How to read an ECG An eight-step met

							Interpreting an electrocardiogram (ECG) is a skill you can master only with practice.
The three basic elements of an ECG waveform are the P wave, the QRS complex, and
the T wave. Use these elements to develop a consistent approach for reading
waveforms, following this eight-step approach.

1. Evaluate the P wave.

Observe its size, shape, and location in the waveform. If the P wave consistently
precedes the QRS complex, the electrical impulse is being initiated bv the sinoatrial
node.

2. Evaluate the atrial rhythm.

The P wave should occur at regular intervals, with only small variations associated
with respiration. Using calipers, you can easily measure and compare the interval
between P waves (the P-P interval).



3. Determine the atoll rate.

A quick method is to count the number of P waves in two 3-second segments and
multiply by 10. For a more accurate approach, count the small squares between the
apex of two P waves. Each small square equals 0.04 second; 1,500 squares equal 1
minute. Divide 1,500 by the number of squares you counted to get the atrial rate.

4. Calculate the duration of the PR interval.

Count the small squares between the beginning of the P wave and the beginning of the
QRS complex. Multiply that number by 0.04 second.The normal interval is between
0.12 and 0.20 second, or between three and five small squares wide. If the interval is
wider, the conduction of the impulse to the ventricle is delayed.

5. Evaluate the ventricular rhythm.

Use calipers to measure the R-R intervals. Place the calipers on the same point of each
QRS complex. If the R-R intervals are consistent, the ventricular rhythm is regular.

6. Determine the ventricular rate.

Use the formula for calculating the atrial rate (Step 3), except count the small squares
between two R waves. Also check that the QRS complex is shaped appropriately for
the lead you're monitoring.

7. Calculate the duration of the QRS complex.

Count the squares between the beginning and the end of the QRS complex and
multiply by 0.04 second. A normal QRS complex is less than 0.72 second.

8. Calculate the duration of the QT interval.
Count the number of squares from the beginning of the QRS complex to the end of
the T wave. Multiply this number by 0.04 second. The normal range is 0.36 to 0.44
second, or 9 to 11 small squares.

Copyright Springhouse Corporation Apr 2000
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