Autonomic sinus node dysfunction documented by Holter monitoring studies in 21 patients

Holter recordings were carried out in 21 patients with presupposed sinus node dysfunction (SND). All the patients were evaluated also by complex electrophysiological examinations (overdrive and premature atrial stimulation) before and after pharmacologic autonomic blockade (AB) with propranolol 0.2 mg/kg and atropine 0.04 mg/kg body weight intravenously. Groups of normal and abnormal intrinsic heart rate (IHR) were compared. In patients with normal IHR (n = 13) the prolonged recovery time (5/13), postpacing SA-block (1/13) and chaotic postextrasystolic patterns (4/13) ceased after AB. Intrinsic recovery time became normal with a gradual return to the stable sinus cycle length, and we obtained normal biphasic postextrasystolic intrinsic return responses. In all cases of pathological IHR (n = 8), abnormal intrinsic rhythmicity was verified by electrophysiological means. Holter monitoring revealed significant differences (P less than 0.001) between the minimal HR during sleeping and also in the HR averaged for 24 h between the two groups. In patients with abnormal IHR, the 24 h rhythm recording revealed positive ECG data for SND. In patients with normal intrinsic electrophysiological properties, Holter monitoring revealed severe sinus bradycardia (1 case), SA-arrest (1 case), SA-block (1 case), tachy-brady syndrome (1 case), and atrial fibrillation with AV-block (1 case). For appreciating the role and significance of the autonomic neuro-vegetative tone in SND, continuous rhythm monitoring is necessary.