This is a movie from a fluoroscopic recording (x-ray). It shows dilatation of a balloon catheter (which is filled with contrast and shows up black). Just before the sausage-shaped is fully inflated, there is an indent caused by the pinching of the stenotic valve. Full inflation of the balloon stretches the stenotic valve. Once performed, the balloon is deflated and the catheter completely removed. The balloon is often inflated 2-3 times to insure a good stretch. The pressures in the heart are measured before and after, and if there is an inadequate reduction, then a larger balloon (within predetermined safety limits) is used to further stretch open the stenotic valve.