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Myocardial ischemiaBy Mayo Clinic staff
Original Article: http://www.mayoclinic.com/health/myocardial-ischemia/DS01179
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|Causes of myocardial ischemia|
Myocardial ischemia occurs when blood flow to your heart muscle is decreased by a partial or complete blockage of your heart's arteries (coronary arteries). The decrease in blood flow reduces your heart's oxygen supply.
Myocardial ischemia, also called cardiac ischemia, can damage your heart muscle, reducing its ability to pump efficiently. A sudden, severe blockage of a coronary artery may lead to a heart attack. Myocardial ischemia may also cause serious abnormal heart rhythms.
Treatment for myocardial ischemia is directed at improving blood flow to the heart muscle and may include medications, a procedure to open blocked arteries or coronary artery bypass surgery. Making heart-healthy lifestyle choices is important in treating and preventing myocardial ischemia.
Some people who have myocardial ischemia don't experience any signs or symptoms (silent ischemia). When myocardial ischemia does cause signs and symptoms, they may include:
- Chest pressure or pain, typically on the left side of the body (angina pectoris)
- Neck or jaw pain
- Shoulder or arm pain
- Clammy skin
- Shortness of breath
- Nausea and vomiting
When to see a doctor
If you have chest discomfort, especially if it's accompanied by one or more of the other signs and symptoms listed above, seek medical care immediately. Call 911 or your local emergency number. If you don't have access to emergency medical services, have someone drive you to the nearest hospital. Drive yourself only as a last resort, if there are absolutely no other options. Driving yourself puts you and others at risk if your condition suddenly worsens.
Myocardial ischemia occurs when the blood flow through one or more of the blood vessels that lead to your heart (coronary arteries) is decreased. This decrease in blood flow leads to a decrease in the amount of oxygen your heart muscle (myocardium) receives. Myocardial ischemia may occur slowly as arteries become blocked over time, or it may occur quickly when an artery becomes blocked suddenly.
Conditions that may cause myocardial ischemia include:
- Coronary artery disease (atherosclerosis). Atherosclerosis occurs when plaques made of cholesterol and other cellular waste products build up on your artery walls and restrict blood flow. Atherosclerosis of the heart arteries is called coronary artery disease and is the most common cause of myocardial ischemia.
- Blood clot. The plaques that develop in atherosclerosis can rupture, causing a blood clot, which may lead to sudden, severe myocardial ischemia, resulting in a heart attack.
- Coronary artery spasm. A coronary artery spasm is a brief, temporary tightening (contraction) of the muscles in the artery wall. This can narrow and briefly decrease or even prevent blood flow to part of the heart muscle. Coronary artery spasms are more common in people with risk factors for heart disease, such as high cholesterol and high blood pressure, but the spasms can happen in people who have no risk factors, too. Coronary artery spasms can also occur in people who have conditions that affect their immune systems, such as lupus.
- Severe illnesses. Myocardial ischemia can occur when the metabolic demands of your heart increase or when blood pressure is very low due to infection, bleeding or other severe illness.
Factors that may increase your risk of developing myocardial ischemia include:
- Tobacco. Smoking and long-term exposure to secondhand smoke damage the interior walls of arteries — including arteries in your heart — allowing deposits of cholesterol and other substances to collect and slow blood flow. Smoking also increases the risk of blood clots forming in the arteries that can cause myocardial ischemia.
- Diabetes. Diabetes is the inability of your body to adequately produce or respond to insulin properly. Insulin, a hormone secreted by your pancreas, allows your body to use glucose, which is a form of sugar from foods. Diabetes can occur in childhood, but it appears more often in middle age and among overweight people. Diabetes is linked to an increased risk of myocardial ischemia, heart attack and other heart problems.
- High blood pressure. Over time, high blood pressure can damage arteries that feed your heart by accelerating atherosclerosis. The risk of high blood pressure increases as you age and if you have a family history of high blood pressure. High blood pressure is more common in those who are obese and in smokers. Eating a diet high in salt also may increase your risk of high blood pressure.
- High blood cholesterol or triglyceride levels. Cholesterol is a major part of the deposits that can narrow arteries throughout your body, including those that supply your heart. A high level of "bad" (low-density lipoprotein, or LDL) cholesterol in your blood is linked to an increased risk of atherosclerosis and myocardial ischemia. A high LDL level may be due to an inherited condition or a diet high in saturated fats and cholesterol. A high level of triglycerides, another type of blood fat, may also contribute to atherosclerosis. However, a high level of high-density lipoprotein (HDL) cholesterol (the "good" cholesterol), which helps the body clean up excess cholesterol, is desirable and lowers your risk of heart attack.
- Lack of physical activity. An inactive lifestyle contributes to obesity and is associated with higher cholesterol and triglycerides and an increased risk of atherosclerosis. People who get regular aerobic exercise have better cardiovascular fitness, which is associated with a decreased risk of myocardial ischemia and heart attack. Exercise also lowers high blood pressure.
- Obesity. Obese people have a high proportion of body fat, often with a body mass index of 30 or higher. Obesity raises the risk of myocardial ischemia because it's associated with high blood cholesterol levels, high blood pressure and diabetes.
