Reversal of electrophysiologic effects of flecainide on the accessory pathway by isoproterenol in the Wolff-Parkinson-White syndrome.

Abstract

To determine the reversibility of the effects of flecainide on accessory pathways, electrophysiologic studies were performed in the drug-free control state, after flecainide loading and with isoproterenol infusion during flecainide treatment in 12 patients with symptomatic preexcitation syndrome. After the baseline drug-free evaluation, oral flecainide was given in dosages of 50 to 200 mg twice daily (mean daily dose 282 +/- 75) for at least 4 days before the repeat electrophysiologic study. Isoproterenol infusion was given in dosages of 1 to 4 micrograms/min to increase the heart rate at rest by 50%. Anterograde block in the accessory pathway was observed in 3 patients with flecainide therapy, whereas in the other patients the anterograde refractory period increased from 243 +/- 20 to 315 +/- 23 ms (p less than 0.05). The shortest preexcited RR interval during atrial fibrillation lengthened from 234 +/- 27 ms before flecainide to 313 +/- 38 ms (p less than 0.05). Retrograde block occurred in 2 patients after flecainide, whereas the retrograde refractory period of the accessory pathway increased from 247 +/- 26 to 337 +/- 45 ms in the other patients. Orthodromic atrioventricular reciprocating tachycardia, inducible in 10 patients before therapy, became noninducible in 3 patients. Its rate was significantly slowed in the other 7 patients (from 346 +/- 50 to 471 +/- 81 ms). In 2 patients the tachycardia was nonsustained during flecainide treatment. Atrial fibrillation, inducible in all patients at baseline, was rendered nonsustained and more difficult to induce in 7 patients with flecainide. When isoproterenol was infused during flecainide treatment, complete anterograde (3 patients) or retrograde block (2 patients) persisted in the accessory pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

• Authors: A S Manolis, N A Estes 3rd
• Journal: The American journal of cardiology (Am J Cardiol) Vol. 64 Issue 3 Pg. 194-8 (Jul 15 1989) ISSN: 0002-9149 [Print] United States
• PMID: 2500840 (Publication Type: Journal Article)

Chemical References

• Propranolol
• Flecainide
• Isoproterenol

Topics

• Adolescent
• Adult
• Electrophysiology
• Female
• Flecainide (antagonists & inhibitors, pharmacology)
• Follow-Up Studies
• Humans
• Isoproterenol (antagonists & inhibitors, pharmacology)
• Male
• Middle Aged
• Monitoring, Physiologic
• Propranolol (pharmacology)
• Wolff-Parkinson-White Syndrome (drug therapy, physiopathology)