Hemodynamic and tissue oxygenation responses to exercise and beta-adrenergic blockade in patients with hyperthyroidism.
BACKGROUND
Exercise-induced dyspnea is a frequent feature in patients with hyperthyroidism.


OBJECTIVE
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 l/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.


CONCLUSIONS
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.
Heart Institute (InCor), University of Sao Paulo Medical School, Sao Paulo, SP, Brazil. maristela.monachini@incor.usp.br
Maristela C
MC
Monachini
Silvia G
SG
Lage
Miguel A N
MA
Ran
Rita H A
RH
Cardoso
Caio
C
Medeiros
Bruno
B
Caramelli
Andrei C
AC
Sposito
José A F
JA
Ramires
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000328:Adult; D003971:Diastole / Q000187:drug effects; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006980:Hyperthyroidism / Q000188:drug therapy* / Q000503:physiopathology*; D008297:Male; D008790:Metoprolol / Q000627:therapeutic use; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects*; D011669:Pulmonary Wedge Pressure / Q000187:drug effects; D013223:Statistics as Topic; D013318:Stroke Volume / Q000187:drug effects; D016896:Treatment Outcome; D014655:Vascular Resistance / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D008790:Metoprolol