Heart palpations

I feel like as soon as I fall asleep, or just about deft off, I get these massive heart palpations that wake me up and make me feel like I’m dying. They last literally for a second then go away. This is misery because I can’t seem to sleep, and they FREAK ME OUT.

I got diagnosed with GAD a few months ago and am taking lexapro. The palpations were really bad before my meds, but still occur after. Anyone else get these?

(I’ve been to cardiologist, my heart is fine)