Acute myocardial infarction (AMI)
Acute myocardial infarction
Acute myocardial infarction (AMI) or heart attack appears when blood flow is suddenly cut off from the heart, causing damage to the heart muscle.
To recognize heart attack is possible by chest pain or discomfort which occurs in shoulders, arms, back and neck. Most of all the pain is located in the center or left side of chest. It usually lasts few minutes and reminds heartburn.
Often the pain is accompanied by weakness, sweating, nausea, vomiting, dizziness, agitation.
Elderly patients diagnosed with myocardial infarction can have shortness of breath, which may progress to pulmonary edema. In other cases, heart attack is characterized by a sudden loss of consciousness, a feeling of severe weakness, arrhythmia, or unexplained low blood pressure.
Causes of AMI
The reasons for stopping the blood flow in the heart vessels, as well as for myocardial infarction include:
- Atherosclerosis of the coronary vessels (thrombosis, embolism)
- The spasm of blood vessels of the heart
- Foreign-body embolism
- Surgical procedures on the heart (coronary vessel ligation or complete transaction)
- Coronary artery disease (group of diseases that include stable and unstable angina, myocardial infarction, coronary death).
Also, there are some nutritional causes that are playing no less important role.
- Bad cholesterol: can be found in food as well as produced by your body and not all cholesterol is bad, but the group called low-density lipoprotein (LDL) can stick around your arteries and make a plaque. Then this plaque blocks blood flow in the arteries.
- Satured fats: may lead to building of the same plaque in the coronary arteries and increase LDL in blood
- Trans fats: this another type of fat is also contributing to increasing LDL and reducing good cholesterol in your body.
Risk factors for AMI
There are some risk factors which can make a person to be more sensitive to heart attack.
- High blood pressure (normal blood pressure is 120/80 mm Hg and if the number is increasing, it can create a risk for heart problems). Controlling hypertension by using appropriate medication, you can reduce the risk of AMI.
- High triglyceride and hyperlipidemia (high cholesterol levels, LDL or triglyceride puts you at risk for AMI). The triglyceride is a fatty substance that is stored in some foods and after you eat it, can stay in your fat cells or arteries and cause heart problems.
- Diabetes or high blood sugar (people with diabetes have a bigger risk of acute myocardial infarction because it increase the rate of atherosclerotic progression which has a bad impact on lipid profile, and high blood sugar may damage blood vessels and nerves which contribute to risk of coronary heart disease and heart attacks).
- Obesity (according to many studies it enriches a possibility of heart attack).
- Tobacco use (tobacco is known as one of the damagers of blood vessel walls and the body’s response to it is the formation of atherosclerosis and trigger risk of AMI). It may also cause other cardiovascular diseases.
- Male gender (the studies showed that AMI risk is higher in men than women in all age groups).
- Family history (if someone from family has coronary disease it may influence on individual’s risk of AMI
There are other risk factors for AMI as lack of exercises, unhealthy diet, excessive alcohol, and stress.
Signs and symptoms of AMI
The characteristic symptoms of АMI are:
- Chest pain like feeling a pressure and squeezing in the middle part of the thorax
- Radiation of pain to the left arm, lower jaw, neck, back and abdomen
- Shortness of breath (dyspnea)
- Epigastric discomfort including nausea and vomiting
- Diaphoresis and sweating
- Syncope without other case
- Fast heart rate
The listed signs and symptoms are response actions to pain and blood flow dysfunctions. In addition, AMI can be followed by loss of consciousness and sudden death.
Types of acute myocardial infarction
The simplest classification is based on heart work and it is categorized as primary (spontaneous) and secondary AMI. The first one develops due to cessation of circulation, while the second one occurs due to an increased work of heart. The escalated work of heart causes release of hormones that activates the entire body. Some of those hormones are catecholamines which cause vasospasm of the coronary vessels.
There are two main types of AMI based on pathology:
- Transmural is associated with atherosclerosis and includes all heart muscle. It can be divided into few groups: anterior, inferior, posterior, lateral.
