Treadmill exercise testing in the Wolff-Parkinson-White syndrome

Graded treadmill exercise testing was performed in 54 patients with the Wolff-Parkinson-White syndrome and preexcitation (persistent in 36, intermittent in 9 and concealed in 9). Forty-eight patients had previous paroxysmal supraventricular arrhythmia (spontaneous or induced or both). At initiation of treadmill testing, the nine patients with intermittent and the nine with concealed preexcitation had normal conduction. None manifested preexcitation during exercise. Thirty-six patients had preexcitation at initiation of exercise; exercise produced no change in preexcitation in 2, partial normalization of the QRS complex in 16 (due to enhanced atrioventricular [A-V] nodal conduction), and total normalization of the QRS complex in 18 (due to enhanced A-V nodal conduction in 14 and to rate-dependent anomalous pathway block in 4). Exercise-provoked block of the anomalous pathway reflected prolonged anomalous pathway refractoriness, as measured with atrial stimulation. All 18 patients with either total or partial preexcitation at peak exercise manifested more than 1 mm flat or downsloping S-T segment depression. None had evidence of ischemic heart disease. None of the 54 patients manifested either paroxysmal supraventricular tachycardia or atrial fibrillation during or after treadmill exercise.Treadmill exercise testing in patients with preexcitation frequently produces partial or total normalization of the QRS complex due to enhanced A-V nodal conduction and, less commonly, total normalization due to rate-dependent block of the anomalous pathway. False positive S-T segment changes (suggesting ischemia) are always present in patients manifesting preexcitation during treadmill testing. Treadmill exercise testing in patients with preexcitation does not provoke paroxysmal supraventricular tachycardia or atrial fibrillation and is not useful as a provocative test for arrhythmia.