How to Read a Lifepak 12 Strip

An electrocardiogram, abbreviated as ECG or EKG, is a tracing of the electrical activity of the heart through electrodes placed on the body. This type of monitoring enables trained health care providers to identify and interpret heart rate and rhythm and treat life-threatening conditions appropriately. The Lifepak 12 is a cardiac and vital sign monitoring system used frequently in the prehospital or emergency response setting. The Lifepak records EKG tracings received by attached leads and prints them out onto graph paper for interpretation by health care personnel.

Instructions

• 1

  Hold the strip horizontally. The paper that makes up the strip resembles a grid comprised of many large boxes filled with smaller boxes. There are 20 small boxes within each large box. The boxes represent a measure of time. Each small box represents .04 seconds; each large box represents .20 seconds.

• 2

  Locate the transmitted heart rhythm. The rhythm is represented by a line across the middle of the strip that deflects above and below the baseline and returns. Each deflection is represented by a lettered designation and represents one phase of a heart beat. One heart beat is represented by one complete complex.

• 3

  Calculate heart rate by counting the number of complete complexes across a six-second portion of the strip and multiplying by 12. This number represents the number of beats per minute. Rate also can be calculated by counting the number of boxes between two identical sites, for example, from the top of one peak or "R wave" to the next. This measurement is known as the "R to R interval."

• 4

  Look at the "P wave." The "P wave" is the first positive deflection above the baseline and represents the atria of the heart contracting. It should be small and round, resembling a small hill. The wave should not exceed .12 seconds in duration or 3 small squares.

• 5

  Count the number of small squares from the end of the "P wave" to the beginning of the next complex known as the "QRS complex." This interval represents the time from the contraction of the atria to the contraction of the ventricles. During this time, the lower chambers of the heart are filling with blood and the electricity is traveling from the top of the heart to the lower portions. The length of this measurement should be no longer than three small squares or .12 seconds. An increase in this length may indicate an atrioventricular block is present.

• 6

  Examine the next complex known as the "QRS complex." This complex represents the depolarization or contraction of the ventricles. It resembles an upside down "V." The width of this complex should be between two and three small squares or .08 to .12 seconds.

• 7

  Examine the "ST segment," which is the waveform following the "QRS complex." This complex is used in 12-lead EKGs as a diagnostic marker to determine if a myocardial infarction, commonly known as a heart attack, is evident.

• 8

  Determine if the rhythm is regular or irregular. Regular beats will have complexes that occur at regular intervals. Irregular complexes may have irregularities that occur at a regular interval, making them regularly-irregular, or irregular intervals making them irregularly-irregular.

• 9

  Determine if any arrhythmias are present. Arrhythmias may be indicated by prolonged intervals or by changes in the morphology of those complexes. A normal heart rhythm is referred to as normal sinus rhythm.