BACKGROUND:An important treatment-risk paradox exists in the management of acute coronary syndromes (ACSs). However, the process of risk stratification by physicians and its relationship to the management of ACS have not been well studied. Our objective was to examine patient risk assessment by physicians in relation to treatment and objective risk score evaluation and the underlying patient characteristics that physicians consider to indicate high risk. METHODS:The prospective Canadian ACS 2 Registry recruited 1956 patients admitted for non-ST-segment elevation ACS in 36 hospitals in October 2002 to December 2003. We recorded patient risk assessment by the treating physician and case management on standardized case report forms and calculated the Thrombolysis in Myocardial Infarction (TIMI), Platelet glycoprotein IIb/IIIa in Unstable angina: Receptor Suppression Using Integrilin Therapy (PURSUIT), and Global Registry of Acute Cardiac Events (GRACE) risk scores. RESULTS:Of the 1956 patients with ACS, 347 (17.8%) were classified as low risk, 822 (42.0%) as intermediate risk, and 787 (40.2%) as high risk by their treating physicians. Patients considered as high risk were more likely to receive aggressive medical therapies and to undergo coronary angiography and revascularization. However, there were only weak correlations between risk assessment by physicians and all 3 validated risk scores. In multivariable analysis, history of stroke, worse Killip class, presence of ST-segment deviation, T-wave inversion, and positive cardiac biomarker status were all independently associated with high-risk categorization by the treating physician, while advanced age and previous coronary bypass surgery were independent negative predictors. There was no significant association between the high-risk category and several established prognosticators, such as history of heart failure, hemodynamic variables, and creatinine level. CONCLUSIONS:Contemporary risk stratification of ACS appears suboptimal and may perpetuate the treatment-risk paradox. Physicians may not recognize and incorporate the most powerful adverse prognosticators into overall patient risk assessment. Routine use of validated risk score may enhance risk stratification and facilitate more appropriate tailoring of intensive therapies toward high-risk patients.