Discordance between ambulatory monitoring and programmed stimulation in assessing efficacy of class IA antiarrhythmic agents in patients with ventricular tachycardia

Concordance between programmed stimulation and 24 hour ambulatory electrocardiographic (Hotter) monitoring was studied in 54 patients with sustained ventricular tachycardia during 84 therapeutic trials with class IA antiarrhythmic agents. During baseline studies before treatment, all patients had frequent (≥30/h) ventricular premature complexes on Holter recordings and sustained ventricular tachycardia inducible by one to three extra-stimuli. During treatment, programmed stimulation and Holter monitoring were repeated. Efficacy of treatment determined by programmed stimulation (ventricular tachycardia no longer inducible or nonsustained) was compared with three Holter criteria of efficacy: I = 83% or more reduction of ventricular premature complexes and abolition of ventricular tachycardia; II = 50% or more reduction of ventricular premature complexes and 90% or more reduction of couplets and abolition of ventricular tachycardia; III = abolition of ventricular tachycardia in patients with ventricular tachycardia during a baseline Hotter recording. Treatments were judged effective by programmed stimulation criteria in only 25% of cases but in 51, 63 and 75% of cases by Hotter criterion I, II and III, respectively. Results of programmed stimulation and Hotter monitor were discordant (effective by one criterion but ineffective by the other) in 50% of cases using Hotter criterion I, in 54% using Hotter criterion II and in 61% using Holler criterion III. In the majority of discordant results, treatments appeared efficacious by Holler criteria but ineffective by programmed stimulation criteria, suggesting insensitivity of efficacy by Hotter criteria or nonspecificity of induced ventricular tachycardia during treatment, or both. Conclusions: 1) programmed stimulation and Hotter monitor recording are discordant in assessing efficacy of class IA antiarrhythmic agents; 2) efficacy by Holter criteria is often easier to achieve than efficacy by programmed stimulation (p < 0.001); and 3) the discordance between the two methods, both with very good reported predictive values, calls for long-term follow-up studies to determine sensitivity and specificity of each method.