<s>[INST] I am a physician and have not been able to get a straight answer on thses symptoms myself.  I will wake up from a nightmare where my chest feels like it is going to explode.  I normally have a fast heart rate in the low 90s.  When I wake up I am in the 60s and by 30 seconds am back to a normal rate and the chest pain abates.  I have no history other than HTN and have had these symtoms over a decade.  I have been on anti-hypertensives for about 4-5 years so it is not the medication. [/INST] Hello! Thank you for asking on Chat Doctor! I read your question carefully and understand your concern. Your symptoms seem to be related to nightmares and anxiety. This is a common sleeping disorder, associated with autonomic nervous system activity. Have you measured your blood pressure during these episodes? I recommend consulting with your GP for a careful physical examination, a resting ECG, a chest x-ray and some blood lab tests : - complete blood count-fasting glucose-thyroid hormone levels (thyroid dysfunction could explain some of your symptoms)- kidney and liver function tests - blood electrolytes, etc. An ambulatory 24-48 hour monitoring would be necessary to exclude a possible cardiac arrhythmia. Hope to have been of help! Best wishes,  </s>