Principles and Practical Aspects of Strain Echocardiography

Visual assessment of regional and global ventricular function assessment is subjective and leads to significant variability in interpretation. The heart is a mechanical organ and undergoes cyclic deformation in systole and diastole. This deformation can be measured. Noninvasive assessment of deformation is now feasible with magnetic resonance and echocardiography. The early experience in echocardiographic assessment of deformation used tissue Doppler-based methodology to track tissue motion. Further refinement of these techniques enabled two-dimensional (2D) echo-based assessment of regional deformation via determination of strain using speckle tracking. Strain is a measure of tissue deformation. Strain is defined as a change in length of an object relative to its original length. Strain rate is the rate at which this deformation (length change) occurs. Although myocardial deformation is a three-dimensional (3D) phenomenon, echo-based interrogation techniques have generally been limited to interrogating one or more of three imaging planes-longitudinal, circumferential, and radial. More recently, 3D strain has been introduced. Strain and strain rate allow a clinician to determine regional and global myocardial function at the same level as a muscle physiologist by providing parameters similar to shortening fraction and shortening velocity, respectively. Myocardial dysfunction is characterized by reduced systolic strain and systolic strain rate. More recently, interrogation of diastolic strain rate and diastolic strain have enabled novel insights into regional diastolic mechanics. This review presents the fundamental principles underlying strain echocardiography and summarizes potential clinical applications of strain/strain rate imaging in the diagnosis and management of particular cardiac conditions.