OBJECTIVETo evaluate global genome expression patterns of left ventricular tissues from dogs with dilated cardiomyopathy (DCM).SAMPLE POPULATIONTissues obtained from the left ventricle of 2 Doberman Pinschers with end-stage DCM and 5 healthy control dogs.PROCEDURETranscriptional activities of 23,851 canine DNA sequences were determined by use of an oligonucleotide microarray. Genome expression patterns of DCM tissue were evaluated by measuring the relative amount of complementary RNA hybridization to the microarray probes and comparing it with gene expression for tissues from 5 healthy control dogs.RESULTS478 transcripts were differentially expressed (> or = 2.5-fold change). In DCM tissue, expression of 173 transcripts was upregulated and expression of 305 transcripts was downregulated, compared with expression for control tissues. Of the 478 transcripts, 167 genes could be specifically identified. These genes were grouped into 1 of 8 categories on the basis of their primary physiologic function. Grouping revealed that pathways involving cellular energy production, signaling and communication, and cell structure were generally downregulated, whereas pathways involving cellular defense and stress responses were upregulated. Many previously unreported genes that may contribute to the pathophysiologic aspects of heart disease were identified.CONCLUSIONS AND CLINICAL RELEVANCEEvaluation of global expression patterns provides a molecular portrait of heart failure, yields insights into the pathophysiologic aspects of DCM, and identifies intriguing genes and pathways for further study.