Hi there.
It is very hard to pinpoint the underlying cause of your problem. The diagnosis of tachycardia and
orthostatic hypotension are more likely to be secondary manifestations of an underlying heart or vascular
problem, rather than being the primary causes themselves.
Common underlying conditions that can cause this presentation is thyrotoxicosis or hyperthyroidism. This
would also present with easy fatigability, heat intolerance, and increased frequency of bowel movements.
If the heart is already failing due to chronic conditions like hypertension, ischemic heart disease, or
primary cardiomyopathies, then it may result in loss of power to pump blood leading to low blood pressure and
orthostatic hypotension.
Imbalance in electrolytes of the body mainly Potassium, Sodium, and Calcium can also cause these problems.
Another possibility, especially if all other work ups turn out to be normal, is a primary heart electrical
conduction problem which should be managed and worked up by a cardiac electrophysiologist.
I suggest you have a cardiologist specialist consult to be properly worked up.
Regards.
