A heart monitor, also known as an electrocardiogram or EKG monitor, is a graphical representation of the heart's rhythms over time captured by electrodes attached to a person's skin. The machine captures electrical signals sent out by the heart and displays them as a series of lines that resemble peaks and valleys displayed on a screen and recorded on paper or digitally. Variations in the lines can indicate the presence of heart problems: When the heart isn't functioning normally, the lines deviate from a standard. While it can be useful to know what the variations mean, never attempt to diagnose a problem based on your own reading.
Step 1
Look at the graph displayed behind the EKG reading. Each 1 mm square along the horizontal axis of the graph is a measure of time, equaling about 0.04 seconds. The 5 mm squares indicate 0.2 seconds.
Step 2
Continue looking at the graph on the EKG strip.The vertical axis measures voltage, the strength of the electrical signals produced by the heart. Every 10 mm indicates 1mV (milliVolt) of electricity.
Step 3
Learn the labeling system given to the peaks and valleys present on the line of a heart monitor. The small hump before the first dip is labeled "P." The left-most point of the spike that dips before the sharp spike is labeled "Q." The top of the spike is labeled "R," and "S" is the dip on the right side of the "R" spike. "T" is the label given to the small spike after the "S" dip. Together, these make up one full graphical representation of the heart's rhythm, what is referred to as a "complex."
Step 4
Take note of the image beginning at the point labeled "P" and ending with "R." This wave represents the atria of the heart contracting and pushing blood into the heart's ventricles. A PR complex, or the space of the graphical representation of the lines between the "P" and "R" points, between .12 and .20 seconds is normal.
Step 5
Observe the next segment of the line starting at the point labeled "Q" and ending at the "S" point. This segment represents the ventricle, or lower part of the heart, as it depolarizes. The QRS complex should have a timed interval of .04 to .10 seconds. The QRS complex represents the ventricles filling and then depolarizing, pushing blood out into aorta. The atria also repolarize and relax and fill with blood during this time.
Step 6
Take note of the span of time between the "Q" and "T" points. The QT complex represents the ventricles of the heart relaxing and refilling, and should have a time span of less than .02 seconds.
Step 7
Compare the "P" and "T" bumps, as well as the "R" spike and the sharpness or roundness of these features. Take note of their width. Bradycardia, or a slow heart rate, is indicated by a few wide peaks and a few wide valleys. Tachycardia, or faster heart rhythms, is indicated by an increased number of sharp peaks and valleys.
Step 8
Notice the "Q" and "S" dips. Deep or elevated ST sections can be indicative of a heart attack. Flat or drooping waves can indicate a blockage in the heart.
Step 9
Calculate the heart rate of the person hooked up to the EKG by dividing the number 300 by the number of 5 mm squares that fall between the QRS complexes. For example, someone with four squares between QRS complexes would divide 300 by 4, for a heart rate of 75.
Step 10
Use an alternate method to determine the heart rate of someone with an abnormal sinus rhythm. It might be easier to determine heart rate quickly by looking at the "R" peaks in a 6-second portion of the EKG. Count the sharp "R" peaks in 6 seconds and multiply that number by 10. For example, if there are 10 "R" peaks in a 6-second span, that person has a heart rate of 100.
Tips and Warnings
- Medications, eating, drinking, emotions, stress, physical trauma and the placement of the electrodes can affect the EKG in different ways.
- Speak to your doctor, nurse or technician about any concerns regarding your EKG. They are trained to interpret the results and figure out what problems, if any, are present.
References
- National Institutes of Health: MedlinePlus: Electrocardiogram
- "The Complete Study Guide to Learning the Electrocardiogram"; Douglas Martin Msn Rn; 2007
- RNCeus: How to Read an EKG Strip
- The Med Stud: Reading an EKG
- College Physics for Students of Biology and Chemistry: Pulsatile Flow
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