Oh my god...you said "seizure" in front of someone with epilepsy? You're a terrible person! You should be beaten for that!
Oh wait, that's insensitive to people who have been beaten. My apologies. I meant to say that you suck! No, that's insensitive to people who can't afford a vacuum. What I meant was, how could you be so stupid? Wait wait, that's insensitive to stupid people...
See where I'm going with this, people? If you weren't so goddamned sensitive about every little thing wrong with you, people wouldn't have to worry so much about offending you. I'm not perfect at all, but I've learned to laugh at my own inadequacies and errors. Ultimately I'm happier and so is everyone around me.
I dunno, I don't think that's really offensive, he must've known you weren't being malicious or anything. I have a heart condition and if someone told me they were having a heart attck in a similar sentence I wouldn't care, I doubt I'd even really register it as possibly offensive. Some phrases are, like saying your phone is 'being a spaz', but I don't think what OP said is anything bad. It's not derogatory.