yes, you do
contact your job network person and tell them that you will not risk your health
you have been through a JCA, so that stuff should be on your c'link file. if they breach you, appeal it
if you need to get a med cert from your doctor, i'm sure you could get it, however a simple "no, i have a heart valve problem and will not put my health at risk" should suffice. the aim is to get you sustainable employment (and yes, A job, not THE job) however it wouldn't be sustainable if it puts your heart at risk. perhaps contact them about the physical, and whether you would pass anyway - i'm guessing a heart murmur would be a fail if there is a chance of a workplace virus impacting your heart valves. i doubt anyone would want to open themselves up to potential work cover (or more) liability!