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.