Changes in ventricular effective refractory periods after two extrastimuli and ventricular electrical instability.
Using programmed stimulation with one and three extrastimuli delivered in the right ventricular apex, we compared the effective refractory period (ERP) during sinus rhythm (ERP-SR) and during the third extrastimulus (ERP-S3) in patients without ventricular tachycardias (control group, n = 87) and in patients with documented ventricular tachycardia (VT group, n = 76). The protocol was not completed to determine ERP-S3 in one patient in the control group and in 15 patients in the VT group. We observed a significantly greater change (i.e., shortening) in ERP after two extrastimuli in the VT group compared with patients without VT (delta ERP = 45 +/- 20 msec in the control group and 70 +/- 16 msec in the VT group, P < 0.001). This electrophysiological phenomenon, along with conduction delay, may play an important role in VT induction.
D002304:Cardiac Pacing, Artificial / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012032:Refractory Period, Electrophysiological / Q000502:physiology; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology; D016276:Ventricular Function / Q000502:physiology*