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Myocardial Infarction

Overview

Overview


Myocardial Infarction

Heart attack, technically known as myocardial infarction (MI) or acute myocardial infarction (AMI), occurs due to diminution of blood supply to a part of the heart, causing that particular heart cells to die. Heart attack most commonly occurs due to occlusion (blockage) of a coronary artery following the rupture of a vulnerable atherosclerotic plaque. It results into restriction in blood supply and oxygen shortage ensues. If this situation is left as such without treatment for a sufficient period of time, it can cause damage or death (infarction) of heart muscle tissue (myocardium).

Risk Factors

Unwanted buildup of fatty deposits (atherosclerosis) that narrows arteries throughout your body, including arteries to your heart, is contributed by certain factors. It is possible to improve or eliminate many of these risk factors as this decreases your chances of having a first or subsequent heart attack.

Risk factors for heart attack include:

  • Age. Heart attack is more common in men who are 45 or older and women who are 55 or older.
  • Smoking. Active smoking and/or long-term exposure to secondhand smoke damages the interior walls of arteries allowing deposits of cholesterol and other substances to collect and slow blood flow. These arteries include arteries of your heart, along with other arteries. Risk of deadly blood clots forming and causing a heart attack is also increased by smoking.
  • Diabetes. Diabetes, a disease where body is unable to adequately produce insulin or respond to insulin need properly, occurs more often in middle age and among overweight people. Patients with diabetes are at a great risk of a heart attack.
  • Blood pressure. Increased blood pressure over years damages arteries that feed your heart by accelerating atherosclerosis. As you age, the risk of high blood pressure increases, but the main culprits for most people are eating a diet too high in salt and being overweight.
  • Hypercholesterolemia. Deposits occurring in the arterial walls mainly consist of cholesterol, and can narrow arteries throughout your body, including those that supply your heart. High blood levels of bad cholesterol increases your risk of a heart attack. Low-density lipoprotein (LDL) cholesterol (the “bad” cholesterol) is most likely to narrow arteries. This LDL increases due to a diet high in saturated fats and cholesterol. It is undesirable to have a high level of triglycerides, a type of blood fat related to your diet. But, HDL, a good cholesterol, which helps the body clean up excess cholesterol, is desirable and lowers your risk of heart attack.
  • Family history of heart attack. In case any of your sibling, parents or grandparents have had a heart attacks, you may be at increased risk. You and your family might be genetically predisposed to increased unwanted blood cholesterol levels. High blood pressure also can run in families.
  • No or less physical activity. High blood cholesterol levels and obesity are caused by an inactive lifestyle. Regular aerobic activity leads to better cardiovascular fitness, which decreases overall risk of heart attack. Exercise is also beneficial in lowering high blood pressure.
  • Obesity. Being overweight leads to high proportion of body fat (a body mass index of 30 or higher). Risk of heart attack is increased by being overweight as it’s associated with high blood cholesterol levels, high blood pressure and diabetes.
  • Stress. Inappropriate response to stress can increase your risk of a heart attack. Being constantly under stress leads to overeating or smoking or drug abuse from nervous tension. Too much stress, as well as anger, can also raise your blood pressure.
  • Illicit drug use. Drug abuse with cocaine or amphetamines can trigger a spasm of your coronary arteries that can cause a heart attack.

Causes

Causes

When one or more of the arteries supplying your heart with oxygen-rich blood (coronary arteries) become blocked, it results in heart attack. With passage of time, a coronary artery can become narrowed from the buildup of cholesterol called plaque. This process of plaque of buildup in arteries throughout the body is called atherosclerosis. One of these plaques can rupture during heart attack and a blood clot forms on the site of the rupture. A complete blockage of flow through artery occurs if the clot is large enough. Coronary artery disease occurs when your coronary arteries have narrowed due to atherosclerosis. Most heart attacks occur due to coronary artery disease.

