Discussion
The main purpose of the present study was to identify whether short- and
long-term postoperative outcomes after LVAD implantation were related to
preoperative ESM mass. Pre-LVAD-implantation frailty might affect
postimplant mortality 6. Regarding the evaluation
method of frailty, the condition of the skeletal muscles might reflect
the patients’ frailty, i.e., sarcopenia. Their predictive potential for
clinical outcomes was examined in this study. In the setting of LVAD
implantation, it was demonstrated that the quantity of the pectoralis
major muscle provides predictive information on the clinical outcomes
after LVAD implantation 7,8. However, many authors
have reported that antigravity muscles might reflect the patients’
frailty more effectively in predicting postoperative outcomes5,9. Thus, we focused on the ESM as a predictor of
postoperative outcomes in patients with LVAD in our evaluation.
In contrast to our hypothesis, a smaller ESM mass was not confirmed as
the main determinant of in-hospital mortality, MACE, and follow-up
mortality in this study. In recent years, the ESM has often been
evaluated in the field of pneumology as a useful prognostic factor for
assessing clinical outcomes. Decreased physical activity due to lung
dysfunction, e.g., in chronic obstructive pulmonary disease, pulmonary
fibrosis, infection, and even post-lobectomy status causes muscle
weakness in the antigravity muscles, which predicts the clinical
prognosis of such patients 2,4,5,10. Interestingly, a
study of patients who underwent liver transplantation due to end-stage
liver disease also reported that the paraspinal muscle index, i.e., the
combined mass index of the psoas muscle and ESM, was an independent
predictive factor for early posttransplant survival in male patients3. Regarding the effectiveness of antigravity muscle
analysis as a predictive preoperative factor for the postoperative
outcomes in patients with LVAD, Heberton et al. demonstrated that
sarcopenia patients defined by the psoas muscle area showed a numeric
tendency of higher mortality and longer hospital stay without
significant difference in each clinical outcome, whereas sarcopenia was
an independent predictive factor in patients who suffered from either
higher mortality or had longer hospital stays 11. The
authors concluded that a low psoas muscle area might represent a higher
mortality or longer hospital stay risk in patients with LVAD. This is
similar to our result that a smaller ESM index proved to be an
independent risk factor for a longer hospital stay in this study.
Moreover, we demonstrated that the MELD score and preoperative va-ECMO
implantation are risk factors for MACE and in-hospital mortality,
respectively. Regarding the MELD score, this issue has already been
reported by our team 12. We suppose that this is the
key reason why skeletal muscle evaluation, for example, of the e.g., ESM
or the psoas muscle, would not allow speculation on the clinical
outcomes in LVAD patients. This means that patients undergoing LVAD
implantation who already have visceral organ decompensation have a poor
prognosis regardless of the manifestation of muscle atrophy.
Thus, we conclude that ESM mass is not associated with acute severe
clinical outcomes, such as MACE or in-hospital mortality. In contrast,
the ESM may be used to estimate the length of hospital stay of patients
who survive the acute phase after LVAD operations. Furthermore, ESM mass
did not predict the long-term survival outcome because of the
multifactorial complication risks in LVAD patients.
This study had several limitations. First, this was a retrospective
analysis with a limited cohort size of non-randomized patients. Second,
this was a single-center study, meaning that potential systemic
measurement errors and factors could influence the outcomes. Third, the
patients undergoing LVAD implantation were heterogeneous in their
characteristics, whereas we analyzed all patients as a homogenous cohort
in this study. The subanalysis depending on more defined categories,
e.g., baseline disease or disease status, and even the type of LVAD
devices, provides a more detailed insight into the confirmation of our
conclusions. Therefore, further studies are required.