Clozapine can have a cardiac side effect. I had to go off Seroquel and onto it really slowly/carefully because of it. I think it is called prolonged QT interval. A quick search without reading articles says it can cause tachycardia. And if you have prolonged QT then yes, it needs to have attention paid to it.

Don't trust a heartrate from a pulse ox; they are notoriously inaccurate for that unless it is a very expensive machine that most places don't have. The most accurate way to get a heartrate is to count it for 60 seconds.

I would definitely push to pursue this.