Rate: 60-100 beats per minute? Brady-/ tachycardic?
Rhythm: Regular/irregular?
P wave: Present before each QRS? I.e.is there an orderly contraction of the atria before each ventricular contraction or is the patient in AF?
If no P waves can be seen check lead V1 or lead II.
PR interval: Normal: 0.12 - 0.2s (3-5 small squares)? OR longer, indicating heart block (=AV block)? Or shorter - abnormally fast conduction to ventricles?
QRS complex: Normal <0.12s (< 3 small squares) narrow complexes (impulse originates from atria, normal conduction through AV node) or broad complexes (impulse originates from ventricles)
Normal sinus rhythm -