Omega-3 fatty acids are associated with known cardioprotective benefits. Key among these omega-3s are eicosapentaeonoic acid (EPA) and docosahexanoic acid (DHA) This has been demonstrated in epidemiological studies as well as in one major Italian study, GISSI–2—in which 800 mg/day of omega-3 fatty acids was associated with a 20% reduction in all-cause mortality and almost a 50% reduction in sudden death in a post-myocardial infarction (MI) patient population. That study laid the foundation for current recommendations from the American Heart Association (AHA), who suggest that patients with known coronary artery disease (CAD) consume about 1 g of omega-3 fatty acids a day. The AHA also recommends that non-CAD patients consume at least two servings a week of preferably oily fish to reduce the risk of developing heart disease.
  In addition, there is also some recent evidence to suggest that omega-3 fatty acids may lower the incidence of atrial fibrillation (AF), a particularly common complication in CAD patients following coronary artery bypass graft (CABG). To that end, Dr. Leonardo Calo, San Filippo Neri Hospital, Rome, Italy, and colleagues evaluated the potentially protective benefits of omega-3 fatty acids, given in the form of n-3 polyunsaturated fatty acids (PUFAs) consisting of EPA and DHA at a ratio of 0.9:1.5, in a post-CABG patient population who are at high risk to develop AF. A total of 160 patients were prospectively randomized to two groups: one to usual care before and after elective CABG, and the second to usual care plus PUFAs at a dose of 2 g/day.

“Treatment was initiated a minimum of seven days before CABG and was continued until the day of discharge from the hospital,” Dr. Calo reported. Baseline characteristics between the two groups were similar. The primary endpoint was the incidence of post-operative AF lasting more than five minutes or that caused hemodynamic compromise.

Results revealed that the incidence of post-operative AF was 33.3% in the usual-care group compared with 15.2% in the usual care plus PUFAs group—“an impressive 58% reduction in post-CABG AF with PUFAs at a dose of 2 g/day,” Dr. Calo noted in an interview. Survival cures tracking patients free of AF following CABG out to 17 days’ post-CABG were also highly significant (P=0.009). The reduction in the incidence of AF in the usual care plus PUFAs arm was also associated with a significantly shorter hospital stay at 7.2 days compared with 8.3 days for placebo controls (P<0.05).
No differences were observed in post-operative complications, which occurred in five patients who received additional PUFA (6.8%) and six patients who did not (7.9%).
“This study is the first study to demonstrate that the administration of omega-3, PUFAs, significantly reduces the occurrence of post-operative AF in patients undergoing CABG and that it does so to an extent that is at least in the range of that reported for beta blockers, sotalol or

amiodarone,” Dr. Calo and colleagues concluded, “and [because] PUFA supplementation is safe, [it] can be administered to all patients undergoing CABG.”

It is presumed that the omega-3 fatty acids confer their cardioprotective benefits by reducing susceptibility to fatal arrhythmias, but whether this effect is mediated by changes in myocardial membrane lipid composition or through autonomic factors is not known.
  In an effort to better describe the effects of AHArecommended intakes of omega-3 fatty acids, Dr. William Harris, Professor of Medicine, University of Missouri, Kansas City, and colleagues, assigned 18 men with documented CAD to 1 gram of omega-3 a day or placebo for four months. After four months, the men were crossed over to the alternative treatment for an additional four months. “At the end of each period, a non-invasive cardiovascular profile was obtained,” Dr. Harris observed, “and this included measures of large and small artery compliance, heart rate, blood pressure and estimates of cardiac function.”
  Investigators failed to detect any effect of omega-3 fatty acid supplementation on inflammatory markers, blood pressure or arterial compliance. On the other hand, they found that supplementation reduced resting heart rate by about 5 bpm, per minute “which was very good,” Dr. Harris indicated. While on omega-3 supplementation, patients also had an increase in left ventricular ejection time and stroke volume, while heart rate recovery at one minute post-exercise also tended to increase, the authors added.

“It’s not clear how omega-3 supplementation decreases heart rate,” Dr. Harris said in an interview, “but if this dose of omega- 3 does reduce heart rate, that would reduce the risk of sudden death in and of itself.”
  In an unrelated study also presented by Dr. Harris, a number of demographic factors which might influence variance in the Omega-3 Index were explored. The Omega-3 Index is believed to be largely determined by omega-3 fatty acid intake.

  “The purpose of this study was to estimate normal values for the Omega-3 Index in adults from a mid-Western city and to explore the effects of age, gender, ethnicity, smoking, body mass index (BMI) and diabetes on this index, independent of fish intake,” study authors explained. To that end, investigators measured the Omega-3 Index in blood taken from 163 healthy adults living in Kansas City, none of whom were taking fish oil supplements. “On average, the Omega-3 Index in this population was 4.9%,” Dr. Harris reported.
  On multivariate analysis, several factors were found to significantly influence the Omega-3 Index. The first and “expected” factor was the number of servings of tuna and nonfried fish per month, which increased Index values by 0.24 units with each additional serving of tuna or non-fried fish. Age also affected Index values, rising 0.5 units for each decade in age. The Index in turn fell by 1.13 units in the presence of diabetes and by 0.1 units with each unit increase in BMI. All of these factors were statistically significant.
  Notable, too, was the proportion of purportedly healthy mid-Western adults—only 9% overall—whose Omega-3 Index values fell into the 8% zone that is felt to be desirable for CAD prophylaxis, Dr. Harris added.
  In contrast, some 44% of the study group had Omega-3 Index values that fell into the proposed undesirable zone of less than 4%. “The inverse associations with BMI and diabetes suggest that reduced tissue levels of omega-3 fatty acids may explain at least part of the increase in CAD risk associated with these conditions,” Dr. Harris observed, “and the data also suggest that many Americans may be deficient in omega-3 fatty acids.”

Asked how physicians might encourage their patients to include more omega-3-rich fish in their diet, Dr. Harris suggested that they obtain the appropriate test and measure blood levels for omega-3 fatty acids.
  Available at the Saint Luke’s Mid American Heart Institute’s hospital laboratory where the test originated, the test, called the OmegaMetrix, allows physicians to place a blood sample on a filter paper they can mail back to the laboratory and results can be sent back from the laboratory to the physician. Physicians who are interested in obtaining the test may consult the hospital web site:www.omegametrix.com for further details.