Master ECG Interpretation for Nurses

A regular rhythm is characterized by the same duration between each R-R interval. Normal sinus rhythm is defined as a rhythm starting at the SA node at a rate between 60 to 100 beats per minute and follows the normal conduction pathway. Dysrhythmias are caused by abnormal cardiac conduction. Although many dysrhythmias may be serious, some are benign and require no treatment.

The presence of P waves is a component of a normal ECG. P waves precede the QRS complex and represent atrial depolarization. The absence of P waves may indicate atrial fibrillation or sinoatrial arrest.

A normal ECG has one upright and rounded P wave before every QRS.

The PR interval indicates AV conduction time. To measure the PR interval on the ECG strip, start from the beginning of the P wave and mark until the beginning of the QRS complex. Normally, this interval should be between 0.12 to 0.20 seconds, or less than 0.20 for simplicity. This interval shortens with increased heart rate.

The QRS complex represents ventricular depolarization. Measure the QRS complex from the end of the PR interval to the end of the S wave. Normally, this interval should be between 0.06 to 0.12 seconds, or less than 0.12 for simplicity.