Cardiovascular reflex tests and the resting heart rate at night and during testing

Possible effects of environmental stress-induced elevation of the heart rate on the magnitude of cardiovascular autonomic responses were studied in 123 healthy subjects. The nocturnal heart rate was evaluated using ambulatory 24-h ECG monitoring. Some of the cardiovascular responses were found to be significantly weaker in those subjects whose resting heart rate during testing was greater than 10 beats min-1 higher than the resting nocturnal heart rate. It is thus highly important to minimize the environmental disturbances during autonomic testing.