EVAR is now the most predominant method of repair of AAA, with approximately 65% of AAA in the UK undergoing EVAR[1]. Current NICE guidelines recommend selective use of pulmonary function tests (PFTs) and cardiopulmonary exercise testing (CPEX) to aid in decision making in the pre-operative planning of elective aneurysm repair[2]. Sarcopenia is defined as progressive loss of skeletal muscle volume and function, and is associated with reduced performance status, increasing frailty, and inferior surgical outcomes[3]. Body composition analysis on perioperative CTs provides values of cross-sectional muscle areas (PMI, SMI) and density (SMD) which are associated with sarcopenia. PMI and SMI have shown to provide prognostic value in patients undergoing a range of surgical procedures[4]. High adipose tissue areas (VFI, SFI, TFI) have been shown to confer superior prognosis in patients with cancer[5], though remain unreported in AAA cohorts. The mechanism by which low muscle indices lead to inferior procedural outcomes is poorly defined. Body composition analysis is currently limited to the research setting, however is a promising potential clinical tool for risk stratification. Data describing an association between body composition and performance at CPEX are limited to published abstracts in AAA patients undergoing open surgical repair[6], or studies of patients undergoing major colorectal or hepatobiliary resection for cancer[7], [8]. The relationship between fat indices and CPEX parameters is undescribed. This study aims to describe the relationship between pre-operative CT-derived body composition and CPEX parameters in patients undergoing EVAR and F/B-EVAR for AAA.

This single centre study retrospectively identified 259 consecutive patients who underwent EVAR and F/B-EVAR between 01/01/2015 and 01/01/2021. Patients who did not undergo either PFTs or CPEX were excluded, and patients who underwent the procedure for non-aneurysmal disease were excluded. Where only certain parameters were unavailable, patients were selectively excluded from relevant analyses. Metabolic equivalents (METS) were also recorded from patient pre-assessment records. Body composition analysis was performed on pre-operative CTs at the L3 vertebral level using previously described methodology[9]. Low tertiles of PMI, SMI, VFI, SFI, and TFI were compared with mid and high tertiles. Anaerobic threshold (AT) <11.1 ml/min/kg was considered low in keeping with current practice. Statistical analyses were performed using IBM SPSS v28.0.

178 patients had FEV1 and FVC values available, and 148 had full CPEX results available. 91.9% patients were male and mean (SD) age was 74.7 (5.9) years. There were 2 emergency cases who had undergoing elective planning hence had CPEX available; the remainder were elective cases. There were significantly lower values of FEV1, FVC, and VO2Peak in the low PMI and SMI subgroups (p < 0.01). Patients in the low SMD tertile recorded lower AT and VO2Max (p < 0.01). Patients in the low VFI, SFI, and TFI tertiles recorded higher values for both AT and VO2Max (p < 0.01 for all comparisons), whilst VO2Peak was significantly lower in the low VFI tertile (p < 0.001). METS were significantly lower in the low SMI and SMD tertiles (p <0.05). When analysed as continuous variables, increasing VFI (OR 1.01, 95% CI 1.00 - 1.02, p < 0.01), SFI (OR 1.02, 95% CI 1.01 - 1.03, p < 0.001), and TFI (OR 1.01, 95% CI 1.00 - 1.02, p < 0.001) were all associated with AT < 11.1 ml/min/kg.

The present study describes the relationship between pre-operative CT-derived body composition and functional physiological testing. Our results support those reported in patients with cancer, and add the novel association between fat indices and CPEX performance. SMD is a marker of skeletal muscle function and is associated with superior cardiorespiratory fitness in our patient group in keeping with other authors[7]. Greater physiological fitness is present in patients with low fat indices. The inverse relationship observed between VFI and VO2Peak may relate to the effort-dependent nature of VO2Peak testing. The subjective (patient reported) METS values are associated with skeletal muscle parameters despite their inherent limitations. Our results support the growing body of evidence around body composition analysis as a predictive tool for perioperative risk stratification and patient selection.

[1] VSQIP, "VSQIP 2019 Annual Report." [Online]. Available: https://www.vsqip.org.uk/reports/2019-annual-report/. [2] "NICE Guideline [NG156]| Abdominal aortic aneurysm: diagnosis and management | Guidance | NICE," NICE. Accessed: Aug. 04, 2021. [Online]. Available: https://www.nice.org.uk/guidance/ng156. [3] A. J. Cruz-Jentoft et al., "Sarcopenia: revised European consensus on definition and diagnosis," Age Ageing, vol. 48, no. 1, pp. 16-31, Jan. 2019, doi: 10.1093/AGEING/AFY169. [4] T. Abbass, R. D. Dolan, and D. C. McMillan, "Computed tomography-derived body composition analysis in patients with advanced cancer: clinical utility and future research," Current opinion in supportive and palliative care. 2020, doi: 10.1097/SPC.0000000000000529. [5] M. Ebadi et al., "Subcutaneous adiposity is an independent predictor of mortality in cancer patients," Br. J. Cancer, vol. 117, no. 1, p. 148, Jun. 2017, doi: 10.1038/BJC.2017.149. [6] A. Staniszewska, M. Ramage, J. Miller, and A. Tambyraja, "Sarcopenia, Core Muscle Size and Cardiopulmonary Performance in Patients with Large Aortic Aneurysm," Eur. J. Vasc. Endovasc. Surg., vol. 58, no. 6, p. e151, Dec. 2019, doi: 10.1016/J.EJVS.2019.06.698. [7] M. A. West et al., "Myosteatosis is associated with poor physical fitness in patients undergoing hepatopancreatobiliary surgery," J. Cachexia. Sarcopenia Muscle, 2019, doi: 10.1002/jcsm.12433. [8] A. E. M. Berkel et al., "The association between preoperative body composition and aerobic fitness in patients scheduled for colorectal surgery," Colorectal Dis., vol. 24, no. 1, pp. 93-101, Jan. 2022, doi: 10.1111/CODI.15941. [9] R. D. Dolan, Y.-T. Tien, P. G. Horgan, C. A. Edwards, and D. C. McMillan, "The relationship between computed tomography-derived body composition and survival in colorectal cancer: the effect of image software," JCSM Rapid Commun., vol. 3, no. 2, pp. 81-90, Jul. 2020, doi: 10.1002/RCO2.15.