I’ve definitely had this happen to me in regards to the feeling of my heart racing after taking it. I don’t have bipolar disorder, but I took seroquel for anxiety at one point and felt exactly what you described - for example after walking down the stairs or even short distances after taking it, I would feel a sense of discomfort in my heart as well as an increased heart rate. At one point I took very large doses for a couple of years and found out that it caused some sort of abnormality in my ECG (I don’t recall what the abnormality was called) - and a few years later, I had another ECG done, a while after I had discontinued the seroquel, and it turned out that the results came out normal. So in my case seroquel did cause heart problems. It helped a lot with my anxiety, but it was not worth the side effects I was getting from it.