The symptoms of heart attack should be treated as a medical emergency and ambulance and critical care services should be alerted immediately. However, conditions such as indigestion can also cause severe chest pain. Once a patient is admitted to the hospital, tests need to be performed immediately to check whether the chest pain is indeed being caused by a heart attack.
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An outline of the diagnostic approach to heart attack is given below.
Electrocardiography
An electrocardiogram (ECG) is the most important tool for diagnosing a heart attack. It is usually performed within ten minutes of a patient being admitted to the hospital or en-route in the ambulance using a portable ECG machine. An ECG machine measures the electrical impulses generated by the heart muscle. Each heartbeat originates at the sinoatrial node (SAN) at the top of the heart in the atrium. This impulse travels via major nerve fibers throughout the heart muscle, instructing them to contract and pump blood. ECG captures these impulses and plots them onto graph paper, which a physician can then interpret to see how well the heart is functioning. Any abnormality may lead to an alteration of the ECG. The test is painless and involves the placement of flat metal discs called electrodes onto the arms, legs and chest. Wires from the electrodes send signals from the beating heart to the ECG machine, which records and translates them onto the graph paper. Particular changes in the pattern generated by the ECG machine indicate that a heart attack has occurred. The pattern can also be used to determine which type of heart attack a patient has had.
This can be determined using a measurement called the ST segment. The ST segment corresponds to the degree of heart damage and the higher the ST segment, the more severe the damage is likely to be. Heart attack referred to as ST-segment elevation myocardial infarction (STEMI) is the most serious form of heart attack and the patient is immediately assed for treatment to unblock the coronary artery.
- Other tests for heart attack include those carried out after the patient is stabilized and initial treatment has begun. Blood tests are performed to check the levels of certain enzymes that are raised during a heart attack. These are called cardiac markers and they decline as the heart recovers. Serial measurements are taken over the course of a few days. Chest X-rays may also be taken to rule out other possible causes of a heart attack such as pneumonia.
- An echocardiogram is an ultrasound examination of the heart that pinpoints the exact areas of heart damage.
- Coronary angiography is a specialized test where a catheter is threaded into the heart via a blood vessel in the arm or groin, under X-ray guidance. A contrast agent is then injected into the coronary arteries via the catheter and images are taken as the dye flows through the heart. The site(s) and extent of obstruction of the coronary arteries can then be clearly visualized.
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