Hemodynamic and tissue oxygenation responses to exercise and beta‐adrenergic blockade in patients with hyperthyroidism

• Published in: Clinical cardiology (Mahwah, N.J.) N.J.), 2004-07, Vol.27 (7), p.401-406
• Main Authors: Monachini, Maristela C., Lage, Silvia G., Rati, Miguel A. N., Cardoso, Rita H. A., Medeiros, Caio, Caramelli, Bruno, Sposito, Andrei C., Ramires, José A. F.
• Format: Article
• Language: English
• Subjects: Adrenergic beta-Antagonists - therapeutic use; Adult; autonomic nervous system; Biological and medical sciences; Cardiology. Vascular system; Clinical Investigation; Clinical Investigations; Diastole - drug effects; Endocrinopathies; Exercise - physiology; Female; Heart Rate - drug effects; hemodynamic; hormones; Humans; Hyperthyroidism - drug therapy; Hyperthyroidism - physiopathology; Male; Medical sciences; Metoprolol - therapeutic use; Middle Aged; Non tumoral diseases. Target tissue resistance. Benign neoplasms; oxygen consumption; Oxygen Consumption - drug effects; pulmonary circulation; Pulmonary Wedge Pressure - drug effects; Statistics as Topic; Stroke Volume - drug effects; Thyroid. Thyroid axis (diseases); Treatment Outcome; Vascular Resistance - drug effects
• ISSN: 0160-9289; 1932-8737
• DOI: 10.1002/clc.4960270707

Background: Exercise‐induced dyspnea is a frequent feature in patients with hyperthyroidism. Hypothesis: Data from clinical studies to elucidate the origin of this symptom are lacking. In the current study, we examined the hemodynamic and oxygenation responses to exercise and beta‐adrenergic blockade in patients with hyperthyroidism and their relationship with dyspnea. Methods: Hemodynamic studies were performed under resting conditions and after isotonic exercise in 15 patients with hyperthyroidism and 11 control subjects. Exercise was applied using a bicycle ergometer, with progressive loads. In the hyperthyroid group, measurements were repeated at rest and during supine exercise after administering 15 mg of intravenous metoprolol. Results: End‐diastolic pulmonary artery pressure and cardiac index were higher in the hyperthyroid group than in controls (18.6 ± 5.3 vs. 11.2 ± 4.9 mmHg; p = 0.02, and 6.0 ± 1.7 vs. 2.8 ± 0.5 1/min/m2; p = 0.0001, respectively). After exercise, there was an increase in end‐diastolic pulmonary artery pressure in the hyperthyroid group (18.6 ± 5.3 to 25.5 ± 9.9 mmHg; p = 0.02), revealing impaired cardiocirculatory reserve. Pulmonary arteriolar resistance increased significantly in parallel with end‐diastolic pulmonary artery pressure after drug administration, suggesting an inadequate cardiovascular response after beta blockade in patients with hyperthyroidism. Conclusion: We observed that functional left ventricular reserve is impaired in patients with hyperthyroidism, suggesting an explanation for the frequent symptom of dyspnea and impaired exercise tolerance. Moreover, we also suggest that beta‐adrenergic blockade may adversely affect cardiovascular function in patients with hyperthyroidism.