Hello chelle494 , greetings from healthcaremagic.com . I am Dr Sourav Chakraborty and i will be helping you with your query . First of all the battery of tests that you have gone through are used very commonly to diagnose the usual cardiac arrythmia
and some how they are negative for you. The term palpitation
means uncomfortable feeling of one's own heart beat so are you feeling palpitation or some thing else like anxiety or panic attack
or such equivalent . Ask some one to check your pulse when you have such attack next time , it is very important . Also your resting heart rate
should be monitered . If it is controled with a metoprolol
and alprazolam then please do continue those but keep an eye on yourself. I would not right way ask you to go for electrophysiological study but if your attack keeps on increasing you might need to do that test. Please be in constant touch with your cardiologist regarding this problem . It might be at the end just anxiety but going with your age i will just be careful.