The interaction of heart rate and blood pressure variations for AV dissociation illustrated by a closed-loop heart rate control model

The atrial rate variability measured under an atrial-ventricular (AV) disassociation condition, e.g. fixed-rate ventricular pacing, has shown a pattern in which the main frequency components varied with the ventricular rates that very different with the AV synchronization condition. Some evidences showed that beat-to-beat blood pressure variation might play a role for this phenomenon. To demonstrate the possible mechanism for the interaction between atrial rate variability and blood pressure variability in AV dissociation condition, a close-loop heart rate control model considering the baroreflex was created in this study. In this model, an integrating pulse frequency modulation model was used to generate the heartbeat and its input was transformed from the blood pressure waveform. One simulation is to automatically generate heart rate variability and blood pressure variability. In this case the blood pressure waveform for each beat was shaped using a curve with a variable maximum representing systolic blood pressure that was determined by each AV delay. The other simulation is to generate atrial rate variability using the real blood pressure waveform data recorded from AV-block patient. The results demonstrated that the frequency domain features for the real atrial rate variation could be approximated with real blood pressure waveform data by this model when the mean heart rate was tuned.