Can n-3 PUFA reduce cardiac arrhythmias? Results of a clinical trial

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Abstract

Dietary n-3 polyunsaturated fatty acids (PUFA) derived from fatty fish or fish oil may reduce the incidence of lethal myocardial infarction and sudden cardiac death. This might be due to a prevention of fatal cardiac arrhythmias. So far, however, only few clinical data are available being adequate to define indications for an antiarrhythmic treatment with n-3 PUFA.

In a randomized, double-blind, placebo-controlled study 65 patients with cardiac arrhythmias without coronary heart disease or heart failure were subdivided into 2 groups. One group (n=33) was supplemented with encapsulated fish oil (3 g/day, equivalent to 1 g/day of n-3 PUFA) over 6 months. The other group (n=32) was given 3 g/day of olive oil as placebo. In the fish oil group a decrease of serum triglycerides, total cholesterol, LDL cholesterol, plasma free fatty acids and thromboxane B2 as well as an increase of HDL cholesterol were observed. Moreover, a reduced incidence of atrial and ventricular premature complexes, couplets and triplets were documented. Accordingly, higher grades of Lown's classification switched to lower grades at the end of the dietary period. No changes were seen in the placebo group.

The data indicate an antiarrhythmic action of n-3 PUFA under conditions of clinical practice which might help to explain the reduced incidence of fatal myocardial infarction and sudden cardiac death in cohorts on a fish-rich diet or supplemented with n-3 PUFA. Further studies elucidating the possible link between the reduced incidence of cardiac arrhythmias and sudden cardiac death by dietary intake of n-3 PUFA are warranted.

Introduction

There is increasing evidence from epidemiological and clinical studies that n-3 PUFA exert a beneficial effect on several risk factors of coronary heart disease (CHD) and, accordingly, might be important for primary and secondary prevention [1], [2], [3], [4]. A reduced incidence of fatal myocardial infarction by nearly 50% in populations on a habitual diet rich in fatty fish as well as a decreased rate of lethal reinfarction by 30% despite unchanged plasma cholesterol levels after fish diet or fish-oil supplementation [5], [6] were assumed to be due to diminished coronary thrombosis and lethal cardiac arrhythmias. Moreover, recent epidemiological results indicate a reduced incidence of sudden cardiac death by a diet rich in n-3 PUFA [7], [8], [9]. Sudden death is often found in patients with CHD but will even occur if signs of CHD are absent. It might be predicted by recording cardiac arrhythmias even in patients with asymptomatic or mildly symptomatic ventricular premature complexes (VPC).

In numerous animal experiments an antiarrhythmic action of n-3 PUFA was found [10], [11], [12], [13]. However, only few clinical data are available which suggest an evidence-based recommendation of n-3 PUFA to reduce ventricular arrhythmias in clinical practice [14], [15], [16], [17]. We, therefore, designed a study to examine the antiarrhythmic effect of encapsulated fish oil on cardiac arrhythmias in patients without signs of CHD and heart failure.

Section snippets

Patients

A total of 65 patients (32 male, 33 female) with cardiac arrhythmias without signs of CHD and heart failure were randomly allocated to 2 subgroups. The first group (n=33) was supplemented with 3 g/day of fish oil (3×2 or 2×3 capsules a 0.5 g) over 6 months. The other group (n=32) was given 3 g/day of olive oil (3×2 capsules or 2×3 capsules a 0.5 g) as placebo.

The mean age of the fish oil group (17 male, 16 female) was 45±8 years (mean±SD), the body height being 167±10 cm and body weight 74±10 kg. The

Results

Selected n-6 and n-3 PUFA of serum triglycerides being estimated to verify the patients’ compliance are shown in Table 1. In the fish oil group EPA and DHA were significantly increased whereas linoleic acid (LA) was decreased at the end of the dietary period. The values returned to the initial level 6 months after finishing the fish-oil supplementation (control). In the placebo group except a slight increase of oleic acid the values remained unchanged (not demonstrated).

Biochemical data and

Discussion

Numerous epidemiological, clinical and experimental data indicate a beneficial effect of dietary n-3 PUFA on the risk of CHD and sudden cardiac death [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17]. The reduced incidence of fatal reinfarction [5], [6] despite unchanged plasma cholesterol levels and of sudden cardiac death [7], [8], [9], [10] suggest diminished ventricular arrhythmias in populations ingesting a habitual diet rich in fatty fish or

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