[OBSERVANT: observational study of appropriateness, efficacy and effectiveness of AVR-TAVI procedures for the treatment of severe symptomatic aortic stenosis. Study protocol].

Rationale: Severe symptomatic aortic stenosis (SSAS) is the most common acquired valvular heart disease in the western world, and its prevalence is strongly linked to the phenomenon of population ageing. After symptom onset, patients with SSAS, if untreated, show very poor prognoses, unavoidably reaching complete disability status with a significant reduction in survival. Although aortic valve replacement (AVR) is the definitive therapy for this kind of patients, a new, less-invasive alternative like transcatheter aortic valve implantation (TAVI) has been considered, at least for a large proportion of patients with very high or prohibitive operative risks. OBSERVANT represents the first observational multicenter perspective study on the comparative effectiveness of TAVI, AVR, and medical therapy in the Italian population with SSAS.
Materials and Methods: In the participating hospitals, to define the patient risk profile for each patient with SSAS, data on demographic characteristics, health status prior to intervention and presence of comorbidities will be collected. Moreover, complete information on the type of intervention will be gathered. Mortality within 30 days from intervention is the primary adverse outcome. Secondary outcomes include mortality within 12 and 24 months and the incidence of in-hospital major adverse cardiac and cerebrovascular events. Clinical monitoring procedures will allow assessment of the reliability and completeness of the database and help maintain constant quality control. To compare the effectiveness of AVR, TAVI, and medical treatment in terms of medium- and long-term outcomes, accounting for possible differences in patient case-mix among the three treatment groups, risk adjustment techniques will be applied.
Expected Results: Short-, medium-, and long-term outcome in patients undergoing one of the three SSAS treatments; use, appropriateness, and economic and organizational impact of TAVI and AVR procedures; specific "indication criteria" to guarantee appropriate patient selection for AVR or TAVI; new pre-procedure risk score, specific for the elderly Italian population; guidelines on TAVI procedure coding and a system of administrative follow-up to be proposed to the regional health systems for managing the use of the AVR or TAVI procedures.
Conclusions: The complete knowledge base derived from this study will be directly transferable to professionals and policy makers, giving them evidence-based results for use in their decision-making process.