Kellan is 60 years old and in his doctor’s office for a rout…

Kellan is 60 years old and in his doctor’s office for a routine checkup. The doctor completes his basic exam ans says that Kellan has developed an heart murmur. This surprises him because he has never had this problem before. In a sentence or two….What is a heart murmur and what heart structure is most likely the cause of this new problem?