Effects of dietary omega‐3 fatty acids on the heart rate variability response to myocardial ischemia or exercise

The effects of long chain omega‐3 fatty acids (n‐3 FAs) on heart rate variability (HR & HRV) in response to a physiological stress (e.g., exercise or acute myocardial ischemia) are unknown. Therefore, HR and HRV (0.24 to 1.04 Hz component of R‐R interval variability, an index of cardiac vagal regulation) were evaluated at rest, during exercise, and during a 2 min coronary occlusion at rest, before and 3 months after n‐3 FA treatment (docosahexaenoic acid + eicosapentaenoic acid, as esters: 4 g/day, n = 20) or placebo, (CO, corn oil, 1g/day n = 15) in dogs with healed infarctions. The treatment elicited significant (P<0.01) increases in left ventricular n‐3 FA levels (CO 0.8 ± 0.1 vs. n‐3 FA 7.0 ± 0.4%), reductions in baseline HR (Δ pre–post treatment: CO −0.2 ± 4.0 vs. n‐3 FA −10.3 ± 2.8 bpm), and increases in baseline HRV (Δ pre–post treatment: CO, 0.1 ± 0.2 vs. n‐3 FA 0.6 ± 0.3 ln ms2). However, n‐3 FAs did not alter the changes in HR or HRV induced by either the coronary occlusion or exercise. These data demonstrate that dietary n‐3 FA produced increases in baseline cardiac vagal regulation but did not alter the response to a metabolic challenge. Therefore, it is likely that the putative cardiovascular benefits of n‐3 FA are not mediated solely by increases in cardiac vagal regulation.