In ECG one small division measures:

Ans: a (0.04 sec) Ref: Ganong, 22nd ed, p. 550In ECG one small duration measures 0.04 sec.ECG:PR interval -- 0.12 - 0.2 secQRS -- 0.08 -0.10 secQT interval -- 0.40 - 0.43 secProlonged PR interval:* Hyperkalemia* 1st degree heart block (abnormally prolonged PR)* 2nd degree Mobitz type 1 (gradual prolongation of PR interval with missing of a beat)Short PR interval:* Tachycardia* WPW syndromeAbsent P waves: Atrial fibrillationDelta waveJ wave / Osborn waveSine wave patternInverse tick: WPW syndrome: Hypothermia: Hyperkalaemia: Digoxin