Mitral valve abnormalities were not part of modern pathological and clinical descriptions of hypertrophic cardiomyopathy in the 1950s, which focused on left ventricular (LV) hypertrophy and myocyte fiber disarray. Although systolic anterior motion (SAM) of the mitral valve was discovered as the cause of LV outflow tract obstruction in the M-mode echocardiography era, in the 1990s structural abnormalities of the mitral valve became appreciated as contributing to SAM pathophysiology. Hypertrophic cardiomyopathy mitral malformations have been identified at all levels. They occur in the leaflets, usually elongating them, and also in the submitral apparatus, with a wide array of malformations of the papillary muscles and chordae, that can be detected by transthoracic and transesophageal echocardiography and by cardiac magnetic resonance. Because they participate fundamentally in the predisposition to SAM, they have increasingly been repaired surgically. This review critically assesses imaging and measurement of mitral abnormalities and discusses their surgical relief.

Echocardiograms with standard imaging planes were performed at initial evaluation and last follow-up. Continuous wave Doppler was used to measure LVOT gradient from the apical 5-and 3-chamber views to record maximum velocity parallel to the systolic LVOT flow. Care was taken to separate LVOT signal from that of mitral regurgitation. Gradient was measured during 3 Valsalva maneuvers and after standing. The simplified Bernoulli equation was used to calculate gradient. After 1994, capable patients underwent treadmill testing with Bruce protocol and had gradients acquired after exercise.

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