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.
Also known as congestive heart failure. The heart does not pump blood around the body efficiently. The left or right side of the body might be affected; sometimes both sides are. Coronary artery disease or hypertension (high blood pressure) can over time leave the heart too stiff or weak to fill and pump properly.