[Sinostrial node initial block after digoxin--unmasking by double and multiple stimulation].

After intravenous application of 1 mg digoxin in a 28-year-old patient with condition after myocarditis by means of premature atrial individual stimulation a SA-block I. type II was observed. Also in extremely premature stimuli the post-extrasystolic pauses remained compensating. After atrial double and multiple stimulation--a new method for the calculation of the sinuatrial conduction time--totally irregular poststimulation pauses appeared, which were regarded as an expression of a sinoauricular node initial block. Other possibilities of explanation are discussed.