A model of dynamic vagus-sinoatrial node interactions

Area of Science:

• Cardiovascular Physiology
• Computational Biology
• Cardiac Electrophysiology

Background:

• The vagus nerve plays a crucial role in regulating heart rate through parasympathetic control.
• Understanding the dynamic interactions between vagal input and the sinoatrial (SA) node is essential for explaining cardiac function and dysfunction.

Purpose of the Study:

• To develop and utilize a computer model to simulate dynamic vagus-sinoatrial (SA) node interactions.
• To investigate the effects of single and repetitive vagal stimulation on SA node pacemaker activity.
• To explore the model's ability to predict cardiac rhythms and dysrhythmias.

Main Methods:

• Developed an empirical model of vagus-SA node interactions.
• Utilized experimentally derived phase response curves (PRCs) to simulate vagal effects on pacemaker cycle length.
• Simulated interactions with single and repetitive vagal inputs at various frequencies and cycle lengths.

Main Results:

• The model accurately predicted SA node responses to vagal stimulation, including entrainment patterns.
• Simulations demonstrated stable entrainment at specific vagal frequencies with harmonic relationships (e.g., 1:1, 2:1).
• Identified zones of instability leading to arrhythmic patterns and simulated conditions resembling sinoatrial block and atrioventricular dissociation.

Conclusions:

• The computational model effectively replicates dynamic vagus-SA node interactions and their impact on heart rate.
• The findings enhance the understanding of parasympathetic control of heart rate and provide insights into the mechanisms of cardiac dysrhythmias.
• The model serves as a valuable tool for studying complex cardiac rhythm dynamics.