Myocardial Deformation Imaging

Abstract

Myocardial deformation imaging is a novel echocardiographic method for assessment of global and regional myocardial function. As this technology has evolved, it has been applied to an increasing number of research questions, and the number of publications incorporating deformation imaging has grown in parallel. Although not yet sufficiently vetted for routine clinical use, these methods offer the long-term potential for more complete, accurate, and reproducible assessment of myocardial function. Evaluation of contractile function with echocardiography has traditionally been limited to volume-based assessment of ejection fraction (EF) and assessment of regional wall motion or visual estimation of regional thickening. These methods have suffered from lack of reproducibility and standardization and are generally considered to be extremely sensitive to loading conditions. These limitations have led to an interest in techniques that provide more objective and reproducible measures of contractile function. During systole, the ventricular myocardium simultaneously shortens in the longitudinal and circumferential planes and thickens in the radial plane, with reciprocal changes in diastole (Figure). Deformation imaging, in the broadest sense, allows for more direct assessment of myocardial muscle shortening and lengthening throughout the cardiac cycle by assessing regional myocardial strain and strain rate. Strain is defined as the change in length of a segment of myocardium relative to its resting length and is expressed as a percentage; strain rate is the rate of this deformation. Longitudinal and circumferential shortening results in negative strain values, whereas radial thickening results in a positive strain value. Previously, assessment of myocardial strain could be performed with the use of sonomicrometry crystals, which can only be performed experimentally1 or with magnetic resonance imaging–based myocardial tagging,2,3 which is limited by relatively low temporal resolution and the limited availability and expense of cardiac magnetic resonance imaging. Extension of these techniques to echocardiography has allowed …