Ans. a. HypokalemiaRef: Oxford Handbook of Clinical Medicine; Page No-90P WAVENormally precedes each QRS complex and upright in II, III and aVF but inverted in aVR.Absent P wave: AF, Sinoatrial block, Junctional (AV nodal) rhythm.Complete heart block indicates; dissociation between P waves and QRS complex.P. mitrale: Bifid P wave, it indicates left arterial hypertrophy.P. Pulmonale: Peaked P wave, it indicates right atrial hypertrophy.Pseudo P. Pulmonale seen if K+ decreases.ELECTROCARDIOGRAPHIC FINDINGS IN ELECTROLYTE DISTURBANCESHypokalemia related with ECGHyperkalemia related with ECG*. U and T wave fuse*. Increased QRS amplitude*. Increased QRS duration*. Increased P wave amplitude,*. Increased P wave duration*. ST segment depression*. PR interval slightly prolonged*. T wave inversion*. Prominent U waves*. Long QU intervalMild Hyperkalemia*. P wave Normal*. QRS Normal*. T wave: Tall and tented, often symmetric with narrow base; usually best seen in leads II. Ill, V2 and V4. The corrected QT interval not prolongedSevere Hyperkalemia*. P wave: Amplitude decreases, duration increases until it eventually disappears*. QRS: Broadens, wide S waves in the left precordial leads*. QRS axis: Superior (left axis deviation).*. ST segment: The terminal S waves become continuous with the tall tented T wave ECG changes in HypocalcaemiaECG Changes in Hypercalcaemia*. Hypocalcaemia causes QTc prolongation primarily by prolonging the ST segment*. The T wave is typically left unchanged*. Dysrhythmias are uncommon, although atrial fibrillation has been reported.*. Torsades de pointes may occur, but is much less common than with hypokalaemia or hypomagnesaemia*. The main ECG abnormality seen with hypercalcaemia is shortening of the QT interval*. In severe hypercalcaemia, Osborn waves (J waves) may be seen*. Ventricular irritability and VF arrest has been reported with extreme hypercalcaemia ECG changes in HypomagnesaemiaECG changes in Hypermagnesaemia*. The primary ECG abnormality seen with hypomagnesaemia is a prolonged QTc*. Atrial and ventricular ectopy, atrial tachyarrhythmias and torsades de pointes are seen in the context of hypomagnesaemia*. Tall T wave*. Depressed ST segment*. Prolonged PR interval*. Widened QRS complex