I am a 49 year old female, 5"5 weighing 190 lbs, 30 of which I have gained in less than a year.  I have had leukocytosis (12 to 17) for at least 8 years.  I have postural tachycardia. My supine heart rate is usually high 80's to mid 90's. My standing heart rate is often 125 to 140. I often have PVCs and PACs. I have other orthostatic symptoms but they are relatively mild except for the fatigue.  I am trying to do yoga.  I walk 2 miles four days a week and I am trying to lose the extra weight.  My doctor wants to put me on a beta blocker.  Should I try to find the cause of my symptoms or just take the medicine and not worry about it?  Thanks.

Summarized question: What is postural tachycardia?