Impaired cardiopulmonary exercise capacity in patients with hyperthyroidism.
OBJECTIVE
Hyperthyroidism (H) has been implicated as a primary cause of decreased exercise tolerance. To our knowledge, analysis of respiratory gas exchange, an efficient noninvasive method in evaluating cardiopulmonary capacity, has not been performed in patients with H.


METHODS
Using cardiopulmonary exercise testing, 12 consecutive women with Graves' H were examined and controlled in euthyroidism (E). Eighteen women with E, in whom cardiac catheterization had ruled out heart disease, served as control subjects (C).


METHODS
The ventilatory anaerobic threshold was determined by means of the V-slope method. Ergometry was performed with patients in a semisupine position using a continuous ramp protocol of 20 W/min. Echocardiography at rest was performed in all patients.


RESULTS
In patients with H, heart rate at rest was higher than in patients with E (p < 0.05) and showed a markedly lower increase between rest and anaerobic threshold compared with E patients (p = 0.007) and C (p = 0.009). Work rate was reduced (H, 50% vs E, 70%; p = 0.038). In H patients, the anaerobic threshold occurred at 59.6% of maximal oxygen uptake and 72% in E patients, respectively (p = 0.024). In H patients, the linear regression of the heart rate to oxygen uptake ratio showed a reduced slope in comparison with E patients (p = 0.001) and C (p = 0.004). In patients with H, a reduced tidal volume (p = 0.021) and an increased respiratory rate (p = 0.003) in comparison to patients with E were demonstrated. Echocardiographically, H patients had an increased ejection fraction (p = 0.008) and a higher cardiac index (p = 0.008) in comparison with E patients.


CONCLUSIONS
Analysis of respiratory gas exchange showed marked alterations of cardiopulmonary exercise capacity in H patients, which are reversible in E patients. The impaired chronotropic response during exercise might be the primary limiting factor of reduced work capacity in patients with H.
Kahaly
G
G
Department of Medicine III (Endocrinology/Metabolism), Johannes-Gutenberg-University Hospital, Mainz, Germany.
Hellermann
J
J
Mohr-Kahaly
S
S
Treese
N
N
D000328:Adult; D000368:Aged; D015308:Anaerobic Threshold; D013956:Antithyroid Agents / Q000627:therapeutic use; D002302:Cardiac Output; D004452:Echocardiography; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006111:Graves Disease / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000503:physiopathology*; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000503:physiopathology*; D008713:Methimazole / Q000627:therapeutic use; D008875:Middle Aged; D010101:Oxygen Consumption; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D012146:Rest; D013318:Stroke Volume; D016683:Supine Position; D013990:Tidal Volume
D013956:Antithyroid Agents; D008713:Methimazole