N-3 fatty acids from fish and markers of cardiac arrhythmia

N‑3 fatty acids from fish may protect against heart disease mortality by preventing fatal arrhythmias. The objective of this thesis was to investigate whether this possible antiarrhythmic effect of n-3 fatty acids is supported by short-term effects on electrophysiological markers. We performed two human intervention studies comparing the effects of fish oil capsules supplying 1.5 g very-long-chain n-3 fatty acids with placebo capsules on several markers of arrhythmia risk.In the first intervention study, we observed no effect of n-3 fatty acids on heart rate variability and baroreflex sensitivity in an apparently healthy population. This finding does not support the hypothesis that n-3 fatty acids prevent arrhythmia in healthy subjects via effects on cardiac autonomic control. We also observed no effects of n-3 fatty acids on the standard electrocardiogram of these healthy humans. Additionally, supplementation with n‑3 fatty acids did not lower C-reactive protein concentrations. This makes it less likely that beneficial effects on inflammation are involved in a mechanism explaining the protective effect on heart disease risk of n-3 fatty acids, although we cannot exclude an effect on elevated C-reactive protein concentrations during systemic inflammation. In the second intervention study, we studied a marker closer to arrhythmia endpoints in a more susceptible population. We investigated the effect of n‑3 fatty acids on premature ventricular complexes, a common form of arrhythmia that can provide the trigger for life-threatening arrhythmia. This study was conducted in patients with frequent premature ventricular complexes. N-3 fatty acids were not significantly effective in the treatment of premature ventricular complexes. This makes it less likely that n-3 fatty acids reduce the risk of sudden cardiac death through preventing triggers of arrhythmia. However, we did find a decrease in heart rate<span class=GramE>of 2.1 beat/min</span>on n-3 fatty acids. Such a decrease may predict a risk reduction for sudden cardiac death of about 6% and that can partly explain the cardioprotective effect of n-3 fatty acids. Like in the study with healthy subjects, we did not find effects of n‑3 fatty acids on the standard electrocardiogram in this more susceptible population.</span><span lang=EN-GB style='mso-ansi-language:EN-GB'>The only effect found in our studies that would predict an effect of n-3 fatty acids on arrhythmia risk and subsequent sudden death is a decrease in heart rate. Whether intake of n-3 fatty acids from fish can indeed reduce the incidence of life-threatening cardiac arrhythmia remains to be resolved by clinical trials in high-risk patients