Hello Hill,
I am by no means an expert but having had a fair few heart problems with cardiomyopathy I do know that some of the medications heart patients are given like diuretics and some of the blood pressure medications can cause the blood sugar to rise. That is probably why the hospital suggested that you increase your insulin.
That aside, those numbers are pretty high. Might be an idea to ring 111 and get a bit of advice, especially as you have just come out of hospital.
My DSN was really helpful in the aftermath of some of my heart troubles - perhaps give yours a ring at the surgery on Monday morning?
Hope you are feeling better soon. When I got carted into hospital with chest pains and breathlessness it seemed to come out of the blue and it was a terrible shock. Takes a while to adjust. Don't be at all surprised if you are feeling all at sea at the moment.
All the best,
P