Does all radiation affect the heart or only radiation targeting in areas around the heart?

Generally speaking, radiation damage only effects the heart when it's directed at or near the heart. Radiation therapy to one of the extremities or to the head or some other part of the body, it's pretty targeted so it doesn't have any direct effects on the heart. It can have other effects that can affect the heart. It can affect blood cells. It can affect your immune system, that sort of thing, but direct toxic effects to the heart are generally only considered when there's radiation in or near the heart.