EPS Guided Sotalol Study
Abstract & Commentary
Synopsis: Responses during programmed ventricular stimulation frequently become discordant during long-term follow-up. However, this does not seem to affect the probability of late recurrence.
Source: Mewis C, et al. J Am Coll Cardiol 1999; 33:1989-1995.
This report analyzes the long-term reproducibility of programmed ventricular stimulation in ventricular arrhythmia patients who were treated with sotalol. Mewis and colleagues tested oral sotalol in 195 patients who had inducible ventricular tachycardia (VT) or ventricular fibrillation (VF) at a baseline electrophysiologic study. Seventy-eight of the 195 (40%) patients had complete suppression of VT at the early repeat electrophysiologic (EP) study. Patients were then followed prospectively. After a median of 6.5 months (range, 6-36 months), 30 patients returned for repeat electrophysiologic study. Forty-eight patients, however, were excluded for a variety of reasons: 13 patients experienced nonfatal VT or VF recurrence, five patients died during follow-up, two developed proarrhythmia, 23 had either heart failure or drug side effects, and five patients either did not consent or were lost to follow-up. Repeat electrophysiologic study in the remaining 30 patients showed that 12 of the 30 patients (40%) had an inducible arrhythmia at the third electrophysiologic study. Seven patients required more extrastimuli in the third electrophysiologic study. The results of the third EP study were not used to change therapy. All patients were then followed on their prior sotalol dose. Five of the 30 patients (17%) experienced monomorphic VT recurrence during late follow-up. Four of the recurrences were in patients who had no inducible arrhythmia at the third electrophysiologic study, whereas one of the 12 patients with inducible VT at the third EP study recurred.
Mewis et al conclude that responses during programmed ventricular stimulation frequently become discordant during long-term follow-up. This does not seem to affect the probability of late recurrence.
Comment by John P. DiMarco, MD, PhD
This article is one of several recent series that raise questions about the use of serial electrophysiologic studies for selecting therapy in patients with ventricular arrhythmias. When programmed electric stimulation was first introduced, it was thought that it could be used effectively to select antiarrhythmic drugs that would later prove effective. More recently, however, questions have been raised about this approach. In the ESVEM trial, both serial electrophysiologic studies and serial ambulatory monitoring approaches to selecting antiarrhythmic drugs were associated with high rates of arrhythmia recurrence. Unpublished data from both the Antiarrhythmics vs. Implantable Defibrillators (AVID) trial and the Multicenter Unsustained Tachycardia Trial (MUSST) also suggest that results of programmed stimulation do not correlate well with rates of arrhythmia recurrence. This paper suggests that reproducibility of results may be one of the reasons for these observations since 40% of the patients in the study group had discordant results between two electrophysiologic studies performed during drug therapy 6.5 months apart. The data are even worse than that number would represent. Forty-eight of the original 78 patients discharged on sotalol were not included in the group reported here. Among these 48 patients, 13 had nonfatal arrhythmia recurrences and an additional three patients had sudden death. Two other patients had torsade de pointes. This would suggest that electrophysiologic studies were of almost no value for predicting efficacy of sotalol.
It is unclear why many early papers indicated good predictive values with electrophysiologic studies, but more current reports show a poor predictive accuracy. Perhaps we are dealing with a "healthy responder" phenomenon that misled early investigators. We also don’t know whether the substrate for arrhythmia has changed or whether the use of more aggressive stimulation protocols has substituted specificity for sensitivity. In any case, at this point, the data seem to indicate that serial electrophysiologic studies do not provide data that are accurate enough upon which to base decisions in patients with life-threatening arrhythmias. The major role for EP studies in patients with VT is to confirm the diagnosis if it is in question.
Reference
1. Mason JW. N Engl J Med 1993;329:445-451.
The major role of EP studies in patients with ventricular arrhythmias is:
a. to confirm the diagnosis.
b. to adjust antiarrhythmic therapy.
c. to determine prognosis.
d. to detect drug toxicity.
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