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.
If part of that valve balloons out so that it doesn't close properly, you have mitral valve prolapse. This causes a clicking sound as your heart beats. It's fairly common and it's often not serious. But it can lead to the blood flowing backward through the valve, also called regurgitation. Mitral valve or aortic stenosis: Your mitral or aortic valves are on the left side of your heart. If they narrow, which doctors call stenosis, your heart must work harder to pump blood out to the rest of your body.