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Silent myocardial ischemia in hypothyroidism
R Bernstein1, C Müller, K Midtbø
1Department of Medicine, Oslo City University Hospital, Norway.
Thyroid : Official Journal of the American Thyroid Association
|December 1, 1995
Summary
Thyroxine replacement therapy can paradoxically affect angina in severe hypothyroidism. This study suggests reversible coronary dysfunction, not heart structure changes, causes these cardiac symptoms in hypothyroid patients.
Area of Science:
- Cardiology
- Endocrinology
- Nuclear Medicine
Background:
- Severe hypothyroidism presents a paradox in thyroxine replacement therapy regarding angina pectoris.
- Potential causes include reversible endocrine cardiomyopathy (asymmetric septal hypertrophy) or coronary artery narrowing.
- Previous studies suggest reversible coronary dysfunction is more likely than structural heart changes.
Purpose of the Study:
- To confirm findings of reversible coronary dysfunction in severe hypothyroidism.
- To investigate the role of myocardial perfusion defects during thyroxine replacement therapy.
Main Methods:
- Exercise and redistribution tomographic myocardial thallium-201 imaging (SPECT) used in six hypothyroid patients.
- SPECT performed before, and at 10 days and 2 months during, thyroxine therapy.
- Echocardiography excluded asymmetric septal hypertrophy and coronary artery disease.
Main Results:
- Four patients showed exercise-induced perfusion defects, normalizing at rest.
- These defects normalized during thyroxine therapy in one patient.
- All patients had normal SPECT results upon achieving euthyroidism.
Conclusions:
- Impaired myocardial perfusion in hypothyroidism, indicated by SPECT, is likely due to reversible coronary dysfunction.
- This dysfunction is an inherent and not infrequent manifestation of severe hypothyroidism.
- Findings support reversible coronary dysfunction over structural changes like ASH in this context.