The role of cardiac registries in evidence-based medicine

Cardiovascular disease remains the primary cause of mortality, and a major cause of disability in the developed world.1 This significant burden necessitates ongoing improvements in patient management, to minimize the impact of cardiovascular conditions on both patients and healthcare systems. These improvements in cardiovascular care are promoted by an evidence-based approach, shaped by comprehensive clinical guidelines. The scientific basis of recommendations is an important feature of clinical guidelines, and influences the degree to which they are followed in clinical practice.2 Recent studies have assigned the highest evidence grading to randomized controlled trials (RCTs) that are clinically important, and representative of the clinical population covered by the guideline recommendation.3 For example, this highest grading was assigned to a recommendation based on a meta-analysis of RCTs showing low-dose diuretics to be the most effective first-line treatment for cardiovascular event prevention in hypertensive patients. This study reviewed data from 42 RCTs which were, crucially, representative of the population that the recommendation was made for (i.e. hypertensive patients).3,4 The importance of the applicability of evidence to recommendations highlights the need to consider evidence from clinically relevant situations, not all of which have been assessed by RCTs. This evidence can originate from expert consensus, as well as non-randomized prospective studies. Although generally providing a lower evidence-level than RCTs,3,5 observational studies can make an important contribution to the evidence base when the study outcomes are clinically important, and the populations involved are representative. Indeed, information from several registries was considered in the recent American Heart Association Acute Coronary Care in the Elderly Scientific Statement.6 Non-randomized prospective registries document the treatment and outcomes for consecutive patients in clinical practice. Therefore, data are gained from a ‘real-world’ selection of patients, many of whom would be excluded from RCTs, …