<s>[INST] Hi, so a couple years ago I was diagnosed with a heart murmur and irregular heartbeats. Since then, I ve been having spells where my heart would beat super fast, and depending how bad it was, it s hard to breathe. My first question is, should I get my heart checked out again? And then, for maybe a week or two now, if I stand up too fast I get dizzy and have a pressure on the side of my head, today I got up too quick but instead of feeling dizzy my vision blacked out for a couple seconds but got better when I say down. What could this be a sign of? [/INST] Thanks for your question on Chat Doctor. I can understand your concern. Yes, you should definitely consult cardiologist and get done reports for the diagnosis of type of arrhythmia. Arrhythmias like atrial fibrillation, atrial flutter, supra ventricular tachycardia etc. can cause hypotension during irregular heart beats. And this hypotension can cause dizziness, headache, blocked vision etc. So get done ECG, 2d echo and Holder monitoring (24 hour continuous monitoring of ECG) for the diagnosis of type of arrhythmia. You will need anti arrhythmia Chat Doctor.  Don't worry, with proper diagnosis and treatment, you will be alright. Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks. </s>