Psoas Muscle Area as a Prognostic Factor for Survival in Patients with an Asymptomatic Infrarenal Abdominal Aortic Aneurysm: A Retrospective Cohort Study

Abstract

Loss of muscle mass has been associated with poor survival in several surgical patient populations, including those with an abdominal aortic aneurysm (AAA). We wanted to replicate these findings and assess the association between psoas muscle area (PMA) and survival in patients with an asymptomatic AAA. Patients with an asymptomatic infrarenal AAA who underwent computed tomography (CT) scanning between January 1, 2007, and December 31, 2013, were included in this single-centre retrospective cohort study. PMA was measured with thresholding on an axial image at the centre level of the third lumbar vertebra. The lowest tertile of PMA in all patients was used as a cutoff value for a low PMA. Then, in separate analyses for conservatively and surgically managed patients, survival was estimated with the Kaplan-Meier method. Differences in survival between patients with and without a low PMA were tested with the log-rank test. Of 228 patients, 104 were managed conservatively and 124 underwent AAA repair. Seventy-seven patients (62%) had an endovascular repair. In these 228 patients, the median PMA was 16.83cm2, while the cutoff value for low PMA was 14.56cm2. Patients who were managed conservatively were more often classified as having low PMA (45/104, 43%, vs. 31/124, 25%; p=.004) and were significantly older (mean 73.44±9.05 years vs. 69.03±7.46 years; p<.001). Low PMA was not associated with survival, either in patients managed conservatively, or in those who underwent AAA repair (p=.512 and p=.311, respectively). The association between low PMA and poor survival could not be replicated; in this study, low PMA was not associated with survival in patients with an asymptomatic AAA. Further research is recommended before PMA can be used for pre-operative risk stratification.