Heart valve insufficiency. Coloured magnetic resonance imaging (MRI) scan through the chest of a patient with heart valve insufficiency, where the valves are failing to properly regulate the flow of blood through the heart. The heart and its valves are at upper centre. The valves between the chambers of the heart prevent blood flowing backwards after it is pumped out. If the valves are damaged or defective, then blood can flow back through the heart (regurgitation), resulting in decreased blood flow to the rest of the body and increased work for the heart.