dear friend, welcome to HCM>
I appreciate your concerns.
I think a good advice would be to get checked up in person by your doc.
passing out may be simply due to dehydration
etc. as you think,
but sometiems also a presentation of some serious disorder like arrhythmia/ heart rhythm abnormality.. or others...
pl. get medical attention and be assured..
hope to read you back on progress on the issue.
thanks and take care. p. keep me posted..