Influence of drugs on the relationship between sinus node recovery time and calculated sinoatrial conduction time in man.

Sinus node recovery time (SRT), the pacing rate with the maximal SRT, and calculated sinoatrial conduction time (SACT) were studied by overdrive atrial pacing and programmed premature atrial stimulation in 78 patients before and after the application of several antiarrhythmic drugs or of atropine. The maximum SRT was usually observed at lower rates of atrial pacing after application of a drug that prolonged SACT, whereas the opposite behaviour was observed in the majority of cases in whom the drug tested shortened calculated SACT. However, this relationship was not observed in all cases which may be due to random changes of sinus node automaticity or sinoatrial conduction, or to the inability of programmed premature atrial stimulation to detect changes of SACT. The results of this study further substantiate the importance of the properties of sinoat;ial conduction for achieving a maximal depression sinus node activity during high rate atrial pacing.