Assessment of vagal control of the heart in diabetes. Measures of R R interval variation under different conditions

Abstract

R R intervals and R R interval variation were measured in 2 selected groups of diabetic subjects; one group was selected because vagal control of the heart appeared normal, the other group was selected because they lacked vagal control of the heart. The means of the R R intervals for the 2 groups were not significantly different under various conditions (sleeping, lying, during deep breathing, sitting, standing, and during upright activity). The standard deviations of the R R intervals for the 2 groups were only significantly different during deep breathing and upright activity. It is suggested that cardiac vagal function is not reliably assessed by measurements of R R interval variation during quiet standing, but useful information may be obtained during deep breathing.