In conditions of stable, non-turbulent laminar flow the leaflets rotate strictly clockwise. They make one full turn in 100 – 600 cycles. This characteristic is checked for each valve during a pulse-duplicator test. Video of a valve tested with a pulseduplicator is attached. Though in vivo when the blood flow is unstable, unstable rotation, no rotation, counterclockwise rotation or vibration is possible. This process can be observed using an angiograph.