ECG Test Baseline Information

Question 1

What are normal intervals (PR, QRS, QT)?

Answer 1

Normal PR: 120-200ms
Normal QRS: 60-100ms
Normal QT: 400-440ms

Question 2

What is the intrinsic rate for the SA node, AV node, Purkinje fibers?

Answer 2

SA Node: 60-100bpm
AV Node: 40-60bpm
Purkinje Fibers: 20-40bpm

Question 3

What is the regular rhythm for the P-P and R-R intervals?

Answer 3

P-P Interval: 60-120ms
R-R Interval: 60-120ms

Question 4

What does a wide QRS indicate?

Answer 4

The electrical signal is taking longer than expected to travel through the ventricles (> 120ms)

Question 5

Why does bundle branch block have a notched QRS?

Answer 5

The blocked bundle branch delays depolarization to the ventricle that it supplies. When one of the bundle branches is blocked, that ventricle will depolarize later than the other ventricle

Question 6

Why is the ventricular rate slow and QRS wide in complete heart block?

Answer 6

Rate is slow because the AV node is completely blocked leading to the ventricles beating at their own slower rate. QRS is wide because the ventricular rhythm bypasses the normal conduction system causing a slow cell-to-cell depolarization

Question 7

Big box and little box conversion

Answer 7

• Small box = 0.04 seconds (5 little boxes = 1 big box (0.20 seconds)
• Big Box (bpm) – 300 / 150 / 100 / 75 / 60 / 50

Question 8

Conversion from ms to bpm

Answer 8

60,000 / ms per beat = BPM

Question 9

Conversion from bpm to ms

Answer 9

60,000 / beats per min = MS