Myocardium

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Myocardium is the muscular tissue of the heart.

Relationship to other layers
The other tissues of the heart are:
 * the endocardium (inner lining, effectively a specialised endothelium)
 * the epicardium (a connective tissue layer around the heart with a serous surface. It may be considered as the inner (visceral) layer of the pericardium)

Composition
The myocardium is composed of specialized cardiac muscle cells with an ability not possessed by muscle tissue elsewhere in the body. Cardiac muscle, like other muscles, can contract, but it can also carry an action potential (i.e. conduct electricity), like the neurones that constitute nerves.

The blood supply of the myocardium is by the coronary arteries.

Pathology
Occlusion of the coronary arteries by atherosclerosis and/or thrombosis can lead to myocardial infarction.

Certain viruses lead to inflammation of the myocardium, or myocarditis.

Cardiomyopathies are inherent diseases of the myocardium, many of which are caused by genetic mutations.

Failure of the heart to contract properly (for various reasons) is often termed heart failure although the proper term for this condition is myocardial failure. Heart failure is a general term referring to overwhelming heart disease from many causes (e.g., myocardial failure, valvular heart disease, increased ventricular stiffness) resulting in the inability of the heart to maintain normal ventricular filling pressure (resulting in fluid retention, edema, pulmonary oedema, hepatomegaly) and/or reduced blood flow to the body either at rest or during exercise. Myocardial failure resulting in heart failure results in a shortened life expectancy and decreased quality of life.

Disease of myocardium
Diseases of the myocardium are called a cardiomyopathy.