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Heart attack and acute coronary syndrome

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of heart attack.

Alternative Names

Acute coronary syndrome; Myocardial infarction

Treatment

Treatment options will depend on whether the patient has angina, acute coronary syndrome, or a full-blown heart attack.

Patients who are diagnosed with acute coronary syndrome (ACS) may be at risk for a heart attack. ACS refers to either unstable angina or NSTEMI (non ST-segment elevation myocardial infarction). Unstable angina is potentially serious and chest pain is persistent, but blood tests do not show markers for heart attack. With NSTEMI, the blood tests suggest a developing heart attack, but most likely, injury in the arteries is less serious than with a full-blown heart attack.

Doctors use a patient's medical history, various tests, and the presence of certain factors to help predict which ACS patients are most at risk for developing a more serious condition. The degree of chest pain itself is not necessarily useful for determining the actual damage in the heart.

Depending on how severe the condition is, the patient is then given either medical treatments or more invasive approaches, such as angioplasty. Some experts believe that even if patients with ACS are only given drug therapy, they should still be transferred to centers equipped for angioplasty.

Immediate Treatments to Support the Patient

Early supportive treatments are similar for patients who have ACS or those who have had a heart attack.

Oxygen. Oxygen is almost always administered right away, usually through a tube that enters through the nose. The patient is given aspirin if one was not taken at home.

Medications for Relieving Symptoms.

• Nitroglycerin. Most patients will receive nitroglycerin after a heart attack, usually under the tongue. Nitroglycerin decreases blood pressure and dilates the blood vessels around the heart, increasing blood flow. Nitroglycerin may be given intravenously in certain cases (recurrent angina, congestive heart failure, or high blood pressure). Some evidence suggests that intravenous administration may help reduce long-term heart muscle changes that can occur after a heart attack. (Patients with very low blood pressure or severely slow heart rate will not receive nitroglycerin.)
• Morphine. Morphine not only relieves pain and reduces anxiety but also dilates blood vessels, aiding the circulation of blood and oxygen to the heart. Morphine can decrease blood pressure and slow down the heart. In patients in which such effects may worsen their heart attacks, other drugs such as meperidine (Demerol) or nalbuphine (Nubain) may be used.

Anticlotting Medications. Appropriate anticlotting medications are started immediately in all patients.

• Aspirin (antiplatelet drug) should be taken immediately after a heart attack. It can be either swallowed or chewed, but chewing provides more rapid benefit. If the patient has not taken an aspirin at home, it will be given at the hospital.
• Clopidogrel (a stronger antiplatelet drug) is usually given along with other anticlotting drugs. It is sometimes used in place of aspirin.
• Heparin (an anticoagulant) is usually given to moderate- to high-risk patients. Low-molecular weight heparin (LMWH), such as enoxaparin, is now recommended over standard heparin. Fondaparinux (Arixtra) is another type of blood thinner that is showing promise for treating patients with STEMI (ST-elevation myocardial infarction), a severe type of heart attack. Fondaparinux may also be better than enoxaparin for patients with acute coronary syndrome (ACS).
• Glycoprotein IIb/IIIa inhibitors (antiplatelet drugs), most often tirofiban, are added for patients undergoing angioplasty. These drugs include tirofiban (Aggrastat) and abciximab (ReoPro). They are also beneficial for nonsurgical patients with ACS, notably NSTEMI (non ST-segment elevation myocardial infarction).

Opening the Arteries: Thrombolytic Drugs or Emergency Angioplasty (PTCA)

After a heart attack, clots form in the injured artery within 4 to 6 hours in 90% of patients. Opening a clotted artery as quickly as possible is the best approach to improving survival.

The standard medical and surgical solutions for opening arteries are:

• Angioplasty , also called percutaneous transluminal coronary angioplasty (PTCA) or percutaneous coronary intervention (PCI), is the major surgical procedure for opening the arteries.Coronary artery bypass graft (CABG) is sometimes used as an alternative to angioplasty.
• Thrombolytics are known as blood-clot-busting drugs and are the standard medications used to open the arteries. They are administered as soon as possible in centers where angioplasty is not available or in patients who are not good candidates for angioplasty.

The best candidates for either thrombolytic therapy or angioplasty are:

• Adults younger than 75 years old with elevated ST segments or indications of bundle branch block (an ECG reading showing an interruption in the electrical pathway within the heart).
• Patients whose symptoms occur within 12 hours of treatment.

Specific Candidates for Emergency Angioplasty. Most patients who meet the criteria for either thrombolytic drugs or angioplasty do better with angioplasty (although only in centers equipped to do this procedure).

Good candidates for angioplasty include:

• Elderly patients (including those over age 75) who meet the criteria for both approaches tend to do better with angioplasty than thrombolytic therapy
• Patients with diabetes who meet the criteria for both approaches
• Patients under age 75 who go into shock, provided that angioplasty can be performed within 18 hours of shock (There is no advantage for patients over 75 who are in shock.)

As with thrombolytic treatments, angioplasty is most effective when performed within 12 hours of symptoms, and the sooner the better. Unfortunately not all communities have centers experienced in the procedure. The experience of the medical center's staff is critical for optimal benefits, and not all surgeons are experienced in angioplasty. However, the procedure is becoming increasingly available, and overall mortality rates are improving over time with angioplasty. Patients or their families should be sure their surgeon has performed at least 75 of these procedures and that the medical center has performed at least 200.

