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Abnormal left ventricular function in hyperthyroidism: evidence for a possible reversible cardiomyopathy

J C Forfar, A L Muir, S A Sawers

    The New England Journal of Medicine
    |November 4, 1982
    PubMed
    Summary
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    Hyperthyroidism impairs heart function during exercise, causing a paradoxical drop in left ventricular ejection fraction (LVEF). This abnormal cardiac response in hyperthyroid patients is reversible and not solely due to beta-adrenoceptor activity.

    Area of Science:

    • Cardiology
    • Endocrinology
    • Exercise Physiology

    Background:

    • Hyperthyroidism is associated with cardiovascular changes.
    • Left ventricular ejection fraction (LVEF) may be altered in hyperthyroid patients.

    Purpose of the Study:

    • To investigate the effects of exercise and beta-adrenoceptor blockade on LVEF in hyperthyroid patients.
    • To determine if abnormal cardiac function during exercise in hyperthyroidism is reversible and mediated by beta-adrenoceptors.

    Main Methods:

    • Assessed LVEF using radionuclide ventriculography in nine hyperthyroid patients.
    • Studied patients in both hyperthyroid and euthyroid states during rest and exercise.
    • Administered propranolol (a beta-blocker) to assess its effects.

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    Main Results:

    • Hyperthyroid patients exhibited a high resting LVEF but a paradoxical fall during exercise.
    • Euthyroid state restored the normal rise in LVEF during exercise.
    • Propranolol reduced resting LVEF similarly in both states but did not alter the exercise-induced LVEF fall in hyperthyroidism.

    Conclusions:

    • Abnormal left ventricular function during exercise in hyperthyroidism suggests a reversible cardiomyopathy.
    • This functional cardiomyopathy appears independent of beta-adrenoceptor activation.
    • Excess circulating thyroid hormones may directly cause this cardiac dysfunction.