LAIV

Three years ago (Sept 07) I had an aortic valve replacement. One year ago the LAIV was 31ml/m2, and when checked this year, was 51ml/m2 (first ECHO reading) and 41 ml/m2 (second ECHO reading while doing a recumbent stress test). An abnormal exercise stress EKG was also reported. My physician said, "for the most part everything was normal and there isn’t much to be concerned about." What level does must the LAIV reach before I should be concerned? I'm 70-y-o but play tennis competitively at a high level. Is there any reason to change my active lifestyle?