Significant variability in the mode of ventricular tachycardia induction and its implications for interpretation of acute drug testing.
Fifty-four patients with previous myocardial infarction and sustained ventricular tachycardia on fibrillation underwent two electrophysiologic studies in the drug-free state within 72 hours. Although the concordance of overall ventricular tachycardia induction over the 2 days was good (87% of patients), there was variability in the number of extrastimuli needed to induce sustained ventricular tachycardia on each day in 60% of patients. Of those in whom ventricular tachycardia was inducible on both days, 40% required additional extrastimuli and 20% required fewer extrastimuli. A change by two or more extrastimuli was found in 12% of patients. There was no correlation between the variability observed and multiple clinical and laboratory parameters (including the aggressiveness of the stimulation protocol); however, the direction of the variability (easier or harder to induce) correlated with changes in ventricular refractoriness. Inherent day-to-day variability may affect the reproducibility of electrophysiologic studies and influence the results of serial drug testing.
Department of Medicine, Baylor College of Medicine, Houston, Texas.
K J
KJ
Beckman
C E
CE
Velasco
J
J
Krafchek
H T
HT
Lin
S A
SA
Magro
C R
CR
Wyndham
D000328:Adult; D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D003327:Coronary Disease / Q000503:physiopathology; D004558:Electric Stimulation; D004562:Electrocardiography; D005260:Female; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013610:Tachycardia / Q000188:drug therapy / Q000503:physiopathology*
D000889:Anti-Arrhythmia Agents