It is true that solar flares can push someone who has a natural propensity for a heart attack over the edge into said heart attack, just the same as can will push an area with a propensity for earthquakes into said earthquake. This website talks extensively about the various effects that the sun's radiation fluctuations have on the Earth itself, as well as the assorted species that live on the earth: https://www.youtube.com/user/Suspicious0bservers/featured