The review identified twelve randomised controlled studies involving 32,779 patients and aimed to assess the effect of supplementation on arrhythmic endpoints of sudden cardiac death and pacemaker implantation. Secondary outcomes included all cause and cardiac mortality. In addition, subgroup analyses reviewed the effect of different formulations.
The analysis found no beneficial effect for either arrhythmic outcome or all cause mortality but there was an observed benefit in death from cardiac outcomes. There was no dose response for this outcome based on formulation with respect to EPA and DHA content.
Limitations of the study include wide variability in the fish oil formulation used and statistical heterogeneity among the implantable cardiac defibrillator studies. Additionally, the results are mainly driven by two large studies (Gissi-Prevenzione and JELIS) that account for 92% of the patients reviewed.
Adverse events reported in the studies were usually gastrointestinal in nature and included diarrhoea and dyspepsia.
The authors note that, "the optimal dose or formulation of fish oil is unknown, but it seems reasonable to use a daily formulation similar to that used in the GISSI-Prevenzione trial". They also suggest that future trials might be designed to help clarify the mechanism for the observed benefit in cardiac mortality.
Action: This analysis confirms an association between fish oil consumption and a reduction in cardiac mortality. Clinicians should continue to implement NICE recommendations that encourage adequate dietary intake followed by supplementation in cases where this patients not willing or able to make dietary changes.
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