Hello! Thank you for asking on HCM! I understand your concern and would explain that your symptoms seem to be related to orthostatic tachycardia (also called postural tachycardia syndrome) or orthostatic hypotension. Have you measured your blood pressure in standing up position? A decrease in your systolic blood pressure more than 20 mm Hg during standing up position, compared to sitting position, would indicate an orthostatic hypotension. A head up tilt test is necessary to rule in/out the above disorder. A complete check up, including a physical check up, resting ECG, chest x ray and some blood lab tests (complete blood count, PCR, sedimentation rate, fasting glucose, blood electrolytes, cortisol plasma levels, etc), should be done to exclude other possible metabolic causes that may mimic this symptomatology. Hope to have been helpful! Feel free to ask any other questions, whenever you need! Best wishes, Dr. Iliri