Strain and strain rate. New and clinically relevant echo parameters of regional myocardial function.

Strain (deformation) and strain rate (velocity of deformation) are parameters of regional myocardial function which can be calculated at the bedside from tissue Doppler echocardiographic data. These parameters are less image quality dependent and less subjective than visual assessment of endocardial border motion, and they track myocardial deformation with a considerably higher time resolution than magnetic resonance imaging. Thus, the technique can document short-lived subtle changes in deformation patterns, such as post-systolic shortening/thickening. The ability to detect regional myocardial ischemia and viability has been confirmed in animal experiments and clinical studies. The technique has also been used to detect early cardiomyopathy and to differentiate physiologic and pathologic myocardial hypertrophy, as well as to identify regional dyssynchrony in candidates for resynchronization therapy. Applications in heart transplantation, right ventricular disease and valvular heart disease are under evaluation. Thus, strain and strain rate data offer a new window on regional myocardial function and may, in the future, become an integral part of echocardiographic evaluation.