Hello,
Thank you for your query at DoctorSpring.com.
It doesn't sound like orthostatic hypotension. So I wouldn't stress too much on a possibility of POTS or multi system atrophy.
You have sudden onset headaches with giddiness. I don't know if you have records of BP during these episodes, but if they are normal then it rules out a variety of hypertensive causes of your headache like renovascular hypertension or pheochromocytoma.
Cluster headaches are another possibility. They too are associated with retroorbital pain and redness of eye.
Another possibility that comes to mind is perimenopausal syndrome. Are your menses regular? Are you nearing a menopause?
Hot flashes with adrenaline rush and feeling of giddiness and doom may occur when the menopause is about to occur.
You seem to have some heart rhythm abnormality associated with an old mitral valve problem which is repaired.
So I would suggest you undergo a 24 hour Holter monitoring to rule out any cardiac rhythm disturbance that may be causing these neurological symptoms. Along with that maintain a diary during the 24 hours as to when you have the symptoms, so that we may correlate retrospectively with the heart rate. It would also help if you could record the bp every time you have that headache sensation or you could alternatively have a ambulatory bp monitor during those 24 hours. If we don't find a correlation between an episode of headache and bp and pulse rate and your holter ecg records then cardiac cause can be effectively ruled out.
Hope this helps, please feel free to get back with follow-up queries.
Regards
Dr Vivek Mahajan
DM Cardiology