[Sinus node suppression by ventricular stimulation in retrograde block]

In a patient with a sick-sinus syndrome atrial pacing revealed an abnormal prolongation of the sinus node recovery time. During ventricular pacing no retrograde ventriculoatrial conduction could be detected. In spite of this, complete atrial standstill occurred reproducibly during fixed-rate ventricular pacing. After ventricular pacing was stopped a pause of some seconds ("overdrive recovery") was observed before the reoccurrence of normal sinus rhythm. We have no explanation for this unique finding, unless concealed ventriculosinoidal conduction is postulated.