Electrocardiographic Changes in Patients With Hypokalemia and Their Correlation With Serum Potassium Levels

Dyselectrolytemias can cause significant changes in cardiac electrophysiology detectable through electrocardiography (ECG). Potassium in particular has a strong effect on the cardiac membrane potential, leading to characteristic rhythm variations when potassium levels are reduced or elevated. However, the degree of correlation between specific ECG changes and the severity of hypokalemia remains variably described in the literature.

To study the association between the severity categories of hypokalemia and specific ECG waveform changes, and to examine the mechanisms by which hypokalemia may cause them.

During the study period of three months, ECGs from patients with varying levels of hypokalemia were obtained as per the inclusion and exclusion criteria after obtaining informed consent. ECGs were grouped according to corresponding potassium levels (mild 3-3.4 mEq/L, moderate 2.5-3 mEq/L, and severe <2.5 mEq/L). ECGs were analyzed for morphology and the durations of the waves, segments, and intervals. Statistical analysis was performed with a chi-square test to determine associations between individual ECG features and potassium levels.

Univariate analysis showed no statistically significant relationship between the category of severity of hypokalemia and disordered heart rate (p = 0.292), the presence of a tall P wave (0.089), prolonged PR interval (0.310), and QRS width (0.075). There were statistically significant associations between the category of severity of hypokalemia and prolonged QT interval (p = 0.013), presence of ST segment depressions (p < 0.001), presence of T-wave flattening/inversions (p = 0.007), and presence of U waves (p < 0.001).

ECG changes, particularly the presence of U waves, ST depression, T-wave flattening/inversion, and QT prolongation, are reliable markers of hypokalemia severity, supporting the use of ECG as a rapid bedside diagnostic tool and guiding emergent management. The importance of identifying ECG changes and the mechanisms of these changes has been discussed.