MYOCARDIAL DOPPLER TISSUE IMAGING - PAST PRESENT AND FUTURE

The first Doppler spectral and pulsed tissue recordings in 1992 have g iven way to a new generation of machines which enable cardiologists to study mechanical events of the myocardium during the cardiac cycle by Doppler tissue imaging. This technique provides valuable information about regional function with quantitative analysis of the velocities w ithin the myocardial wall as opposed to the global qualitative or semi -quantitative character of usual echocardiographic data. The velocity mode is the most commonly used in its three different presentations: t wo-dimensional, M mode and, more traditionally, pulsed spectral modes. Two-dimensional imaging gives a global view of the different myocardi al segments and allows a rapid approximation of the differences of vel ocities between these segments and of myocardial wall thickness; howev er, it lacks the temporal resolution of pulsed Doppler and M mode. In addition, M mode with automatic programmes of velocity analysis has th e advantage of providing a continuous spatio-temporal recording of the velocities within the myocardial wall, layer by layer. There is a phy siological gradient of velocities highest at the endocardium and lowes t at the epicardium. Despite the present limitations related to the Do ppler principle itself, the technology, and the complexity of myocardi al architecture, Doppler tissue imaging is a useful complement-to info rmation already available concerning pressures, flow and cardiac struc tures. The future is promising and should exceed this simple complemen tarity to existing ultrasound methods. Progress in the fields of ultra sound physics, technology, computerisation for acquisition of two-and three-dimensional imaging should provide a new physiopathological appr oach to the understanding of wall motion changes during cardiac diseas e.