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.
Heart valve disease. If one or more of your heart valves becomes damaged or diseased, it can affect the flow of blood through your heart. There are four chambers in your heart and the valves make sure that the blood flows through them in one direction. The two large blood vessels that leave the heart also have valves to make sure that the blood does not go back into the heart once it has been pumped out.