Test for autonomic function to establish the norm: a useful tool for evaluation in various clinical disorders

ABSTRACT

Little information is available regarding the responses of the Jamaican population to the Valsalva manoevre (VM), a test to investigate the integrity of the autonomic nervous system (ANS). This study is aimed at investigating the cardiac autonomic control in the Jamaican population, to explore the range of responses and to establish the norm. Such an explorative investigation provides an important tool to uncover autonomic dysfunction in psychosomatic, cardiopulmonary, metabolic and neural disorders. Fifty male and fifty female Jamaicans, who were apparently healthy and did not indulge in any drug use and smoking, are asked to perform the VM in a semirecumbent position. A tachograph (Grass model) and standard electrocardiographic leads are used for the graphic presentation of the subjects' beat-to-beat heart rate changes. The Valsalva ratio (VR) is calculated by dividing maximum tachycardia and maximum bradycardia during the VM. The mean VR for the female (2.41ñ0.18) is greater than that for the male (1.63ñ0.27) (p<0.001). Female subjects exhibit a higher basal heart rate (88+6 as against 77ñ7 in the male) and a greater magnitude of bradycardia (33 as against 4 in the male). The values for VR are above the minimum of 1.5 proposed in the literature. Relative roles of the sympathetic and parasympathetic nervous systems may differ in the male and female subjects, thus accounting for a higher VR in the female. This test is simple, safe, noninvasive and reproducible and is useful to detect the abnormal autonomic function in various conditions, including states of pregnancy and stress (AU)