Hey,
I have Tachycardia, I don't have "episodes", I have CONSTANT exteme tachycardia where my heart rate has NEVER been below 120 my entire life (or atleast the past 7-8 years where I have been monitored). I also don't have depression/anxiety. Because of that, I can't really give much advice on episodes of tachycardia, but I can tell you that you NEED a very good cardiologist. You should also look into the ingredients of the meds you are taking, as my guess is that they contain stimulants (anti depression meds usually do, therefore they make your heart rate go up). Especially if you took large doses of it like you said, it's a reaction to the chemicals.... don't do that, and maybe you won't get tachy

Maybe it could all go back to normal (80s) if you stopped taking the meds, which I know would be tough. If they put you on anti-anxiedty meds, you probably shouldn't just stop them cold turkey, it could be a jolt to your system, which could have caused your last episode. I'm not a doctor, but I've been to about a bazillion doctors and have researched like crazy. Get a good psych and a good cardio and make sure they work TOGETHER, so you aren't prescribed anything that could affect the other symptoms, unless you wanna be prescribed more meds ontop of more meds, etc etc.
Hope it all works out for you!!