Contemporary roles of registries in clinical cardiology : when do we need randomized trials?

Clinical registries are established as tools for auditing clinical standards and benchmarking quality improvement initiatives. They also have an emerging role (as electronic health records) in cardiovascular research and, in particular, the conduct of Randomized Controlled Clinical Trials (RCTs). Whilst the RCT is accepted as the most robust experimental design, observational data from clinical registries has become increasingly valuable for RCTs. Data from clinical registries may be used to augment results from RCTs, identify patients for recruitment and as an alternative when randomization is not practically possible or ethically desirable. Here we appraise the advantages and disadvantages of both methodologies, with the aim of clarifying when their joint use may be successful.