BS30 Heart rate variability derivatives: frequency domain as a measure of autonomic nervous system function in rabbit coronary-artery ligation model

Background Disturbance in the autonomic nervous system (ANS) is a strong prognostic marker following myocardial infarction (MI), where mortality is still high as a result of sudden death due to lethal arrhythmias. Whilst post-MI neuro-cardiac remodeling is noted, the precise arrhythmogenic mechanisms remain poorly understood. Heart rate Variability (HRV) is a useful measurement of autonomic stone which can add insight. These markers include high frequency (HF) power and LF/HF ratio where HF power is a measure of vagal tone and LF/HF ratio measures both branches of the ANS. Objective To compare HRV measurements using frequency domain markers (HF Power, LF:HF ratio) in post-MI rabbits with Sham controls during high activity (Active) and low activity (Passive) states. Method 10 white adult male New Zealand Rabbits were used for this study. 5 underwent coronary artery ligation, while the other 5 underwent a sham thoracotomy procedure with ligation. Telemetry devices were implanted in both groups. Recordings were taken in 3-hour periods, over 7 weeks. Two key frequency domain markers (HF power and LF/HF ratio) were extracted from Physiozoo and analyzed utilizing the Fast Fourier Transform. Result During Passive recordings, normalized HF Power was higher in Sham (MI:8.31 ± 0.54 nu, Sham: 11.05 ± 0.89 nu, p=0.013). However, during Active recordings, MI rabbits had a higher average HF Power (MI: 5.68 ± 0.55 nu, Sham: 4.00 ± 0.29 nu, p=0.013). Albeit non-significant, in the 24-hour recording Sham group showed a higher HF power compared to MI group (MI: 3.24 ± 0.28 nu, Sham: 3.58 ± 0.31 nu, p=0.42). The LF/HF ratio was higher during Active compared to Passive recordings in both groups with the difference in changes between activity states in MI compared to Sham. Conclusion Autonomic remodeling is seen during the early post-MI period in rabbits following coronary ligation suggesting a reduction in vagal tone which may be an important mechanistic marker of lethal arrhythmias causing sudden death. Conflict of Interest No relevant conflict of interest