- Background Major changes occurred recently in the definition and recommended management of non-ST segment elevation acute coronary syndromes (NSTE ACS). The impact of these changes on the coronary care unit (CCU) is incompletely characterized. Methods ACSIS is a national survey gathering data every other year among all ACS patients in all CCUs in Israel. We compared case load, baseline variables, management, outcome and distribution of diagnoses among NSTE ACS patients admitted before (during 2000 [N = 729]) and after (during 2002 [N = 970]) the widespread introduction of troponin and the new AMI definition. Results The number of NSTE ACS patients in 2002 increased by 33% compared to 2000, with no change in the number of beds, while the number of ST elevation ACS patients remained unchanged. The rate of AMI rose by 16% and hospital stay decreased by 1 day (p = 0.005). The availability of troponin values increased from 20% in 2000 to 60% in 2002; The proportion of patients given the diagnosis of NSTE AMI rose significantly more in centers with high utilization of troponin (p = 0.023). During 2002 significant increases occurred in the utilization of guideline-recommended medications, as in the use of coronary angiography and intervention. Mortality at 30 days decreased by 35%. Conclusions This is the first large registry of ACS to describe the significant actual changes which occurred in the CCU following the introduction of troponin and the new AMI definition. We observed a substantial increase in the burden of NSTE ACS coupled with a shortened length of stay. These changes may impact significantly upon patient care and resource utilization.