Effect of oral potassium supplementation on QT dispersion in anorexia nervosa


F Galetta, Department of Internal Medicine, University of Pisa School of Medicine, Via Roma 67, IT-56126 Pisa, Italy (Tel. +39 05099 3373, fax. +39 05055 3414, e-mail. fgaletta@med.unipi.it)


The aim of this study was to evaluate the degree of QT dispersion in a group of young women with anorexia nervosa and its changes after oral potassium supplementation. Twenty-eight patients with self-induced starvation were matched with 20 thin and 20 normal-weight women (body mass index ≪20). All participants underwent a complete clinical examination, including electrocardiogram (ECG) for QT interval measurements. QT dispersion was defined as the difference between the longest and the shortest QT interval occurring in the 12-lead ECG. QT dispersion was corrected (QTc) with Bazett's formula. Anorexic patients were later allocated two subgroups of 14 to receive or not to receive potassium aspartate (2 vials K-Flebo d-1= 60 mEq d-1, per os). ECG was repeated in both the subgroups of anorexic patients after 4 wk. QT dispersion was significantly greater in starving patients than in thin or normal-weight women (QT dispersion = 62.2 ± 12.4 vs 33.4 ± 7.1 or 31.7 ± 6.3 ms; QTc dispersion = 56.5 ± 12 vs 34 ± 9.1 or 33.2 ± 11 ms, p > 0.001). After 4 wk, anorexic women treated with oral potassium aspartate supplementation, compared with untreated patients, showed an increased kalaemia (4.21 ± 0.16 vs 3.91 ± 0.32 mmol 1-1, p > 0.05) and a significant reduction in the QT interval dispersion (QT dispersion = 44.2 ± 8.1 vs 63.2 ± 9.1 ms, QTc dispersion = 41.3 ± 9.7 vs 57.4 ± 9 ms, p > 0.001).

Conclusion: Patients with anorexia nervosa have greater QT dispersion than constitutionally thin and normal-weight women, and oral potassium supplementation tends to reduce it. This suggests that the reduction in the pool of potassium may be the critical factor inducing the enhancement of the QT dispersion in anorexia nervosa.