In this longitudinal study, routine contrast-enhanced thoracic CT angiography (CTA) proved instrumental for established the prognostic role of sarcopenia evolution and its association with mortality risk in patients undergoing transcatheter aortic valve replacement (TAVR). To this end, the pectoralis muscle index (PMI), a surrogate for sarcopenia, was measured at baseline and 1-year follow-up in 258 TAVR patients (median age: 72.86), who were categorized as non-sarcopenic, early-onset sarcopenic, late-onset sarcopenic, or persistently sarcopenic. During a median follow-up of 1,495 days, overall mortality was 12.79%. Both baseline and follow-up PMI values independently correlated with survival outcomes, with median PMI values of 1,067.19 mm²/m² and 1,145.95 mm²/m², respectively. Patients with persistent sarcopenia, accounting for 17.83% of the cohort, showed a significantly higher risk of mortality compared with non-sarcopenic subjects, with a hazard ratio of 3.94 (95% CI: 1.44–10.80; p = 0.008). These findings highlight the potential value of routine thoracic CTA as a clinically feasible method for prognostic stratification in TAVR recipients. This imaging tool may contribute to identify persistently sarcopenic individuals at high risk of mortality who could benefit from targeted nutritional interventions and structured rehabilitation strategies.