Objective: Evaluate the presence of cardiovascular autonomic nerve dysfunction in children and adolescents with insulin-dependent diabetes mellitus.
Methodology: We studied 110 patients (54 male, 56 female) and 100 healthy sex and age-matched children. Autonomic nerve function was assessed by standard cardiovascular reflex tests: (1) Fall in systolic blood pressure in response to standing. (2) Heart rate in response to standing. (3) Beat-to-beat rate variation during deep breathing. (4) Quotient of heart rate during and after Valsalva manoeuvre. (5) Change in blood pressure response to sustained handgrip. The coefficient of variation of heart rate was determined from 150 systoles using a microcomputer-based technique. The lower limits of normal were defined according to statistical analysis taking into account the relationship between heart rate variability and age.
Results: Forty-seven of the 110 diabetic children and adolescents studied showed one or more abnormal tests for cardiovascular autonomic dysfunction; many patients had an abnormality in more than one test. Twenty-two patients showed early involvement, 18 patients had definite and 7 severe involvement. No correlation was found between sex, glycaemic control, duration of diabetes or presence of retinopathy and persistent microalbuminuria and the autonomic nerve function.
Conclusions: In the paediatric age group also, autonomic nerve dysfunction can be present in asymptomatic diabetic patients. Heart rate variation during Valsalva manoeuvre and maximum/minimum 30:15 ratio are the most sensitive indices to detect autonomic abnormalities in children.