RESEARCH METHODS IN CLINICAL CARDIOLOGY . 7. EXPERIMENTAL STUDIES IN CARDIOLOGY

Experimental designs in clinical investigation are discussed in this a rticle. Guideline examples have been used in the area of Cardiology us ing always the same one only one whenever possible. We have looked for a different perspective from what is generally used in the discussion of the general characteristics of experimental designs, and more spec ifically of clinical trials and we deal with the aspects of clinical t rials which are usually ignored due to their marginal character. We al so discuss those characteristics which differentiate clinical trials i n respect to other designs and types of questions which are answered b y clinical trials. And we finally discuss various aspects such as rand omization and its various types (simple, block, stratified, pre-random ized) and variable types of evaluating the answers, masking and the pr oblems in its maintenance, with certain kinds of designs, sample size, etc. There is a brief mention of two particular cases: factorial and cross over designs are both discussed, mentioning their strong and wea k points. Likewise, we discuss community trials as another experimenta l design and examples are provided. Finally, we discuss aspects of cri teria: such as, When to stop the trials? or Who are the results applic able to?, and we suggest points to take into consideration when these decisions are made.