 12. Exercise durations for the qualifying treadmill tests at Visits 1 and 2 must satisfy at least one of the two following conditions: a they differ by less than or equal to 20 of the longer time; b they differ by less than or equal to 60 seconds. Subjects whose ETTs at Visits 1 and 2 do not satisfy at least one of these two conditions are allowed a third ETT, at the investigators discretion, from 5 to 7 days after Visit 2. If a third ETT is done, then when compared with the second ETT it must satisfy at least one of the two conditions above. 