Vent away! and welcome to NeuroTalk

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I've had the near black out faint spells before, but mine I know to have been caused by hormonal changes. Perhaps this too can affect men?
It could definitely be an MS 'thing', but it could be something else entirely as well.
I'd definitely bring this to your neurologist/GP's attention. I wouldn't want to mess around with a racing heart during physical activity resulting in fainting spells. I'd again, definitely have that looked into.