Heterogeneous contraction of the left ventricle demonstrated by 2-dimensional strain imaging.

Abstract

Tissue Doppler imaging (TDI) is useful in quantifying regional myocardial function, but has a significant limitation of Doppler angle dependency. The recently developed 2-dimensional strain imaging (2DS), based on speckle tracking imaging (STI) technology, enables us to evaluate myocardial function independent of ultrasound beam direction. The aim of this study was to assess the mode of contraction of the left ventricle. Circumferential, radial and longitudinal strains were measured in 18 segments (anteroseptal, anterior, anterolateral, inferolateral, inferior and inferoseptal walls at the base, mid-ventricle and apex) from apical and short-axis views using 2DS in 24 healthy subjects (mean age, 33±5years). We divided the left ventricle into 2 sites: septum (anterior, anteroseptal and inferoseptal walls) and free walls (anterolateral, inferolateral and inferior walls). We then compared the mode of contraction between the septum and free walls. At the base and mid-ventricular levels, circumferential strain was larger in the septum (-22.6±3.6 vs. -18.3±4.1% and -24.1±4.8 vs. -18.4±5.7%, respectively; p<0.0001 each), and radial strain was larger in the free walls (33.4±12.4 vs. 38.7±14.5% and 37.8±12.6 vs. 43.0±11.6%, respectively; p<0.001 each) at the basal and mid-ventricular levels, whereas both were relatively homogeneous at the apex. The longitudinal strain did not differ among walls. Heterogeneous contraction is seen in the left ventricle. The septum mainly contracts circumferentially, whereas the free walls contract radially. 2DS is helpful in understanding the mode of 3-dimensional myocardial contraction.