[Reproducibility of sinus node recovery time in relation to the time of the day and the overdrive stimulation rate (author's transl)].

Corrected sinus node recovery time (CSRT) was tested in 9 patients with (CSRTI) and 6 patients without sick sinus syndrome = SSS (CSRTII) at 6 constant time intervals each, on 3 consecutive days using 5 rates of atrial overdrive stimulation (AST) via a stable loop mounted atrial electrode. From the results presented it can be concluded: CSRTI is reproducible with high rates when corresponding time periods and the same AST rate are used. A stepwise CRST increase by 60% is consistent up to AST 140 bpm only; up to AST 200 bpm the pattern varies within maximal pathological CSRT ranges for each of the 6 time periods measured, as an expression of influences unidentified in this study. The implication is: For an optimal diagnostic yield in CSRT testing several AST rates above 140 bpm are required and the time intervals of 17 and 8 hours represent a "high" and at 14 hours a "low" for CSRT testing; there are factors, other than the sinus node dysfunction, that added to the pathologic significance of the CSRT.