CARDIOVASCULAR AUTONOMIC NERVOUS-SYSTEM TESTS - DETERMINATION OF NORMATIVE VALUES AND EFFECT OF CONFOUNDING VARIABLES

Objective: To determine normative values for heart rate variation to d eep breathing (VAR) and Valsalva ratio (VAL) as well as the effect of various confounding variables on these measures using data from a larg e group of normal subjects collected from multiple centers. Research d esign and methods: VAR and VAL were measured on 611 normal subjects, a ge range 9-79, fi om 63 centers and was analyzed at a single Autonomic Nervous System Reading Center. Using simple and stepwise logistic reg ression the effect of age, gender, height, weight, mean arterial blood pressure (MAP) and body mass index (BMI), on VAR and VAL was evaluate d. Results: The 95% normative values range (values at 2.5 to 97.5 perc entile) for VAR (n = 580) was 12.8-103.5 (mean 49.7) and for VAL (it = 425) was 1.31-2.97 (mean 1.97). No gender effect was found for either VAR or VAL (p > 0.05). VAR correlated inversely with both age and MAP , while VAL correlated inversely with both age and BMI. Since age is t he principal confounding variable for both VAR and VAL, normative valu es are also presented stratified by age. Conclusion: Normative values for VAR and VAL based on a large population sample are presented. Howe ver, the values presented may not be valid in patients with morbid obe sity or malignant hypertension. These data are applicable for either i ndividual patients or for use in multicenter research trials.