Magnitude of transmural heterogeneity as a dominant factor for LVEDP elevation in HCM

Using the Phased Tracking Method (Doppler frequency: 3 MHz, PRF: 9 kHz), we examined the transmural response to mitral inflow in ten hypertrophic cardiomyopathy (HCM) patients to determine if transmural physical heterogeneity could be a determinant factor of the left ventricular end-diastolic pressure (LVEDP) elevation in HCM. In normal and AS patients, no heterogeneity in the transmural response of the vertical velocity at each preset point (0.75 mm-intervals in depth) and the change in each transmural layer thickness across the septum to the mitral inflow was observed. In HCM, the magnitude and the timing of the velocity at each preset point showed remarkable variation among myocardial layers across the septum. The "passive thickening" by atrial inflow was observed at several layers by these temporal and amplitude heterogeneities of transmural velocity distribution. The % of layers showing "passive thickness" during the atrial contraction period was strongly correlated to LVEDP. We concluded that the transmural heterogeneity plays an important role in the LVEDP elevation in HCM patients.