Digitalic toxicity produce the following changes in ECG except -

Ans. is 'b' i.e., Prolongation of QT interval ECG changes produced by digitalis o First see the relation of ECG and cardiac cycle. P wave represents atrial depolarization. QRS complex represents ventricular depolarization. PR interval represents conduction through AV node. QT interval corrosponds with ventricular depolarization +- ventricular repolarization. ST interval and T wave represent ventricular repolarization. o Digitalis causes PR interval --> due to delayed conduction in AV node. QT interval --> Due to increased contractility and better emptying of ventricle --> L systole. Decrease amplitute or inversion of T wave and ST depression --> Due to interference with repolarization.