title: Electropharmacologic effect of a standard dose of intravenous procainamide in patients with sustained ventricular tachycardia.
abstract: BACKGROUND
  Patients with inducible sustained ventricular tachycardia (VT) sometimes receive intravenous procainamide during electrophysiologic testing. Unfortunately, the responses to intravenous and subsequent oral drug therapy are variable and may be discordant.
  
  
  OBJECTIVE
  It was the aim of this study to determine whether this variability might be explained by heterogeneity in the electropharmacologic response, even in a homogeneous population.
  
  
  METHODS
  We studied 42 patients who had spontaneous malignant ventricular arrhythmia and were inducible to sustained monomorphous VT during electrophysiologic testing. Each received 15 mg/kg of intravenous procainamide followed by a 2 mg/min infusion. Serum levels were drawn immediately following programmed stimulation. The mean procainamide level was 6.7 +/- 1.4 mcg/ml with an N-acetyl procainamide level of 1.0 +/- 0.5 mcg/ml. The 14 procainamide responders (5 of whom were noninducible and 9 whose VT cycle length increased > 100 ms) and the 28 nonresponders had similar procainamide and NAPA levels (6.5 +/- 1.4 vs. 6.7 +/- 1.4 mcg/ml).
  
  
  RESULTS
  There was no significant difference in baseline clinical parameters, His to ventricular electrogram (HV) interval, effective refractory period, or VT cycle length. Prolongation of the effective refractory period and infra His conduction time occurred to a similar extent in responders and nonresponders.
  
  
  CONCLUSIONS
  We conclude that procainamide has a consistent dose-response relationship with respect to refractoriness and conduction in patients with malignant arrhythmias. However, acute antiarrhythmic efficacy of procainamide cannot be predicted by clinical factors, drug levels, or drug-induced changes in common electrophysiologic parameters.
authors.affiliation: Cardiovascular Division, The Lankenau Hospital and Medical Research Center, Wynnewood, Pennsylvania, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Rials
authors.forename: D
authors.initials: D
authors.lastname: Britchkow
authors.forename: R A
authors.initials: RA
authors.lastname: Marinchak
authors.forename: P R
authors.initials: PR
authors.lastname: Kowey
mesh_terms: D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology* / Q000627:therapeutic use; D002036:Bundle of His / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects*; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D011342:Procainamide / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology* / Q000627:therapeutic use; D017180:Tachycardia, Ventricular / Q000188:drug therapy*
chemical_list: D000889:Anti-Arrhythmia Agents; D011342:Procainamide