Eat More Fish for Irregular Heartbeat?

Summarized by Robert W. Griffith, MD
June 4, 2004

Introduction

The many benefits of eating fish have long been known. One of them is due to what are known as long-chain n-3 polyunsaturated fatty acids, or PUFA, which are found in deep-sea fish. PUFA have been shown to have anti-arrhythmic properties, i.e. they help prevent irregularities of heartbeat that can prove fatal.

In one study, men who had experienced a heart attack were put on one of three diets: lowered saturated fat, increased fiber, and increased fatty-fish intake.¹ There was a 29% reduction in deaths in those who ate at least two portions of fatty fish a week; on the other hand, there was no difference in the rate of non-fatal heart attacks. This suggested that PUFA might have anti-arrhythmic properties, as sudden cardiac death is usually caused by intense irregularity of the heart ventricle beats.

To test this further, German scientists have recently performed an interesting study, which is reported in the Lancet, and summarized here.

What was done

The purpose of this lab study was to see if PUFA has a direct anti-arrhythmic effect. Ten patients who had repeated bursts of high-speed ventricular beats (ventricular tachycardia) and who were at risk of sudden death were asked to participate. They had been fitted with implanted defibrillators.

The defibrillator was used to produce ventricular tachycardia by appropriate increases in stimulation, with measurement of the amount of stimulation and the time taken to achieve the tachycardia.

The same procedure was carried out after introducing 100 mL of n-3 PUFA (a preparation of omega-3 marine triglycerides) through the implanted defibrillator.

What was found

It was possible to induce sustained ventricular tachycardia in 7 of the 10 patients at baseline. After infusion of PUFA in these 7 patients, tachycardia could only be produced in 2 of them, while tachycardia was not persistent in 3 others. Thus n-3 PUFA completely inhibited or reduced the severity of ventricular tachycardia in 5 of 7 patients, indicating that the excitability of the heart muscle had been reduced.

The PUFA didn't cause any arrhythmia in these patients.

What this means

The small pilot study summarized here represents an important addition to the evidence that n-3 PUFA does not cause cardiac irregularities, and is indeed likely to prevent them (i.e. act as an anti-arrhythmic agent). This provides a possible explanation for the reduced mortality associated with eating deep-sea fish. Clinical studies are now running to see if such a diet can prevent ventricular tachycardia in susceptible patients. If these are positive, we can include fish oil among our ways of treating heart-beat irregularities. But there are still plenty of other good reasons to start eating more fish, right now!

Source

• Immediate effects of n-3 fatty acid infusion on the induction of sustained ventricular tachycardia. R. Schrepf, T. Limmert, PC. Weber,  et al., Lancet, 2004, vol. 363, pp. 1441--1442

Footnotes
1. Effects of changes in fat, fish, and fibre intakes on death and myocardial reinfarction: Diet and Reinfarction Trial (DART). ML. Burr, AM. Fehily, JF. Gilbert,  et al., Lancet, 1989, vol. 2, pp. 757--761

Related Links
High Blood Levels of Omega-3s May Lower Your Risk of Death
Food Shopping? Add Fish to Your List
Omega-3s, the Heart-Healthy Fats
Nuts Linked to Heart Health in Men

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