QT INTERVAL IN ANOREXIA-NERVOSA

Objectives-To determine the incidence of a long QT interval as a marke r for sudden death in patients with anorexia nervosa and to assess the effect of refeeding. To define a long QT interval by linear regressio n analysis and estimation of the upper limit of the confidence interva l (95% CI) and to compare this with the commonly used Bazett rate corr ection formula. Design-Prospective case control study. Setting-Tertiar y referral unit for eating disorders. Subjects-41 consecutive patients with anorexia nervosa admitted over an 18 month period. 28 age and se x matched normal controls. Main outcome measures-maximum QT interval m easured on 12 lead electrocardiograms. Results-43.6% of the variabilit y in the QT interval was explained by heart rate alone (p < 0.00001) a nd group analysis contributed a further 5.9% (p = 0.004). In 6(15%) pa tients the QT interval was above the upper limit of the 95% CI for the prediction based on the control equation (NS). Two patients died sudd enly; both had a QT interval at or above the upper limit of the 95% CI . In patients who reached their target weights the QT interval was sig nificantly shorter (median 9.8 ms; p = 0.04) relative to the upper lim it of the 60% CI of the control regression line, which best discrimina ted between patients and controls. The median Bazett rate corrected QT interval (QTc) in patients and controls was 435 v 405 ms.s(-1/2) (p = 0.0004), and before and after refeeding it was 435 v 432 ms.s(1/2) (N S). In 14(34%) patients and three (11%) controls the QTc was > 440 ms. s(-1/2) (p = 0.053). Conclusions-The QT interval was longer in patient s with anorexia nervosa than in age and sex matched controls, and ther e was a significant tendency to reversion to normal after refeeding. T he Bazett rate correction formula overestimated the number of patients with QT prolongation and also did not show an improvement with refeed ing.