Diagnostic value pharmacological autonomic blockade in patients with suspected sick sinus syndrome.

The study comprised 67 subjects, mean age 43.7 years, with suspected sick sinus syndrome, in whom rapid atrial pacing before and after combined atropine and propranolol was performed by Narula's method. Three groups were formed: group I--with normal sinus node recovery time (SNRT) and corrected sinus node recovery time (CNRT) before and after the autonomic blockade; group II--with functional disorders of the sinus node and group III--with intrinsic sinus node dysfunction. After autonomic blockade in groups I and II mean SNRT, CNRT, post-stimulation cycle lengths (except No. 2 and Nos. 5, 6, 10, respectively) shortened, whereas HR rose. In contrast, in group III mean SNRT, CNRT, post-stimulation cycle lengths (Nos. 1, 2, 6, 10) and HR increased. Significant differences in post-stimulation cycle lengths were observed between groups I and III as well as groups II and III. In conclusion, rapid atrial pacing after combined atropine and propranolol helps us to diagnose latent sick sinus syndrome and extrinsic sinus node dysfunction more precisely, and significant differences in post-stimulation cycle lengths between the groups confirm diagnostic value.