Varying postprandial abdominovagal and cardiovagal activity in normal subjects

BACKGROUND: Several studies have supported the hypothesis of different presentations in the autonomic nervous system (ANS) between cardiac and gastric vagal activity. Due to the regionality of the ANS, different responses among different organ systems to the same stimulation (such as a meal) are quite possible. METHODS: In this study we monitored the postprandial changes of heart rate variability (HRV) and gastrointestinal (GI) hormones to determine whether both responded in a similar pattern. Twenty-two healthy volunteers (6 males and 16 females) were enrolled. After recording a baseline ECG rhythm, further recordings were made at 20 min intervals for 120 min after a test meal. Serum human pancreatic polypeptide (PP), leptin, and total and active ghrelin levels were measured. KEY RESULTS: After the meal, HR increased significantly from baseline at each time point, except for 20 min after the meal. The high frequency (HF) power decreased significantly from 40 min to 120 min after the meal. In addition, the low frequency (LF) power also decreased significantly from 60 min to 120 min. However, the LF:HF ratio increased significantly from 20 min to 120 min. There was a marked increase (>2 fold) of PP at 20 min after the meal, and the increase was sustained throughout the test period. CONCLUSIONS & INFERENCES: These findings suggest that HRV reflects cardiac, but not equivalently, abdominovagal activity. Therefore, HRV as an abdominovagal activity measurement in patients with GI functional problems should be used with caution, and other markers such as PP should be included.