Role of deformation imaging in diagnosing myocardial ischemia

Velocity and deformation imaging by Doppler and newer techniques based on "speckle tracking" in 2-D datasets have substantially added to the ability of echocardiography to detect myocardial ischemia. Typical parameters include tissue velocities and regional deformation ("strain") and deformation rate ("strain rate"), which with the Doppler-independent new techniques ("2-D strain", "velocity vector imaging") can be measured in several directions, largely independent of insonation angle. All of these techniques can be readily combined with stress echocardiography; so far, published results are mostly based on the combination with dobutamine echocardiography. Typical signs of myocardial ischemia include a decrease in tissue velocities, deformation rates, and deformation. Additionally, systolic deformation occurs later in systole and often still goes on after aortic valve closure (postsystolic deformation). While tissue velocities are unable to clearly identify regional ischemia because of tethering of the neighboring wall segments and a physiological variation in regional tissue velocities, deformation parameters are better suited to detect regional ischemia. The limited literature on the detection of myocardial ischemia by these techniques clearly shows a value of velocity and deformation imaging especially in those cases where qualitative visual assessment of wall motion remains ambiguous. Due to rapid evolution of these techniques, a final assessment of their potential is not possible yet.