Grading of Myocardial Dysfunction by Tissue Doppler Echocardiography: A Comparison Between Velocity, Displacement, and Strain Imaging in Acute Ischemia
The aim of the study was to compare the ability of the tissue Doppler echocardiographic imaging (TDI) modalities velocity, strain, and displacement to quantify systolic myocardial function.
Background
Several TDI modalities may be used to quantify regional myocardial function, but it is not clear how the different modalities should be applied.
Methods
In 10 anesthetized dogs we measured left ventricular pressure, longitudinal myocardial velocity, strain, and displacement by TDI at baseline and during left anterior descending coronary artery (LAD) stenosis and occlusion. Reference methods were segmental shortening by sonomicrometry and segmental work. In 10 patients with acute anterior wall infarction (LAD occlusion) and 15 control subjects, velocity, strain, and displacement measurements were performed.
Results
In the animal study, systolic strain correlated well with segmental shortening (r = 0.96, p < 0.01) and work (r = 0.90, p < 0.01), and differentiated well between non-ischemic (−13.5 ± 3.2% [mean ± SD]), moderately ischemic (−6.5 ± 2.8%), and severely ischemic myocardium (7.1 ± 13.2%). The ratio post-systolic strain/total strain also differentiated well between levels of ischemia. Displacement and ejection velocity had weaker correlations with segmental shortening (r = 0.92 and r = 0.74, respectively) and regional work (r = 0.85 and r = 0.69), and there was marked overlap between values at baseline and at different levels of ischemia. In the human study, systolic strain differentiated well between infarcted and normal myocardium (1.0 ± 5.0% vs. −17.8 ± 3.8%), whereas systolic displacement (−0.3 ± 1.3 mm vs. −2.3 ± 0.6 mm) and ejection velocity (0.9 ± 0.6 cm/s vs. 2.2 ± 0.6 cm/s) showed overlap. In the infarction group, strain was reduced in segments with infarcted tissue, while systolic velocity and displacement were reduced in all segments and did not reflect the extension of the infarct.
Conclusions
Strain was superior to velocity and displacement for quantification of regional myocardial function. Provided technical limitations can be solved, strain Doppler is the preferred TDI modality for assessing function in ischemic myocardium.
