Clinical evaluation and analysis of heart valve substitutes.

We discuss the clinical assessment of heart valve substitutes, primarily with regard to pre-market evaluation. We concentrate on the current FDA heart valve guidance document. This guidance is self-acknowledged to be an evolving document, scheduled to be revised between three and five years after its initial release on December 1993. We outline the history and some of the strengths of the present system, and discuss areas for possible improvement. We selected one important statistical issue to address thoroughly how to compute the confidence limit of a linearized rate.