A prospective comparison of progrmti ventricular stimubtion with tr versus sing4-e and do&He extr infusion of isoproterenol

This prospective study compared the yield of programmed ventrtcular stimulation with single and double extrastimuli during an infusion of isoproterenol with that of programmed stimulation with triple extrastimuli. The subjects of this study were 58 patients who underwent programmed stimulation and did not have inducible ventricular tachycardla (VT) with single or double extrastimuli at two basic drive cycle lengths and at two right ventricular sites; 17 patients had a history of uniform VT unrelated to exercise, and 41 had no history of documented or suspected VT or ventricular fibrillation (VF). Programmed stimulation was performed with triple extrastimuli at both right ventricular sites. lsoproterenol was infused as a dose titrated to increase the sinus rate by 25% or to a rate of 100 beats/min, whichever was greater, and sttmulatlon then was repeated with single and double extrastimuti. Among the 17 patients with a history of uniform VT, the clinical VT was induced by three extrastimuli in five patients (29%) and by two extrastimuli during isoproterenol infuston in six patients (35%, p > 0.05). Among the total study population of 58 patients, nonclinical multiform VT or VF was induced by three extrastimuli in 29 patients (50%), and by two extrastimuli during isoproterenol infusion in 15 patients (28%, p < 0.05). Therefore stimulation with two extrastimuli during isoproterenol infusion has the same probability of inducing a clinical form of VT as does stimulation with extrastimuli, but the former has a significantly lower probability of inducing nonclinical multiform VT and VF. (AM HEART J 1989;117:342.)