Hi rick,
Anytime we think there is something wrong with our children we all get worried. I am not sure what they were looking for on the echocardiogram based on an innocent murmur and unfortunately am not sure what to tell you. Hypertrophic cardiomyopathy echos are usually pretty straight forward on physical exam. If the echocardiogram is normal, then you probably do not have much to worry about. If they are concerned about hypertrophic cardiomyopathy, you should be reassured that you and your twin do not have it, but follow up echos are important. Hypertrophic cardiomyopathy can show up later in life or as kids grow older. It is very easy for me to say this -- but try not to worry about what they don't have. As a parent, I know this is hard.
I hope this helps. Good luck and thanks for posting.
Does this help?
Thank you