For example, I had a question about a kid who is brought to the ER because he fainted for no reason; he also had a history of hearing problems, and had a family history of sudden cardiac death. "Ok, brain," I thought to myself. "This sounds vaguely familiar as that prolonged QT syndrome, right?" "Right," my brain answered genially because we often agree on things like that.
But the question was actually asking what to treat him with - propranolol (a beta blocker), verapamil (a calcium-channel blocker), quinidine (errrr, ummm...), ethosuximide (anti-seizure maybe?), or phenobarbital (definitely anti-seizure).
So I immediately crossed off the alleged anti-seizure meds, and then I was left with the cardiac ones. I knew propranolol (and verapamil?) lower blood pressure, and the only thing I could remember about quinidine is that it had sooomething somewhere to do with the QT interval. Since the prolonged QT syndrome has nothing to do with your blood pressure, I went with my gut and picked quinidine.
. . . . Nope.
Turns out quinidine proloooooongs the QT interval, so it is most certainly contraindicated in a patient with an already-prolonged QT interval. I was right that it had something to do with the QT interval! Huzzah! I do know something! Happy face! But that led me to the very wrong answer (quite possibly the wrongiest answer of all of them - but at least I didn't think he was having a seizure, right?) Sad face? Happy and sad face?
(For the record, the answer was propranolol, and the syndrome is called Jervell-Lange-Nielson syndrome, duh. I'll definitely remember that for next time...)