HCM心内血流异常如何诊断？2020 ACC指南手术指征详解

Intracardiac hemodynamic abnormalities in HCM are diverse and play a key role in defining the disorder’s phenotype. These abnormalities primarily arise from the pressure gradient in the left ventricular outflow tract (LVOT), left atrial enlargement, the severity of mitral valve insufficiency, and increased pressure in the pulmonary trunk. The pressure gradient varies widely, and in clinical guidelines, a gradient greater than 50 mmHg is one of the indications for surgical intervention (Elliot et al., 2014; Gersh et al., 2011; Mestres et al., 2018; Ommen et al., 2020). Despite ongoing references in the literature to the Venturi effect as the underlying mechanism of systolic anterior motion (SAM) of the mitral valve, this is an oversimplification and crucially affects the choice of surgical approach. In HCM, the mitral valve is dysplastic; the anterior leaflet is elongated, and coaptation occurs with displacement of the leaflets into the left ventricular cavity. During contraction of the papillary muscles (before blood is ejected from the left ventricle), the anterior leaflet shifts toward the interventricular septum due to changes in tension within the hypertrophic region. As the heart contracts, the leaflet is further displaced to the right by the blood flow, resembling a sail catching the wind. This appearance may falsely suggest that blood velocity plays a significant role in leaflet displacement. However, SAM is observed even at normal blood velocities, typically below 1 m/second (Sherrid et al., 2000). The lack of proper apposition between the anterior and posterior mitral valve leaflets, resulting in insufficient coaptation, causes an upward-slanting regurgitant jet into the left atrium. When this jet is centrally positioned, it suggests structural mitral valve abnormalities, including chordal rupture due to elevated left ventricular pressure, or dysplasia of the valve and chordal apparatus. Mitral regurgitation, in turn, contributes to left atrial enlargement. An even more significant cause, in my view, is left ventricular diastolic dysfunction, which results from reduced ventricular volume due to generalized myocardial hypertrophy and increased ventricular wall stiffness, caused by progressive myocardial fibrosis. These hemodynamic changes underlie major clinical manifestations, including apnea, syncope, atrial fibrillation, and eventually congestive heart failure.