Mathematical explanations for alterations of heart-rate variability after autonomic blockade and during exercise

Some inconsistent results occurred in the assessment of autonomic activity using the spectral analysis of heart rare variability (HRV) in some physiological and pharmacological conditions. In this study, we attempted to clarify the alterations of HRV after sympathetic blockade, vagal blockade and during exercise using a mathematical model. The autonomic activity in normal conditions was assumed first according to experimental evidence. Then autonomic activities after sympathetic blockade, vagal blockade and during exercise were appropriately set accordingly for simulations. Results showed that the alternations of HRV in these conditions were similar to those in actual measurements. We found that the mean heartbeat interval played an important role in the alterations of HRV in these conditions. The inconsistencies for HRV analysis could be explained mathematically by taking the mean heartbeat interval into account.