cardioplegic arrest with a double-armed 3-0
polypropylene suture with a pledget placed in a horizontal mattress
fashion, similar to the technique described to control a stab wound to
the heart in close proximity myectomy to a coronary artery. Left
ventricular free wall rupture may be associated with excessive subaortic
resection to the mitral anterior commissure when the incision that began
just to the right of the nadir of the right aortic sinus was made.
Although abnormal papillary muscles were corrected, left ventricular
free wall rupture was indicated via operative exploration to not be
associated with the excision of muscle bundles. In principle, aortic
valve injury and iatrogenic septal perforation were prone to occur in
young patients with small aortic roots and old patients without severe
septal hypertrophy, respectively. In this series, ventricular septal
perforation occurred in one female patient aged 70 years with a
preoperative septal thickness of 17.0 mm. Although the perforation was
repaired using a bovine pericardium patch, a residual ventricular septal
defect was observed during follow-up and may be associated with the thin
myocardium surrounding of the perforation and the small patch that was
not large enough to extend beyond the edge of the perforation at a
certain distance.
This study had some potential limitations. First, this was a
single-center, single-armed observational study with a limited sample
size, which may have influenced the generalizability of the results.
Second, only a minor part of patients received cardiac magnetic
resonance imaging, as it did not serve as a regular examination modality
in the early times at our institution. Third, a functional capacity
assessment tool, such as the 6-minute walking test, and a quality of
life assessment tool, such as the SF-36 questionnaire, were not utilized
in this study. Finally, the duration of follow-up was relatively short.
It needed longer observation to confirm our findings.
Conclusion
The application of special surgical instruments may contribute to
reducing the technical difficulty of myectomy. Transaortic septal
myectomy procedure with the aid of special surgical instruments achieved
favorable and reproducible results, and thus may be a promising
treatment option for HOCM.