Step four
Measurement of the P-R interval is the fourth step in rhythm strip analysis. The P-R interval is measured from the beginning of the QRS complex. A normal P-R interval measures 0.12-0.20 seconds (3-5 small boxes). The P-R intervalreflects depolarization of the atria and the spread of the impulse through the atrioventricular (AV) node. Aprolonged P-R interval (greater than 0.20 seconds) indicates a delay in conduction through the atria and/or AV node (Huff,2006).