Welcome to HCM,
You are having high blood pressure
and Over weight and taking treatment for hypertension
, I presume your Blood pressure is reasonable control.
In such case if routine EKG is being done, I do not know what she meant by shadow but may be your EKG may be abnormal which could be effect of High blood pressure on heart which shows in the changes as Hypertrophy, or there are subtle changes which could point out in adequate blood supply to heart.
In both the cases opinion of cardiologist would be useful for you.
I am glad to learn that you do not smoke and please keep trying for reducing those extra pounds.
Hope nothing serious is there and you continue to have good health.
Please take care of yourself.