I can identify with you. I am 76 and had 2 heart attacks and now have a pacemaker. As well, I am 25 lbs overweight.
I have both a diamond Trek road bike and a Catrike.
This spring I injured my left leg, but I found that while I couldn't ride my Trek, I was comfortable on the recumbent Catrike.
I rode the Catrike 18 km (11 miles) about 3 times a week.
Now I am back on the Trek doing 32 km (20 miles) 3 times a week and projecting to increase it to my usual 50 km (30 miles).
The disclaimer is this:
1. Short rides will not reduce your weight.
2. With a trike, you need clipless pedals (and matching shoes) or else on bumps your foot can slide off the pedal. I know this from experience. I have clipless pedals on my Trek and used to have them on the Catrike, but I replaced them with standard pedals and toe clips so that my friends could take the Catrike for a spin. I hit a bump and hurt my ankle when my foot slipped off the pedal.
3. Recumbent trikes are low to the ground and for some people, it can be a struggle getting out of the seat.
4. Trike seats are usually just mesh and not so very comfortable. I added an ObusForme (TM) padded seat to mine for great comfort.