Are there valves in your heart?

Very poorly. Let's consider the left side of the heart which pumps blood into the aorta, the main artery leading from the heart. At the peak of a contraction (squeeze) of the heart it pumps blood into the aorta. The aorta is very elastic and expands as the squeeze of the heart pushes blood into it. Some of the blood, of course, continues on, and under normal circumstances, the aortic valve then closes, and as the heart fills with blood for the next squeeze, the elasticity of the aorta shrinks the aorta and pumps more blood into the body. If the valve is damaged (or, in your question, absent) then as the aorta's elasticity shrinks it, the blood would be forced back into the heart, not letting new blood come in to be pumped out on the next contraction. Thus the pumping would become very inefficient. It is exactly because of damage like this (aortic insufficiency) that the valve sometimes has to be replaced.