Analysis of myocardial deformation based on ultrasonic pixel tracking to determine transmurality in chronic myocardial infarction

Pixel tracking-derived myocardial deformation imaging is a new echocardiographic modality which allows quantitative analysis of segmental myocardial function on the basis of tracking of natural acoustic markers in 2D echocardiography. This study evaluated whether myocardial deformation parameters calculated from 2D echocardiography allow assessment of transmurality of myocardial infarction as defined by contrast-enhanced cardiac magnetic resonance imaging (ceMRI). Methods In 47 patients with ischaemic left ventricular dysfunction, transmurality of myocardial infarction was assessed using pixel-tracking-derived myocardial deformation imaging and ceMRI. For each left ventricular segment in a 16-segment model, peak systolic radial strain, circumferential strain, radial strain rate, and circumferential strain rate were calculated from parasternal 2D echocardiographic views using an automatic frame-by-frame tracking system of natural acoustic echocardiographic markers (EchoPAC, GE Ultrasound). Myocardial deformation parameters were related to the segmental extent of hyperenhancement by ceMRI. The relative amount of contrast-enhanced myocardial tissue per segment was used to define no infarction (0% hyperenhancement), non-transmural infarction (1-50% hyperenhancement), or transmural infarction (51-100% hyperenhancement). Results Analysis of myocardial deformation parameters was possible in 659 segments (88%). Systolic strain and strain rate parameters decreased with increasing relative hyperenhancement defined by ceMRI. Radial strain was 27.7+/-8.0, 20.5+/-9.7, and 11.6+/-8.5% for segments with no infarction (n=422), non-transmural infarction (n=106), and transmural infarction (n=131), respectively (P<0.0001). Radial strain allowed distinction of non-transmural infarction from transmural infarction with a sensitivity of 70.0% and a specificity of 71.2% (cut-off value for radial strain 16.5%).

Frame-to-frame tracking of acoustic markers in 2D echocardiographic images for the analysis of myocardial deformation allows discrimination between different transmurality states of myocardial infarction.