Heterogeneity of left ventricular segmental wall thickening and excursion in 2-dimensional echocardiograms of normal human subjects

Abstract

Regional abnormalities of left ventricular (LV) wall thickening and excursion have been demonstrated by 2-dimensional (2-D) echocardiography. However, the variability of normal segmental contraction has not previously been defined. We performed 2-D echocardiography in 12 normal men aged 19 to 27 years. We obtained short-axis images at the level of the mitral valve, chordae tendineae, papillary muscles, and apex at end-diastole and end-systole. A computer-based system divided each short-axis image into 12 cavity and wall segments, and analyzed percent systolic wall thickening along each radius and percent area change of each cavity segment. Overall variability of contraction as well as the contributions of several sources of variability were determined. The overall range of cavity segment area change was 0 to 100% and of segmental wall thickening was 0 to 150% in these normal subjects. Average contraction was similar at different ventricular levels. Significant differences were found between adjacent segments at each level as well as between subjects. Intrathoracic cardiac rotation and motion were minimal; correction for these movements did not significantly alter the variability of contraction as calculated from 2-D echocardiograms. Temporal asynergy of contraction did contribute to variability; correction resulted in a significant alteration in mean segmental area change (from 59 ± 20% [standard deviation] uncorrected to 66 ± 16% corrected, p < 0.001) and in mean segmental wall thickening (58 ± 29% uncorrected to 71 ± 34% corrected, p < 0.01). Substantial interexamination variability also occurred with an average difference in cavity segment area change of 20% per segment and in segmental wall thickening of 29% per segment between 2 analyses by the same observer. Thus, considerable intersegmental and intersubject variability of LV contraction occurs in normal subjects as exhibited on 2-D echocardiograms, exaggerated by technical difficulties in analyzing and reproducing the echocardiographic tracings. Significant differences in segmental wall thickening and endocardial excursion may occur in adjacent segments in normal subjects, and therefore such differences alone may not indicate cardiac disease.