Specific Candidates or Non-Candidates for Thrombolytics. People who meet the criteria for either thrombolytics or angioplasty may benefit from thrombolytic drugs even if they have high-risk conditions such as diabetes, high systolic blood pressure less than 180 mm Hg, or a history of heart attack.

Several studies report that women do worse after thrombolytic therapy. Evidence indicates, however, that they are generally older and have more serious medical conditions when they seek treatment. One study also reported that women were given these drugs an average of 14 minutes later than men were. Women on thrombolytic therapy still do better than those not given these drugs. The bottom line is that thrombolytic therapy is life-saving, and appropriate candidates, regardless of age or gender, should not be denied this therapy.

Thrombolytics should be avoided or used with great caution in the following patients:

• People older than age 75 -- a 2000 study suggested that their risk of death was 38% higher than patients in their age group who were not given therapy; a higher risk exists in such older patients even if they are otherwise healthy
• Patients with elevated ST segments whose symptoms have continued beyond 12 hours
• Pregnant women
• People who have experienced recent trauma (especially head injury) or invasive surgery
• People with active peptic ulcers
• Patients who have been given prolonged CPR
• Current users of anticoagulants

Thrombolytics should not be used in the following patients:

• Patients who have experienced any recent major bleeding
• Patients with low ST segments
• Patients with a history of stroke
• Patients with uncontrolled high blood pressure

Other Heart Supportive Drugs

After a heart attack, the patient may need a number of different medications, depending on their risk factors for a future heart attack:

• Beta-blockers reduce the oxygen demand of the heart by slowing the heart rate and lowering arterial pressure.
• Angiotensin converting enzyme (ACE) inhibitors should be given on the first day to all patients, unless there are medical reasons for not taking them.
• Calcium channel blockers may provide relief in patients with unstable angina whose symptoms do not respond to nitrates and beta blockers. They are also useful for patients with Prinzmetal's angina.
• Statins. Statins are important cholesterol lowering drugs that are beneficial for patients who have experienced a heart attack. They may also have heart-protective properties that go beyond lowering cholesterol.
• Atropine. Atropine may be given for a very low heart rate (bradycardia) or signs of atrioventricular (AV) block, in which electric conduction of nerve impulses to specialized muscles in the heart is slowed or interrupted.

Treatment for Patients in Shock or with Heart Failure

Severely ill patients, particularly those in shock (a dangerous condition that includes a drop in blood pressure and other abnormalities) or with heart failure, will be monitored closely and stabilized. Oxygen is administered, and fluids are given or replaced when it is appropriate to either increase or reduce blood pressure. Such patients may be given dopamine, dobutamine, or both. Other treatments depend on the specific condition.

Heart failure. Intravenous furosemide may be administered. Patients may also be given nitrates, and ACE inhibitors, unless they have a severe drop in blood pressure or other conditions that preclude them. Clot-busting drugs or angioplasty may be appropriate and life-saving in many of these patients, although heart failure patients are less likely to be given these treatments.

Shock. A procedure called intra-aortic balloon counterpulsation (IABP) is proving to help these patients when used in combination with thrombolytic therapy. IABP involves inserting a catheter containing a balloon, which is inflated and deflated within the artery to boost blood pressure. Left ventricular assist devices and early angioplasty might be considered.

Treatment of Arrhythmias

An arrhythmia is a deviation from the heart's normal beating pattern caused when the heart muscle is deprived of oxygen and is a dangerous side effect of a heart attack. A very fast or slow rhythmic heart rate often occurs in patients who have had a heart attack, and is not usually a dangerous sign.

Premature beats or very fast arrhythmias called tachycardia, however, may be predictors of ventricular fibrillation . This is a lethal rhythm abnormality, in which the ventricles of the heart beat so rapidly that they do not actually contract but quiver ineffectually. The pumping action necessary to keep blood circulating is lost.

Preventing Ventricular Fibrillation. People who develop ventricular fibrillation do not always experience warning arrhythmias, and to date, there are no effective drugs for preventing arrhythmias during a heart attack.

• Potassium and magnesium levels should be monitored and maintained
• Intravenous beta-blockers followed by oral administration of the drugs may help prevent arrhythmias in certain patients

Treating Ventricular Fibrillation.

• Defibrillators. Patients who develop ventricular arrhythmias are given electrical shocks with defibrillators to restore normal rhythms. Some studies suggest that implantable cardioverter-defibrillators (ICDs) may prevent further arrhythmias in heart attack survivors of these events who are at risk for further arrhythmias. Patients with ICDs should not take fish oil supplements, as they may increase the risk of ventricular fibrillation.
• Antiarrhythmic Drugs. Antiarrhythmic drugs include lidocaine, procainamide, or amiodarone. Amiodarone or another antiarrhythmic drug may be used afterward to prevent future events.

Managing Other Arrhythmias. People with an arrhythmia called atrial fibrillation have a higher risk for stroke after a heart attack and should be treated with anticoagulants such as warfarin (Coumadin). Other rhythm disturbances called bradyarrhythmias (very slow rhythm disturbances) frequently develop in association with a heart attack and may be treated with atropine or pacemakers.

• Review Date: 4/15/2006
• Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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