['To investigate the impact of new myocardial infarction definition based on troponin, the rate of myocardial infarction diagnosis, patients characteristics, and short-term prognosis.', 'We enrolled 1,255 consecutive myocardial infarction patients from the Kuwait Registry of Acute Coronary Syndromes from December 2003 to May 2004. Two patient groups were identified, those diagnosed with elevated creatine kinase-MB (CK group) and those diagnosed with elevated troponin with normal CK-MB (Troponin group).', 'The use of troponin have increased the number of myocardial infarctions by 49%. Compared with the CK group, the Troponin group were older [age 60.3 +/- 12.5 years versus 53.7 +/- 12.2 years, p<0.001], more likely to have diabetes (59% versus 41%, p<0.001), hypertension (59% versus 36%, p<0.001), and hypercholesterolemia (37% versus 24%, p<0.001). The Troponin group were more likely to suffer heart failure at presentation than the CK group (32% versus 14%, p<0.001) and, subsequently, increase incidence of heart failure during their hospital stay (17% versus 8%, p<0.001).'] Does troponin estimation identify myocardial infarction patients with different characteristics?