title: Comparison of the effects of exercise and isoproterenol on the antegrade refractory period of the accessory pathway in patients with Wolff-Parkinson-White syndrome.
abstract: The effects of exercise and isoproterenol infusion on the antegrade effective refractory period of the accessory pathway (ERP-AP) were compared in 10 patients with Wolff-Parkinson-White (WPW) syndrome. During an electrophysiologic study, the ERP-AP (paced cycle length: 400 msec) was measured before and during isoproterenol infusion at a rate of 1 microgram/min. On the next day, a symptom-limited ergometer exercise test was performed and the ERP-AP (paced cycle length: 400 msec) was measured before and during the test using an indwelling atrial electrode catheter. Isoproterenol infusion and the exercise test increased the heart rate from 84 +/- 24 to 122 +/- 17 beats/min and from 85 +/- 25 to 128 +/- 25 beats/min, respectively (p = NS isoproterenol versus exercise). The ERP-AP was shortened from 268 +/- 34 to 230 +/- 19 msec with isoproterenol infusion (p < 0.001) and from 273 +/- 42 to 237 +/- 31 msec with the exercise test (p < 0.001). There was no significant difference between the effects of isoproterenol and exercise. The percent change in the ERP-AP with exercise (Y) was significantly correlated to that with isoproterenol infusion (X) (Y = -3.04 + 0.70X, r = 0.92, p < 0.001). In conclusion, isoproterenol infusion at the present dose shortens the ERP-AP to the same degree as exercise, and thus is useful for predicting the exercise-induced shortening of the ERP of the accessory pathway in patients with WPW syndrome.
authors.affiliation: Division of Cardiology, Kumamoto University Medical School, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yamabe
authors.forename: K
authors.initials: K
authors.lastname: Okumura
authors.forename: H
authors.initials: H
authors.lastname: Yasue
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005080:Exercise Test; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects / Q000503:physiopathology*; D006801:Humans; D007263:Infusions, Parenteral; D007545:Isoproterenol / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion; D012032:Refractory Period, Electrophysiological / Q000187:drug effects / Q000502:physiology*; D014927:Wolff-Parkinson-White Syndrome / Q000503:physiopathology*
chemical_list: D007545:Isoproterenol