Velocity Vector Imaging: standard tissue-tracking results acquired in normals--the VVI-STRAIN study

Echocardiographic imaging assessment of left ventricular mechanics is a new technology that is offered by various vendors. Different software algorithms have at times yielded conflicting results. The aim of this study was to determine normal myocardial mechanical parameters in a healthy population using Velocity Vector Imaging.

One hundred twenty subjects were selected for this study, including healthy subjects referred for echocardiography to evaluate minor symptoms or murmurs, who had normal echocardiographic findings and healthy volunteers. Study subjects were recruited in Haifa, Israel and Toronto, Canada. Echocardiography was performed using commercially available systems to analyze archived studies. Endocardial and epicardial longitudinal and circumferential strain and strain rate were calculated as well as rotational mechanical parameters. Age and gender differences were evaluated.

Average endocardial longitudinal, circumferential, and radial strains and twist were -19.6 ± 2.0%, -27.6 ± 3.9%, +30.1 ± 7.5%, and 9.6 ± 3.9°, respectively. Epicardial circumferential strain and twist were -11.3 ± 2.2% and 4.0 ± 1.9°, respectively. Shortening increased from base to apex longitudinally (10%) and circumferentially (33%). Thickening at the apex was 16% lower than at the base. Men and older subjects had increased endocardial circumferential strain and apical rotation.

Mechanical parameters differ with location (endocardial vs epicardial, basal vs apical strain gradients), age, and gender. Care should be taken when comparing regional strain measurements between systems, and gender and age should be matched between and within two-dimensional strain systems.