Concern, Interest
noun
The things related to your heart are the things that concern and interest you the most.
かんしん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
アイツは他人に関心がないんだよ。
He's not interested in others, you know.
うちの場合は、父親の子育への関心がゼロだったんですよね。
In our case, my father had absolutely zero concern in parenting.
皆さん、もっと政治に関心を持ってください。
Everyone, please take more interest in politics.