[Neuroendocrine effects on one's awareness of the action of the heart]

Heart rate under mental and physical stress and the incidence of cardiac arrhythmias (by 24-hour ECG monitoring) as well as their awareness of these two types of cardiac activity were analysed in 11 insulin-dependent diabetics (manifestation before the age of 40 years) with autonomic neuropathy, five patients with hyperthyroidism and 13 healthy subjects. In hyperthyroidism the heart rate was increased as was the incidence of ventricular premature systoles; spontaneous variations and exercise-induced adaptation in heart rate were preserved. In diabetic neuropathy spontaneous heart-rate variations were absent, but adaptation reactions to mental and physical stress were normal. Patients of both groups had an impaired awareness of normal and arrhythmic cardiac activity. Lack of vagal inhibition in diabetic neuropathy and noradrenergic activation in hyperthyroidism may be the respective causative factors in the described disorders of regulation and awareness.