- Family history. If you have a family history of heart attack or coronary artery disease, you may be at increased risk of myocardial ischemia.
Myocardial ischemia can lead to a number of serious complications, including:
- Heart attack (myocardial infarction). If a coronary artery becomes completely blocked, the lack of blood and oxygen can lead to a heart attack that destroys part of the heart muscle, causing serious and in some cases fatal heart damage.
- Irregular heart rhythm (arrhythmia). Your heart muscle needs sufficient oxygen to beat properly. When your heart doesn't receive enough oxygen, the electrical impulses in your heart that coordinate your heartbeats may malfunction, causing your heart to beat too fast, too slow or irregularly. In some cases, arrhythmias can be life-threatening.
- Heart failure. Myocardial ischemia can damage the heart muscle itself, leading to a reduction in its ability to effectively pump blood to the rest of your body. Over time, this damage may lead to heart failure.
Preparing for your appointment
If myocardial ischemia is causing chest pain, you will likely be evaluated in an emergency setting, rather than at a doctor's appointment. If you don't have chest pain but are experiencing other symptoms or are concerned about your risk of myocardial ischemia, make an appointment with your doctor for an evaluation. Your doctor may refer you to a heart specialist (cardiologist).
Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be prepared for your appointment. Here's some information to help you get ready for your appointment, and what to expect from your doctor.
What you can do
- Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as restrict your diet. Some blood tests, for example, require that you fast beforehand.
- Write down any symptoms you're experiencing, including any that may seem unrelated to myocardial ischemia.
- Write down key personal information, including a family history of heart disease, stroke, high blood pressure or diabetes, and any major stresses or recent life changes.
- Make a list of all medications, vitamins or supplements that you're taking.
- Take a family member or friend along, if possible. Sometimes it can be difficult to soak up all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
- Be prepared to discuss your diet and exercise habits. If you don't already follow a diet or exercise routine, be ready to talk to your doctor about challenges you might face in getting started.
- Write down questions to ask your doctor.
Your time with your doctor is limited, so preparing a list of questions will help you make the most of your time together. List your questions from most important to least important in case time runs out. Some basic questions to ask your doctor include:
- What is likely causing my symptoms or condition?
- What are other possible causes for my symptoms or condition?
- What kinds of tests will I need?
- What's the best treatment option?
- What foods should I eat or avoid?
- What's an appropriate level of physical activity?
- How often should I be screened for heart disease? For example, how often do I need a cholesterol test?
- What are the alternatives to the approach that you're suggesting?
- I have other health conditions. How can I best manage them together?
- Are there any restrictions that I need to follow?
- Should I see a specialist?
- Is there a generic alternative to the medicine you're prescribing me?
- Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:
- Do you have a family history of heart disease, high blood pressure or high cholesterol?
- When did you first begin experiencing symptoms?
- Have your symptoms been continuous or occasional?
- How severe are your symptoms?
- What, if anything, seems to improve your symptoms?
- What, if anything, appears to worsen your symptoms?
Tests and diagnosis
Along with a review of your medical history and a thorough physical exam, the tests and procedures used to diagnose myocardial ischemia include:
- Electrocardiogram (ECG). This test records the electrical activity of your heart via electrodes attached to your skin. Certain abnormalities in your heart's electrical activity may indicate myocardial ischemia.
- Blood tests. Certain heart enzymes slowly leak out into your blood if your heart has been damaged. To help diagnose myocardial ischemia, your doctor may take samples of your blood to test for these enzymes.
- Echocardiogram. This test uses sound waves to produce an image of your heart. During an echocardiogram, sound waves are directed at your heart from a transducer, a wand-like device, held on your chest. The sound waves bounce off your heart and are reflected back through your chest wall and processed electronically to provide video images of your heart. An echocardiogram can help identify whether an area of your heart has been damaged and isn't pumping normally.
- Nuclear scan. This test helps identify blood flow problems to your heart. Small amounts of radioactive material are injected into your bloodstream. Special cameras can detect the radioactive material as it flows through your heart and lungs. Areas of reduced blood flow to the heart muscle — through which less of the radioactive material flows — appear as dark spots on the scan.
- Coronary angiography. Coronary angiography uses X-ray imaging to examine the inside of your heart's blood vessels. During coronary angiography, a type of dye that's visible by X-ray machine is injected into the blood vessels of your heart. The X-ray machine rapidly takes a series of images (angiograms), offering a detailed look at the inside of your blood vessels.
- Cardiac CT scan. CT scans can determine if you have coronary artery calcification — a sign of coronary atherosclerosis. The heart arteries can also be seen using CT scanning (CT coronary angiogram).
- Stress test. A stress test usually involves walking on a treadmill or riding a stationary bike while your heart rhythm, blood pressure and breathing are monitored. Because exercise makes your heart pump harder and faster than it does during most daily activities, a stress test can reveal problems within your heart that might not be noticeable otherwise. It can be particularly useful if your doctor suspects you may have myocardial ischemia but you don't have any signs or symptoms.