Spasm of a coronary artery that shuts down blood flow to part of the heart muscle is another uncommon cause of a heart attack. Life-threatening spasm can occur due to drugs such as cocaine. A tear in the heart artery (coronary artery dissection) can also cause heart attack. Small blood clots or tumors that have traveled from other parts of the body (coronary embolism) are other uncommon causes of heart attack.

The heart attack is culmination of a several hours long process. More heart tissue is deprived of blood and deteriorates or dies with each passing minute. Damage to the heart can be limited or prevented if blood flow can be restored in time.

Symptoms

Symptoms

Most common symptoms of heart attack are:

  • A feeling of pressure, fullness or a squeezing pain in the center of your chest that lasts for more than a few minutes
  • Chest pain extending to your shoulder, arm, back, or even to your teeth and jaw
  • Frequent episodes of chest pain
  • Prolonged pain in the upper abdomen
  • Shortness of breath
  • Sweating
  • Impending sense of doom
  • Fainting
  • Nausea and vomiting

Women patients have different or atypical signs and symptoms of heart attack, which include:

  • Pain in abdomen or heartburn
  • Cold Clammy skin
  • Dizziness or lightheadedness
  • Unusual or unexplained fatigue

Symptoms of heart attack may vary. All patients of heart attack do not experience the same symptoms or experience them to the same degree. Another interesting feature is that many heart attacks aren’t as dramatic as the ones you’ve seen on TV. In some patients, there are no symptoms at all. Still, the more signs and symptoms you have, the greater the likelihood that you may be having a heart attack.

The timing of heart attack is not fixed and it can occur at any time of the day— at work or play, while you’re resting, or while you’re in motion. In some patients heart attacks strike suddenly, but many people who experience a heart attack have warning signs and symptoms hours, days or weeks in advance. Most common and earliest warning of a heart attack may be recurrent chest pain (angina) that’s triggered by exertion and relieved by rest. A temporary decrease in blood flow to the heart causes angina.

Diagnosis

Diagnosis

If a patient is having a heart attack or is suspecting having one, his/her diagnosis will likely happen in an emergency setting. You will be undergoing certain tests that will help check if your signs and symptoms, such as chest pain, signal a heart attack or another condition. These tests include:

  • Electrocardiogram (ECG). It is an electrical recording of the signals as they travel through your heart. Evidence of a previous heart attack can be revealed by an ECG. If the signs and symptoms of your atherosclerosis is more evident during exercise, your doctor may ask you to walk on a treadmill or ride a stationary bike during an ECG.
  • Blood tests. Blood is tested for elevation of certain heart enzymes that slowly leak out into your blood if your heart has been damaged by a heart attack.
Additional tests

After taking immediate steps to treat your condition, doctor may order for these additional tests:

  • Stress test. Stress test is also an exercise stress test. It is used to gather information about how well your heart works during physical activity. By doing exercise on bike or treadmill your heart pump harder and faster than it does during most daily activities. Testing of the heart during and after exercise can reveal problems within your heart that might not be noticeable otherwise. The procedure usually involves walking on a treadmill or riding a stationary bike while your heart rhythm and blood pressure and breathing are monitored. In some types of stress tests, pictures will be taken of your heart, such as during a stress echocardiogram (ultrasound) or nuclear stress test. In patients who are unable to exercise due to some or other reason, a medication that mimics the effect of exercise on heart is used to make it pump harder.
  • Chest X-ray. Images of your heart and lungs are displayed by this test. Also, other conditions can be looked into that might explain your symptoms and to see if you have an enlarged heart.
  • Echocardiogram. It is a type of ultrasound examination of your heart to produce images of the heart. These images are seen by the doctor to identify heart attack-related problems, including whether there are areas of your heart not getting enough blood or heart muscle that’s been damaged by poor blood flow. Sometimes, an echocardiogram is performed during a stress test.
  • Nuclear stress test. This test is performed to assess blood flow to your heart muscle at rest and during stress. It is similar to a routine stress test but uses a radioactive substance.
  • Coronary angiography. Narrowing or blockade in coronary arteries can be revealed by this test. The test involves injecting a liquid dye into the arteries of your heart through a long, thin tube (catheter) that’s fed through an artery, usually in your leg, to the arteries in your heart. The arteries become visible on X-ray, as the dye fills your arteries. Any area of blockage can then be revealed.
  • Cardiac computerized tomography (CT) scans. During performance of this test, you lie on a table inside a doughnut-shaped machine. Inside the machine there is an X-ray tube which rotates around your body and collects images of your heart and chest. These images can show if any of your heart’s arteries are narrowed or if your heart is enlarged.
  • Cardiac MRI: In this test, the patient is made to lie on a table inside a long tube-like machine that produces a magnetic field. The magnetic field aligns atomic particles in some of your cells. Signals are produced when radio waves are broadcast toward these aligned particles. These signals vary according to the type of tissue they are. The signals create images of your heart.

