The myocardium is the thick, middle layer of the heart and is composed of cardiac muscle. Cardiac muscle is very unique because it possesses the characteristics of skeletal muscle and smooth muscle. Skeletal muscle controls. The muscles of the body. The myocardium acts on its own, with no conscious effort.
Myocardium consists of thousands of muscle fibers, which are striated (they have many striped fibers) and are distributed at irregular intervals throughout the muscle. They connect with each other in points called intercalated disks. They are small membranes that separate the ends of muscle cells. These fibers actually use calcium to cause electrical conduction.
The cardiac muscle is the muscular middle layer of the heart wall. It consists of spontaneously contracting myocardial fibers that allow the heart to contract. Heart contraction is an autonomic (involuntary) function of the peripheral nervous system. The cardiac muscle surrounds the epicardium (the outer layer of the heart wall) and the intradermal (inner layer of the heart).
Myocardium stimulates heart contractions to pump blood from the chambers of the heart and relaxes the heart to allow the atria to take blood. These cramps generate the so-called Heartbeat. The heartbeat drives the cycle of the heart that pumps blood to the cells and tissues of the body.
Stunning myocardial is a reversible reduction in the function of cardiac contraction after reperfusion, which is not due to tissue damage or reduced blood flow. When complete myocardial ischemia occurs, it immediately switches from aerobic glycolysis to anaerobic glycolysis, resulting in a reduced ability to produce high-energy phosphates such as ATP and creatinine phosphate. At this point, lack of energy and the accumulation of lactate stops the contraction within 60 seconds of ischemia (ie occlusion of the vessel). The next stage is “stun heart muscle” in which there is a reversible ischemic injury. About 30 minutes after complete ischemia, the lesion becomes irreversible, ending the phase of myocardial stunning.
The clinical situations of stunned heart muscle are:
acute myocardial infarction (AMI)
after percutaneous coronary angioplasty (PTCA)
after cardiac surgery
“neurogenic” stun of the myocardium after acute cerebrovascular accident, such as subarachnoid haemorrhage