Myocardial Infarction

A myocardial infarction (MI) is damage to the heart that is not reversible. It is also called a heart attack. An MI usually occurs when a heart (coronary) artery becomes blocked or narrowed. This cuts off the blood supply to the heart. When one or more of the heart (coronary) arteries becomes blocked, that area of the heart begins to die. This causes pain felt during an MI.

ExitCare ImageIf you think you might be having an MI, call your local emergency services immediately (911 in U.S.). It is recommended that you take a 162 mg non-enteric coated aspirin if you do not have an aspirin allergy. Do not drive yourself to the hospital or wait to see if your symptoms go away. The sooner MI is treated, the greater the amount of heart muscle saved. Time is muscle. It can save your life.

CAUSES

An MI can occur from:

  • A gradual buildup of a fatty substance called plaque. When plaque builds up in the arteries, this condition is called atherosclerosis. This buildup can block or reduce the blood supply to the heart artery(s).

  • A sudden plaque rupture within a heart artery that causes a blood clot (thrombus). A blood clot can block the heart artery which does not allow blood flow to the heart.

  • A severe tightening (spasm) of the heart artery. This is a less common cause of a heart attack. When a heart artery spasms, it cuts off blood flow through the artery. Spasms can occur in heart arteries that do not have atherosclerosis.

RISK FACTORS

People at risk for an MI usually have one or more risk factors, such as:

  • High blood pressure.

  • High cholesterol.

  • Smoking.

  • Gender. Men have a higher heart attack risk.

  • Overweight/obesity.

  • Age.

  • Family history.

  • Lack of exercise.

  • Diabetes.

  • Stress.

  • Excessive alcohol use.

  • Street drug use (cocaine and methamphetamines).

SYMPTOMS

MI symptoms can vary, such as:

  • ExitCare ImageIn both men and women, MI symptoms can include the following:

  • Chest pain. The chest pain may feel like a crushing, squeezing, or "pressure" type feeling. MI pain can be "referred," meaning pain can be caused in one part of the body but felt in another part of the body. Referred MI pain may occur in the left arm, neck, or jaw. Pain may even be felt in the right arm.

  • Shortness of breath (dyspnea).

  • Heartburn or indigestion with or without vomiting, shortness of breath, or sweating (diaphoresis).

  • Sudden, cold sweats.

  • Sudden lightheadedness.

  • Upper back pain.

  • Women can have unique MI symptoms, such as:

  • Unexplained feelings of nervousness or anxiety.

  • Discomfort between the shoulder blades (scapula) or upper back.

  • Tingling in the hands and arms.

  • In elderly people (regardless of gender), MI symptoms can be subtle, such as:

  • Sweating (diaphoresis).

  • Shortness of breath (dyspnea).

  • General tiredness (fatigue) or not feeling well (malaise).

DIAGNOSIS

Diagnosis of an MI involves several tests such as:

  • An assessment of your vital signs such as heart rhythm, blood pressure, respiratory rate, and oxygen level.

  • An EKG (ECG) to look at the electrical activity of your heart.

  • Blood tests called cardiac markers are drawn at scheduled times to measure proteins or enzymes released by the damaged heart muscle.

  • A chest X-ray.

  • An echocardiogram to evaluate heart motion and blood flow.

  • Coronary angiography (cardiac catheterization). This is a diagnostic procedure to look at the heart arteries.

TREATMENT

Acute Intervention. For an MI, the national standard in the United States is to have an acute intervention in under 90 minutes from the time you get to the hospital. An acute intervention is a special procedure to open up the heart arteries. It is done in a treatment room called a "catheterization lab" (cath lab). Some hospitals do no have a cath lab. If you are having an MI and the hospital does not have a cath lab, the standard is to transport you to a hospital that has one. In the cath lab, acute intervention includes:

  • Angioplasty. An angioplasty involves inserting a thin, flexible tube (catheter) into an artery in either your groin or wrist. The catheter is threaded to the heart arteries. A balloon at the end of the catheter is inflated to open a narrowed or blocked heart artery. During an angioplasty procedure, a small mesh tube (stent) may be used to keep the heart artery open. Depending on your condition and health history, one of two types of stents may be placed:

  • Drug-eluting stent (DES). A DES is coated with a medicine to prevent scar tissue from growing over the stent. With drug-eluting stents, blood thinning medicine will need to be taken for up to a year.

  • Bare metal stent. This type of stent has no special coating to keep tissue from growing over it. This type of stent is used if you cannot take blood thinning medicine for a prolonged time or you need surgery in the near future. After a bare metal stent is placed, blood thinning medicine will need to be taken for about a month.

  • If you are taking blood thinning medicine (anti-platelet therapy) after stent placement, do not stop taking it unless your caregiver says it is okay to do so. Make sure you understand how long you need to take the medicine.

Surgical Intervention

  • If an acute intervention is not successful, surgery may be needed:

  • Open heart surgery (coronary artery bypass graft, CABG). CABG takes a vein (saphenous vein) from your leg. The vein is then attached to the blocked heart artery which bypasses the blockage. This then allows blood flow to the heart muscle.

Additional Interventions

  • A "clot buster" medicine (thrombolytic) may be given. This medicine can help break up a clot in the heart artery. This medicine may be given if a person cannot get to a cath lab right away.

  • Intra-aortic balloon pump (IABP). If you have suffered a very severe MI and are too unstable to go to the cath lab or to surgery, an IABP may be used. This is a temporary mechanical device used to increase blood flow to the heart and reduce the workload of the heart until you are stable enough to go to the cath lab or surgery.

HOME CARE INSTRUCTIONS

After an MI, you may need the following:

  • Medicine. Take medicine as directed by your caregiver. Medicines after an MI may:

  • Keep your blood from clotting easily (blood thinners).

  • Control your blood pressure.

  • Help lower your cholesterol.

  • Control abnormal heart rhythms.

  • Lifestyle changes. Under the guidance of your caregiver, lifestyle changes include:

  • Quitting smoking, if you smoke. Your caregiver can help you quit.

  • Being physically active.

  • Maintaining a healthy weight.

  • Eating a heart healthy diet. A dietitian can help you learn healthy eating options.

  • Managing diabetes.

  • Reducing stress.

  • Limiting alcohol intake.

SEEK IMMEDIATE MEDICAL CARE IF:

  • You have severe chest pain, especially if the pain is crushing or pressure-like and spreads to the arms, back, neck, or jaw. This is an emergency. Do not wait to see if the pain will go away. Get medical help at once. Call your local emergency services (911 in the U.S.). Do not drive yourself to the hospital.

  • You have shortness of breath during rest, sleep, or with activity.

  • You have sudden sweating or clammy skin.

  • You feel sick to your stomach (nauseous) and throw up (vomit).

  • You suddenly become lightheaded or dizzy.

  • You feel your heart beating rapidly or you notice "skipped" beats.

MAKE SURE YOU:

  • Understand these instructions.

  • Will watch your condition.

  • Will get help right away if you are not doing well or get worse.