NCLEX RN Practice Question # 888.
nclex examination
Basics of Electrocardiography
▪ An electrocardiogram (ECG) reflects the electrical activity of cardiac cells and records electrical activity at a speed of 25 mm/second.
▪ An electrocardiographic strip consists of horizontal lines representing seconds and vertical lines representing voltage.
▪ Each small square represents 0.04 second.
▪ Each large square represents 0.20 second.
▪ The P wave represents atrial depolarization.
▪ The PR interval represents the time it takes an impulse to travel from the atria through the atrioventricular node, bundle of His, and bundle branches to the Purkinje fibers.
▪ Normal PR interval duration ranges from 0.12 to 0.2 second.
▪ The PR interval is measured from the beginning of the P wave to the end of the PR segment.
▪ The QRS complex represents ventricular depolarization.
