Characterization of Myocardial Repolarization Reserve in Adolescent Females with Anorexia Nervosa
Background—Patients with anorexia nervosa exhibit abnormal myocardial repolarization and are susceptible to sudden cardiac death. Exercise testing is useful in unmasking QT prolongation in disorders associated with abnormal repolarization. We characterized QT adaptation during exercise in anorexia.
Methods and Results—Sixty-one adolescent female patients with anorexia nervosa and 45 age and sex matched healthy volunteers performed symptom-limited cycle ergometry during 12-lead ECG monitoring. Changes in the QT interval during exercise were measured, and QT/RR interval slopes were determined using mixed-effects regression modeling. Patients had significantly lower BMI than controls however resting heart rates, and QT/QTc intervals were similar at baseline. Patients had shorter exercise times (13.7±4.5 vs 20.6±4.5 min; p<0.001), and lower peak heart rates (159±20 vs 184±9 bpm; p<0.001). The mean QTc intervals were longer at peak exercise in patients [442±29 vs 422±19 msec; p<0.001]. During sub-maximal exertion at comparable heart rates [114±6 vs 115±11 bpm; p=0.54], the QTc interval had prolonged significantly more in patients than controls (37±28 vs 24±25 msec; p<0.016). The RR/QT slope, best described by a curvilinear relationship, was more gradual in patients compared to controls (13.4 [95%CI=12.8-13.9] vs 15.8 [95%CI=15.3-16.4] msec QT change per 10% change in RR interval; p<0.001), and steepest in patients within the highest BMI tertile vs the lowest (13.9 [95%CI=12.9-14.9 vs 12.3 [95% CI=11.3-13.3]; p=0.026).
Conclusions—Despite the absence of manifest QT prolongation, adolescent anorexic females have impaired repolarization reserve compared to healthy controls. Further study may identify impaired QT dynamics as a risk factor for arrhythmias in anorexia nervosa.
- Received March 27, 2015.
- Revision received November 16, 2015.
- Accepted December 29, 2015.