You forgot to account for one case, which is what applies to me: my heart rate "jumps" from 160, during peak physical exertion, to 230+ BPM, when I get this tachycardia, and then "jumps" back after a while if I sit down to relax. At that rate the heart doesn't have enough time to contract fully, like you said.

I got prescribed verapamil, and there's also this trick of trying to breathe out with mouth and nose closed, to use the lungs to put pressure on the heart. This can trigger some kind reflex (I forgot the name) that slows down the heart rate.

> The silver lining here is that in all likelihood your heart was/is fine. Anxiety has also been proposed as a risk factor for CVD but my understanding is that this is still debated. So don't go thinking your history means you'll definitely have an MI.

From what the cardiologist told me the 230 BPM is abnormal, but OTOH, my heart rate maintains a regular rhythm, so it's fairly harmless, and I'm likely not in any high risk group.