Complications

Complications

Complications of heart attack are often related to the damage done to your heart during a heart attack. Most common problems arising due to damage to heart are:

  • Abnormal heart rhythms (arrhythmias). Electrical “short circuits” can develop if your heart muscle is damaged from a heart attack. These can cause abnormal heart rhythms, some of which can be serious, even fatal.
  • Heart failure. It is a condition where the damaged tissue in your heart can’t do an adequate job of pumping blood out of your heart. Reduced pumping activity reduces blood flow to tissues and organs and may produce shortness of breath, fatigue, and swelling in your ankles and feet.
  • Heart rupture. A hole in a part of wall of heart can occur due to rupture of areas of heart muscle weakened by a heart attack. This rupture is often fatal.
  • Valve problems. Valves of the heart get damaged during a heart attack and may develop severe, life-threatening leakage problems.

Treatment

Treatment

Treatment of a heart attack varies depending on the situation. The patient might be treated with medications, undergo an invasive procedure or both — depending on the severity of the condition and the amount of damage to heart.

Medication

Medication

More heart tissue loses oxygen and deteriorates or dies with each passing minute after a heart attack. Restoration of blood flow quickly is the main way to prevent heart damage. Medications given to treat a heart attack include:

  • Aspirin. It reduces blood clotting, thus helping maintain blood flow through a narrowed artery.
  • Thrombolytics. Also called clot busters, these drugs help dissolve a blood clot that’s blocking blood flow to your heart.
  • Superaspirins. These are aspirin like drugs with improved ability to prevent clot forming, and include clopidogrel.
  • Blood-thinning medications. Medications like heparin might be given to make your blood less “sticky” and less likely to form more dangerous clots.
  • Pain relievers. Heart attack is associated with intense chest pain and you may receive a pain reliever, such as morphine, to reduce your discomfort.
  • Nitroglycerin. This medication temporarily opens arterial blood vessels, improving blood flow.
  • Beta blockers. These medications help relax your heart muscle, slow your heartbeat and decrease blood pressure making your heart’s job easier.
  • Cholesterol-lowering medications. Unwanted blood cholesterol levels are lowered by these medications.
Surgical and other procedures

Additionally, to medications, one of the following procedures might be done to treat your heart attack:

  • Angioplasty and stenting. These are used when unstable angina or lifestyle changes and medications don’t effectively treat your chronic, stable angina.
  • Coronary artery bypass surgery. This is done when stenting doesn’t help. It is a major surgery on heart arteries and involves creating a graft bypass using a vessel from another part of your body or a tube made of synthetic fabric. With this procedure, blood flow is maintained around the blocked or narrowed artery.

After these medications/procedure, the blood flow to your heart is restored and your condition is stable following your heart attack. You may be kept in the hospital for observation.

Lifestyle Measures for Prevention

Lifestyle changes can help you prevent or delay the occurrence of heart attack.

  • Stop smoking.
  • Exercise most days of the week.
  • Eat healthy foods.
  • Lose extra pounds and maintain a healthy weight.
  • Manage stress.
  • If you have high cholesterol, high blood pressure, diabetes or another chronic disease, work with your doctor to manage the condition and promote overall health.
  • If you have high cholesterol, high blood pressure, diabetes or another chronic disease, work with your doctor to manage the condition and promote overall health.
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