Pacemaker Failure in Complete Heart Block

Atrioventricular conduction blocks were produced in dogs, and ventricular stimulation was accomplished by the use of electrodes implanted either into normal myocardium or scar tissue on the myocardium. Stimulation through scar tissue requires several times the power necessary for stimulation through normal myocardium, but both are well within the limit of standard, commercially available, transistorized pacemakers. Failure of stimulation of the ventricle was not due to excessive scarring. Failure of stimulation was in every instance due to wire breakage or actual loss of contact between the wire and the myocardium.