To be relieved or not. Results from IR

My son had a new set of arteriograms yesterday at Children's Hospital of Philadelphia.
Jimmy was born with Parkes-Weber syndrome. His entire right leg, from hip to toes, is affected. Other than the appearance, this has been mainly asymptomatic for years.
Last year, Jimmy was having pain in his PWS knee. Ortho determined that parts of the knee had bone that was dying. She scoped the knee and he was on crutches for 11 weeks. Soon after putting the crutches away, Jimmy was complaining of foot pain. Once again, Ortho found area of bone cysts with stress fractures and put Jimmy in a walking boot. He wore this all summer long. At this point our otho told us we needed to get him seen by a vascular specialist. We decided to take him to the vascular malformations team at CHOP.
About 2 months ago, Jimmy got faint in church, had severe heart palpitations and was very frightened. Took him to the ER. They found nothing but did mention his heart was enlarged. This freaked my husband and I out, so we had him to his cardiologist that same week. Cardiologist did an echo, ekg and physical assessment and felt Jimmy had high-output cardiac failure.
After more freaking out, I called Dr. Ann Marie Cahill and scheduled the studies. She was going to see if there were any areas to embolize or shunt in order to slow blood flow and decrease work load on heart.
Our cardiologist indicated that if we could not find a solution, his leg would have to be amputated to protect his heart. More freaking out.....
Yesterday IR determined there was nothing they could do to slow blood flow down. Even though his leg is essentially a giant AVM, all the connections are normal. We prepared to schedule a cardia MRI to figure out where they would have to amputate.
Dr. Cahill had asked the cardiologist that works with the vascular malformations team to consult on the case. He did an Echo and new ekg. He also listened to my son's heart for what seemed like forever. He felt Jimmy's heart was fine and was handling the flow just fine. It is larger, but that is normal for him. He saw NO REASON to take the leg because of the heart. More freaking out...but happy!
After having a day to digest the rollercoaster ride that was yesterday I am left wondering how two cardiologists can see the same thing so differently.
What would you do? I am thrilled with the idea of not taking my sons leg. Do we just go to monitor mode?

Mamakosco, I think you will get good feedback on this question from others with PWS from the Facebook group I recommend earlier and also from Sean: http://www.avmsurvivors.org/profile/Sean

I would also recommend you consult the team at Cincinnati Children's and get an opinion. Denise Adams is an expert in complex vascular anomalies. She is also conducting a trial on sirolimus, a drug which may stabilize malformations, particularly those with a lymphatic component.

Also, I forgot to ask: does Jimmy wear compression garments to help with pain? Or are they contraindicated?

Eileen, your insight was just what I needed! Thank you.
Dancer mom, he wears light compression from the knee down.

My prayers to your family…I live in NYC and we have excellent physicians here I would get a second opinion and further testing. Please keep hope some hospital I have in mind if interested are Columbia Presbyterian, Lenox hill, Roosevelt, and Mount Siani to name a few. Best wishes and God bless you.