The movements of the mitral valve flaps studied by a new method

The desirability of a more accurate knowledge of the movements of the auriculo-ventricular valves led to the adoption of the following method of study in the perfused cat's heart: The margins of an opening in the left auricle are stitched to the bottom tube of a small cylindrical reservoir in which the height of pressure is regulated and varied by a set of lateral overflow-tubes. To one of the mitral valve flaps is attached a human hair communicating with a short and delicate lever of straw, held upward by slight spring tension. Whenever the valves move up the lever is elevated and a small mirror attached to the axis of the lever system is depressed. Upon this mirror is projected a beam of light and through its reflection the movements of the mirror are recorded upon a moving bromide surface. In this way the oscillations of the valve flaps may be optically recorded and compared with simultaneous optical tracings of auricular and ventricular activity. To prevent the transfer of ventricular movements to the threads connecting with the valves, the heart is fastened by stitches, carefully placed around the auriculo-ventricular ring to a neatly fitted ring of metal.

A study of the records thus far obtained indicates that the following movements of the auriculo-ventricular valves occur in every cardiac cycle: A very short interval after the onset of auricular systole, the cusps are slightly depressed toward the ventricle, but before the end of auricular systole they quickly ascend toward the auricle. With the onset of auricular diastole (which in these experiments began a distinct interval before subsequent ventricular systole) the valves move ventricle-ward to their former position.

With the onset of ventricuzar systole the cusps immediately move upward and close completely.