ECG Rules

<< Cardiac << ECG Basics << ECG Rhythms ECG Rules

ECG Rules

To be able to diagnose problems on an ECG is not a matter of just looking at the strip, an ECG needs to be read to see what is being shown. If you follow Professor Chamberlains 10 rules they'll give you an understanding of what is normal.

The 10 Rules for a Normal ECG

Rule 1

PR interval should be 120 to 200 milliseconds or 3 to 5 little squares

Rule 2

The width of the QRS complex should not exceed 110 ms, less than 3 little squares
Rule 3

The QRS complex should be dominantly upright in leads I and II

Rule 4

QRS and T waves tend to have the same general direction in the limb leads

Rule 5

All waves are negative in lead aVR

Rule 6
1. The R wave in the precordial leads must grow from V1 to at least V4 (See Below)
2. The S wave in the precordial leads must grow from V1 to at least V3 and disappear in V6. (See Below)
1. Top blue line indicates the R wave
2. Bottom blue line indicates the S wave
Rule 7

The ST segment should start isoelectric except in V1 and V2 where it may be elevated

Rule 8

The P waves should be upright in I, II, and V2 to V6

Rule 9

There should be no Q wave or only a small q less than 0.04 seconds in width in I, II, V2 to V6

Rule 10

The T wave must be upright in I, II, V2 to V6