Referral to outpatient cardiac rehabilitation: intervention research at the patient, provider, and health system levels.

This article sets out the clinical context of the research presented by Grace et al. in an accompanying article in this journal. Secondary preventive measures against cardiovascular disease, such as outpatient cardiac rehabilitation (OCR), can greatly reduce associated burden on health systems. Here, I discuss the study carried out by Grace and colleagues--a multilevel study of the contribution of patient and physician factors to cardiac rehabilitation referral. Grace et al. demonstrate that both physician and patient factors have key roles in OCR referral. In this commentary I explore the limitations of studying the factors that contribute to referral alone as a final end point given the lower-than-desired rates of enrollment among referred patients.