- Holter monitoring. A Holter monitor is a small, wearable device that records your heart rhythm. You usually wear a Holter monitor for one to three days. During that time, the device will record all of your heartbeats. A Holter monitor test is usually performed if an electrocardiogram isn't able to give your doctor enough information about your heart's condition or if your doctor suspects silent myocardial ischemia.
Treatments and drugs
Treatment of myocardial ischemia is directed at improving blood flow to the heart muscle. Depending on the severity of your condition, you may be treated with medications, undergo a surgical procedure or both.
Medications that can be used to treat myocardial ischemia include:
- Aspirin. Your doctor may recommend taking a daily aspirin or other blood thinner. This can reduce the tendency of your blood to clot, which may help prevent obstruction of your coronary arteries. There are some cases where aspirin isn't appropriate, such as if you have a bleeding disorder or if you're already taking another blood thinner, so ask your doctor before starting to take aspirin.
- Nitroglycerin. This medication temporarily opens arterial blood vessels, improving blood flow to and from your heart.
- Beta blockers. These medications help relax your heart muscle, slow your heartbeat and decrease blood pressure so blood can flow to your heart more easily.
- Cholesterol-lowering medications. By decreasing the amount of cholesterol in your blood, especially low-density lipoprotein (LDL), or "bad," cholesterol, these drugs decrease the primary material that deposits on the coronary arteries. Boosting your high-density lipoprotein (HDL), or "good," cholesterol, may help, too. Your doctor can choose from a range of medications, including statins, niacin, fibrates and bile acid sequestrants.
- Calcium channel blockers. Calcium channel blockers, also called calcium antagonists, relax and widen blood vessels by affecting the muscle cells in the arterial walls. This increases blood flow in your heart. Calcium channel blockers also slow your pulse and reduce the workload on your heart.
- Angiotensin-converting enzyme (ACE) inhibitors. These drugs help relax blood vessels and lower blood pressure. ACE inhibitors prevent an enzyme in your body from producing angiotensin II, a substance in your body that affects your cardiovascular system in numerous ways, including constricting your blood vessels.
- Ranolazine (Ranexa). This medication helps relax your heart arteries. Ranolazine is an anti-angina medication that may be prescribed with other angina medications, such as calcium channel blockers, beta blockers or nitroglycerin.
Procedures to improve blood flow
Sometimes more aggressive treatment is needed to improve blood flow. Surgical procedures that may help include:
- Angioplasty and stenting. During angioplasty — also called a percutaneous coronary intervention (PCI) — your doctor inserts a long, thin tube (catheter) into the narrowed part of your artery. A wire with a tiny, deflated balloon is passed through the catheter to the narrowed area. The balloon is inflated to widen the artery, and then a small wire mesh coil (stent) is usually inserted to keep the artery open. Some stents slowly release medication to help keep the artery open. This procedure improves blood flow in your heart, reducing or eliminating myocardial ischemia.
- Coronary artery bypass surgery. During this procedure, a surgeon creates a graft to bypass blocked coronary arteries using a vessel from another part of your body. This allows blood to flow around the blocked or narrowed coronary artery. Because this requires open-heart surgery, it's typically reserved for cases of multiple narrowed coronary arteries.
Lifestyle and home remedies
In addition to other treatments, your doctor will likely recommend that you adopt a heart-healthy lifestyle. You doctor may advise that you:
- Quit smoking. If you smoke, stop. If you need help quitting, talk to your doctor about smoking cessation strategies.
- Avoid secondhand smoke. Secondhand smoke can damage the lining of your arteries and increase your risk of developing myocardial ischemia.
- Manage underlying health conditions. Treat diseases or conditions that can increase your risk of myocardial ischemia, such as diabetes, high blood pressure and high blood cholesterol.
- Eat a healthy diet. Eat a healthy diet with limited amounts of saturated fat, lots of whole grains, and many fruits and vegetables. Know your cholesterol numbers and ask your doctor if you've reduced them to the recommended level.
- Exercise. Exercise can improve blood flow to your heart. Talk to your doctor about starting a safe exercise plan.
- Maintain a healthy weight. If you're overweight, talk to your doctor about weight-loss options.
- Decrease stress. Reduce stress as much as possible. Practice healthy techniques for managing stress, such as muscle relaxation and deep breathing.
In addition to healthy lifestyle changes, remember the importance of regular medical checkups. Some of the main risk factors for myocardial ischemia — high cholesterol, high blood pressure and diabetes — have no symptoms in the early stages. Early detection and treatment can set the stage for a lifetime of better heart health.
The same lifestyle habits that can help treat myocardial ischemia can also help prevent it from developing in the first place. Leading a heart-healthy lifestyle can help keep your arteries strong, elastic and smooth, and allow for maximum blood flow. To follow a heart-healthy lifestyle, you should:
- Avoid secondhand smoke and quit smoking or chewing tobacco
- Control conditions such as high blood pressure, high cholesterol and diabetes
- Eat a low-fat, low-salt diet that's rich in fruits, vegetables and whole grains
- Maintain a healthy weight
- Reduce and manage stress
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