Infantile idiopathic restrictive cardiomyopathy, and noncompaction of the left ventricular myocardium. The product of a hypoxic myocardium can be hyperirritable myocardial cells. It may be due to fibrous change of the myocardium from a previous myocardial infarction. The individual myocytes that make up the myocardium also differ between cardiac chambers. Electrical systole opens voltage-gated sodium, potassium and calcium channels in cells of myocardium tissue. Coronary arteries supply blood to the myocardium and other components of the heart. The vessels that deliver oxygen-rich blood to the myocardium are the coronary arteries. Blood is brought to the myocardium by the coronary arteries. Procaine may also induce weakening of the myocardium leading to cardiac arrest. Injury to the myocardium occurs also during re-perfusion time. The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries. The artery supplies the anterolateral myocardium, apex, and interventricular septum. The coronary arteries that run deep within the myocardium are referred to as subendocardial. This makes it easier for depolarization and repolarization in the myocardium. This property allows rapid, synchronous depolarization of the myocardium.