The Wenckebach phenomenon between electric pacemaker and ventricle.
Two cases which exhibited a Wenckebach form of exit conduction between an electrical pacemaker and the ventricular myocardium are presented. This manifests with increasing latency (stimulus to QRS  intervals) and ultimate stimulus failure (block). The cycle then repeats itself. The QRS duration also increases progressively within each cycle. The phenomenon connotes an adverse prognosis. Several postulates regarding the mechanism are discussed.
D005260:Female; D006327:Heart Block / Q000209:etiology*; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial / Q000009:adverse effects*; D011379:Prognosis; D013997:Time Factors