Hoping you can tell me, is 240 bpm heart beat dangerous?

Can be: By itself, you'd probably be ok, but at 43, there's a chance of some blockage in the arteries causing chest pain or damage. These rates, by the way, are never normal, and a cardiac electrophysiologist should be consulted to figure out where it's coming from and if it can be treated (spoiler alert: if you find a good ep, it usually can). Maybe ed gerstenfeld at ucsf or eric topol @ scripps?