The test was ended immediately if symptoms of cardiorespiratory
problems occurred (angina pectoris, serious
dyspnea, dizziness, extreme paleness, turning blue, abnormal
course of heart rate). Test failure was defined as patient
inability to complete the 6 minutes of the test, failure to
reach minimum heart rate of 120 beats per minute, or heart
rate variation more than 5 beats per minute during the last
minute of the steady-state phase.