Risk Score represents the total risk factors for the patient. Risk Category 1 is the lowest risk group. A typical patient in this risk category would be a 55 year old male with a normal ejection fraction requiring a first time bypass operation. Risk Category 6 is the highest risk group group. A typical patient in this risk category would be an 80 year old person with an acute myocardial infarction requiring balloon pump support before operation. Risk Factors included are: age; ejection fraction (heart function); emergency status; previous heart operation; obesity; history of diabetes; history of myocardial infarction; type of operation, etc. Risk Category - Number of Patients 1 2 3 4 5 6 Total 1990-1992 539 (18%) 556 (18%) 614 (20%) 615 (20%) 468 (15%) 281 (9%) 3073 1993-1994 287 (17%) 298 (18%) 335 (20%) 309 (19%) 261 (16%) 158 (10%) 1648 1995-1996 252 (17%) 284 (19%) 327 (21%) 290 (19%) 203 (13%) 171 (11%) 1527 1997 206 (19%) 188 (17%) 221 (20%) 203 (18%) 171 (16%) 113 (10%) 1102