I know that there are many diseases one can have growing up that might just "go away" when you get older, and we usually blame it on hormonal imbalances, and your body growing up and figuring things out. I wonder we're underestimating how the many anxieties that teenagers suffer from might cause or amplify these issues.
[0] Since you're in the medical profession, I'm sure you know what tachycardia is, but for others: it's when the heart rhythm becomes so fast that the heart muscles can't keep up, and are no longer pumping blood properly. Luckily my form of tachycardia is regular and fairly harmless on its own. Anyway, in my case it would trigger when startled, usually when I was doing some kind of "inconsistent" physical exertion (by which I mean that it never happened when running or cycling, even if I pushed myself to my physical limit). So it seems to require a mix of social and physical stress, plus something unexpected happening (I guess the adrenaline triggers it?)