What causes a heart murmur?
A heart murmur is caused by a turbulent flow of blood. Normal laminar flow of blood is silent. Turbulence occurs when there is a narrowing of a valve or there is a leaky valve. It can also occur when blood flows at high velocity through a normal valve. This occurs when there is anemia or hyperthyroidism. An abnormal open between the chambers like a ventricular septal defect or atrial septal defect can also cause a murmur. The intensity of the murmur is usually dependant on the magnitude of the flow as well as the pressure gradient. A high pressure gradient also produces a high pitched murmur.