BACKGROUND:

There had been no prospective, randomized studies that compared the accuracy of EPS versus HM in guiding long-term drug therapy for ventricular tachycardia or ventricular fibrillation. Success had been reported using both techniques. Using a rigorous ECG monitoring protocol in patients, a less than five percent per year incidence of sudden death had been reported. Several investigators reported that the results of electropharmacologic testing were predictive of clinical response. One of the largest studies, by Mason and Winkle, reported that, in 51 patients with recurrent ventricular tachycardia who were treated with drugs predicted to be effective based on the results of electropharmacologic testing, ventricular tachycardia did not recur in 68 percent at 18 months of follow-up. In contrast, ventricular tachycardia did not recur in only 11 percent of patients treated with drugs predicted to be ineffective.

Two prior studies had compared, in a non-randomized fashion, the predictive accuracy of EPS and HM in treating patients with ventricular tachycardia/ ventricular fibrillation. A retrospective analysis of 44 patients with ventricular tachycardia/ventricular fibrillation who underwent both HM and EPS was performed in which the elimination of ventricular tachycardia on the HM and the suppression of ventricular tachycardia induced during programmed stimulation was the therapeutic goal. The positive and negative predictive value of EPS was found to be 88 percent and 94 percent, respectively. The corresponding values for ECG monitoring were found to be 70 percent and 50 percent, respectively. It was concluded that EPS provided a higher degree of accuracy than HM in predicting the long-term clinical response to drug therapy, over a mean follow-up of 18 months. However, in this study the criterion for judging efficacy by HM was a liberal one and involved only the elimination of ventricular tachycardia.

A second study examined the results of HM in 19 patients with ventricular tachycardia who were treated based on EPS. Among eight patients, in whom inducible ventricular tachycardia was suppressed during electrophysiologic testing, six had no change or worsening of premature ventricular contractions on the HM. These patients had a benign follow-up despite the continued presence of frequent or complex ventricular ectopy. It was concluded that EPS was superior to HM in predicting successful drug therapy.

Existing data suggested that both electrophysiologic testing and Holter monitoring might be effective techniques for determining effective drug therapy for ventricular tachycardia/ventricular fibrillation. However, there was not enough data available to assess which technique was more effective. A prospective, randomized comparison of the two techniques would be a very significant contribution which could potentially have a major impact on the medical community.

DESIGN NARRATIVE:

Randomized, fixed sample, multicenter trial conducted at 14 institutions. Patients meeting clinical criteria underwent Holter monitoring. Those having an average of 30 premature ventricular contractions per hour underwent EPS. Those having inducible ventricular tachycardia were randomized into an EPS arm or to a Holter exercise treadmill arm of drug testing. Each patient received, in random sequences, up to six antiarrhythmic drugs. When an effective drug was found, patients underwent a predischarge HM and exercise test. Follow-up continued for one year after the last subject had been randomized. The primary endpoint in the trial was time to arrhythmia recurrence during therapy with a drug predicted to be effective by either EPS or HM.