There are two different words for heart in the OT, leb & lebab. I don't know any difference in meaning.
The Hebrew "heart" is used where we would use conscience. Sometime I wish to investigate if the Apostle Paul has the earliest references to syneidesis, conscience in history. But in the OT David's heart smote him, where we would have probably have said, "his conscience hurt him." There are many references to heart in the OT, a lot to study. Of course heart is not limited to conscience in the OT.