Several recent observational registries have suggested that patients with low risk scores had good clinical outcome after TAVR. Going one step further, three studies used propensity score analysis to match pairs of TAVR and SAVR patients with STS scores between 3 and 8 % [32–34], (Table 26.2) and showed similar mortality at 30 days and 1 year. However, even a careful propensity score adjustment analysis can only compensate partially for the imbalance in characteristics between groups and the only way to perform an accurate comparison is randomised studies between SAVR and TAVR in patients at intermediate risk. Acknowledging all the limitations previously described in the definition of this group, several trials have been designed to provide such an evidence-based comparison in intermediate risk patients: PARTNER 2a cohort A in the USA, which has completed enrolment; SURTAVI, the UK TAVI trial and finally the Nordic aortic valve intervention trial, which are still enrolling patients in Europe.

Tables 26.3 and 26.4 show the current clinical outcomes at 30 days in recent registries. The most recent trials and registries show a decrease in mortality form 15–20 % to 5–7 % [5, 7–11]. This is in large part due to a decrease in complications with improved case selection, device and procedural refinements and increased operator experience [35]. Rare but dramatic complications such as annular rupture or coronary occlusion may occur during the procedure in less than 0.5 %. The incidence of such complications will decrease if not disappear due to very careful pre-procedural screening and their consequences could be limited by an efficient surgical back-up [36, 37]. Paravalvular leaks remain a concern and a comprehensive multiparametric evaluation is key during the procedure. Moderate to severe paravalvular leak carries a poor prognosis while the prognostic impact of mild paravalvular leak is still debated [38]. In the future paravalvular leaks will decrease due to better sizing using 3D imaging and new valve technology. In this respect the results obtained by the new devices are very promising with moderate to severe paravalvular leaks occurring in less than 5 % [39, 40]. Strokes remain an issue. TAVR-associated strokes are multifactorial in origin. Over time it seems that stroke frequency after TAVR has been declining. A recent randomised comparison, including a neurologic assessment, showed that the incidence of major stroke after TAVR is not higher than that of surgery [5]. In the future the incidence of stroke is likely to decrease due to the use of protection devices for which there are promising signs of efficacy, and better pharmacology and prevention of arteriosclerosis. Major vascular complications and bleeds still occur in around 10 % of cases [41]. The reduction of sheath size, which is now down to 14 French, and refinement of the percutaneous suture device technique will improve these figures. Careful patient selection using an integrative approach, including MSCT and angiography, and heart team discussion as regards the use of an alternative approach, will no doubt further decrease these complications. The need for a permanent pacemaker varies considerably and is significantly higher with a self-expandable prosthesis than with a balloon-expandable prosthesis. The negative influence on outcome is still debated in the elderly population currently treated [42] but could be significant when dealing with younger patients. The incidence of renal failure is also an important predictor of poor outcome and should decrease by lowering the use of contrast media and better patient selection.

Overall, the incidence of TAVR-related complications is most likely to further decrease over time thanks to better patient selection and also better management by the Heart Team as well as the availability of more refined devices.

Durability is a very important issue. It is important to know when and how the prosthetic valves are going to fail. TAVR prostheses and surgical bioprostheses have similar features and the same major causes of failure are expected: calcification and tears in the valve cusp resulting in regurgitation or stenosis. However, transcatheter heart valves are prepared and placed into a delivery system and long-term effect on the longevity of valve leaflet is unknown and may only become apparent on long-term follow-up. TAVR is a relatively new therapy and long-term data over 5–6 years are scarce [21]. However, the studies currently available don’t show an alarming incidence of structural degeneration, leaflet thickening, calcification, thrombus formation, or endocarditis over time [43]. A larger number of patients together with longer follow-up is needed for an accurate assessment of durability. It will be difficult to extrapolate data obtained in the current patient population, that’s to say elderly patients (over 80 years old), to younger patients where the deterioration of bioprostheses occurs earlier. In the event of accelerated valve failure low-risk patients would remain candidates for surgery or valve-in-a-valve TAVR could be an option. The positive results obtained so far with valve-in-valve in failing bioprostheses are encouraging but the experience in valve-in-valve after TAVR is very limited.

Finally, the specific problem of the feasibility of subsequent percutaneous coronary intervention in patients who have a TAVR prosthesis in place could be an issue and data are very limited.