<s>[INST] In the past I have had an issue where my heart beats really fast for a few seconds (and feels like it is beating really hard), then skips a beat then goes back to normal. It happens (at most) once a day and I have had it all checked out and it is quite normal apparently and nothing to worry about.Over the past few hours at work I feel like it has happened maybe 5/6 times. It is a little off-putting and I am not sure if there is anything to worry about. I almost feel like it is a little harder to breath (not a lot though)...your thoughts? [/INST] Hello, When our heart starts to beat up very fast or notably, this is because heart itself is trying to fix that has been wrong. When heartbeats are associated with difficulty in breathing then it's time to run a few diagnostic tests to determine the cause. So to me, you should consult with your cardiologist and run a complete cardiac checkup: EKG, echocardiogram, Holder monitoring to check it out. There are various causes but first should check your cardiovascular system. Hope I have answered your query. Let me know if I can assist you further.  </s>