Study of left ventricular wall thickness and dimension changes using echocardiography.

The relation between transverse left ventricular cavity dimension and posterior wall thickness has been studied using digitised echocardiograms from 10 normal subjects and 63 patients with heart disease. In normal subjects, the peak systolic rate of wall thickening (4.6 ± 1-2 cm/s) is less than the peak diastolic rate of wall thinning (10.7 + 1-7 cm/s). Maximum wall thickness, minimum dimension, and mitral valve opening are synchronous, and there follows a distinct early period of rapid thinning of the wall (100 + 20 ms) which corresponds to the rapid filling period. In ischaemic heart disease the rate and duration of rapid thinning are normal, but the onset precedes mitral valve opening (by 50 + 30 ms). In hypertrophic cardiomyopathy the rate (7 4 + 4-6 cm/s) and pattern of wall thinning are more variable than normal, and closely predict the pattern of change in cavity dimension. Inflow obstruction, associated with slow and protracted increase in cavity dimension, causes the thinning period to be prolonged, but the peak rate of thinning is often not reduced to the same extent as the rate of increase in dimension. This entails reversal of septal movement. We conclude that rapid wall thinning is an intrinsic property of the left ventricular myocardium, normally associated with rapid filling, which may, however, be dissociated from filling by asynchronous relaxation or inflow obstruction, or modified by myocardial disease.