<s>[INST] I feel like theres a bubble in my heart sometimes and Ive been out of breathe a lot lately. I had to stop going to the gym bc my heart rate was too high and now anytime I simply get up to walk to a class, my heart races and I get light headed. Im only 21, whats wrong with me? [/INST] Hello and thank you for using Chat Doctor. I carefully read your question and I understand your concern. I will try to explain you something and give you my opinion. You should know that this bubbling sensation has to do with a rhythm issue. There are some electrical impulses that generates in some part of the heart different from normal sinus rhythm. They cause a premature heart contraction that it's not a normal one. It might be just an extra systolic beat or a chaotic arrhythmia. In these cases you might experience palpitation, flattering or bubble sensation, anxiety, difficulties in breathing deeply, dizziness etc. There might be different causes of this rhythm issue like simple stress, coffee and alcohol consumption or pathologies like anemia, hyperthyroidism or electrolyte imbalance. So, if I was your treating doctor I will recommend some examination like an electrocardiogram, a cardiac echo to evaluate heart function and walls, a full blood analyze to exclude anemia, hyperthyroidism and of course a holder rhythm monitoring to evaluate your rhythm tendency. Only after this we can better understand what we are dealing with and how to treat it. Hope I was helpful. Best regards Chat Doctor.  </s>