Transformation of Cardiac Muscle Isoforms

There are two types of cardiac muscle fiber isoforms, β-MHC (myosin heavy chain), also known as Type 1, and α- MHC, also known as Type 2. Although 91% identical in motor domain sequence, these two myosin isoforms have distinct mechanical and biochemical properties. With normal aging, and in certain cardiac pathologic conditions, much of the α-MHC is replaced by β-MHC. This review examines their transformation, and its effects on cardiac structure and function.