I haven't had open heart surgery but I was in a car accident and broke my back in 1991. At the time I was a CAT 2 cyclist and a VERY active backpacker and skier. 5 months laying on my back was a real killer, particularly in terms of mental well being. Suspension mountain bikes were just coming out and as a "GOAL" I purchased one and had it placed in my room, hanging high on the wall so I could see it. It was a slow comeback with plenty of challenges but ultimately I was back (pun intended) nearly 100%. You need to be patient and give yourself time to heal while pushing toward your goals.
BTW, I just received my new Swift a couple of weeks ago and as a big Starlight fan, this one looks good. Last night I packed in all my gear and it felt good with 20lbs. I am very sensitive to weight on my shoulders as a result of the accident and typically carry as much weight as possible on my hips. Load transfer on the Swift is very good but I am already exploring adding a stiff frame sheet and/or stays with load lifters. I use an inflatable down mat and as a result I have cut a piece of closed cell foam for the pad pocket. I really like the pockets on the hipbelt, the simple design, the size, and the fact that the mesh pockets are very useable even with the main bag stuffed full.
Best wishes on a speedy recovery and order the pack - it will really help the process.