Your sons appears to have right ventricular hypertrophy. I am uncertain what the cause of this is. He also has electrical conduction changes sch that his heart is more excitable ( short pr) and also, due to the LVH has a conduction delay in the right ventricle. His medical history is complex and i would recommend a full evaluation by a pediatric cardiologist who specializes in arrhythmias.
I would recommend Dr. Rick Sterba, here at CCF if you have any concerns.