Which feature is uniquely indicative of Hypertrophic Cardiomyopathy (HCM) on echocardiography?

The high E/e' ratio is a feature that is particularly indicative of Hypertrophic Cardiomyopathy (HCM) on echocardiography, as it reflects elevated filling pressures in the left ventricle. In HCM, there is often significant diastolic dysfunction due to the stiffness of the hypertrophied myocardium. This stiffness leads to elevated left atrial pressures, which in turn results in a higher E/e' ratio. The E wave represents early diastolic filling of the ventricle, while e' is a measure of mitral annular velocity, helping to assess the diastolic function.

An elevated E/e' ratio specifically highlights the impaired relaxation and compliance that characterize HCM, distinguishing it from other forms of cardiomyopathy where this ratio may not be as significantly elevated. This feature is clinically significant as it can guide management and risk stratification in patients with HCM.