Background: The Canadian Cardiovascular Society (CCS) grading of angina pectoris was described in the medical literature in 1976.
Objectives: To describe the origin of this grading, its worldwide acceptance, critiques, perceived limitations and alternative systems.
Methods: The present author, who chaired the CCS ad hoc committee that developed this grading system in 1972, used documentation based on personal correspondence, and information from medline and international citation indexes searches.
Results: The CCS committee's mandate was to standardize the definition of terms used in reporting studies of coronary artery disease and coronary artery bypass graft surgery. The committee defined a four-level system modelled on the New York Heart Association functional classification of patients with diseases of the heart, and the American Medical Association classes of organic heart diseases. Threshold activities that produced angina were detailed to assess reliably the severity of exertional angina by independent observers, and changes over time. The grading system has been cited over 650 times in the literature since its official publication in 1976. Although this grading system was found to be generally relevant and practical, several imperfections and potential limitations were reported, the most pertinent being the criterion "anginal syndrome may be present at rest" included in grade IV, which was found to be inappropriate and confusing. The prognostic significance of the grading system, despite the finding that this was not its primary goal, was also thought to be inadequate.
Conclusion: Although this grading system of the severity of effort angina has been accepted throughout the world over the past 30 years, a revision is desirable considering its potential imperfections and inconsistencies with present day management of ischemic heart disease.