Cardiac autonomic nervous function during long-term nonpulsatile left heart bypass

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Research
• Medical Device Engineering

Background:

• Cardiac autonomic nervous activity is crucial for cardiovascular regulation.
• Ventricular assist devices (VADs) are used to support failing hearts.
• Understanding the impact of different bypass modes on autonomic function is essential.

Purpose of the Study:

• To investigate the effects of long-term nonpulsatile left heart bypass (NLHB) on cardiac autonomic nervous activities.
• To compare autonomic responses between pulsatile left heart bypass (PLHB) and NLHB.
• To analyze heart rate variability (HRV) changes during prolonged NLHB.

Main Methods:

• Utilized a pulsatile ventricular assist device in 3 goats for an initial 2-week PLHB period.
• Transitioned to a 4-week NLHB period following the PLHB phase.
• Analyzed R-R interval data using maximum entropy spectral analysis to assess HRV parameters.

Main Results:

• Mean R-R intervals increased from 511 ms to 692 ms.
• Coefficient of variation of R-R increased from 10.2% to 14.1%.
• Low frequency (LF) power increased from 747 ms² to 2,855 ms², and high frequency (HF) power increased from 512 ms² to 1,270 ms².
• The LF to HF ratio increased from 2.6 to 6.5, indicating heightened sympathetic and parasympathetic activity.

Conclusions:

• Long-term NLHB leads to a significant increase in cardiac autonomic nervous activity.
• Both sympathetic and parasympathetic nervous systems are activated during prolonged NLHB.
• These findings have implications for the management and design of VADs.