I'm sorry to hear of your continued problems. It must be quite frustrating.
Some links and thoughts. my.clevelandclinic.org/heart/services/procedures/pericardiectomy.aspx
I started to ponder imaging techniques, just as an inquisitive type, not from any professional background, which I don't have.
Nevertheless, this article addresses causes of pericarditis, briefly, and imaging techniques used for diagnosing same.m.circimaging.ahajournals.org/content/3/3/333.full
I'm curious if they have used advanced imaging techniques. Please read this article if you have not yet done so, you may glean additional information.
Another on imaging and again info on pericarditis. imaging.onlinejacc.org/article.aspx?articleid=1109614
Another, more focused on imaging techniques. emedicine.medscape.com/article/349447-overview
And another, very comprehensive discussion of the images and findings. www.jcmr-online.com/content/11/1/14
I hope these are of some assistance. You have decisions to weigh, I have been there before as well. My son was born without a muscle group on one side of his chest. The original pediatricians told us that my son would be fine without the group, another doctor told us that without surgery and procedures he would be deformed. We elected not to have the procedures, he's in his 30's now, he's just fine.
Myself, not being fully aware of all the factors and not having the education to understand them, would probably be careful, I'd want to be sure of the cause of the pericarditis, rule-out inflammatory processes by testing (if possible), and would want to be sure the heart and pericardium are clearly imaged to preclude any surprises.
Best wishes for health for your family.