The Mitral Valve in Obstructive Hypertrophic Cardiomyopathy

Abstract

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.

The mechanisms, diagnosis and management of mitral regurgitation in mitral valve prolapse and hypertrophic cardiomyopathy

“…1,102 As evidence shows, SAM has been observed independently from HCM 113 and precedes the increase of LVOT flow gradients.…”

“…Studies have shown the possibility of a longitudinal excision to thin the abnormal papillary muscle which caused the obstruction. 102 The surgical reorientation is performed to prevent ischemia, by suturing the fibrous portion of the papillary muscle in order to realign them as necessary and to reduce the hypermobility. The mean perioperative (114 mmHg) and predischarge (16 mmHg) LVOT gradients, show the effectiveness of this method.…”

“…The severity of obstruction in the LVOT is highly influenced by SAM, as the longer the mitral leaflets are dragged anteriorly, the narrower the LVOT becomes and the flow velocity increases further. 102,118 LV outflow gradients are measured using continuous-wave Doppler imaging primarily in the apical long-axis view 3 . Increased velocities from the LVOT to the aortic valve plane due to SAM are marked by the turbulent appearance of the color Doppler flow.…”

“…102 Chordal and papillary muscle displacement also interferes with leaflet coaptation, as they impose the limits of mobility allowed.…”

“…While TTE shows elongated leaflets in patients coming to surgery 102,121 , TEE may also identify any additional concurrent organic cause of obstruction such as a subaortic membrane associated with dynamic obstruction. 106 Three-dimensional echocardiography By means of real-time 3D echocardiography the following morphological changes were identified to be responsible for SAM: leaflet elongation 115 and thickening as a consequence of repetitive septal contact and hypertrophied, anteriorly displaced papillary muscles.…”