Normal values:

 

Parameter

Normal values

P wave

·   3 squares wide (≤0.12s)

·   ≤3 squares high (actually <2.5mm)

·   Best seen in II (should be upward) V1 (should be upward or biphasic)

PR interval

·   2-5 squares (0.12 – 0.2s)

·   Isoelectric

QRS complex

·   <3 squares (<0.12s)

Q wave

·   ≤1 square wide (≤0.04s)

·   ≤2 squares deep (≤2mm, and ≤25% height of QRS complex)

ST segment

·   <2 squares (<2mm) deviation from isoelectric in V1-2-3

·   <1 squares (<1mm) deviation from isoelectric elsewhere

T wave

·   <5 squares high (<5mm)

QT interval

·   Bazett formula: QTc = QT/√(RR)

·   ≤440 in men, ≤460 in women

·   > 350ms in both