A treadmill machine is used to perform an exercise or stress test. The stress test may be performed as part of the evaluation of patients with an arrhythmia. At other times, it is used to see if a patient with an obstructed valve or blood vessel develops any symptoms or abnormalities in the electrocardiogram or blood pressure response to exercise. This is also a helpful test in order to determine the exercise tolerance in patients with different types of heart defects. On exercise test, the treadmill angles up and goes faster every three minutes. Several parameters are evaluated during and after the stress test. These include the heart rate and blood pressure response to exercise, any arrhythmias or symptoms induced by the exercise and for any ECG abnormalities.