[Correction of T wave-induced pacemaker bradycardia by quinidine (author's transl)]

Intermittent pacemaker bradycardia (down to 46 and 52/min, respectively) occurred in two patients with a demand pacemaker (Variopacemaker Elema-Schonander EM 169 B with unipolar endocardial electrode EMT 288B/62). The cause was a disorder of pacemaker function by an increased or especially steeply rising T wave which, outside the refractory period of the pacemaker, was mistakenly sensed as an R wave. The rapid rise was in some additional way caused by the P wave falling onto the T wave. Quinidine bisulphate changed the shape of the T wave, and pacemaker function returned to normal. The results were confirmed by a return of the disturbance when quinidine was discontinued.