Material and Methods
The UK TAVI registry collected data from 100% of the patients who underwent TAVI in any of the 36 TAVI centres in the United Kingdom. Patients undergoing TAVI in England and Wales are linked to the Office of National Statistics by the National Health Service (NHS) Central Register via a unique NHS number. This provides the system for tracking all-cause mortality. Each UK TAVI centre uses the same database, National Institute for Cardiovascular Outcomes Research (NICOR) recommended, and these data are routinely transferred to the National Central Cardiac Audit Database (NCCAD). The NICOR complies the section 251 of the NHS Act 2006, so ethical approval was not mandatory for this retrospective analysis. However, each patient provided a written informed consent both for surgery and research purpose at the time of its TAVI as per standard institutional protocol. Validated life status data were available for patients up to July 2015 so, from January 2007 (UK TAVI registry start) to January 2015, among the 8,320 patients who received a TAVI procedure, we selected the 1,506 patients who underwent SC or TA TAVI. We analysed patients’ demographics, indications for TAVI, procedural characteristics, and adverse outcomes up to the hospital discharge. In our study, the primary outcomes were procedural and in-hospital complications according to VARC-2 criteria (i.e., stroke, major/minor vascular complications, major/minor bleeding, tamponade, permanent pacemaker implantation, acute kidney impairment within 7 days, renal replacement therapy, emergency valve in valve needs, paravalvular leak, balloon re-dilatation), and in-hospital, 30-day, and 1-year mortality. Meanwhile, in our analysis the secondary outcome which was explored was the long-term survival up to 2,900 days. Long-term follow-up was completed in 96% of patients. The average follow-up was 836 days. Statistical analyses were performed using SPSS 25.0 (IBM Corporation, Armonk, NY) and R (The R Project for Statistical Computing). The chi-square and Kruskal-Wallis tests were used as appropriate. For survival analysis, Kaplan-Meier curves were computed, and a log-rank p value was calculated. For the time-to-death analysis, a Cox regression model analysis was applied and a propensity score (PS) matching analysis was employed to address biases, which are related to an observational study. Adjustment for confounding variables was performed by weighting regression model with PS. A Cox proportional hazard model was applied for the primary outcome measure, corrected for Euro SCORE, valve type (self vs balloon expandable), presence and severity of coronary artery disease (one, vs two, vs three coronary arteries), access route (SC vs. TA), heart rhythm (atrial fibrillation vs. sinus rhythm), and year of implantation (2015 vs. 2007). A 2-sided p value <0.05 was considered significant.