A hypokalemic index ECG as a predictor of hypokalemia.

ECGs of 36 hypokalemic patients (K/s 1.0-3.5 mM/l) were analysed. The sum of the S-T depression and the U wave amplitude in leads II and V3 was used and constituted the uncorrected hypokalemic index. To correct the hypokalemic index, the figure obtained during normokalemia is subtracted from that obtained during hypokalemia. The corrected hypokalemic index gives an approximation of the K/s irrespective of other factors permanently influencing the ECG, such as treatment with antiarrhythmic drugs, coronary insufficiency, and ventricular hypertrophy. The corrected index was greater than 4.0 at a K/s of less than 2.0 mM/l. Eight out of nine patients with a K/s 2.1-2.6 had an index of 1.5-3.5. All patients with a K/s greater than 2.6 mM/l had an index less than 1.5.