The Duke treadmill score is a quantitative means of expressing cardiac risk derived entirely from the exercise ECG. It incorporates depth of ST depression, treadmill time (METS) and angina on the treadmill. The score is calculated as duration of exercise in minutes - (5 x the maximal net ST-segment deviation) during or after exercise, in millimetres - (4 x the treadmill angina index). The angina index has a value of 0 if there is no angina during exercise, 1 if the patient had nonlimiting angina and 2 if angina was the reason the patient stopped exercising. High risk scores of < - 10 give a 5 year survival rate of <75%, intermediate score of -10 to 4+ give a 5 year survival risk of 75 - 95% and low risk scores of > + 5 give a 5 year survival rate of > 95%.