Vagal rebound and recovery from psychological stress.

OBJECTIVE: To characterize cardiovascular recovery and examine the possible relationship of vagal activity and reflexes to risk for heart disease. METHODS: Subjects performed cold pressor and mental arithmetic tasks. Heart rate, heart period variability, and pre-ejection period were obtained for 1 minute before, during, and after each task (Experiment 1). In the second experiment, subjects performed a Stroop color-word task and a mental arithmetic task. Heart rate, heart period variability, blood pressure, and baroreflex sensitivity were obtained during the 5-minute baseline, task, and recovery periods (Experiment 2). RESULTS: In Experiment 1, heart rate during recovery was lower than baseline despite continued pre-ejection period shortening, whereas recovery heart period variability was higher than baseline. In Experiment 2, blood pressure increased throughout the session. However, recovery heart rate after mental arithmetic was lower than baseline heart rate, and heart period variability was higher during both recovery periods than during baseline. Vagal rebound, a sharp increase in variability in the first minute of recovery, was reduced in men in Experiment 1 and in individuals with a family history of cardiovascular disease in Experiment 2 and was associated with degree of change in baroreflex sensitivity between task and rest. CONCLUSIONS: Cardiovascular recovery from stress is associated with increased vagal modulation despite residual sympathetic activation. Vagal rebound may be involved in mechanisms resetting the baroreflex sensitivity at the onset and offset of stress. Diminished vagal rebound during recovery from stress is associated with standard risk factors for cardiovascular disease. The results support an association between attenuated vagal reflexes and risk for cardiovascular disease.