How is an ECG interpreted?

It is called ECG as an electrocardiogram, if it is an evaluation that is done to know the electrical activity of the heart, are performed in the emergency and internal medicine units, consists in the placement of electrodes in different parts of the body, these electrodes send a signal that is recorded in an electrocardiograph, there are ways to perform the examination, one at rest where the patient is relaxed and still, and another where stress test where the patient is kept practicing some physical activity. 

It is important to read these results, which are reflected in the role of the ECG, it should be emphasized that this reading or interpretation should be made by a specialist physician and should not be interpreted by the patient himself, avoiding self-medication; what is recorded on paper are electrical signals from the heart in waves transmitted to the electrode immediately, so that the doctor is in the ability to make a faithful and effective diagnosis. 

Interpretation of an ECG

In an electrocardiogram are present different waves, compression of these will help us to determine the possible anomalies or to make sure that the electrical impulse of the heart is normal, first, we must identify the waves: 

  • The P waves tell us the time between the heartbeat, it’s represented as a straight line between the lowest and highest point. 
  • The T wave represents the small perceptible beat after the first and marks the end of the heartbeat. However, in order to know if everything is normal during the test, the time between one beat and another must be fairly regular throughout the test, if this does not occur and the time elapsed is variable, this indicates an irregularity in the heartbeat. 
  • To know the heart rate you must locate in the ECG the highest point known as “R,” count the number of large squares between one “R” point and another, and divide the result by 300.

At rest, a normal heart rate varies between 60 and 100 beats per minute, below that figure is known as bradycardia, and above that as tachycardia.

Characteristics of the recording waves in an ECG

  • The P wave should not exceed 0,25mV, i.e. 2,5 mm high, and should not last longer than 0,11 seconds in an adult. It is usually rounded. 
  • The T wave is always positive (convex shape) with a length of about 3 mm and is asymmetric and rounded.
  • The R wave is the first upward deflection; no absolute criteria were defined for its height or normal size.

With these characteristics it is easier to perform a basic interpretation of an electrocardiogram, to determine if there is any anomaly or on the contrary everything works correctly, it is recommended that the patient ask the doctor any doubts or concerns you have about his results, considering that only qualified medical personnel can correctly interpret the ECG.

Alterations of waves in an ECG

  • In the case of P waves that present irregularities in their height or shape, it is a sign of different anomalies such as atrial enlargement caused by stenosis and mitral insufficiency or by arterial hypertension.
  • When T-wave disturbances are present, for example, if it is bitten it may indicate potassium disturbances, if it is concave in shape it implies ischemic origin alterations, and if it is flattened alterations in the repolarization.
  • Lower R waves may be due to ventricular hypertrophy. A second upward deflection in the QRS complex is called R′.

Steps for a Correct Interpretation in an ECG

  1. To face the electrocardiogram through a systematic reading
  2. Differential knowledge of normal and abnormal in an electrocardiographic plot
  3. Interpret the patient, not just his electrocardiogram.
  4. Know the origin of each wave and each of its pathological deviations
  5. Know how to perform an electrocardiogram.

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