Greater Intakes of Dietary Omega-3 Associated with Lessened Arrhythmia Risk in Patients after Heart Attack
Smith, PJ et al., Am. J. Clinical Nutr. , 89: 1-6 ,2009
Depts. Of Psychiatry and Behavioral Sciences and Medicine, Duke Univ., Durham, NC ,USA
Higher intakes of omega-3 fatty acids (DHA plus EPA) via fatty fish or fish oil supplements have shown beneficial effects with respect to a reduced risk of sudden cardiac death after a myocardial infarction (heart attack). Further, such protective effects of DHA/EPA omega-3 have been related in part to their anti-arrhythmic effects. Since ventricular ectopy is frequent in patients with coronary heart disease as well as being particularly predictive of a greater risk of cardiac death in post-myocardial infarction (MI) patients , the present researchers studied the relationship between omega-3 intakes and ventricular ectopy in such patients.
A total of 260 post-MI patients (average age of 57 yrs , 63 % male) completed the study . During hospitalization after their MI, the subjects provided information on their average frequency of consumption of various types/categories/servings of food items during the past year from which average daily intakes of omega-3 (n-3) fatty acids could be estimated. The average total intake of all omega-3 fatty acids combined (DHA plus EPA plus LNA) was found to be 760 mg per 1000 kcal (the equivalent of approx. 1750 mg/day for a typical intake of 2300 calories/day). The average combined intake of the fish-based omega-3 fatty acids (as DHA plus EPA) was 19 % of the total omega-3 with the remainder (majority) being consumed as the plant-based LNA (alpha-linolenic acid). Ventricular ectopy was measured in the post-MI patients via 24-hour Holter-monitoring during or immediately after hospitalization for MI. This monitoring indicated that the average number of VPBs (ventricular premature beats) for all patients was 350 per patient per day with a very wide range across individual patients.
Statistical analyses indicated that higher intakes of total omega-3 fatty acids or DHA plus EPA were associated with fewer VPBs during the 24-hour Holter monitoring. A one- gram daily increase in total omega-3 (DHA/EPA/LNA) or (DHA/EPA) were associated with reductions of approx. 2850 and 800 VPBs, respectively, per day. These effects were considered to be ‘clinically meaningful’ by the authors who also suggested that these results could have important implications for the management of patients during the early post-MI period in view of their increased risk for malignant ventricular arrhythmias and sudden cardiac death.
Ventricular ectopy – frequent ventricular ectopic activity refers to frequent (higher than normal) ectopic impulses (ventricular ectopic activity) in the heart. Such frequent ventricular arrhythmias (including VBPs as measured by Holter monitoring) can be a significant risk factor for cardiac death in both apparently healthy individuals and those with a abnormal heart condition.
Dr. Holub's Comments:
The present results are of particular interest to the dietary management of post-MI patients as discussed by the authors. It is noted that the average intake of DHA plus EPA in this population of US-based post-MI patients was only 140 mg/1000 calories which is the equivalent of only 322 mg/day (based on a typical intake of 2300 calories/day). Such a daily intake is only one-third of the intake of 900 mg/day as recommended by the American Heart Association for patients with coronary heart disease (Circulation , 106: 2747(2002). It will be of considerable interest to evaluate the effects of higher intakes of DHA/EPA (via diet and/or supplementation) in other patient groups where ventricular ectopy is recognized as a predictor of cardiac death. Such groups would include those patients showing frequent ventricular ectopy after exercise testing despite their having no history of heart failure or arrhythmia (Frolkis et al., NEJM, 348: 1508 (2003)) as well as heart failure patients showing frequent ventricular ectopy after exercise (O’Neill et al., 44: 820 (2004)).