ECG Conventions:Some examples

 Let talk about some ECG Conventions.

Depolarisation towards electrode: +ve deflection

Depolarisation away from electrode: −ve

deflection

Sensitivity: 10 mm = 1 mV

Paper speed: 25 mm per sec

Each large (5 mm) square = 0.2 sec

Each small (1 mm) square = 0.04 sec

Heart rate = 1500/RR interval (mm) (i.e. 300 ÷

number of large squares between beats)

Reference: 

Newby DE, Grubb NR.Cardiology. In: Ralston SH, Penman ID, Strachan WJ, Hobson RP.(eds). Davidson’s Principles and Practice of Medicine. 23rd ed. Edinburgh: Elsevier;2018.p.450