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

Abstract

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 (0.75mm-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.

Two-dimensional speckle-tracking echocardiographic assessment of left ventricular mechanical synchrony in clinically normal cats

“… 1 A marked variation in segmental heterogeneity reflects a regional variation in the myocardial disarray and fibrosis that is characteristic of human HCM. 17 , 19 A marked variation in transmural heterogeneity is also an indicator of increased left ventricular end-diastolic pressure in human patients with HCM. This phenomenon has not been observed in human patients with HCM associated with aortic stenosis.…”

“…This phenomenon has not been observed in human patients with HCM associated with aortic stenosis. 19 Application of circumferential strain and transmural heterogeneity is clinically important in differentiating HCM of different etiologies in human patients. 17 – 19 The disarrangement of muscle fibers has also been reported in cats with HCM.…”