Myocardial Infarction - Prevention and Causes

You may know what a heart attack is, but probably do not know why it occurs. In this paper we explain how comes the obstruction of the coronary arteries and what are the treatment options for preventing heart attack and angina pectoris. Let's start with some basics.

Myocardial infarction
Myocardial infarction
 


What is coronary arteries, myocardial ischemia and infarction?

The arteries that bring blood to nourish the myocardium (heart muscle) are called coronary arteries. Our heart is vascularized by two coronary arteries - left and the right, which branch repeatedly to cover the entire heart muscle.

Infarction means death (necrosis) of a tissue from lack of blood supply. Many people immediately associate the word infarction with myocardial infarction, but it can occur in any tissue or organ of the body that suffer an interruption of its blood supply, such as cerebral infarction, myocardial infarction or pulmonary tract, for example.

Coronary arteries
Coronary arteries
 
Myocardial infarction, which is the necrosis of part of the heart muscle, occurs when one of the coronary arteries or their branches undergo an obstruction causing the insufficient blood flow to a specific region of the heart.

Before we go ahead with the text you need to understand another concept: the difference between ischemia and infarction.

Ischemia is the pre-condition of a heart attack, when a tissue is receiving less blood than necessary, but not sufficient for him to go into necrosis. When there is an ischemia, the tissue undergoing blood shortage will die if blood flow is not restored promptly.

An ischemic tissue is a tissue suffering under imminent risk of necrotic, while an infarcted tissue is a tissue already dead, with no chance of recovery.

Well understood these concepts, we then explain why a coronary artery can become blocked causing ischemia or myocardial infarction.


How does myocardial infarction occur?

Everyone has heard that high cholesterol is a risk factor for myocardial infarction, which is true, because excessive blood cholesterol causes fatty plaques deposited in the blood vessels, a process called atherosclerosis.

The fat plates occupy space within the vessel, causing blood flow be reduced. This accumulation of fat in the vessels is asymptomatic until well advanced stages. The symptoms of infarction begin to arise when more than 70-80% of an artery is obstructed. This lack of symptoms until the late stages occurs for two reasons:
  • when we are at rest the heart does not need a very high blood flow
  • when needed, the arteries can dilate temporarily increasing blood flow passing through them

However, when the obstruction becomes very large, the artery can no longer adapt the amount of blood that reaches the heart muscle being sufficient only when the patient is at rest and insufficient when the heart needs to accelerate and there is greater blood supply. At this moment angina pectoris arises, pain that is caused by ischemia of heart muscle.

Typically angina is chest pain that occurs during physical exertion or emotional stress, moments when the heart muscle demands more blood supply. Therefore, angina is a symptom that arises due to ischemia - when partially obstructed coronary artery cannnot provide this extra blood flow to the heart. Another characteristic of angina is their improvement after a few minutes of rest. When the heart slows, blood is less demanded and ischemia disappears.

The infarction occurs when the coronary artery blockage is complete, when the blood flow to the muscle is zero or so low that it cannot be sufficient even for the minimum operation of the heart. Contrary to what you may be thinking, infarction does not occur normally for a progressive growth of the fatty plaques that will slowly close the artery. This may occur in some cases, but the infarction is, in most cases, a sudden event that occurs after a rapid obstruction of the coronary artery by a clot. Here we need an explanation.

Note the picture. Usually the fatty plaques are well adhered to the vessel wall, rising slowly over time. Eventually, however, these plates may suffer injury by continuous passage of the blood, causing a small crack. This is the critical time of infarction, the body interprets this crack in cholesterol plaque like a crack in the vessel wall. The result of this misinterpretation is the activation of coagulation factors heading into the injury site in order to form a clot and stop the alleged injury to the vessel wall rupture and cause bleeding. Then a coronary artery which previously had about 70% of their light blocked by fatty plaque in the presence of a clot tends to rapidly clog the space 30% of that still allowed the blood passage.

The severity of infarction depends on the artery that is clogged and especially the extension of the area of heart muscle necrosis. The massive heart attack is one that affects such a large portion of the heart, that it becomes insufficient to pump blood to the rest of the body. Another possibility is a stroke that causes instability of cardiac electrical activity, causing severe cardiac arrhythmias.


Prevention

Knowing that the infarction is caused by the accumulation of fat in the arteries and the formation of a clot upon this board, we can make use of some actions in an attempt to prevent ischemic heart disease.

Let's talk a little about how we can try to reduce the risk of injury and atherosclerosis fatty plaques in the vessels.

Myocardial infarction prevention
Myocardial infarction prevention
 
Stop smoking: smokers have a 50% greater chance of having atherosclerosis than nonsmokers, causing cholesterol not only adhere more easily to the walls of the arteries, but also grow faster. Smoking also causes an inflammation of blood vessels, facilitating the rupture of plaques and clots. Finally, nicotine has a vasoconstrictor effect, preventing the arteries to dilate when needed to increase the flow of blood.

Controlling blood pressure: it is ideal to try to keep blood pressure below 130/80 mmHg with weight loss, control of salt in the diet and medications if needed.

Controlling cholesterol: HDL (good cholesterol) and / or LDL (bad cholesterol) levels are associated with an increased risk of coronary heart disease. Diet and weight control helps, but it is often necessary to use drugs to reduce cholesterol to satisfactory level. The statins, major group of drugs for the control of dyslipidemia, also seem to increase the stability of the fatty plaque, reducing the risk of injury thereof.

Controlled diet: a diet low in saturated fat and rich in fiber, vegetables and fruits. Give preference to fish.

Regular physical activity: 30 minutes of walking daily is sufficient to reduce the risk of coronary heart disease.

Control diabetes: Diabetes is a major risk factor for cardiovascular disease. A good control of glucose levels in blood is associated with a significant reduction in mortality.

Avoid obesity: Obese people (BMI greater than 30 kg/m2) are twice more likely to develop cardiovascular disease than people without excess weight. Obesity also increases the risk of hypertension, dyslipidemia (high cholesterol) and diabetes, risk factors for coronary heart disease, as stated above.


Aspirin to prevent heart attack

Aspirin
Aspirin
Aspirin (acetylsalicylic acid) is a drug that at low doses is capable of inhibiting the action of platelets, blood cells that initiate coagulation process. Thus, it decreases the formation of fat clots when a plate suffers injury. Aspirin reduces the risk of stroke in patients who have certain risk factors. Every time the cardiologist, clinical assessment, find data to suggest that the patient has a risk greater than 10% chance of a heart attack in the next 10 years, the prescription of aspirin is indicated. The suggested dose is between 75 and 325 mg / day.

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