Hello!
Thank you for asking on HCM!
I understand your concern and would explain that your diastolic blood pressure is below the normal limits, which is indicative of low blood pressure (your symptoms confirm this).
This changes may be related to your antihypertensive therapy, though all these drugs act in both systolic and diastolic blood pressure.
I recommend consult with your attending physician to perform a physical examination, a resting ECG and a cardiac
ultrasound (to exclude any possible cardiac related cause of low diastolic blood pressure).
If your cardiac ultrasound is normal, you should discuss with your doctor the possibility of making some changes to your antihypertensive therapy, to avoid further diastolic blood pressure decrease.
Meanwhile, I recommend taking plenty of fluids and laying down.
Hope to have been helpful!
Best wishes,
Dr. Iliri