Conditions: Myocardial Infarction
Commonly known as a “heart attack,” myocardial infarction is when heart muscle dies due to lack of oxygen. This may be life-threatening.
What is Myocardial infarcion (MI) or “heart attack”?
A myocardial infarction (MI), commonly known as a heart attack, occurs when oxygen delivery by blood to the muscle of the heart is not enough to keep the muscle alive.
Why is MYOCARDIAL INFARCTION a problem?
Simply put, we need the heart to pump blood to the body for the organs to function. A myocardial infarction may cause minor, major, or complete lack of blood flow to the body.
Image Source: Blausen Medical Communications, Inc., CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
What causes MYOCARDIAL INFARCTION?
There are several ways this might occur. Narrowing of one or more arteries to the heart (the coronary arteries) may occur gradually over time in a process known as atherosclerosis. The inner lining of these arteries is abnormal from atherosclerosis, and if the abnormal surface lining breaks, the irregular surface at this break may cause a clot to form within the artery and the clot can further narrow or completely block the artery. Less commonly, the arteries, which have muscle in their walls, can constrict temporarily, causing narrowing of the artery and decreased blood flow. Usually, myocardial infarction is thought of as decreased blood flow to the heart muscle from the perspective of blood and therefore oxygen delivery. Another way to think of the problem is that when the heart is working very hard (fast rate or pumping at high pressure), the oxygen requirement increases. When oxygen demand is greater than oxygen delivery, whether from decreased blood flow, too few oxygen carrying red blood cells, or from oxygen requirements that outstrip what might ordinarily be adequate flow, some of the cells of the heart muscle (or the nerves within the heart) die. Dead heart muscle does not contract. Dead nerves do not conduct electricity. If the dead muscle extends full-thickness through the heart wall, the heart may spring a leak, causing compression of the heart from outside.
HOw is myocardial infarction prevented?
Strategies to avoid myocardial infarction are based on avoiding the various causes noted above. Some of the causes of myocardial infarction can be modified, but some cannot. Genetics and age are not under one’s control, yet play a major role in risk for myocardial infarction. Physical activity, and diet are part of a long-term lifestyle approach to minimize risk. Certain medications may also be used over time to lessen risk, while other medications are used at the time of a heart attack to limit the damage. In the time during and around surgery, avoiding high or low blood pressure, low amount of red blood cells (anemia), and a very fast heart rate may help.
Common locations of pain in myocardial infarction. Image Source: J. Heuser JHeuser, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons
How is myocardial infarction identified?
Symptoms that a patient may experience include pain (in the chest, back, abdomen, left arm, and/or jaw), pressure on the chest, sweating, nausea and/or vomiting, shortness of breath, indigestion, dizziness and loss of consciousness, but many of these symptoms could be attributed to something else and sometimes myocardial infarction may occur with no symptoms. Monitoring with an electrocardiogram is a more definitive way to diagnose myocardial infarction, and blood testing is also confirmatory, but may require repeat testing over a day or so to be definitive. Imaging (echocardiogram, as an example) may also demonstrate myocardial infarction.
How is myocardial infarction treated?
Generally, treatment strategies involve unblocking blood vessels, reducing blood clot enlargement, reducing inadequate oxygen delivery, and modifying risk factors with the aim of preventing future problems. In the longer term, recovery consists of building heart strength with therapy and modifying risk factors to help prevent another myocardial infarction.