Decreased Vagal Influence on the Heart After 24-week Carnitine Supplementation

摘要

L-carnitine which shuttles fatty acid into the mitochondria is known diet supplement used by athletes to improve physical performance. It is also used in supplementary treatment in cardiac insufficiency. Since effect of L-carnitine on cardiovascular regulation is unclear we investigated whether its prolonged supplementation would affect autonomic nervous system (ANS) control upon the heart in healthy elderly volunteers.Thirteen apparently healthy women aged 64 to 71 were supplemented in the double-blinded fashion with either 1.5 g of L-carnitine or placebo for 24 weeks. High resolution electrocardiogram was recorded before and after the supplementation. Time- and frequency-domain heart rate variability (HRV) analysis was performed to assess ANS control on the heart.Following L-carnitine supplementation the overall HRV represented by TSP or SDNN insignificantly decreased with a significant reduction of parasympathetic-related HRV indexes: rMSSD, HF and SD1. Consistently, a tendency towards an increase of indexes of sympathovagal balance: SDNN/rMSSD and SD2/SD1 may reflect vagal withdrawal. Reduction of autonomic control on the heart after L-carnitine chronic supplementation may be regarded as its adverse effect related to reported increased risk of severe cardiac events.