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Figure 1 Multidimensional scaling (MDS) and similarity matrix/exact test demonstrating clear and significant effect of left ventricular assist device (LVAD) support on gene expression. (A) All gene expression data for pre-LVAD (green) and post-LVAD (red) patients ( 6,800 average difference values from Affymetrix per patient) were subjected to MDS using Pearson dissimilarities. The image represents convergence of the MDS algorithm, stress (measure of image validity) = 0.03. (B) Similarity matrix based on the Pearson correlation of the 12 samples (6 pre- and 6 post-LVAD). Following an exact test (random combinations of the 12 samples assigned to two groups), the most significantly divergent was the actual pre- and post-LVAD grouping, with a significance value of 0.002, illustrating the significant effect of LVAD support on gene expression.
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