Although the phenomenon of resetting has been studied in several experimental and clinical rhythms, it has not been systematically analyzed in ventricular tachycardia. To define the incidence and determinants of resetting as well as its relation to ventricular tachycardia termination, the response to programmed stimulation was prospectively studied during 78 electrically induced episodes of sustained, uniform ventricular tachycardia (mean cycle length 365 +/- 59 ms) in 53 patients. Single and double ventricular extrastimuli were introduced during 78 and 39 episodes of ventricular tachycardia, respectively. Rapid ventricular pacing was performed during 27 episodes. Resetting occurred in response to single ventricular extrastimuli in 43 (55%) of 78 ventricular tachycardias, to double extrastimuli in 31 (79%) of 39 ventricular tachycardias and to rapid pacing in 23 (85%) of 27 ventricular tachycardias. No ventricular tachycardia characteristic distinguished those tachycardias that were reset from those not reset. Termination of ventricular tachycardia occurred in 7 (9%) of 78 episodes with single ventricular extrastimuli, 14 (36%) of 39 episodes with double ventricular extrastimuli and 13 (48%) of 27 episodes with rapid pacing. Termination was less frequent than resetting with both single (9 versus 55%) and double (36 versus 79%) extrastimuli, as well as rapid pacing (48 versus 85%). Resetting preceded termination in 7 of 7 ventricular tachycardias terminated with single ventricular extrastimuli, 12 of 14 terminated with double ventricular extrastimuli and 9 of 13 terminated by rapid pacing. Ventricular tachycardias that were terminated could not be differentiated from those that were reset without termination.
In conclusion: Resetting with programmed extrastimuli is common in hemodynamically stable sustained ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)