[The effect of drugs on "sino-atrial conduction time" and on sinus-node automaticity in man]

The effect of atropine, propafenone, and disopyramide on sinus node automaticity and "sino-atrial conduction" was tested in normal patients and patients with the sick sinus-syndrome. "Sino-atrial conduction time" was estimated indirectly by the extrastimulus technique. Atropine (n = 11) caused a significant increase in heart rate in all patients. The sinus node recovery time was shortened in 10 patients. "Sino-atrial conduction time" decreased on an average 35% (P less than 0.01). Three patients with a sick sinus-syndrome demonstrated a change of the pattern of the postextrasystolic pauses indicating great improvement in sino-atrial conduction. Propafenone (n = 10) led to a significant prolongation of the sinus node recovery time by 17% and of the "sino-atrial conduction time" by 27%. Disopyramide (n = 8) had no significant influence on heart rate and "sino-atrial conduction time". Sinus node recovery time was not changed in 6 patients. However, in two patients with a sick sinus-syndrome a dangerous prolongation of the sinus node recovery time after application of disopyramide occurred. The results indicate that atropine enhances sinus node function and sino-atrial conduction. On the other hand, propafenone and disopyramide exert either a depressant influence on sinus node automaticity or on sino-atrial conduction.