I haven't had any heart issues but I am diabetic on insulin and wear a continuous glucose monitor. With that I can see a graph of my glucose levels and quickly see what eating certain foods and doing certain exercises does to it. A week ago I switched from doing a fast walk on a treadmill using some incline to walking outside. I do about 4 miles and the middle 1/3 of it I'm walking a 7yr old very sweet but very fat Labrador Retriever. She slows me down a bit but I still manage to average 19 minute miles. Without her I can do 17-18 minute miles. I've noticed on my Apple Watch my heart rate is about 20 less than when I did the treadmill. 120 vs. 100. I enjoy the walking over the treadmill and I like getting my "dog fix" in (wife refuses to get a dog). Either exercise causes my glucose levels to fall off a cliff, I even have to carry a glucose tablet with me when walking just in case I get too low.
The point is you don't need to do heavy exercise to get good health benefits. My knees are in great shape and I hope to die with the same ones I was born with.