His ECG during testing demonstrated the WPW pattern at baseline, which is consistent with a posteroseptal accessory tract. ST segments were normal at rest (Fig 1
, top left, a). An ST-segment depression of 1 mm began at 2 min and 50 s (Fig 1, left top middle, b), reaching a maximum of 2 mm in leads V4 to V6 at 8 min and 50 s (Fig 1, left bottom middle, c). The delta wave suddenly and completely disappeared, and the PR interval lengthened at 9 min and 15 s (Fig 1, left bottom, d) at a heart rate of 151 beats/min with immediate normalization of ST segments extending through maximum exercise (Fig 1, right top, e). In recovery, ST segments remained normal until a heart rate of 90 beats/min occurred, at which time the delta wave reappeared with a recurrence of 1-mm ST-segment depressions (Fig 1, right top middle, f, and right bottom middle, g). At 5 min into recovery, the ECG had returned to baseline (Fig 1, right bottom, h), demonstrating resolution of the ST-segment depression with the normalization of the depolarization abnormality.