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.