Myocardial Infarction - Pathophysiology


See also: Acute coronary syndrome

Acute myocardial infarction refers to two subtypes of acute coronary syndrome, namely non-ST-elevated myocardial infarction and ST-elevated myocardial infarction, which are most frequently (but not always) a manifestation of coronary artery disease. The most common triggering event is the disruption of an atherosclerotic plaque in an epicardial coronary artery, which leads to a clotting cascade, sometimes resulting in total occlusion of the artery. Atherosclerosis is the gradual buildup of cholesterol and fibrous tissue in plaques in the wall of arteries (in this case, the coronary arteries), typically over decades. Blood stream column irregularities visible on angiography reflect artery lumen narrowing as a result of decades of advancing atherosclerosis. Plaques can become unstable, rupture, and additionally promote a thrombus (blood clot) that occludes the artery; this can occur in minutes. When a severe enough plaque rupture occurs in the coronary vasculature, it leads to myocardial infarction (necrosis of downstream myocardium).

If impaired blood flow to the heart lasts long enough, it triggers a process called the ischemic cascade; the heart cells in the territory of the occluded coronary artery die (chiefly through necrosis) and do not grow back. A collagen scar forms in its place. Recent studies indicate that another form of cell death called apoptosis also plays a role in the process of tissue damage subsequent to myocardial infarction. As a result, the patient's heart will be permanently damaged. This myocardial scarring also puts the patient at risk for potentially life threatening arrhythmias, and may result in the formation of a ventricular aneurysm that can rupture with catastrophic consequences.

Injured heart tissue conducts electrical impulses more slowly than normal heart tissue. The difference in conduction velocity between injured and uninjured tissue can trigger re-entry or a feedback loop that is believed to be the cause of many lethal arrhythmias. The most serious of these arrhythmias is ventricular fibrillation (V-Fib/VF), an extremely fast and chaotic heart rhythm that is the leading cause of sudden cardiac death. Another life-threatening arrhythmia is ventricular tachycardia (V-Tach/VT), which may or may not cause sudden cardiac death. However, ventricular tachycardia usually results in rapid heart rates that prevent the heart from pumping blood effectively. Cardiac output and blood pressure may fall to dangerous levels, which can lead to further coronary ischemia and extension of the infarct.

The cardiac defibrillator is a device that was specifically designed to terminate these potentially fatal arrhythmias. The device works by delivering an electrical shock to the patient in order to depolarize a critical mass of the heart muscle, in effect "rebooting" the heart. This therapy is time dependent, and the odds of successful defibrillation decline rapidly after the onset of cardiopulmonary arrest.

Read more about this topic:  Myocardial Infarction

Other articles related to "pathophysiology":

Atrax Morgue - Partial Discography
... Slaughter Productions 1995 Homicidal Texture (Cass) Slaughter Productions 1995 Pathophysiology (Cass) Old Europa Cafe 1995 Untitled (Cass) Slaughter Productions 1995 Autoerotic Death (Cass, Ltd) BloodLust! 1996 Cut. 2002 La Casa Dalle Finestre Che Ridono (CDr) Slaughter Productions 2002 Pathophysiology (CDr) Transf/Order 2002 Sweetly (CDr, Album) Spatter 2002 Death - Orgasm Connector (CD) Slaughter Productions 2003 No More (CD ...
Pathophysiology - Uses
... Pathophysiology is a required area of study for nearly all healthcare professional school programs (medical, dental, physician assistant, occupational therapy, physical therapy ...
University Of Ostrava - Faculties and Departments - Faculty of Medicine - Department of Physiology and Pathophysiology
... The Department of Physiology and Pathophysiology is divided into Institute of Physiology and Institute of Pathophysiology ... addition to providing undergraduate teaching, the Department of Physiology and Pathophysiology carries out scientific research and produces expert reports ...
Tension Headache - Cause
... Recent studies of nitric oxide (NO) mechanisms suggest that NO may play a key role in the pathophysiology of CTTH ... thalamus, and cerebral cortex) is believed to be involved in the pathophysiology of chronic tension-type headache ... Moreover, a dysfunction in pain inhibitory systems may also play a role in the pathophysiology of chronic tension-type headache ...