Which condition is most likely demonstrated by this M-mode image?

The M-mode image shows characteristic diastolic doming or “hockey stick” appearance of the anterior mitral leaflet with restricted leaflet motion. This is a classic sign of mitral stenosis, where leaflet thickening and fusion cause limited opening during diastole.

Dilated cardiomyopathy shows increased chamber sizes and decreased systolic function but not mitral leaflet doming. Hypertrophic cardiomyopathy is characterized by septal thickening and SAM of the mitral valve. Mitral valve prolapse shows leaflet billowing into the left atrium during systole.

This pattern is well described in ASE valvular heart disease guidelines and echocardiography texts【12:ASE Valve Imaging Guidelines†p.180-185】【16:Textbook of Clinical Echocardiography, 6e†p.200-205】.