What class was diagnosed? Over a class 5 is serious, below that not so much. Echocardiogram will tell the vet the chin has a heart but not much beyond that since the resolution on something that small I:E heart valves is not there, that was what was told to me by my vet cardiologist who dealt with my severe heart murmur chin. Severe murmur chins need to be watched for congestive heart failure symptoms, can have sudden death from heart attack, need to be on a low protein, low fat diet with no treats, need to be watched for overexertion during play-they can pass out so play is to be somewhat limited, usually they will not play alot anyway since they become tired easily. They can be treated with BP meds if congestive heart failure happens, lasix and lisinopril daily can keep them alive and somewhat normal for years.