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Echo Strain Variability and Reproducibility
Study Questions:
How much variability exists in the measurement of left ventricular (LV) segmental strain using different ultrasound machines and post-processing software packages?
Methods:
The study cohort included 63 volunteers with LV infarct scar proven by cardiac magnetic resonance imaging, and segmental LV function ranging from normal to severely impaired. Subjects were examined within 2 hours by a single expert sonographer with machines from multiple vendors. All three apical views were acquired twice to determine the test-re-test and the intervendor variability. Segmental longitudinal peak systolic (PS), end-systolic (ES), and post-systolic strain (PSS) were measured using seven vendor-specific systems (Hitachi, Esaote, GE, Philips, Samsung, Siemens, Toshiba) and two independent software packages (Epsilon and TOMTEC), and compared among vendors.
Results:
Image quality and tracking feasibility differed among vendors (ANOVA p < 0.05). The absolute test-re-test difference ranged from 2.5% to 4.9% for PS, 2.6% to 5.0% for ES, and 2.5% to 5.0% for PSS. The average segmental strain values varied significantly between vendors (up to 4.5%). Segmental strain parameters from each vendor correlated well with the mean of all vendors (r2 ranging from 0.58 to 0.81), but showed very different ranges of values. Bias and limits of agreement were up to -4.6 ± 7.5%.
Conclusions:
In contrast to global longitudinal strain (GLS), LV segmental longitudinal strain measurements have a higher variability, in addition to known intervendor bias. The fidelity of different software to follow segmental function varies considerably. The authors concluded that single segmental strain values should be used with caution in clinical settings, and that segmental strain pattern analysis might be a more robust alternative.
Perspective:
In 2010, the European Association of Cardiovascular Imaging (EACVI) and the American Society of Echocardiography (ASE) initiated the Strain Standardization Task Force in response to concerns for intervendor variability in the assessment of LV strain. Previously published data suggest that GLS performs reasonably well in terms of both intraobserver and intervendor variability, supporting its use as a reliable means to assess myocardial function. However, data from this study suggest that the ability to identify regional LV abnormalities using strain varies substantially between vendors. It follows that single segmental strain measurements should be used with caution.
Keywords: Cardiac Imaging Techniques, Echocardiography, Heart Failure, Magnetic Resonance Imaging, Systole, Ventricular Function, Left
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