Interesting information! I use Omega 3s for joint lubrication, dry eyes, and venous support. I have found that Flax seed Omega 3s work a lot better for me, although they are a little higher.
The slight increase in heart health (below 3% in this study) is likely from the venous support. Using Omega 3s help the tubing in the circulatory system, (with the flax seed oil seeming to work better long term) helps reduce the blood pressure by making the vessels more elastic. This lower BP, would reduce the load on the heart, and is the likely source of the slight improvement.
This Meta Analysis of multiple studies is done very professionally, and I would trust the results! Very good information, Thank You! :)