Interpreting the current data on transcatheter aortic valve implantation: a difficult task

Since 2002, more than 20 000 transcatheter aortic valve procedures have been performed worldwide. The Edwards SAPEIN heart valve and Medtronic CoreValve system share the wealth of this experience. Up until now, the medical evidence in support of transcatheter aortic valve implantation (TAVI) has relied upon single-arm clinical studies: first-in-man (FIM) trials, European pre-marketing safety and feasibility trials, post-marketing surveillance registries and studies, and physician-driven, single-centre observational series. Although critical for market launch, these studies do not address the important clinical questions: Is TAVI associated with less morbidity and mortality compared to conventional surgical aortic valve replacement (SAVR) in high surgical risk patients? Is TAVI associated with less morbidity and mortality compared to balloon aortic valvuloplasty/medical therapy in prohibitive risk surgical patients? The difficulty with interpreting the current data on TAVI also relates to the significant heterogeneity in clinical endpoint definitions that exist across studies. Not only have the definitions differed, but also the components of safety and efficacy.1 An overview of clinical trials either completed or in progress with Medtronic or Edwards Lifesciences transcatheter heart valves is presented in Figure 1 . It is beyond the scope of this communication to review the clinical results of these trials. Figure 1 ( A and B ) TAVI clinical trials completed, ongoing, or planned with either the (A) Medtronic CoreValve System or (B) Edwards transcatheter heart valve. Although clinical evidence forms the backbone of the pre-market conformity assessment process, pre-market clinical investigations are typically associated with inherent limitation. The relatively short follow-up periods and small patient numbers may not allow physicians and manufacturers to appreciate the occurrence, severity, and best detection methods for infrequent complications (e.g. prosthetic valve thrombosis or endocarditis) or for those complications which may be associated with longer term follow-up (e.g. structural valve dysfunction). Furthermore, pre-market assessment occurs within the confines …