I am sorry I am just responding now to your post. I am not very familiar with this disorder and I was hoping another member may have input for you. I can understand your fear and kudos to your hubby for getting you in for an MRI sooner rather then later.
Here is a link to Cleveland Clinic that you may find helpful:
I don't usually do this but I have found an online support forum that may be helpful and supportive for you as we don't seem to have any members that are dealing with this problem. I feel bad that we are unable to give you awesome advice but please know we do care about you and want you to have the best care and support during this difficult time.
I hope that you will stay with us and that you will share what you learn about ARVD with all of us. We have a huge following of people that read the forums but never post so know anything you share will help others .