title: [Use-dependence of propafenone. Clinical demonstration of the hypothesis of modulated receptors].
abstract: The aim of this study was to assess use-dependence in patients with ventricular premature contractions (VPC's) treated with propafenone, by means of the increase in heart rate using transesophageal atrial pacing. It was also analyzed whether this phenomenon was related to the antiarrhythmic effect. Fifteen patients with more than 30 symptomatic VPC's/sour were evaluated. Esophageal pacing was performed with cycles of 600 and 400 msec during periods of 1 min and with simultaneous recording of 2 or 3 EKG leads with a paper speed of 100 mm/sec. Holter monitoring (HM) was carried out in all patients. Propafenone was administered in doses of 450 and 900 mg/day, during 5-7 days, at which moment another HM and esophageal stimulation were repeated. The QRS duration (pre-treatment) was 82.6 +/- 13.5 msec (basal) and 82.4 +/- 13 msec during pacing with 600 msec cycle length (p: NS). The QRS duration with P (900 mg/day) was 96.6 +/- 20 msec (basal) (p:NS vs. pre-treatment) but during atrial pacing with 600 msec cycle length it increased to 109.3 +/- 23 msec (p < 0.0004). This use-dependence was also observed with pacing at 600 msec in patients receiving doses of 450 mg/day: 95.3 +/- 13 msec (p < 0.0001 vs. baseline QRS) (Table 1).
  
  
  CONCLUSIONS
  1) there was no significant increase in the QRS duration with P without pacing; 2) propafenone showed use-dependence during atrial stimulation, even with cycle length of 600 msec and with the lower doses.
authors.affiliation: División Cardiología, Hospital Municipal Dr. Cosme Argerich, Buenos Aires, Argentina.
authors.forename: C D
authors.initials: CD
authors.lastname: Labadet
authors.forename: A
authors.initials: A
authors.lastname: Peralta
authors.forename: J
authors.initials: J
authors.lastname: González Zuelgaray
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005117:Cardiac Complexes, Premature / Q000188:drug therapy*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008151:Lown-Ganong-Levine Syndrome / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D011405:Propafenone / Q000008:administration & dosage / Q000494:pharmacology*; D011930:Reaction Time; D012044:Regression Analysis; D013268:Stimulation, Chemical
chemical_list: D011405:Propafenone
vernacular_title: Uso-dependencia con propafenona. Demonstración clínica de la hipótesis de los receptores modulados.