Fish oil meta-analysis: lack of protective antiarrhythmic effect in ICD patients

In total, 1148 patients were included. They all had an ICD and prior malignant ventricular tachycardia (VT) or ventricular fibrillation (VF). In all three trials, patients received either fish oil or placebo capsules.

The primary outcome of the meta-analysis was time to first confirmed VT or VF or death from any cause. Subgroups were also analysed—those having a left ventricular ejection fraction (LVEF) ≤ 30 or > 30, those with ischaemic heart disease or coronary artery disease (CAD), and those with spontaneous VT prior to trial entry.

The meta-analysis showed no convincing protective effect of fish oil versus placebo (relative risk [RR] 0.90; 95% CI 0.67-1.22). Subgroup analysis showed no statistically significant difference in risks of fish oil versus placebo in those with LVEF ≤ 30 (hazard ratio [HR] 0.80; 95% CI 0.58-1.12) or > 30 (HR 1.18; 95% CI 0.64-2.18). In patients with CAD, the hazard ratio was 0.79 (95% CI 0.60-1.06).

The effects of fish oil may vary according to the patient’s disease history and electrophysiology. There appeared to be a trend towards a protective effect in patients with previous CAD or ischaemic heart disease (HR 0.79). The risk of VT or VF tended to be higher (HR 1.48) in patients with a previous VT who took fish oil but did not take anti-arrhythmic drugs. ICD patients taking beta blockers tended to have a higher risk on fish oil (HR 1.29). There may also be a higher risk of ventricular tachyarrhythmia in users of fish oil who are taking lipid-lowering therapy such as statins (adjusted HR 1.48).

Further study is indicated to find out which patients may benefit from fish oil and those in whom it may be harmful.

Reference

1. Brouwer IA, Raitt MH, Dullemeijer C et al. Effect of fish oil on ventricular tachyarrhythmia in three studies in patients with implantable cardioverter defibrillators. Eur Heart J 2009; 30: 820-6.