Cardiopulmonary parameters in hyperthyroidism

Background: Hyperthyroid patients often suffer from impaired exercise capac ity with dyspnoea. Two well established, non-invasive methods were used to evaluate the influence of hyperthyroidism on cardiopulmonary function. Patients and Methods: In 42 patients with hyperthyroidism we performed spir ometry and cardiopulmonary exercise testing before and after 7 days of prop ranolol therapy as well as in euthyroidism. Results: In hyperthyroidism reduced vital capacity and 1-second capacity we re observed (95.5 +/- 2.4% vs 102.6 +/- 1.5%; p = 0.0087; 89.4 +/- 2./3% vs . 95.2 +/- 2.2%; p = 0.0179). No changes showed during beta-blockade. At th e anaerobic threshold reduced tidal volume and enhanced respiratory frequen cy were noted (1119.8 +/- 48.9 ml v. 1289 +/- 62.7 ml; p = 0.0227; 28.3 +/- 0.8 vs 25.4 +/- 0.9; p = 0.0012). A significant tachycardia could be shown . Impaired response to exercise in pulse and respiratory frequency were obs erved. Work at the anaerobic threshold was impaired in hyperthyroidism (70 +/- 5 watts vs 86.9 +/- 5.7 watts; p = 0.016) and did not change during pro pranolol therapy. Oxygen pulse at the anaerobic threshold was reduced in hy perthyroidism (7.7 +/- 0.4 ml O-2/beat vs 9.1 +/- 0.4 ml O-2/beat; p = 0.00 12) and increased with propranolol (8.9 +/- 0.4 ml O-2/beat; p = 0.0001). Conclusion: In hyperthyroidism significant changes in cardiopulmonary funct ion were noted at rest and exercise. High resting function and impaired res ponse to exercise suggest a cardiopulmonary work with low efficiency. Propr anolol leads to economization and lowers patients complaints.