OBJECTIVES: Aortic valve stenosis is a chronic and progressive valvular heart disease. The standard treatment of this condition involves a major open surgery. For patients currently ineligible for surgery, medical management is the only option available. Transcatheter aortic valve implantation (TAVI) devices recently appeared as a new less invasive treatment option. The objective of this study was to develop an exploratory cost-effectiveness analysis of TAVI vs Optimal Medical Treatment (OMT) in the Portuguese Setting. METHODS: This analysis used a Markov model developed by Oxford Outcomes to assess costs and benefits of TAVI vs OMT. A short term sub-model represents the first 30 days after TAVI  (cycle length of one day), whereas a long term model (cycle length of one month) considers a 10-year time horizon. For TAVI patients the health states considered are ICU, General Wards, Home, Re-operation and Death. OMT patients are in either Home or Dead health states, receiving medication until death and at risk of co-morbidity-related hospitalisations. Portuguese NHS healthcare resource consumption was retrospectively collected at Hospital de Santa Cruz in Lisbon for a cohort of 44 high risk AS patients (21 TAVI; 23 OMT), over a period of 11 months. Clinical parameters, transition probabilities and utility values were derived from relevant literature. Costs were taken from the official Portuguese published tables and hospital reports. Costs and benefits were discounted at 5% p.a. Probabilistic and one-way sensitivity analysis were performed. RESULTS: Treatment with TAVI compared to OMT increased life years by 1.7 (3.13 vs. 1.46) and quality-adjusted life years (QALYs) by 1.4 (2.23 vs. 0.80). Direct costs were 32,067€ with TAVI and 4,662€ with OMT. Incremental Cost Effectiveness Ratios (ICERs) estimated are 16,375 € /LYG and 19,180 € /QALY. CONCLUSIONS: TAVI is highly likely to be a cost-effective intervention for the treatment of AS in patients who are currently ineligible for surgery.