When blood washes BACK into your heart, it s not a problem with the atrioventricular valves. Problems in the mitral or tricuspid valves causes blood to flow back into the atria. Problems with the left or right semilunar valves (aka the aortic valve and pulmonic valve) cause blood to flow back into the heart during atrial contraction. These problems can have many causes such as an infection or a congenital defect. They can be treated or left untreated, depending on the severity. The outcome depends on the cause. The surgeries that are performed to correct these problems tend to work well depending on the condition of the person. If the problem led to cardiac arrest myocardium died, then the odds suck. If the problem is found and corrected early, the success rate is excellent.