Abnormal Myocardial Strain Indices in Children Receiving Anthracycline Chemotherapy

During the past several years, strain and strain rate imaging have emerged as a quantitative technique to accurately estimate myocardial function and contractility. Non-Doppler, 2-dimensional (2D) strain imaging is a new echocardiographic technique for obtaining strain and strain rate measurements. It analyzes motion by tracking speckles in the ultrasonic image in two dimensions. Current available software allows spatial and temporal image processing with recognition and selection of such elements on ultrasound image. The geometric shift of each speckle represents local tissue movement. By tracking theses speckles, 2D tissue velocity, strain, and strain rate can be calculated. Non-Doppler 2D strain imaging is simple to perform. It requires only one cardiac cycle to be acquired; further processing and interpretation can be done after image data acquisition. Because it is not based on tissue Doppler measurements, it is angle independent. Data regarding accuracy, validity, and clinical application of non-Doppler 2D strain imaging are rapidly accumulating. This technique may prove to be of significant clinical value, enabling rapid and accurate assessment of global and segmental myocardial function.

A new 2-dimensional strain echocardiography (2DSE) method has been introduced that measures myocardial deformations by tracking localized acoustic markers. We compared strains measured in vitro and in vivo by 2DSE with those obtained by sonomicrometry. For the in vitro study, a tissue-mimicking gelatin block was cyclically compressed and longitudinal strains obtained by 2DSE and sonomicrometry crystals. For the in vivo study, arrays of crystals were implanted into the apical anteroseptal (test region) and midposterior (control region) in 16 open-chest pigs and strains measured by 2DSE and crystals at baseline and after acute ischemia. In vitro, pooled data demonstrated good correlation (r = 0.99, P < .0001) and close agreement (bias +/- 2SD = 0.7 +/- 2.2%) of 2DSE and sonomicrometry. For a combination of low testing strains (5.4%) and strain rates (0.8 and 1.2 Hz), 2DSE overestimated strains by sonomicrometry. In vivo, linear regression analysis of pooled measurements demonstrated again a good correlation (r = 0.94, P < .0001) and agreement (1.1 +/- 7.5%) of 2DSE with sonomicrometry with a trend toward lower absolute values of strains by 2DSE. The 2DSE demonstrated good overall correlation and agreement with sonomicrometry for the tested in vitro and in vivo values. Some caution with 2DSE measurements is needed for combinations of low strains and strain rates.