Significance of QT Dispersion as a Prognostic Factor in Hyperkalemia

Choi, Sung Il; Lim, Heon Kil; Kim, Jeong Hyun; Shin, Dae Hee; Park, Ui Soon; Shin, Jin Ho; Lee, Jae Ung; Kim, Kyung Soo; Kim, Soon Gil; Lee, Bang Hun

Abstract

PURPOSE
To date, it has been impossible to relate the occurrence of ventricular arrhythmia to survival in hyperkalemia. QT dispersion is thought to reflect the inhomogeneity of ventricular repolarization and to be related to ventricular-arrhythmia-induced sudden cardiac death in various medical conditions. Therefore, the purpose of this study was to investigate to use QT dispersion as a prognostic marker in hyperkalemia and to suggest treatment guidelines for hyperkalemia by analyzing the correlations between the QT dispersion on the initial ECG and the treatment outcomes.
METHODS
This study's population was comprised of 104 patients with serum potassium concentrations > or =5.5 mEq/L, who were divided into 2 groups; group 1 was the survival group (n=81), group 2 was the death group (n=23). We reviewed retrospectively the underlying diseases, electrolytes, treatment outcomes and the clinical and ECG findings during the initial and the recovery states. The QT interval for each lead was measured manually on an enlarged (X1.5) ECG. The QT interval was measured from the first deflection of the QRS complex to the point of the T wave offset, and the corrected QT interval was obtained by using B a z e t t's formula. The QT dispersion and the corrected QT dispersion were defined as the differences between the minimal and the maximal QT values and between the corresponding corrected QT values for each of the 12 leads, respectively.
RESULTS
The treatment outcomes were not related to the initial serum potassium and the hourly serum potassium change rates. For hyperkalemia > or =7.0 mEq/L, the death group had significantly larger QT dispersion than the survival group (death group = 95.6+/-15.4 msec, survival group = 51.8+/-17.5 msec, p<0.01). However, the QT dispersions of the two groups were not different for serum potassium levels <7.0 mEq/L. For hyperkalemia > or =7.0mEq/L, QT dispersion above 65 msec had a 93.8% sensitivity, a 79.4% specificity, and a 68.2% positive predictive value for death.
CONCLUSION
For hyperkalemia > or =7.0 mEq/L, QT dispersion above 65 msec should be considered to be a prognostic marker for prediction of the treatment outcome.