Reading mich's post closely, the first sentence only says that thyroid problems, Lyme disease, and "other issues" may present like ADHD. Maybe the reference to heart problems is due to worries about exacerbating them with stimulants used to treat ADHD?

ETA: It makes sense in retrospect. Oxygen levels-- of course.

Striving to increase my rate of flow, and fight forum gloopiness. sick