OBJECTIVE : Computed tomography (CT)-determined skeletal muscle measures have been used for predicting postoperative outcomes in patients undergoing transcatheter aortic valve implantation (TAVI). We investigated the impact of CT-determined muscle quantity (measured as psoas muscle area [PMA] and psoas muscle index [PMI]) and quality (measured as psoas muscle density [PMD]) on hospital length of stay (LOS) after TAVI. METHODS : We retrospectively identified 182 consecutive patients who underwent TAVI between March 2013 and August 2017 with adequate preprocedural CT imaging. Baseline demographic and clinical data, the Society of Thoracic Surgeons score, the essential frailty toolset (EFT) frailty rating, and precontrast PMD, PMA, and PMI were obtained in all study patients. The primary outcome was prolonged postoperative LOS defined as greater than 14 days. RESULTS : Patients with prolonged LOS had a significantly higher Society of Thoracic Surgeons score (p < 0.001) and significantly lower PMD (p < 0.001) than those with LOS ≤14 days. More patients with prolonged LOS had concomitant peripheral vascular disease (p = 0.001), had undergone percutaneous coronary interventions (p = 0.022), and had an EFT score ≥4 (p < 0.001) compared to those without prolonged LOS. Neither PMA (p = 0.123) nor PMI (p = 0.271) were associated with prolonged LOS. Multivariate analysis identified EFT score ≥4, the presence of peripheral vascular disease, and PMD as independent predictors of prolonged LOS. CONCLUSIONS : The precontrast CT-determined muscle quality measurement PMD is a simple and objective predictor of prolonged LOS after TAVI.