What I will do here is write a series of short explanations to help people interpret cardiac rhythms. As I will be breaking up the sections please feel free to come in with questions and feedback. Because I am doing this in the most long distance manner imaginable it is important for you to tell me if something does not make sense. Oh! and P.S. I call them ECGs not EKGs
1. Working out the rate
Each small square on the ECG paper is 0.04 of a second there are five of these small squares to one large square. Each large square is therefor 0.2 of a second and there are then 300 large squares a minute.
Although there are many different methods of calculating the rate of a rhythm on an ECG most of them are "overkill". Usually it is not necessary to get an exact figure - that can be gotten from the pulse counter anyway - what is important is to work out whether the rate is too fast (tachycardia) normal or too slow(bradycardia).
So a quick method of working out the rate is this. If you have a QRS complex in every ;large square then the rate has to be 300/minute if it there is a complex every 2 large squares it is 150 every 3 = 100 and so on. Not very accurate but it gives us the broad determination we need.
The following link shows an ECG with bradycardia
An example of sinus tachcardia
When reading these ECG's it is important only to look at the PQRS the shape of the T wave is not a factor in reading rhythms - IT IS important when reading the entire ECG and determining myocardial damage but for rhythms it is not important.
Look at the two examples I have given. The lead that is best to use to read rhythm is lead II.