Altered exercise performance and abnormal sympathetic responses to exercise in patients with anorexia nervosa

We evaluated the cardiovascular and sympathetic responses to exercise in patients with anorexia nervosa to determine whether their bradycardia results from a high level of physical fitness. Twenty adolescent patients with anorexia nervosa underwent maximal exercise tests, and the results were compared with those in 15 age-matched adolescent girls. In the patients with anorexia, maximal values were heart rate 174 +/- 2.8 bpm, systolic blood pressure 127 +/- 3.4 mm Hg, oxygen consumption 31 +/- 1.1 ml/kg/min, and plasma norepinephrine concentration 1581 +/- 238 pg/ml (n = 16). In the controls, corresponding values were significantly higher (P less than 0.025): heart rate 193 +/- 2.1 bpm, systolic blood pressure 163 +/- 4.4 mm Hg, oxygen consumption 39.3 +/- 1.6 ml/kg/min, and plasma norepinephrine 2695 +/- 413 (n = 10). Anaerobic threshold occurred at the same percent of maximal work in patients and controls. Results of exercise ECGs in all controls were normal, but five patients with anorexia nervosa developed significant ST segment depression. Thus, in patients with anorexia nervosa there is abnormal working capacity and cardiovascular responses to exercise and abnormal sympathetic responses to the stimulus of exercise, and a myocardial abnormality manifested as ST segment depression during exercise in some.