9 Steps to ECG Interpretation

Reading an electrocardiogram (ECG) correctly can more precisely pinpoint any cardiovascular anomalies a patient may experience. Medicomp, leaders in ECG patch technology, offers the following guidelines to interpret an ECG since every patient relates symptoms differently, and cardiac rhythms will vary from one individual to the next.

  1. Is the rhythm regular? Check the QRS segment of the ECG to determine if the depolarization within the ventricles is regular. Measuring the distance between one R to the next can determine if that baseline measurement matches all other R-to-R distances within a given amount of time, typically six to ten seconds. If any irregularities are noted, ask the patient if these abnormalities are persistent. If so, look for symptoms associated with C.H.A.P.S. – chest pain, hypotension, altered mental state, poor perfusion, or shortness of breath.
  2. Calculate heart rate. Take a six- or ten-second radial pulse and multiply for a one-minute reading. Determine from the reading whether the patient is experiencing bradycardia, tachycardia, superventricular tachycardia, or ventricular tachycardia with a pulse.
  3. Diagnose the P waves. Determine if the P waves are present, upright on the cardiac monitor, and followed by the QRS segment. If all three are within normal limits, chances are the electrical impulse began in the SA node, as it should.
  4. Measure the P-R interval. Calculate the time between the P wave and the beginning of the QRS segment. A typical P-R interval is 0.12 to 0.20 seconds, with a prolonged P-R interval suggesting a blockage or delay through the AV node.
  5. Measure the QRS segment. The normal duration of the QRS segment is 0.04 to 0.10 seconds. A prolonged QRS segment could signify a bundle branch block. Bundle branch blocks may be benign, but combined with other factors may indicate heart disease.
  6. Check the T wave. The T wave should be upright and follow the QRS segment. Inverted T waves may indicate a lack of oxygen to the heart, peaked T waves suggest hyperkalemia, flat T waves may indicate low potassium, and a raised ST segment may suggest a heart attack.
  7. Note any ectopic beats. Fibers outside the SA node that stimulate the heart to beat cause premature atrial contractions, premature junctional contractions, or premature ventricular contractions. Any ectopic beats should be counted to determine the interval, shape, and whether they appear singularly or in groups.
  8. Determine the origin. With all the above information in place, look for these elements.
    1. Sinus: regular rhythm with 60-100 beats per minute; P waves upright, round, and occurring before the QRS segment; normal P-R interval; normal QRS duration.
    2. Atria: Rhythm may or may not be regular; QRS segment is normal with abnormal P waves (premature, flat, notched, peaked, inverted, or hidden).
    3. Junctional: Is the P wave junctional, inverted before, during or after the typical QRS segment?
    4. Ventricular: If the rhythm originates below the SA node, the QRS segment will be wide and unusual with no P waves.
    5. Paced rhythm: Low voltage pacer spikes before the QRS should be reviewed.
  9. Correctly identify the rhythm. Measure the information from the ECG against the patient’s symptoms and vital signs. This will give a much better understanding of how to begin treatment.

Following these steps will assist in determining the precise location of cardiac arrhythmis to give your patient the proper care. Read more information pertaining to patient care as well as the latest technology in heart rate monitors, such as an ECG patch, by reading our blogs. Feel free to contact one of our cardiac professionals at (800) 23-HEART (234-3278) for more information.

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