[Decreased vagal tone in hyperkinetic heart syndrome?]

Increasing amounts of atropine (0.03 mg + 0.07 mg + 0.01 mg + 0.25 mg + 0.5 mg + 1.0 mg + 1.5 mg; sigma = 3.5 mg, interval between injections: 30 min) were injected intravenously in a cumulative manner in five patients with hyperkinetic heart syndrome and in seven healthy volunteers. The heart rate increased from 93 to 127 beats per min in patients, and from 63 to 104 beats per min. in controls. The diastolic blood pressure slightly increased in both groups, whereas the systolic blood pressure did not change significantly. The accommodation diminished from 6 to 2 dioptries in patients, and from 8 to 5 dioptries in controls. Salivary flow fell from 1.6 to 0.1 g/min in patients with hyperkinetic heart syndrome, and from 1.3 to 0.1 g/min in control persons, respectively. The maximum occupancy of muscarinic receptors (m2-glandular), as measured in plasma specimens by means of a radioreceptor assay, reached more than 80% in each group. The dose-response-curves of atropine were highly comparable in patients and controls. It is concluded that the effects of atropine are essentially the same in patients with hyperkinetic heart syndrome and in healthy control persons. There is no evidence for a diminished vagal tone in such patients.