The most common cause of vascular obstruction is a blood clot, also known as a DVT. This type of vascular problem usually occurs in one leg (not both), and leads to swelling of the soft tissues throughout the foot and ankle. The swelling can also extend further up the leg.
The hypothalamus is a part of your brain that controls body temperature. When you exercise, your body temperature increases, causing the hypothalamus to signal the brainstem to further increase your heart rate.
It is true that anxiety can increase your heart rate-but unless you are only getting anxious when you are standing up and doing light activity, you should also notice increases in heart rate over your normal resting heart rate while laying or sitting as well when anxious.