Rasmussen College: N3 Exam 3 /Concept Review for Test 3 NUR
2795 Spring 2020
Module 5 – Rhythms
Measurements of Rhythms
PR Interval
• represents the delay from the AV node to
allow for ventricular filling
• normal PR interval size is 0.12-0.20 seconds or
3.5-5 small squares (should fit in one big box)
QRS Complex
• depolarization of the ventricles, triggers main pumping action
• normal= 0.08 and 0.10 seconds (should fit in half of one big box)
,• greater than 0.12 seconds is considered abnormal
, (think ventricular tachycardia)
ST Segment
• represents the interval between ventricular depolarization and repolarization
• measures from the end of the QRS complex to the start of the T wave
• normal measurements are 0.005 to 0.150 seconds and SHOULD BE FLAT on the isoelectric line
• most common reason for elevated ST segment is a myocardial infarction
• most common reason for a depressed ST segment is ischemia
QTc (QT interval)
• represents the time of ventricular activity including both depolarization and repolarization
• the normal QT interval is 0.36 to 0.44 seconds (should fit in 2-2 ½ big boxes)
• it is measured from the beginning of the QRS complex to the end of the T wave
• the QT interval will vary with patient gender, age, and heart rate
• another guideline is that a normal QT interval is less than half of the R-R
interval for heart rates below 100bpm
T Wave
• represents ventricular repolarization (recovery)
• can be upright, inverted, notched, large or small
• many different reasons for T wave changes – some are medical, others are not
• important to verify patient’s history and medication use when validating T wave abnormality
2795 Spring 2020
Module 5 – Rhythms
Measurements of Rhythms
PR Interval
• represents the delay from the AV node to
allow for ventricular filling
• normal PR interval size is 0.12-0.20 seconds or
3.5-5 small squares (should fit in one big box)
QRS Complex
• depolarization of the ventricles, triggers main pumping action
• normal= 0.08 and 0.10 seconds (should fit in half of one big box)
,• greater than 0.12 seconds is considered abnormal
, (think ventricular tachycardia)
ST Segment
• represents the interval between ventricular depolarization and repolarization
• measures from the end of the QRS complex to the start of the T wave
• normal measurements are 0.005 to 0.150 seconds and SHOULD BE FLAT on the isoelectric line
• most common reason for elevated ST segment is a myocardial infarction
• most common reason for a depressed ST segment is ischemia
QTc (QT interval)
• represents the time of ventricular activity including both depolarization and repolarization
• the normal QT interval is 0.36 to 0.44 seconds (should fit in 2-2 ½ big boxes)
• it is measured from the beginning of the QRS complex to the end of the T wave
• the QT interval will vary with patient gender, age, and heart rate
• another guideline is that a normal QT interval is less than half of the R-R
interval for heart rates below 100bpm
T Wave
• represents ventricular repolarization (recovery)
• can be upright, inverted, notched, large or small
• many different reasons for T wave changes – some are medical, others are not
• important to verify patient’s history and medication use when validating T wave abnormality
