A. Genetics
Shaw et al. stated in an editorial that the genetic heterogeneity of DCM is illustrated by the autosomal dominant form with several foci and gene mutations identified that include Iq32 (cardiac troponin-T), 14q11 (beta myosin heavy chain), 4q12 (beta –sarcoglycan), and 15q14(actin). Figure 5 shows some proteins involved in DCM and their cellular location.
The mechanisms by which individual mutations cause idiopathic DCM require further clarification. The end result of the disease is a weakened heart muscle that leads to heart failure. Abnormalities in force transmission and velocity of contraction of the heart muscle appear to result from mutations of contractile proteins, actin, alpha-tropomyosin, and desmin. Cardiac beta myosin heavy chain and troponins-T mutations are believed to result in reduced force generation by the sarcomere. Mutations in both sarcoglycans are believed to cause DCM. Mutations in the mitochondrial respiratory chain also can lead to DCM.
B. Clinical Features
1. Progressive shortness of breath on exertion appears over weeks or months. This then progresses to shortness of breath in bed (orthopnea) and paroxysmal nocturnal dyspnea.
2. Signs and symptoms of right and left heart failure become evident.

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