I am 56.
At 47 I was diagnosed with an aortic aneurysm.
Surgery fixed the aneurysm and replaced the aortic valve.
I found that for a time after the surgery I had a problem starting my pull start engines. I have tweaked the design and had numerous trialists over the world (they asked me a for a unit after seeing early versions on you tube).
Anyway - its now available - I hope the unit allow other people to keep doing what they love doing.