Induction of clinical ventricular tachycardia using programmed stimulation: Value of third and fourth extrastimuli

Abstract

Initiation of ventricular tachycardia (VT) by right ventricular extrastimulation was analyzed in 142 consecutive patients, 53 with electrocardiographically documented episodes of spontaneous VT or ventricular fibrillation (VF) and 68 with no spontaneous VT or VF; 21 patients with a history of sudden death but no documented arrhythmia were excluded from further analysis, All patients received 1 to 4 extrastimuli (S 2, S 3, S 4 and S 5) during pacing at fixed cycle lengths of 600 or 500 msec at 1 or 2 right ventricular sites. Clinical VT was reproduced by extrastimulation in 28 of 43 patients (65%) with sustained VT and in 0 of 10 patients with nonsustained VT. Clinical VT was induced by S 2 or S 3 in 16 patients and by S 4 or S 5 in 12 patients. Ventricular burst pacing reproduced clinical VT in 3 other patients. Nonclinical VT, which was most often polymorphic and nonsustained, was induced in 24 of 121 patients (20%), In 11 by S 2 or S 3 and in 13 by S 4 or S 5. Ventricular burst pacing induced nonclinical VT in 4 other patients. In patients with spontaneous sustained VT, the use of S 4 and S 5 in the right ventricle increases the yield of inducible clinical VT compared with use of S 2 and S 3 alone, but at a cost of increased induction of nonclinical VT. Frequent induction of nonclinical VT limits the interpretation of the results of such stimulation in patients without previously documented VT.