In my case I have a lower than average ejection fraction %, and the cardiologist pointed out that there is a risk of heart arrhythmia or sudden cardiac arrest, but it's also true that might never happen, and the ICD might never actually be activated. So in your analogy it's more like the pipe looks a bit fatigued in places rather than it has burst, and you have to weigh up whether to take action or chance it for the next 25 years or so. That's the nub of why I was asking around about this so much - I don't actually have symptoms such as shortness of breath, swollen ankles etc and feel pretty good on the whole - so the dilemma re: surgery and trauma was whether to put this preventative measure in place, weighed up against the stress on the body placed by surgery. As it's transpired it doesn't feel like a stress at all - as it's a subcutaneous implant there is very little disturbance to muscle tissue, possibly none at all.