R-R variations, a test of autonomic dysfunction.

Beat-to-beat variation of the heart rate was studied as a test of autonomic function. Recordings were made during quiet breathing, deep breathing and tilting from supine to upright position. The heart rate variations were expressed as a % of mean R-R interval. In order to establish normal criteria, the influence of age, wakefulness and intra-individual variations was studied in healthy volunteers. A negative correlation with age was found for all measured parameters. Patients with diabetic polyneuropathy differed from age-matched controls. Patients with symptoms of autonomic failure showed smaller variations than those without such symptoms.