Clinical significance of the resting heart rate in the assessment of autonomic function by cardiovascular reflex tests.

The effect of the resting heart rate on heart rate responses in standard cardiovascular autonomic function tests was studied in a sample of 845 subjects. The responses, which were calculated using instantaneous heart rate changes and R-R interval ratios, were divided into quantiles according to their absolute values. The effect of resting heart rate on each cardiovascular index was studied by linear regression analysis, first in the whole group and then in the group with responses belonging to the lowest quantile. As regards the whole group, eight out of ten indices diminished significantly with increasing resting heart rate. However, no response-attenuating effect of increasing resting heart rate could be found among the responses in the lowest quantile. Since particularly low heart rate responses in cardiovascular reflex testing are of clinical importance when autonomic neuropathy is diagnosed, it can be concluded that the usefulness of standard cardiovascular reflex test based on heart rate changes is not limited by the level of the resting heart rate.