Myocardial Infarction

Meaning:

Myocardial infarction is also known as a heart attack, coronary, occlusion, or simply a “coronary”, which is a life- threatening condition characterized by the formation of localized necrotic areas within the myocardium. MI usually follows the sudden occlusion of a coronary artery and the abrupt cessation of blood and oxygen flow to the heart muscle. Because the heart muscle must function continuously, blockage of blood to the muscle and the development of necrotic areas can be lethal.

Incidence: Every 29 seconds an American suffers a coronary event and approximately every 1 minute someone dies of a coronary event. Every year about 1.1 million Americans have Acute Myocardial Infarction (AMI). Indeed, AMI is the leading cause of death in America and is responsible for an estimated 529,000 deaths each year. About 250,000 people a year die before they reach the hospital.

Etiology and Risk Factors:

Modifiable risk factor: obesity, hypertension, Diabetes mellitus, cigearette smoking, sedentary life style, obesity, physical inactivity etc.

Non-modifiable risk factor: Age, Heriditory, gender (Race)

The most common cause of AMI is complete or nearly complete occlusion of a coronary artery, usually precipitated by rupture of a vulnerable atherosclerotic plaque and subsequent thrombus formation. Plaque rupture can be precipitated by both internal and external factors.

Internal factors: Include plaque characteristics, such as the size and consistency of the lipid core and the thickness of the fibrous cap as well as conditions to which it is exposed, such as coagulation status and degree of arterial vasoconstriction. Vulnerable plaques most frequently occur in areas with less than 70% stenosis and are characterized by an eccentric shape with an irregular border, a large, thin lipid core, and a thin, fibrous cap.

External factors: Results from actions of the client or from external conditions that effect the client. Strenuous physical activity and severe emotional stress, such as anger, increase sympathetic activity, which in turn increases hemodynamic stress that may lead to plaque rupture. At the same time, sympathetic activity increases myocardial oxygen demand. Scientists have reported that external factors, such as exposure to cold and time of day, also affect plaque rupture. Acute coronary events occur more frequently with exposure to cold and during the morning hours. Researchers hypothesize that the sudden increases in sympathetic activity associated with these factors may contribute to plaque rupture.

Category: Medicine Notes