I developed constrictive pericarditis following earlier heart valve surgery. When I was 48 years old, I had a pericardiectomy at the Mayo Clinic. That was definitely the right decision for me.
As a pretty active guy, I noticed the symptoms of constrictive pericarditis early - a lot of pressure in my head whenever I bent over, tiring early during exercise, ascites, the pulsing jugular vein on my neck, and swollen ankles and hands. My doctor noticed that my blood test showed that certain liver enzymes were higher than they should be. about 6 months after my symptoms showed up, I had a correct diagnosis, which I understand is better than most. about 1.5 years after my first symptoms, I had a pericardiectomy at the Mayo Clinic.
For me, the decision was pretty easy. Even though I wasn't feeling pain, I didn't want to continue feeling sick the rest of my life, when there was a possible solution. Plus, I read that constrictive pericarditis is usually a progressive disease. Most likely, my health would continue to deteriorate. Plus, there have been studies that show that having the surgery relatively early rather than later results in better outcomes. This wasn't an easy decision because I had 3 young sons that I wanted to be alive for, but I also didn't want them to feel that they had a sick dad, and I wanted to be around for them a long time.
It's hard to say what would happen if you didn't have surgery now. You would likely continue to get worse, but nobody knows how fast. I have heard of cases where people had constrictive pericarditis for decades. On the other hand, it could get worse quickly. My cardiologist was beginning to notice bad changes in my heart echocardiogram that would likely be permanent. The condition was getting in the way of me carrying out my normal life activities. It became tougher to play with the kids or go for a run. Permanent damage was being done to my body - I wanted to take care of the situation as quickly as possible.
It appears that you've got a more slowly progressing case than I had. My cardiologist did tell me that I could wait longer, to see how things progressed, but after reading a lot of research articles on constrictive pericarditis, that did not seem to be the right approach for me. I wanted to feel better, and I wanted to maximize my life expectancy. Several studies have shown that early surgery produces better results.
The good news is that with constrictive pericarditis you have the potential for a total cure via surgery. You are right that the surgery itself is risky. However, the key there is to find a doctor that has performed a lot of these procedures, and has sufficient experience. When I met with my surgeon, he mentioned the 15% mortality rate nationwide, but he told me because he performed so many, because I was relatively young, and because I was in good shape otherwise, the mortality rate was much lower for me (I'm trying to remember... maybe just a couple percent). Constrictive pericarditis is a pretty rare condition - you want to find a surgeon at a major heart center that has had a lot of experience dealing with it. I traveled a good distance to find the best surgeon for this condition. Hopefully you've got that flexibility in the UK.
I hated having constrictive pericarditis. It made me feel miserable and depressed. But for me, pushing for an early resolution was the right thing to do - and I have been very happy with that decision. These days, I have no symptoms of constriction, I am active, and I am living a much better life than if I hadn't had the surgery.
Best of luck! It sounds like you've been through *very* trying times. If it were me, I wouldn't try to put off surgery beyond the period that the doctors recommend, and would want to get it done soon. This is a difficult, awful time in your life, but you can and will get through it.