All are true regarding ECG except:

Ref: Pal GK. Electrocardiogram. In: Textbook of medical physiology. 2nd ed. Ahuja Publishing House. 2011: 72: 582-83. Explanation: P wave - Atrial depolarization before atrial contraction begins QRS complex - Depolarization wave spreads through the ventricles T wave - Ventricles recover from the state of depolarization P-Q or P-R Interval - It is the interval between the beginning of electrical excitation of the atria and the beginning of excitation of the ventricles Incomplete Atrioventricular Heart Block - First-degree block - P-R interval increases to greater than 0.20 - second - Second-degree block o Mobitz Type I - PR interval is prolonged progressively till a ventricular beat is dropped (Wenckebach phenomenon) o Mobitz Type II - a ventricular beat occurs in every 2 or 3 atrial beats Complete A-V Block - Third-degree block - complete block of the impulse from the atria into the ventricles; P waves become dissociated from the QRS-T complexes