How to Read an EKG Tape

An electrocardiogram is a test that measures the heart's electrical activity. Bewilderment strikes most people when they look at the various markings of an electrocardiogram (EKG) tape. Nevertheless, you can get a general idea of what it means by knowing how electrical impulses normally travel through the heart and how these are seen on basic EKGs. The grid pattern and other markings on the EKG tape are also essential in reading EKG tracings. Since there are numerous abnormal rhythms (dysrhythmias), we will primarily focus on normal sinus rhythm.

Things You'll Need

• An EKG tape preferably at least six seconds long

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Instructions

• 1

  Study the grid pattern of the tape. Tiny squares comprise larger squares. From left to right each tiny square indicates .04 seconds. Five in a row mean .2 seconds, so each larger square represents .2 seconds. Find tic marks or indicators at the top or bottom of the tape. There are 15 large squares between two indicators, representing three seconds. Heart rate is best estimated on a tape at least six seconds long.

• 2

  Take a piece of paper and place its straight edge along a vacant series of tiny squares. Make two tic marks near the edge of the paper that correspond to a total of three tiny squares and label it as .12 seconds. At another location make a tic mark at each of the vertical borders of a large square and label that area as .2 seconds.

• 3

  Know the heart's electrical conduction path. Normal conduction begins in electrical cells near the top of the right atrium at the Sinoatrial (SA) node, the normal pacemaker. An impulse occurs there, then travels over to the left atrium and also goes centrally downward through the Atrioventricular (AV) junction, the bundle of His, then the ventricular right and left bundle branches which terminate with the Purkinje fibers.

• 4

  Evaluate the P wave. It looks like a little bump shortly before some angled lines (the QRS complex). Each normal cardiac cycle has only one P wave. No P waves might mean the normal pacemaker is damaged. However, it could also mean ventricular recharging (T wave) during atrial discharge, so a T wave might cover a P wave. More than one P wave can mean a second-degree heart block.

• 5

  See if the time from the start of the P wave to the start of the Q wave (usually the first downward stroke) is less than .2 seconds by placing the first tic mark of the .2 seconds section of your measuring paper above where the P wave starts. More than .2 seconds could mean a first-degree heart block. No relationship between the P wave and QRS complex might mean a third-degree heart block.

• 6

  Observe the QRS complex which usually appears as a short downward angled line (Q), an upward stroke making a peak (R), then a deep downward peak (S) which concludes with a line angled upward to about the middle of the tape. There should be only one QRS complex per cycle and be from .06 to .11 seconds wide. Check the time with the .12 tic marks on your measured paper.

• 7

  Find the T wave which comes after the QRS complex. It's usually a bump larger than the P wave. This shows ventricular recharging. Atrial recharging also occurs, but that wave is often hidden in the QRS complex.

• 8

  Estimate heart rate by counting the number of QRS complexes in a six-second strip and multiplying by 10. Normal sinus rhythm is between 60 to 100 beats per minute. Less than 60 is generally termed bradycardia, while greater than 100 as tachycardia.