Programmed electrical stimulation studies for ventricular tachycardia induction in humans. II. Comparison of indwelling electrode catheter and daily catheter replacement.

Suppression of the ability to induce ventricular tachycardia by programmed electrical stimulation during serial drug testing has been used as a therapeutic end point to identify long-term prophylactic antiarrhythmic therapy. However, ventricular tachycardia induction, particularly with an indwelling electrode catheter, has not been systematically assessed over the time period required for serial drug testing. In this study, the results of programmed electrical stimulation were evaluated daily during serial drug-free conditions before testing various antiarrhythmic drugs. Twenty-four patients were randomly allocated to be studied with the electrode catheter left in place or replaced daily. All patients had inducible sustained ventricular tachycardia during the first study. Loss of the ability to induce ventricular tachycardia occurred in 8 of 13 patients whose catheter was left in place whereas this did not occur in patients whose catheter was replaced daily (p less than 0.01). In addition, use of an in situ catheter was accompanied by significant (p less than 0.05) changes in other electrophysiologic measurements, including number of extrastimuli required to induce ventricular tachycardia and length of ventricular functional and effective refractory periods. The serial changes seen with indwelling catheters in the drug-free state may mimic effective antiarrhythmic drug action.