Diagnostic Value of an Electrocardiogram for Hyperkalemia

ABSTRACT

BACKGROUND: Hyperkalemia is a common and potentially life-threatening metabolic disorder. The electrocardiogram(ECG) is known to be a relatively sensitive diagnostic tool hyperkalemia. However many exceptions, in which patients showed normal ECG findings even though hyperkalemic, have been reported. The purpose of this study was to determine the extent of correlation between the ECG findings and hyperkalemia and to determine when the ECG has value for diagnosing hyperkalemia. METHODS: Patients who had been diagnosed as having hyperkalemia at two university hospitals during three years were enrolled in this study. We reviewed the medical records of the patients and evaluated the following 6 ECG abnormalities: tall T waves, narrow T waves, QRS widening, atrioventricular block, loss of P waves, and sine waves. We defined tall T waves and narrow T waves as 20 percentiles of heights and widths of the T waves from the 100 patients with normokalemia. RESULTS: During the study period, there were 100 hyperkalemic patients, and we analyzed 69 available electrocardiograms. Abnormal ECG findings were revealed in 67% of 69 patients. The higher the serum potassium level, the more abnormal ECG findings. The common ECG abnormalities were tall T waves and loss of P waves. The patients with normal ECGs even though hyperkalemic had relatively low potassium levels. And whether chronic renal disease was not correlated to the ECG abnormality. CONCLUSION: The electrocardiogram is a good diagnostic tool for hyperkalemia if it is used with accurate diagnostic criteria. Thus, hyperkalemia should be considered when the ECG shows tall T waves or loss of P waves.