Two-dimensional strain - a Doppler-independent ultrasound method for quantitation of regional deformation: Validation in vitro and in vivo

Background: 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. Methods: 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. Results: 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. Conclusion: 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.