Effects of low-level carotid baroreflex stimulation on atrial electrophysiology

This study aimed to investigate the effects of low-level carotid baroreflex stimulation (LL-CBS) on atrial electrophysiology.

In protocol 1 (LL-CBS on physiological state), anesthetized rabbits were subjected to LL-CBS (n = 10) or surgical exposure (n = 6) for 1 h. In protocol 2 (LL-CBS on acute rapid atrial pacing), anesthetized rabbits underwent 3 h of rapid atrial pacing (RAP) with concomitant LL-CBS in the third hour (n = 7) or 3h-RAP without LL-CBS (n = 6). Carotid baroreceptor surrounded by electrodes allowed LL-CBS at 20 % below the voltage required to reduce systolic blood pressure or heart rate. Effective refractory period (ERP) and monophasic action potential duration (MAPD) were determined, and power spectral of heart rate variability (HRV) was analyzed at baseline as well as after interventions in all groups, respectively.

In protocol 1, LL-CBS significantly prolonged the ERPs, MAPD90, and MAPD50 and increased high-frequency (HF) HRV component but it decreased low-frequency (LF) HRV component and LF/HF ratio. In protocol 2, 3h-RAP significantly shortened ERPs, MAPD90, and MAPD50 and decreased HF but it increased LF and LF/HF ratio. However, LL-CBS reversed the variations caused by RAP.

LL-CBS prolongs ERPs and MAPD of the left atrium and attenuates RAP-induced atrial electrical remodeling including the shortening of ERPs and MAPD, probably by modulating the autonomic nervous system.