Changes on the electrocardiogram in anorexia nervosa: A case control study

Changes to the electrocardiogram during exercise in anorexia nervosa

BACKGROUND

Anorexia Nervosa (AN) is an eating disorder characterized by low body weight, distorted body image, and an intense fear of gaining weight. Electrocardiogram (ECG) changes, particularly in the QT interval, have been implicated in AN-associated sudden death but not well defined.

OBJECTIVES

To characterize QT interval changes during exercise in anorexia nervosa.

METHODS

The QT interval was evaluated in a prospective cohort undergoing structured exercise. Patients from the St. Paul's Hospital Provincial Adult Tertiary Eating Disorders Program underwent a 6-minute modified exercise test protocol. A single lead ECG patch recording device was used to record a Lead I equivalent, due to challenges applying standard ECG monitoring in subjects with low body mass. Heart rate (HR) and QT interval were assessed.

RESULTS

Eighteen eating disorder patients (16 female) completed testing (age 31 ± 12 years, BMI 16.5 ± 3.8 kg/m²). Patients were compared to age- and sex-matched healthy controls. HR was similar between patients and controls (baseline: 65 (55-70)bpm vs. 69 (53-73)bpm, p = 0.83; maximum: 110 (94-139) bpm vs. 108 (93-141) bpm, p = 0.96; end recovery: 62 (54-68) bpm vs. 66 (55-75) bpm, p = 0.39). QTc intervals were similar between groups at baseline (381 ± 17 ms vs. 381 ± 46 ms, p = 0.93) and end recovery (397 ± 42 ms vs 398 ± 42 ms, p = 0.91). However, AN patients demonstrated QTc prolongation while controls showed QTc shortening at maximum HR (426 ± 70 ms vs. 345 ± 59 ms, p = 0.001).

CONCLUSION

Low level exercise HR increases are similar between AN patients and controls, but the QTc interval fails to shorten, which may explain the increased arrhythmic risk in AN.