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What Are Causes Of Myocardial Infarction? Myocardial infarction (MI), or more commonly known as heart attack, occurs when the blood supply to the heart has been cut off and some portion of the heart muscle has died because of lack of oxygen. A person who has MI can develop symptoms including chest pain that travels from left arm to neck, shortness of breath, sweating, nausea, vomiting, abnormal heart beating, anxiety, fatigue, weakness, stress, and depression. Being an acute event, MI is, in most cases, a result from the sudden rupture or erosion of a coronary artery plaque that immediately leads to blood clot formation in the artery. This phenomenon is referred to as acute coronary syndrome (ACS). ACS associated with typical coronary artery disease is the most common cause of heart attack. The consequences of ACS depend on the extent to which the artery is blocked. The clot will often dissolve rather quickly, and the patient will experience only an episode of unstable angina. However, the blockage can be severe enough to cause the death of at least some of the heart muscle and subsequently trigger a heart attack. If only some of the heart muscle dies, the patient will have a non-ST segment myocardial infarction (NSTEMI). If nearly all of the muscle supplied by the occluded artery dies, an ST-segment elevation myocardial infarction (STEMI) occurs.
In addition to ACS, there are other conditions
that can also lead to MI. These include coronary artery spasm, microvascular
angina, stress cardiomyopathy, viral myocarditis, and coronary artery embolism.
Coronary artery spasm is a brief, sudden narrowing of one of the coronary arteries. The spasm usually occurs in coronary arteries that have not become hardened due to plaque build-up, though it can also occur in arteries with plaque build-up. It may occur without cause, or it may be triggered by alcohol withdrawal, emotional stress, exposure to cold, medicines that cause narrowing of blood vessels, stimulant drugs, cocaine use and cigarette smoking. Most people with coronary artery spasm will experience episodes of angina rather than an actual heart attack. Nevertheless, a severe and prolonged episode of coronary artery spasm can result in permanent damage to a portion of the heart muscle. Also called cardiac syndrome x, microvascular angina is caused by problems with the tiny arteries within the heart muscle that play a crucial role in regulating blood supply to the heart. Women, particularly around or after the menopause, are more likely than men to get microvascular angina. Women are twice as likely as men to have normal-looking heart arteries (without apparent blockages) when they actually have a heart attack. Stress cardiomyopathy, also referred to as broken heart syndrome, is a condition in which intense emotional or physical stress can cause rapid and severe heart muscle weakness (cardiomyopathy). This potentially life-threatening condition can happen following a variety of emotional stressors such as grief, fear, extreme anger, and surprise. It can also occur following numerous physical stressors to the body such as stroke, seizure, difficulty breathing, or significant bleeding. With aggressive treatment, most people who have this condition can survive with normally-functioning hearts. But for some, at least some part of the heart muscle is permanently damaged. Viral myocarditis is a viral infection directly affecting the heart muscle. A viral infection usually causes myocarditis, which is an inflammation of the heart muscle. But it can also result from a reaction to a drug or be part of a more general inflammatory condition. Besides affecting the heart muscle, myocarditis can affect the heart's electrical system, reducing the heart's ability to pump and causing rapid or abnormal heart rhythms (arrhythmias). It often causes permanent heart muscle damage.
Lastly, MI can be caused by coronary artery
embolism (CE). An embolism is an obstruction in a blood vessel due to a blood
clot, usually originating within the heart, or other foreign matter that gets
stuck while traveling through the bloodstream. Several conditions that can cause
this include atrial fibrillation, dilated cardiomyopathy, and the presence of an
artificial heart valve. A paper published July 28, 2015 in AHA Journal
‘Circulation’ found that atrial fibrillation is the most frequent cause of CE.
Patients with CE represent a high-risk subgroup of patients with heart attack
and require close follow-up. Date: March 28, 2019
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