Myocardial ischemia and myocardial infarction

Myocardial ischemia is a condition in which the demand for oxygen by the myocardium exceeds supply and this leads to systolic dysfunction (Kusumoto, 1999). The damage is temporary and it is usually due to inability of the coronary artery to increase its supply to match increased myocardium oxygen demands (Kusumoto, 1999). This usually results due to reduced blood flow to the heart muscle and an example of a cause of blood flow restriction is coronary atherosclerosis. Myocardial ischemia presents as symptomatic ischemia and silent ischemia.

Symptomatic ischemia is characterized by angina where patients usually experience pressure, heaviness, or tightness inside the chest (Kusumoto, 1999). These are usually triggered by exercise, emotional stress or heavy meals (Kusumoto, 1999). The pain also radiates to the back, jaw, arm and neck. Other symptoms include sweating and dyspnea. Silent ischemia is not characterized by angina. On the other hand, myocardial infarction refers to a condition that is characterized by death of cardiomyocytes as a result of lack of oxygen supply to the myocardium (Kusumoto, 1999).

The damage is always permanent. It is usually due to rupture of an intracoronary plaque which blocks flow of blood to myocardium. An example of a situation which can cause plaque rupture is sympathetic stimulation (Kusumoto, 1999). It is usually manifested by an acute chest pain which is usually more intense and which lasts longer than angina (Kusumoto, 1999). This pain usually radiates to the left arm though at times it involves the jaw, back, and the right arm. 2) Describe coronary artery disease. How does it develop?

What is the pathophysiological basis of how the various risk factors can lead to this disorder? Coronary artery disease refers to a condition where a plaque develops inside the coronary artery which is the artery responsible for supplying cardiac muscle with both nutrients and oxygen. Development of the plaque leads to narrowing of the coronary artery lumen which reduces blood flow to cardiac muscle. This leads to cardiac problems such as angina, heart attacks, arrhythmias, and heart failure (Kaplow & Hardin, 2007).

The most common cause of this disease is atherosclerosis. This is a condition in which plaques develop in arteries. Development of these plaques is believed to be initiated by an endothelial injury after which a chain of reactions is triggered which results in formation of hard structures which are made of cholesterol, fats, calcium, fibrin, and cellular waste (Kaplow & Hardin, 2007). There are several factors that put one at risk of developing this disorder. One is low levels of HDL cholesterol and high levels of LDL cholesterol.

This is because the HDL cholesterol which removes LDL cholesterol from the plaque and takes it to liver for elimination is reduced thus development of the plaque is not controlled (Kaplow & Hardin, 2007). High blood pressure is another factor and it increases risk by causing damage in the endothelium due to sheer stress thus initiating formation of plaque (Kaplow & Hardin, 2007). Smoking increases chances of endothelial damage which can trigger formation of plaque. In addition, it increases blood pressure.

Diabetes can lead to formation of glycated proteins which damage blood vessels triggering atherosclerosis (Kaplow & Hardin, 2007). Lack of exercise increases risk of coronary artery disease by increasing risk of hypertension, obesity, and diabetes. Obesity increases the amount of body fats in the body which can accelerate formation of plaque if endothelium is damaged. Family history puts one at risk since one can inherit genes that alter lipid metabolism leading to low levels of high levels of LDL cholesterol and low levels of HDL cholesterol (Kaplow & Hardin, 2007).

Another risk factor is age as the plaque builds up over a period of time leading to restriction of blood flow. Sex is another factor as in men the levels of estrogen are low and low estrogen levels are associated with low levels of HDL (Kaplow & Hardin, 2007). References Kaplow, R. & Hardin, S. R. (2007). Critical care nursing: Synergy for optimal outcomes. Sadbury, MA: Jones & Bartlett Learning. Kusumoto, F. M. (1999). Cardiovascular pathophysiology. USA: Hayes Barton Press.

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