### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
hello i am 17 years old, male, about 140 pounds, skinny, and have this weird thing going on, ok so whenever i stand up my heart beats hard and at a low rate but not life threatening rate maybe like to 55 or 60 then it speeds up really quickly, when im having this thing, i feel kind of out of breath but i can breath fine but it feels like i have to breath a little harder, and rarely it happens whenever im sitting down. also when im taking a hot shower my heart races. i tryed to look this up all i found simular to this was orthostatic hypotension, because it feels like im going to black out, but it onlys happens for about 5 seconds then my heart races goes to normal after that please can anyone tell me what do i have, also i have not fainted or blacked out before, my family and i have gone through 10 tests on my heart and went to a cardiologist to take a cardiogram, to take pictures of my heart, and they said i was fine, but dont know what going on right now, so if anyone can help me with this or if i can get treatment for this?

### output:

Hello! Thank you for asking on Chat Doctor! I carefully passed through your question and would explain that your symptoms could be related to orthostatic intolerance. In orthostatic hypotension there is a decrease in your blood pressure during standing up. I would recommend measuring your blood pressure in sitting and then in standing up position. A decrease more than 20 mm Hg when standing up from sitting position could indicate possible orthostatic intolerance. Another disorder, related to orthostatic intolerance is Postural tachycardia. In such case heart rate increase more than 30 bpm while standing up from sitting position. A head Up Tilt test is necessary to rule in/out this possible disorder. Hope you will find this answer helpful! Kind regards, 