Optimal delivery of health care is a common goal of individual physicians, professional organizations, hospital structures and governmental authorities. A growing concern has emerged from the public, media and third payer organizations concerning the quality of care and the amount of resources spending. In the United States, large databases, guidelines and performance evaluation have been elaborated by medical societies, particularly in the area of cardiac surgery. These tools are useful for improvement of patients' care, resources distribution, pay for performance and public and practitioners' awareness. The evaluation of quality is based on composite models combining structure, process and outcome indices. However, pitfalls such as patien...