ELECTROCARDIOGRAPHIC CORRELATES OF CLINICAL STATUS IN ADOLESCENTS WITH EATING DISORDERS--A CASE-CONTROL STUDY. † 29

Objectives. To determine the prevalence of electrocardiographic(ECG) abnormalities and their clinical correlates in adolescents with eating disorders. Methods. Subjects (mean age 15.0±1.4 yr; 95% were female) included 62 adolescents with anorexia nervosa (AN), 9 with bulimia nervosa (BN) and 26 with eating disorder-not otherwise specified (EDN) assessed from 3/95 and 9/96. Clinical and laboratory data at initial assessment were reviewed. ECG's for cases were compared to ECG's of age and sex-matched normal controls regarding heart rate, QTc and QTc dispersion. QTc was calculated with Bazett's correction and averaged over 12 leads. Results. There were no significant differences between groups regarding age at assessment, gender and duration of illness. Body mass index was standardized as a Z score (zBMI) using published normal values, and was significantly lower (p=.0001) in AN (-2.12±1.26 standard deviations; p=.0001 vs. normal) than BN (0.66±0.43; p=.002) and EDN(0.10±0.80; p=.54). Lower zBMI was not related to duration of illness, but was significantly correlated with lower body temperature (r=.39; p=.0001), lower PO₄ (r=.41; p=.0001), higher Mg (r=-.49; p=.0001), higher BUN(r=-.49; p=.0001) and creatinine (r=-.34; p=.0008), lower LH (r=.36; p=.0006) and estradiol (r=.45; p=.0001), and higher cortisol (r=-.45; p=.0001). Cases(vs. matched controls; paired t test) had lower heart rates (mean difference-15±19 bpm; p=.0001) and lower ventricular forces (diff. RV₆-2.0±5.2 mm; p=.0003), but did not differ regarding mean QTc (diff.-0.004±0.036 sec; p=.32). Cases had slightly lower QTc dispersion(diff. QTc range -0.007±0.030; p=.04). Lower zBMI was significantly related to lower heart rates (r=.35; p=.0005), lower RV₆ (r=.42; p=.0001) and shorter mean QTc (r=.42; p=.0001). After controlling for zBMI, there were no significant differences between diagnostic groups regarding any ECG parameter. Longer mean QTc was related to lower Mg (r=-.36; p=.0004), higher PO₄ (r=.27; p=.007), lower creatinine (r=-.36; p=.0003) and higher LH, estradiol and thyroxine. Conclusion. While adolescents with eating disorders do not appear to have significantly prolonged QTc, electrocardiographic changes are associated with clinical parameters.