Two dimensional speckle tracking echocardiography: basic principles

Two dimensional (2D) speckle tracking echocardiography (STE) is a promising new imaging modality. Similar to tissue Doppler imaging (TDI), it permits offline calculation of myocardial velocities and deformation parameters such as strain and strain rate (SR). It is well accepted that these parameters provide important insights into systolic and diastolic function, ischaemia, myocardial mechanics and many other pathophysiological processes of the heart. So far, TDI has been the only echocardiographic methodology from which these parameters could be derived. However, TDI has many limitations. It is fairly complex to analyse and interpret, only modestly robust, and frame rate and, in particular, angle dependent. Assessment of deformation parameters by TDI is thus only feasible if the echo beam can be aligned to the vector of contraction in the respective myocardial segment. In contrast, STE uses a completely different algorithm to calculate deformation: by computing deformation from standard 2D grey scale images, it is possible to overcome many of the limitations of TDI. The clinical relevance of deformation parameters paired with an easy mode of assessment has sparked enormous interest within the echocardiographic community. This is also reflected by the increasing number of publications which focus on all aspects of STE and which test the potential clinical utility of this new modality. Some have already heralded STE as ‘the next revolution in echocardiography’. This review describes the basic principles of myocardial mechanics and strain/SR imaging which form a basis for the understanding of STE. It explains how speckle tracking works, its advantages to tissue Doppler imaging, and its limitations. ### Deformation parameters—strain and strain rate Strain is a dimensionless quantity of myocardial deformation. The so-called Langrangian strain (e) is mathematically defined as the change of myocardial fibre length during stress at end-systole compared to its original length in a relaxed state at end-diastole=(l-l)/l (figure 1). …