Hypokalemia is associated with lengthening of QT interval in psychiatric patients on admission

Several studies have revealed a relatively high frequency of hypokalemia in the general psychiatric population. This may be explained by adrenergic stimulation observed in the acute phase of psychiatric disorders. Little is known about the effects of hypokalemia on cardiac repolarisation in these circumstances. The current study was designed to determine if the hypokalemia observed among patients with acute psychiatric disorders can cause significant QT interval prolongation, and thus increase the risk of ventricular arrhythmia. Electrocardiograms were obtained in 282 non-selected patients admitted to a psychiatric unit. Heart-rate adjusted QT intervals (QTc) were compared to serum potassium levels and to other risk factors for QT prolongation (bradycardia, age, gender, and administration of antipsychotics). Hypokalemia, diagnosed in more than 11% of the patients, was associated with a significantly longer QTc interval (means 423.5+/-40 ms vs 408.5+/-31 ms), as was female sex. Multiple linear regression analysis on the studied risk factors revealed that only hypokalemia and female sex were independently associated with lengthening of the QT interval. According to our results, hypokalemia seems to be one of the most important risk factors for QT prolongation. We therefore strongly recommend that psychiatric patients should be screened for hypokalemia on admission.