Resetting of Tachycardia Cycle by Single and Double Ventricular Extrastimuli in Recurrent Sustained Ventricular Tachycardia

Abstract

In two cases with recurrent sustained ventricular tachycardia (VT) due to re-entry, the response pattern to extrastimuli during the tachycardia was studied. In each case, right ventricular extrastimuli with longer coupling intervals during VT were followed by fully compensatory pauses and with shorter coupling intervals reset the tachycardia cycle. In one case, a plateau was produced by a single extrastimulus, resembling that seen in the response curve of sinus node automaticity as well as ectopic atrial tachycardia. Two successive stimuli produced three definite zones, i.e., fully compensatory, reset producing a plateau, and progressive prolongation zones with shortening of the coupling intervals between the two stimuli, and terminated the tachycardia with further shortening of the coupling intervals. In conclusion, resetting phenomenon was confirmed on two cases with re-entrant VT. This phenomenon cannot be used as a criterion to determine the mechanism responsible for VT.

Resetting response patterns during sustained ventricular tachycardia: relationship to the excitable gap.

“…Criteria for entry into this study included: (1) sustained uniform VT reproducibly initiated by programmed electrical stimulation (PES) in patients with chronic coronary artery disease and prior myocardial infarction, (2) stability of the cycle length of VT (i.e., '<20 msec difference in the cycle length of 20 consecutive beats), (3) hemodynamic tolerance of VT, and (4) demonstration of resetting of the VT in response to PES. Resetting was observed during 37 morphologically distinct VTs in 32 patients undergoing PES.…”