[Influence of cycle length shortening, atropine and beta-receptor blockage on sinus node recovery time (SRT) in patients with healthy sinus node (author's transl)].

Sinus node recovery time (SRT) was measured in 30 patients with healthy sinus nodes to examine the influence of the increase in atrial frequency, atropine and beta-receptor blockade. The measurements were performed following pacing with 3 atrial frequencies before and after administration of 1 mg atropine i.v. (13 patients) and 0.4 mg prindolol (Visken) i.v. (17 patients). Total group; Increase of frequency alone caused prolongation of the SRT in 17 patients and shortening in 13 patients. Atropine group: Blockade of the parasympathicus alone induced a highly significant reduction in the SRT. Simultaneous increase in frequency and blockade of the parasympathicus led to greater SRT-shortening during low frequency than with high frequency. This interrelationship of frequency and blockade of the parasympathicus influencing the SRT is statistically significant. Visken-group: Blockade of the sympathicus causes a highly significant prolongation of the SRT. Simultaneous increase in frequency and blockade of the sympathicus led to greater SRT-prolongation during low frequency than with high frequency. This interrelationship of frequency and blockade of the sympathicus influencing the SRT has slight statistical significance. The results are discussed in respect to the electrophysiological influences of atrial cycle length shortening, acetylcholine and catecholamines on the sinus node, the perinodal atrial fibres and the atrial working myocardium.