- Subendocardial extend though small area in the subendocardial wall of the left ventricle, ventricular septum, or papillary muscles.
The most common classification of acute myocardial infarction is to divide it to ST elevation AMI and non-ST elevation AMI. The difference is in ST vs. non-ST segments evaluation happening during poor oxygenation of the heart.
In 2007, the new separation in 5 types were approved:
- Spontaneous AMI related to ischemia
- Secondary AMI
- Sudden cardiac death
- AMI associated with coronary angioplasty
- AMI related to GABS (Coronary artery bypass surgery)
If your doctor suspects you had a heart attack, it should be checked by performing several possible tests.
The first diagnostic test is electrocardiography (ECG a.k.a. EKG), which can show if myocardial infarction is still developing or already occurred. To compare heart tracing during AMI and normal pattern, it will show typical changes which are called pathological Q waves and ST elevation. ECG can be done for diagnosis of reperfusion during thrombolytic therapy in acute myocardial infarction.
The second type of test that could be performed is blood test that measures chemicals called troponin and creatine kinase to confirm AMI. If the heart muscle is damaged, these chemicals will be released in blood. Troponin test will give results for an AMI happening now. Creatine Kinase will give results from a short time after the AMI.
Other blood test is myoglobin test which can check if heart muscle is damaged by measuring amount of myoglobin in blood. Myoglobin is a protein in heart and skeletal muscles and has oxygen attached to it, so when your muscles are active and need extra oxygen, it could be provided by it.
But when the muscle is injured, myoglobin is released in blood and can be recognised by special test set. Myoglobin test will give the results from an AMI that happended some time ago. There are also combo-tests available that test for markers of all Troponin/Creatine Kinase/Myoglobin, and will give results if there are any concentration present.
Advanced blood tests are also able to monitor reperfusion during thrombolytic therapy.
In some cases, doctors can propose an echocardiogram (an ultrasound scan of the heart) or a test called myocardial perfusion scintigraphy.
In addition to these tests, professionals can advise you to monitor your heart tracing per few days to check the heart rhythm with a portableECG device and measure your blood pressure regularly. One more additional diagnostic tool is stress test which is realized by checking how your heart reacts to stressful situations.
Myocardial infarction can be prevented by some medical treatments and changes in your lifestyle. You can reduce the risk of AMI by eating healthy food low in LDL cholesterol and fat, doing exercises few times per week to improve your cardiovascular health, quit smoking if you do, reduce alcohol intake to the minimum.
Treatment of Acute myocardial infarction
Treatment includes various types according to situation and individual case. Most treatments start in the emergency room because heart attack needs immediate help. The most common way to use procedure named angioplasty that is supposed to help to unblock the arteries or blood thinners to break the blood clots in arteries.
There are following actions and types of treatment that can be arranged:
- Antiplatelet medicines like aspirin, clopidogrel or ticagrelor (this kind of medicine can help to reduce the stickiness of platelets).
- Pain relief (in order to relief a pain, doctors may use morphine or other medicine).
- Heparin injection (this medicine or similar one can help to prevent from forming of blood clots).
- Treatment to restore blood flow in the blocked coronary artery (For this purpose, various medications can be used that affect blood clotting. At the pre-hospital phase and in hospital, the first 3-6 hours after myocardial is advisable to use thrombolytic agents: streptokinase, alteplase, and others. Be sure to use anticoagulants (heparin, fraxiparine, fragmin) and Antiplatelet agents (aspirin, plavix) as substances that prevent further thrombosis. Nitrates (nitroglycerin, perlinganit etc.) are required, along with analgesics, since they lead to the expansion of the coronary vessels.
- Beta-blocker medicine (block the action of particular hormones like adrenaline that increase the rate of heartbeat).
- Insulin (to control the blood sugar levels if it rises during AMI).
- Oxygen (to reduce risk of damage of heart muscle).
- Thrombolytic therapy (used for immediate treatment of stroke and heart attack and usually performed with help of a drug tissue plasminogen activator (tPA). This kind of treatment must be given within 30 minutes from arriving to the hospital.
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