By Olaf Wendler and Martyn Thomas
The outstanding results of Cohort B of the PARTNER trial have now been published. It is interesting to compare these randomised trial results with those of the “real world” SOURCE European registry and to speculate on any reasons for differences in outcomes. The 30-day results of the >2,300 patients in the SOURCE registry having both transfemoral (TF) and transapical (TA) procedures are displayed in Figure 1.
It is important to note that all patients receiving TAVI in the Cohort B of the PARTNER trial were treated using the transfemoral approach. Nonetheless, the 5% all-cause 30-day mortality reported is a remarkable achievement by the operators. Both these results and the SOURCE registry data indicate that, with appropriate training and proctorship, balloon-expandable TAVI can be safely introduced into clinical practice. It can now reasonably be quoted to a patient that the 30-day transfemoral mortality for TAVI using the Edwards Sapien device is in the region of 5–8%.
The one-year results for the PARTNER trial and the SOURCE registry are shown in Figures 2 and 3. Figure 2 shows the one-year mortality in the PARTNER trial, Cohort B and Figure 3 shows the one-year survival in Cohort 1 of the SOURCE registry.
The remarkable treatment effect of TAVI in the PARTNER trial is displayed in Figure 2 with only five patients requiring treatment to avoid a single mortality at one year. However, it is interesting to see that the initial improved 30-day survival in the PARTNER trial is not resulting in improved one-year survival, which is 70% compared to >80% in the transfemoral group in the SOURCE registry.
This almost certainly is explained by the differences of the patient populations in both studies (Figure 4). In contrast to the PARTNER trial, where only absolute surgical turn-downs were included in Cohort B, the SOURCE registry patients were selected based on their high risk for conventional aortic valve surgery.
Although a direct comparison between studies with different selection criteria is always difficult to make, Figure 4 demonstrates that in the PARTNER trial, Cohort B randomised patients seem to have higher risk profiles than the transfemoral SOURCE patients. This difference in comorbidities is likely to explain the difference in one-year outcomes between the two studies. Nonetheless, it is clear that balloon-expandable TAVI should become the “standard of care” in the PARTNER trial, Cohort B inoperable types of patients, if deemed appropriate by a multidisciplinary team.
Results of Cohort A of the randomised trial (patients considered appropriate, but high risk surgical candidates) will be available in 2011. The demographics of this cohort are likely to be more similar or even lower risk compared to the SOURCE registry patients, which is likely to result in improved one-year survival. The comparison of these survival rates with the Cohort A surgical arm in the randomised trial will have a huge influence on the speed of adoption for the TAVI procedure.
The next challenge for the technology will be to reduce the incidence of paravalvular leakage, stroke and vascular complications; as well as acquiring quality of life information to allow cost-effectiveness to be assessed. In addition, the development of a dedicated TAVI “risk score” to predict 30-day and one-year survival is urgently required. It will also be important to see what impact the next generation of transcatheter heart valves (Edwards Sapien XT) and delivery systems, released in Europe this past year, will have on outcomes. These major goals will be addressed with the next line in the SOURCE family of registries, with SOURCE XT registry, commencing early in 2011.
Olaf Wendler is clinical director for Cardiology and Cardiothoracic Surgery, King’s College Hospital, London, UK, and co-principal investigator SOURCE registry. Martyn Thomas is clinical director of Cardiovascular Services, Guy’s and St Thomas’, London, UK, and co-principal investigator for the SOURCE registry