Several randomised controlled trials and epidemiologic studies have demonstrated the cardioprotective effects of omega-3 fatty acids, in particular docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). While these fatty acids are believed to decrease susceptibility to heart arrhythmia, it remains unclear as to whether this effect is mediated by direct cardiac mechanisms of classic risk factors.
In this randomised, double-blind, placebo-controlled trial, 18 white men with a history of myocardial infarction were randomised to receive three capsules containing a total of 810 milligrams of omega-3 fatty acids (585 mg of DHA and 225 mg of EPA) per day or identical placebo capsules for two four-month periods in a crossover design. At the end of each period, heart rate (HR), heart rate variability and heart rate recovery after exercise were determined, along with effects on arterial compliance, blood pressure, cardiac function and other measurables.
“Our principal findings were that omega-3 fatty acids significantly decreased HR at rest, accelerated the return to a normal HR after standing and exercise, and increased HR variability,” the researchers stated. Omega-3 fatty acid supplementation decreased resting heart rate from an average of 73 beats per minute to 68 beats per minute. Also, omega-3 supplementation was associated with a 19% decrease in heart rate one minute after exercise, which was accompanied by “appropriate increases in stroke volume and ejection times”.
A high HR at rest (especially in men) has been strongly linked to cardiovascular events, including mortality. The decrease in HR noted in the present study is in the same range as that observed with beta-blocker therapy, another intervention that has been shown to decrease the risk of sudden death. A recent meta-analysis has associated a small but significant decrease in HR with increased omega-3 fatty acid intakes. Our observations extend these findings and suggest that modulation of HR can be achieved in patients with known coronary heart disease who consume recommended amounts of EPA plus DHA.