## Steps of Rhythm Analysis

A consistent step-by-step approach to rhythm interpretation and analysis is required for accurate analysis.

Determine the rhythm’s regularity. The rhythm is said to be regular when there is a constant distance between similar waves (P-P or R-R). Generally a variation of 10% is acceptable. For example, if there are 10 small boxes in an R-R interval, an R wave could be off by 1 small box and still be considered regular. In an irregular rhythm if the variation between the shortest and longest R-R interval is less than four small boxes (0.16 sec) the rhythm is

Calculate the heart rate. The

Identify and examine P waves. One P wave should precede every QRS complex, look similar in shape, size and position. If P waves are absent it indicates the rhythm originated in the AV junction or the ventricles.

Assess intervals. Measure the PR interval. Is it constant, lengthening, of normal duration? Measure the QRS interval. Is it narrow or wide, occurs regularly.

Evaluate the overall appearance of the rhythm. Determine whether there is depression or elevation of the ST segment from the isoelectric line. Evaluate the T waves to see if they are upright and of normal height.

**Step One**Determine the rhythm’s regularity. The rhythm is said to be regular when there is a constant distance between similar waves (P-P or R-R). Generally a variation of 10% is acceptable. For example, if there are 10 small boxes in an R-R interval, an R wave could be off by 1 small box and still be considered regular. In an irregular rhythm if the variation between the shortest and longest R-R interval is less than four small boxes (0.16 sec) the rhythm is

*essentially regular*. If the R-R intervals vary by more than 0.16 seconds the rate is*irregular*. A*regularly irregular rhythm*is where the R-R intervals are not the same and vary by more than 0.16 sec but have a repeating pattern of irregularity.**Step Two**Calculate the heart rate. The

*Small**Box Method*is the most accurate. Count the number of small boxes between R-R or P-P and divide into 1500.**Step Three**Identify and examine P waves. One P wave should precede every QRS complex, look similar in shape, size and position. If P waves are absent it indicates the rhythm originated in the AV junction or the ventricles.

**Step Four**Assess intervals. Measure the PR interval. Is it constant, lengthening, of normal duration? Measure the QRS interval. Is it narrow or wide, occurs regularly.

**Step Five**Evaluate the overall appearance of the rhythm. Determine whether there is depression or elevation of the ST segment from the isoelectric line. Evaluate the T waves to see if they are upright and of normal height.

**Step Six**Interpret the rhythm and evaluate its clinical significance. Specify the site the rhythm originates (sinus), the mechanism (bradycardia). Example: sinus bradycardia. Evaluate the patient’s clinical presentation to determine how they are tolerating the rate and rhythm.