How is a heart attack diagnosed?
Classical cases of myocardial infarction are often identified by ambulance staff or emergency room doctors without further investigations. Nevertheless, for a complete diagnosis, the medical history, combined with electrocardiogram results and blood tests, is vital. The most important factor in diagnosing and treating a heart attack is prompt medical attention. Rapid
evaluation allows early treatment of potentially life-threatening abnormal rhythms such as ventricular fibrillation and allows early reperfusion (return of blood flow to the heart muscle) by procedures that unclog the blocked coronary arteries. The more rapidly blood flow is reestablished, the more heart muscle that is saved.
Electrocardiogram: Electrocardiogram (ECG/EKG) findings suggestive of MI are elevations of the ST segment and changes in the T wave. After a myocardial infarction, changes can often be seen on the ECG called Q waves, representing scarred heart tissue. An electrocardiogram (ECG) is a recording of the electrical activity of the heart. Abnormalities in the electrical activity usually occur with heart attacks and can identify the areas of heart muscle that are deprived of oxygen and/or areas of muscle that have died. In a patient with typical symptoms of heart attack (such as crushing chest pain) and characteristic changes of heart attack on the ECG, a secure diagnosis of heart attack can be made quickly in the emergency room and treatment can be started immediately. If a patient's symptoms are vague or atypical and if there are pre-existing ECG abnormalities, for example, from old heart attacks or abnormal electrical patterns that make interpretation of the ECG difficult, the diagnosis of a heart attack may be less secure. In these patients, the diagnosis can be made only hours later through detection of elevated cardiac enzymes in the blood.
Myocardial markers: Cardiac enzymes are proteins from cardiac tissue found in the blood. Until the 1980s, the enzymes SGOT and LDH were used to assess cardiac injury. Then it was found that disproportional elevation of the MB subtype of the enzyme creatine phosphokinase (CPK) was very specific for myocardial injury. Current guidelines are generally in favor of troponin isoenzymes I or T, which are thought to rise before permanent injury develops. A positive troponin in the setting of chest pain may accurately predict a high likelihood of a myocardial infarction in the near future. The diagnosis of myocardial infarction used to require all three components, history, ECG, and enzymes, were positive for MI. Currently the cardiac enzymes have become so reliable that enzyme elevations alone are considered reliable measures of cardiac injury, with ECG serving to determine where in the heart the damage has occurred, and history serving to screen patients for further enzyme and ECG testing. In difficult cases or in situations where intervention to restore blood flow is appropriate, an angiogram can be done (see below for an image). Using a catheter inserted into an artery (usually the femoral artery), obstructed or narrowed vessels can be identified, and angioplasty applied as a therapeutic measure (see below). Angiography requires extensive skill, especially in emergency settings, and may not always be available out of hours. It is commonly performed by cardiologists or radiologists. There is a small risk of dissection (tearing) of the blood vessels and of hemorrhage at the insertion site of the catheter.
Blood tests: Blood tests are performed to evaluate organ function in a patient with a heart attack. A particularly important diagnostic test is the measurement of cardiac or heart enzymes. When heart muscle is damaged, these enzymes are released into the blood. Their measurement is one of the best ways to confirm a heart attack has occurred. The first blood sample for this test is usually taken in the emergency room. Additional blood samples are obtained every six to eight hours for the first 24 hours after hospital admission.
Chest x-ray: Chest x-ray may be performed to detect abnormalities in the size and shape of the heart and to detect the accumulation of fluid in the lungs, which may indicate decreased blood flow.
Echocardiogram: Echocardiogram uses sound waves to produce an image of your heart. In an echocardiogram, sound waves are directed at your heart from a wand-like device (transducer) 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 by a heart attack and isn't pumping normally or at peak capacity.
More information on heart attack (myocardial infarction)
What's a heart attack (myocardial infarction)? - A heart attack (myocardial infarction) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot.
What're the signs and symptoms of a heart attack? - Symptoms of a heart attack include pain and pressure in the chest, which often spread to the shoulder, arm, and neck.
What're the women's heart attack symptoms? - A woman's heart attack has more varied symptoms than a man's. Women are more likely to have nausea and pain high in the abdomen.
What're the warning signs of a heart attack? - Warning signs of a heart attack include uncomfortable pressure, fullness, squeezing, or pain in the center of the chest, cold sweat or paleness.
What causes a heart attack? - Heart attack is caused by a lack of blood supply to the heart for an extended time period. The most common cause of heart attack is atherosclerosis.
What're the complications of a heart attack? - Complications of a heart attack include ventricular tachycardia, ventricular fibrillation, cardiogenic shock, arrhythmias, heart failure.
What're the risk factors for heart attack? - Heart attack risk factors can be devided into two groups: Inherited (or genetic) risk factors and acquired risk factors.
How is a heart attack diagnosed? - The most important factor in diagnosing and treating a heart attack is prompt medical attention. For a complete diagnosis, the medical history is vital.
What're the treatments for heart attack? - The goal of treatment for heart attack is to quickly open the blocked artery and restore blood flow to the heart muscle, a process called reperfusion.
What drugs are used to cure heart attack? - Medications used to treat heart attacks include blood vessel dilators, clot busters, beta blockers, antiarrhythmic drugs, pain relievers.
What surgeries treat heart attacks? - Surgeries to treat heart attacks include coronary angioplasty, coronary artery bypass surgery, transmyocardial revascularization, and atherectomy.
Aspirin and heart attacks - Aspirin is taken daily following a heart attack to reduce the risk of another heart attack. Aspirin reduces heart attacks and improve survival in the patients.
How to survive a heart attack? - In wilderness first aid, a possible heart attack justifies medical evacuation by the fastest available means. Heart attacks are survivable.
How to prevent a heart attack? - Heart attack can be prevented with a healthy liestyle. Daily aspirin therapy or other medical treatment help prevent heart disease and heart attack.
How to recover after a heart attack? - Following discharge from the hospital, patients continue their recovery at home. Lowering cholesterol can reduce the risk for another heart attack.