Abstract
The intial phase of the ventricular contraction (C-l interval), measured from the onset of the systolic wave in the apex cardiogram to the onset of the main vibrations of the 1st mitral sound in the phonocardiogram, is a more reliable index in the diagnosis of mitral stenosis than the transformation time (Q-l interval). The C-l interval shows the actual delay of the 1st mitral sound. The diagnostic value of the Q-l interval is diminished by the electromechanical delay, which may change the results.