Returning to the case of HCM introduced at the beginning of this chapter, consider in Figure 49.8 how HCM can impair the function of the left ventricle. First, in many cases the septum between the ventricles is greatly modified by the hypertrophy, and this can disrupt the conducting fibers that run down through the septum. Second, the thickening of the septum near the aorta can block the entrance to the aorta and therefore impede blood flow and the emptying of the ventricle. How can these effects be prevented? In Investigating Life: Silencing Mutant Myosin Genes we describe a recent study on mice that have been genetically engineered to carry mutations of a gene for one of the myosin chains of cardiac muscle that is associated with a large percentage of human HCM cases. These mice develop the pathologies that are seen in humans who inherit the genes causing HCM. The investigators found that by using *RNAi to silence the mutated genes, they could prevent the development of the HCM pathology.

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