<prompt> Digitalic toxicity produce the following changes in ECG except -Inveed T waveProlonged QT intervalST depressionProlonged PR interval  <response>: 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. 