MYOCARDIAL INFARCTION

Understanding myocardial infarction

AMI(acute myocardial infarction), also referred to as a heart attack, caused by a decrease or stoppage of blood flow to a portion of the heart. leading to necrosis of heart muscle. it is a life threatening condition that occurs due to low blood flow to the heart muscle causing tissue damage. this is generally the result of a blood clot in the epicardial artery that supply blood to that area of heart muscle. 

it is now discovered that not all cases necessarily require blood clot etiologically. All the tissue of the body require oxygen demand to function so that heart muscle also require blood supply which is must equal the oxygen demand of the muscle. this is the supply-demand ratio. And it is now saying that imbalance in this ratio- too little supply or too much demand of oxygen may lead to myocardial damage without the presence of blood clot.

Types of MI

Mainly it is divided in to two types based on changes to an ECG, that is-
  • ST elevation MI (STEMI): it makes up to 25% to 45% of myocardial infarction 
  • non- ST- elevation MI(NSTEMI)
It is also classified in to five types, based on the international consensus:
  • Spontaneous MI
  • MI related to ischemia
  • sudden unexpected cardiac death 
  • MI associated with coronary angioplasty or stent
  • associated with CABG

Sign and symptoms related to MI

Patient with the typical MI may have the following symptoms(typical STEMI may occur suddenly without warning):

Chest pain

  • Pain in chest is the most common sign of acute AMI that is described as sensation of tightness, pressure or squeezing.
  • it is intense and continuous for 30-40 min.
  • chest pain radiate up to the neck, shoulder, jaw, and back and down the left arm.
  •  sometimes it is epigastric, with a feeling of indigestion or of fullness and gas

symptoms other than chest pain 

it is important to note that not all people who have heart attack experience the same symptoms or the same severity of symptoms. chest pain and shortness of breath are the most symptoms reported. some other symptoms include:
  • weakness
  • sweating 
  • nausea 
  • vomiting
  • anxiety 
  • a cough
  • a fast heart rate 
  • increased respiratory rate 

Causes of acute myocardial infarction

Our heart is a main organ in cardiovascular system which include different types of blood vessels(arteries) in transporting the oxygen and blood to all over the body tissues including heart muscle. coronary artery involved in transporting oxygen rich blood to the cardiac muscle. when these arteries become blocked and narrowed due to a buildup of plaque, the blood flow to heart can decrease significantly or stop completely. this may lead to heart attack. several factors are responsible for blockage of coronary arteries.

Atherosclerosis

It is the most common cause of myocardial infarction. it is the rupture of an atherosclerotic plaque on an artery supplying blood heart muscle. plaque can be unstable and rupture which promote the formation of blood clot that block the artery. 
Atherosclerosis is characterized by progressive inflammation of the wall of the arteries.

Approximately 90% of myocardial infarction results from an acute thrombus that obstruct an atherosclerotic coronary artery. plaque rupture and erosion are considered to be the major trigger for coronary thrombosis and this results in platelet activation and aggregation, coagulation pathway activation, and endothelial vasoconstriction occur. 

Cholesterol

Cholesterol, also called low density lipoprotein(LDL), one of the leading cause of blockage in the arteries. not all cholesterols are bad but LDL can stick to the walls of your arteries and produce plaque. it is a colorless substances found in food that you eat. our body also produce it naturally. blood platelets which help the blood to clot, may stick to the plaque and build up over time.   

Tissue death 

If blood flow to the heart muscle not enough for longer time, it triggers ischemic cascades. heart cells of the blocked area may die through necrosis. when an artery is blocked cell lacks oxygen which is needed to produce ATP in mitochondria. cells in the worst area of the blood supply just below the inner surface of heart are most susceptible to damage.

Who is at most risk of heart attack      

  • People with high blood pressure(Hypertension)
  • people with low level of HDL, high level of LDL, and high level of triglycerides.
  • cigarette smoker
  • people who are under a lot of stress
  • people who drink too much alcohol
  • people overweight 30% or more 
  • people who eat a diet high in saturated fat
  • people with type 2 diabetes

Risk factors

Age

People(men) aged 45 or older and women 55 and older are more likely to have a heart attack than are younger men and women.

Tobacco smoking

smoking tobacco products may increase the risk of heart attack. tobacco smoking also cause the different cardiovascular diseases.

High level of blood pressure

you are at greater risk of heart attack if you have high blood pressure. High blood pressure increase the risk of artery damage and development of plaque.

High blood cholesterol and triglyceride levels

A high level of cholesterol specifically low density lipoprotein(LDL) "Bad Cholesterol" may lead to narrowing the arteries. high triglyceride level also increase the risk of heart attack. However, high level of high density lipoprotein(HDL) "good cholesterol" may lower your risk.

Obesity

obesity directly linked with uses of higher amount of  cholesterol, triglycerides and increased blood pressure and diabetes. losing just 10% of your body weight can lower the risk.

Diabetes

diabetes caused by improper functioning of pancreas which is not able to secret insulin hormone responsible for glucose maintenance in blood, lower the amount of insulin increase the amount blood sugar, may increase the risk of heart attack.

stress 

stress have all over impact on increasing the risk of heart attack. working on your stress lower the risk of heart attack.

Diagnosis