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


METHODS
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 ± 5 years). 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.


RESULTS
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.


CONCLUSIONS
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.
Department of Cardiovascular Medicine, Shinshu University Graduate School of Medicine, 3-1-1 Asahi, Matsumoto, Japan.
Hirohiko
H
Motoki
Department of Health Sciences, Osaka University Graduate School of Medicine, 1-7 Yamadaoka, Suita, 565-0871, Japan. nakatani@sahs.med.osaka-u.ac.jp.
Satoshi
S
Nakatani
Division of Cardiovascular Medicine, National Hospital Organization Osaka Minami Medical Center, 2-1 Kidohigashimachi, Kawachinagano, Japan.
Haruhiko
H
Abe
Division of Cardiovascular Medicine, National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Japan.
Hideaki
H
Kanzaki
Division of Cardiovascular Medicine, National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Japan.
Masafumi
M
Kitakaze
Mechanics; Myocardial contraction; Speckle tracking imaging; Strain; Ventricles