Sudden death in dilated cardiomyopathy and skeletal myopathies

It is obvious to assume that diseases that affect skeletal muscle also affect the heart. Indeed, different myopathies share common cardiac abnormalities. While many different skeletal myopathies can be recognized, only a few different types of cardiomyopathies can be clinically distinguished. This suggests that different skeletal myopathies cause actually quite similar cardiac abnormalities. The reason for this is not clear. It might indicate that the underlying defects in skelatal myopathies all induce common pathways in the heart despite their underlying different pathobiological mechanisms. This probably reflects the very different capacities of skeletal muscle and cardiac muscle. A very important difference between cardiac and skeletal muscle is that unlike the heart, skeletal muscle can be electrically activated only by neurons. Another important difference is the existence of a specialized conduction system within the heart. A third important difference is the type of fibers that make up the contractile elements. The skeletal muscles are all composed of a mixture of fast and slow fibers.Fast fi bers contain large amounts of glycolytic enzymes, have an extensive sarcoplasmic reticulum, and have less blood supply and are therefore ideal for fast contraction with great strength of contraction. Slow fi bers contain large amounts of mitochondria, have a more extended blood supply, and contain myoglobin for oxygen storage, which makes these fi bers red. The heart is built up of striated muscle fi bers, similar to skeletal muscle, but consists of single cardiac myocytes that can pass through electrical signals via the intercalated disc.