All Direct Subsidized and Unsubsidized Loans disbursed between July 1, 2014 and June 30, 2015 carry a fixed interest rate of 4.66% for undergraduates. Graduate or professional students receiving a Direct Unsubsidized Loan disbursed between July 1, 2014 and June 30, 2015 will have a fixed interest rate of 6.21%.
There is a problem when the valve that controls what blood is good and what blood is used, no longer is strong enough to control this flow. Heart valves get damaged or simply wear out. I think you are asking what causes blood to flow in the wrong direction. My guess is that it would be a faulty heart valve.
Most congenital heart defects affect how blood flows through the heart or through the blood vessels near the heart. Some defects may cause blood to flow in a pattern that isn't normal. Others can completely or partially block blood flow. There are many different types of congenital heart defects. They can be fairly simple, such as a hole between the chambers of the heart or a heart valve that has not formed right. Others are more serious and complex, such as a missing heart valve or heart chamber.