The electrocardiogram is a fairly sensitive indicator of changes in plasma concentration of potassium, and is useful in the recognition of these changes.
However, because of combined abnormalities of electrolytes, wide range of normal values and many underlying diseases, the effects of electrolytes imbalance on electrocardiogram were complicated and not always parallel with serum electrolytes levels.
Authors analyzed electrocardiogram in case of abnormal serum potassium and following results were obtained.
1. QX/QT ratio, T-wave duration and duration of T-wave/QT interval ratio were not related with serum potassium levels.
2. The height of T-wave, T/R ratio, height/ duration ratio of T-waves, T/U ratio and T-wave area were increased with increasing serum potassium levels and decreased with decreasing serum potassium levels and the height of U-wave was increased with decreasing serum potassium levels and decreased with increasing serum potassium levels.
3. Height/duration ratio of T-wave (in Lead 2 and V3), T-wave area (in V3) and T/U ratio (in Lead 2 and V3) were good indicators in serum potassium abnormalities, but there were considerable false positive and false negative cases.
4. Authors applied scoring system of height/duration ratio of T-wave (±2 points), T-wave area (±1 point) and height of T-wave (±1 point) on the diagnosis of serum potassium abnormalities, and the result was considered to be better criteria for diagnosis than individual criteria.
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