[Inactivation of implanted demand pacemaker through external stimulation]

External chest wall stimulation was performed in 87 patients in order to overdrive and thereby suppress the implanted pacemaker. The impossibility to inactivate the implanted pacer suggested a disturbed "sensing" function in 12 patients. Marked changes of the escape rhythm were found in 77 patients with suppressable pacemaker when compared with the tracings before pacemaker implantation. Increasing degree of A-V block or marked changes in heart rate were observed in 14 of 35 cases with advanced A-V block. Minor alterations were noted in cases with sick sinus syndrome and atrial fibrillation. Overdrive suppression is a helpful method for the selection of pacemaker dependent patients.