Waveform Components

Question 0

QRS complex

Answer 0

Represents ventricular depolarization and contraction
Measure from the end of the PR interval to the end of the S wave
Normally this interval is 0.06-0.12 sec

Question 1

P wave

Answer 1

Indicates the atria are contracting (depolarization) and that blood is pumping into the ventricles
Amplitude is normally 0.5-0.25
Normal duration is 0.6-0.11 sec

Question 2

PR interval

Answer 2

Indicates transit time for electrical signal to travel from the sinus node to the ventricles (AV conduction time)

Onset of atrial depolarization to onset of ventricular depolarization.

Measure from beginning of P wave to beginning of QRS complex

Normally 0.12-.20 sec
This interval shortens with increased heart rate

Question 3

T wave

Answer 3

Represents ventricular repolorization

Question 4

How do u measure ventricular rhythm

Answer 4

Regular rhythm:
R-R intervals
6 sec strip #R x 10

Irregular rhythm:
R-R intervals
6 sec strip # large boxes/300

Question 5

How do u measure atrial rhythm

Answer 5

Measure P-P intervals

Question 6

How can heart rate be determined

Answer 6

Measure QRS complexes over a 6 second interval
Multiply by 10 to determine heart rate
Or
Count the number of small boxes for a typical R-R interval
Divide this number into 1500 to determine heart rate

Irregular rhythm:
R-R intervals
6 sec strip # large boxes/300

Question 7

QT interval

Answer 7

Represents the time of ventricular activity including both de & re polarization

It is measured from the beginning of he QRS complex to the end of the T wave

Normally the interval is 0.36-0.44 sec
- varies w age, gender & HR
Typically less than half of the R-R interval for HR below 100

Question 8

ST segment

Answer 8

Represents the early part of ventricular repolorization

Measured from the end of the QRS complex to the beginning of the T wave