What is ECG?
The heart is a rhythmic beating muscle to pump blood throughout the body. In the heart there is a natural pacemaker (sinoatrial node) that automatically generates a series of electrical impulses. These impulses are transmitted by a series of specific pathways to the rest of the heart (first to the atria and then to the ventricles) and thanks to them the cardiac muscle fibers contract. The ECG (electrocardiogram) is a test that allows us to measure this electrical activity of the heart.
The device used is the electrocardiograph, which detects the electrical impulses of the heart and registers them on a strip of paper. This record is known as an electrocardiogram and allows us to detect heart rhythm disturbances (arrhythmias), as well as alterations in the conduction of electrical impulses through the heart (blockages) that can be caused by various diseases.
What is a resting ECG used for?
Information obtained on an electrocardiogram can be used to discover different types of heart disease. It may also be helpful to find out how the patient is responding to treatment.
Tracing an ECG may be normal, even in the presence of significant heart disease. Therefore, a complete cardiac study may be indicated by the practice of other examinations.
It can be a good examination, if symptoms such as shortness of breath, chest pain, fainting, palpitations, or when someone believes that their heartbeat is abnormal.
This test can detect signs of disease in the coronary arteries (as in the case of angina pectoris or acute myocardial infarction). Unfortunately, in many people who suffer a significant narrowing of the arteries, which are the ones that bring blood to the heart muscle, the ECG record at rest, is normal. Therefore, when a significant reduction in arterial diameter is suspected, it may be necessary to perform an ECG while the patient is making an effort (effort test or ergometry), since this test is more likely to show the problem.
An ECG will dictate whether the patient has had a coronary crisis, or if there is evidence of previous seizures. The effect of the drugs used for coronary disease also can be analyzed over time by the ECG.
The ECG may reveal heart rhythm problems (arrhythmias) such as slowing (bradycardia), acceleration (tachycardia), and other abnormal rhythm disturbances. The ECG may show the presence of an enlarged heart muscle (called ventricular hypertrophy).
With the ECG you can know if there is a shortage of certain minerals in the blood, such as potassium.
Under what conditions is an ECG performed?
It depends on what is going to be measured. In general, an ECG is recorded while the patient is at rest, although when there is a possibility that their symptoms may be due to coronary artery disease, the test may be performed while the patient exerts a strain on a static bicycle or a treadmill.
This test is also used to evaluate the success of drug treatment or achieved by coronary vessel clearing techniques, such as by-pass surgery. Occasionally, an ECG may need to be supplemented with other additional tests, such as isotope perfusion imaging (heart imaging, obtained by the emission of radioactivity from chemical elements injected into the patient’s blood) or coronary angiography Of the coronary arteries by x-rays).
How is ECG recorded?
Before the test, the patient should inform the doctor if he is following other treatments, due to the possibility that they affect the cardiac conduction. Occasionally, it is recommended not to consume too much food within the eight hours prior to the test.
Up to 12 self-adhesive electrodes are placed in selected areas of the skin of the wrists, ankles and thorax. First, the skin is cleansed. In the thorax, if there is hair, it may be necessary to shave the area where the electrode is to be placed. The test is completely painless, and once the electrodes are placed, it is completed in less than a minute. The doctor will check the paper record of the ECG.
Is the ECG dangerous?
When this test is performed with the patient at rest, it is completely harmless.
When practiced while the patient performs an exercise, there is a possibility of chest pain, pain that will disappear when the effort stops. This type of examination should be supervised by a physician. The stress test will be stopped at the appropriate time, such as when the patient experiences major chest pain, when ECG changes are detected, blood pressure decreases, or increases more than is due, or simply when the patient Reaches the relevant heart rate.