My 14 Year Old Son Just Had A Physical On

My 14 year old son just had a physical on Friday for the 2016/2017 school year and since he is going into high school. He is very athletic and aspires to play on the basketball and baseball team so the school needs a physical. During the physical, our doctor conducted an EKG test on him since he is an athlete. The results were abnormal stating the wall of his Heart was thickening. She is sending us for an ultra sound next week. She did however state he did not have to stop playing sports, she just wanted to get it checked since the EKG can be inaccurate at times. Is there cause for concern? My son loves sports and if he is told he can't play, he is going to be devastated.